<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:fc0110c4-d13f-43e8-acc5-5a3d0bfbf059,g:f4b2eca7-b9aa-4d3a-927a-8a4443a3b633-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:roleRef roleURI="http://www.div.energy/role/ConsolidatedBalanceSheets" xlink:type="simple" xlink:href="dec-20251231.xsd#ConsolidatedBalanceSheets"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/ConsolidatedBalanceSheets" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OilAndGasPropertySuccessfulEffortMethodNet_019b2f39-78bb-73f6-a22e-cf603ce9023f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OilAndGasPropertySuccessfulEffortMethodNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvedOilAndGasPropertySuccessfulEffortMethod_019b2f39-78bb-7f6a-aad1-672e44908257" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProvedOilAndGasPropertySuccessfulEffortMethod"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OilAndGasPropertySuccessfulEffortMethodNet_019b2f39-78bb-73f6-a22e-cf603ce9023f" xlink:to="loc_us-gaap_ProvedOilAndGasPropertySuccessfulEffortMethod_019b2f39-78bb-7f6a-aad1-672e44908257" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnprovedOilAndGasPropertySuccessfulEffortMethod_019b2f39-78bb-74c1-bb3b-f1d2e0427ddf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnprovedOilAndGasPropertySuccessfulEffortMethod"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OilAndGasPropertySuccessfulEffortMethodNet_019b2f39-78bb-73f6-a22e-cf603ce9023f" xlink:to="loc_us-gaap_UnprovedOilAndGasPropertySuccessfulEffortMethod_019b2f39-78bb-74c1-bb3b-f1d2e0427ddf" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OilAndGasPropertySuccessfulEffortMethodAccumulatedDepreciationDepletionAmortizationAndImpairment_019b2f39-78bb-7713-aeb8-10a0c4bbd15a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OilAndGasPropertySuccessfulEffortMethodAccumulatedDepreciationDepletionAmortizationAndImpairment"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OilAndGasPropertySuccessfulEffortMethodNet_019b2f39-78bb-73f6-a22e-cf603ce9023f" xlink:to="loc_us-gaap_OilAndGasPropertySuccessfulEffortMethodAccumulatedDepreciationDepletionAmortizationAndImpairment_019b2f39-78bb-7713-aeb8-10a0c4bbd15a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019b2f28-2be1-7453-b419-10767244d7d3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_019b2f28-2be1-7555-9370-530495cb1b96" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019b2f28-2be1-7453-b419-10767244d7d3" xlink:to="loc_us-gaap_CommonStockValue_019b2f28-2be1-7555-9370-530495cb1b96" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_019b2f28-2be1-72e9-83f1-e3eb38418309" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019b2f28-2be1-7453-b419-10767244d7d3" xlink:to="loc_us-gaap_AdditionalPaidInCapital_019b2f28-2be1-72e9-83f1-e3eb38418309" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019b2f28-2be1-7013-91ff-357e66b11fae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019b2f28-2be1-7453-b419-10767244d7d3" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019b2f28-2be1-7013-91ff-357e66b11fae" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019b2f28-2be1-7ce5-ab87-ccb29f7fc099" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019b2f28-2be1-7453-b419-10767244d7d3" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019b2f28-2be1-7ce5-ab87-ccb29f7fc099" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_019b2f28-2be1-77bb-ac1b-444c94de29fd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019b2f28-2be1-7200-aec1-163b9d4d9b3b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019b2f28-2be1-77bb-ac1b-444c94de29fd" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019b2f28-2be1-7200-aec1-163b9d4d9b3b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashCurrent_019b2f28-2be1-7069-967a-5023a0bb7ace" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedCashCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019b2f28-2be1-77bb-ac1b-444c94de29fd" xlink:to="loc_us-gaap_RestrictedCashCurrent_019b2f28-2be1-7069-967a-5023a0bb7ace" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_019b2f28-2be1-7850-b17d-7ac5bea3b9a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019b2f28-2be1-77bb-ac1b-444c94de29fd" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_019b2f28-2be1-7850-b17d-7ac5bea3b9a6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsCurrent_019c0aa4-ac4a-7ce3-b129-e99d03906f9b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetsCurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019b2f28-2be1-77bb-ac1b-444c94de29fd" xlink:to="loc_us-gaap_DerivativeAssetsCurrent_019c0aa4-ac4a-7ce3-b129-e99d03906f9b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_019c0aa4-ac4a-7fa7-891e-d83d736b4ffc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019b2f28-2be1-77bb-ac1b-444c94de29fd" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_019c0aa4-ac4a-7fa7-891e-d83d736b4ffc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_019b2f28-2be1-746a-b635-dccbe36ac98d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019b2f28-2be1-70ff-84b0-384d64d74ee8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Liabilities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019b2f28-2be1-746a-b635-dccbe36ac98d" xlink:to="loc_us-gaap_Liabilities_019b2f28-2be1-70ff-84b0-384d64d74ee8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_019b2f28-2be1-78ae-909c-88e8ff5687cc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019b2f28-2be1-746a-b635-dccbe36ac98d" xlink:to="loc_us-gaap_CommitmentsAndContingencies_019b2f28-2be1-78ae-909c-88e8ff5687cc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019b2f28-2be1-7334-8ff4-8acdc2e25aa5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019b2f28-2be1-746a-b635-dccbe36ac98d" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019b2f28-2be1-7334-8ff4-8acdc2e25aa5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019b2f28-2be1-7deb-8fe9-4c5f6e622c15" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019b2f28-2be1-7e1a-99f4-c4bc8f80624d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019b2f28-2be1-7deb-8fe9-4c5f6e622c15" xlink:to="loc_us-gaap_StockholdersEquity_019b2f28-2be1-7e1a-99f4-c4bc8f80624d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterest_019b2f28-2be1-7718-b0e5-01929b07822a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MinorityInterest"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019b2f28-2be1-7deb-8fe9-4c5f6e622c15" xlink:to="loc_us-gaap_MinorityInterest_019b2f28-2be1-7718-b0e5-01929b07822a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019b2f28-2be1-75a7-8df0-8c9ec10abd07" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_019b2f28-2be1-7395-a030-81cedb236b76" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019b2f28-2be1-75a7-8df0-8c9ec10abd07" xlink:to="loc_us-gaap_AssetsCurrent_019b2f28-2be1-7395-a030-81cedb236b76" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OilAndGasPropertySuccessfulEffortMethodNet_019b2f28-2be1-7635-bd64-2dfa3c7fdd82" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OilAndGasPropertySuccessfulEffortMethodNet"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019b2f28-2be1-75a7-8df0-8c9ec10abd07" xlink:to="loc_us-gaap_OilAndGasPropertySuccessfulEffortMethodNet_019b2f28-2be1-7635-bd64-2dfa3c7fdd82" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_019b99b4-fc27-7423-92a6-e3c301ce32ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019b2f28-2be1-75a7-8df0-8c9ec10abd07" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_019b99b4-fc27-7423-92a6-e3c301ce32ba" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashNoncurrent_019b99b4-fc27-7509-9315-6da6011e55e2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedCashNoncurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019b2f28-2be1-75a7-8df0-8c9ec10abd07" xlink:to="loc_us-gaap_RestrictedCashNoncurrent_019b99b4-fc27-7509-9315-6da6011e55e2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_019b99b4-fc27-726f-b1a5-ebe898a59459" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019b2f28-2be1-75a7-8df0-8c9ec10abd07" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_019b99b4-fc27-726f-b1a5-ebe898a59459" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_019c7686-29fc-726f-b4f9-f2480a9855d6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019b2f28-2be1-75a7-8df0-8c9ec10abd07" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_019c7686-29fc-726f-b4f9-f2480a9855d6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019b2f28-2be1-74ae-9477-437da6022d5a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Liabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_019b2f28-2be1-7e60-b8b6-4ce74874c8d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019b2f28-2be1-74ae-9477-437da6022d5a" xlink:to="loc_us-gaap_LiabilitiesCurrent_019b2f28-2be1-7e60-b8b6-4ce74874c8d8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetRetirementObligationsNoncurrent_019b2f28-2be1-7954-9b8b-72d464aab703" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetRetirementObligationsNoncurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019b2f28-2be1-74ae-9477-437da6022d5a" xlink:to="loc_us-gaap_AssetRetirementObligationsNoncurrent_019b2f28-2be1-7954-9b8b-72d464aab703" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_019b99c1-2c52-7e77-b71e-2e68a583d2ec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019b2f28-2be1-74ae-9477-437da6022d5a" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_019b99c1-2c52-7e77-b71e-2e68a583d2ec" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesNoncurrent_019b99c1-2c52-745c-b5ca-852882bc0a52" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilitiesNoncurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019b2f28-2be1-74ae-9477-437da6022d5a" xlink:to="loc_us-gaap_DerivativeLiabilitiesNoncurrent_019b99c1-2c52-745c-b5ca-852882bc0a52" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_019b99c1-2c52-786a-a7f4-e76441773e18" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019b2f28-2be1-74ae-9477-437da6022d5a" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_019b99c1-2c52-786a-a7f4-e76441773e18" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_019b2f28-2be1-78c5-afb8-1b5a4e887f27" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_019b2f28-2be1-75f7-b937-58bae1dae796" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019b2f28-2be1-78c5-afb8-1b5a4e887f27" xlink:to="loc_us-gaap_AccountsPayableCurrent_019b2f28-2be1-75f7-b937-58bae1dae796" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_019b2f28-2be1-7f7a-bac2-c1cb53d3cc7f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019b2f28-2be1-78c5-afb8-1b5a4e887f27" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_019b2f28-2be1-7f7a-bac2-c1cb53d3cc7f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_019b2f28-2be1-713d-bff3-6ca3d1e08bc8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019b2f28-2be1-78c5-afb8-1b5a4e887f27" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_019b2f28-2be1-713d-bff3-6ca3d1e08bc8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_019b99bb-c357-7196-9758-512aad86f01b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019b2f28-2be1-78c5-afb8-1b5a4e887f27" xlink:to="loc_us-gaap_LongTermDebtCurrent_019b99bb-c357-7196-9758-512aad86f01b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesCurrent_019b99bb-c357-7080-9afd-3ea2533f20d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilitiesCurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019b2f28-2be1-78c5-afb8-1b5a4e887f27" xlink:to="loc_us-gaap_DerivativeLiabilitiesCurrent_019b99bb-c357-7080-9afd-3ea2533f20d1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesCurrent_019b99bb-c357-7435-9726-43db859cfc4a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherLiabilitiesCurrent"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019b2f28-2be1-78c5-afb8-1b5a4e887f27" xlink:to="loc_us-gaap_OtherLiabilitiesCurrent_019b99bb-c357-7435-9726-43db859cfc4a" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/ConsolidatedStatementsofComprehensiveIncome" xlink:type="simple" xlink:href="dec-20251231.xsd#ConsolidatedStatementsofComprehensiveIncome"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/ConsolidatedStatementsofComprehensiveIncome" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019c495c-d3d0-7204-8a3c-b785b0327b57" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Revenues"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c495c-d3d0-7307-808f-bd4beafe8227" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Revenues_019c495c-d3d0-7204-8a3c-b785b0327b57" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c495c-d3d0-7307-808f-bd4beafe8227" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDerivativeInstrumentsNetPretax_019c495c-d3d0-711a-84d2-11f62d7a836e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnDerivativeInstrumentsNetPretax"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Revenues_019c495c-d3d0-7204-8a3c-b785b0327b57" xlink:to="loc_us-gaap_GainLossOnDerivativeInstrumentsNetPretax_019c495c-d3d0-711a-84d2-11f62d7a836e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019b2f63-77e7-7d7d-b92e-844dc4830d5e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019b2f63-77e7-7471-a815-c8178c4322e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Revenues"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingIncomeLoss_019b2f63-77e7-7d7d-b92e-844dc4830d5e" xlink:to="loc_us-gaap_Revenues_019b2f63-77e7-7471-a815-c8178c4322e6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_019b2f63-77e7-7611-91ae-a37d0804430e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingExpenses"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingIncomeLoss_019b2f63-77e7-7d7d-b92e-844dc4830d5e" xlink:to="loc_us-gaap_OperatingExpenses_019b2f63-77e7-7611-91ae-a37d0804430e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019b2fa9-6c22-7e95-9a7d-85ae7e870d2d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019b2fa9-6c22-7b98-96d7-3ce18e4e708a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019b2fa9-6c22-7e95-9a7d-85ae7e870d2d" xlink:to="loc_us-gaap_OperatingIncomeLoss_019b2fa9-6c22-7b98-96d7-3ce18e4e708a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiRealizedGainLoss_019b2fa9-6c22-7e3d-8f76-3ab8a79f8786" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquitySecuritiesFvNiRealizedGainLoss"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019b2fa9-6c22-7e95-9a7d-85ae7e870d2d" xlink:to="loc_us-gaap_EquitySecuritiesFvNiRealizedGainLoss_019b2fa9-6c22-7e3d-8f76-3ab8a79f8786" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseNonoperating_019c09d2-b32c-7629-ae93-e021986e70c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseNonoperating"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019b2fa9-6c22-7e95-9a7d-85ae7e870d2d" xlink:to="loc_us-gaap_InterestExpenseNonoperating_019c09d2-b32c-7629-ae93-e021986e70c9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019c09d1-c1f6-7b76-84bb-a23d701d952f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019b2fa9-6c22-7e95-9a7d-85ae7e870d2d" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019c09d1-c1f6-7b76-84bb-a23d701d952f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019b2fa9-6c22-77eb-a5a0-45222111fc43" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019b2fa9-6c22-7e95-9a7d-85ae7e870d2d" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019b2fa9-6c22-77eb-a5a0-45222111fc43" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_019b2f9e-5854-7362-a22c-9b629587b521" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingExpenses"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseExpense_019b2f9e-5855-7ca2-9527-23b24537b6f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseExpense"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019b2f9e-5854-7362-a22c-9b629587b521" xlink:to="loc_us-gaap_OperatingLeaseExpense_019b2f9e-5855-7ca2-9527-23b24537b6f3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductionTaxExpense_019b2f9e-5855-7f7d-8959-686e93e281d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductionTaxExpense"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019b2f9e-5854-7362-a22c-9b629587b521" xlink:to="loc_us-gaap_ProductionTaxExpense_019b2f9e-5855-7f7d-8959-686e93e281d8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_MidstreamOperatingExpense_019b2f9e-5855-7050-ade7-d4e191721213" xlink:href="dec-20251231.xsd#dec_MidstreamOperatingExpense"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019b2f9e-5854-7362-a22c-9b629587b521" xlink:to="loc_dec_MidstreamOperatingExpense_019b2f9e-5855-7050-ade7-d4e191721213" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResultsOfOperationsTransportationCosts_019b2f9e-5855-77c8-846b-c574258b2529" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResultsOfOperationsTransportationCosts"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019b2f9e-5854-7362-a22c-9b629587b521" xlink:to="loc_us-gaap_ResultsOfOperationsTransportationCosts_019b2f9e-5855-77c8-846b-c574258b2529" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetRetirementObligationAccretionExpense_019b2f9e-5855-7968-b21c-7e17a8c0cbed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetRetirementObligationAccretionExpense"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019b2f9e-5854-7362-a22c-9b629587b521" xlink:to="loc_us-gaap_AssetRetirementObligationAccretionExpense_019b2f9e-5855-7968-b21c-7e17a8c0cbed" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_019b2f9e-5855-77e1-b136-35550f6922bd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019b2f9e-5854-7362-a22c-9b629587b521" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_019b2f9e-5855-77e1-b136-35550f6922bd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_019b2f9e-5855-7d64-8fe3-22b596e8661c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019b2f9e-5854-7362-a22c-9b629587b521" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_019b2f9e-5855-7d64-8fe3-22b596e8661c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfOilAndGasProperty_019bbaf9-35d6-7188-8487-77de0961ceb2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnSaleOfOilAndGasProperty"/>
    <link:calculationArc order="8" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019b2f9e-5854-7362-a22c-9b629587b521" xlink:to="loc_us-gaap_GainLossOnSaleOfOilAndGasProperty_019bbaf9-35d6-7188-8487-77de0961ceb2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_019b2f96-6b20-79dd-91ef-0956ef568d32" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019b2f96-6b20-7469-b834-51bfb9b520a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfitLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_019b2f96-6b20-79dd-91ef-0956ef568d32" xlink:to="loc_us-gaap_ProfitLoss_019b2f96-6b20-7469-b834-51bfb9b520a4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019b2f96-6b20-7b0a-add3-d1df7994e2a5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_019b2f96-6b20-79dd-91ef-0956ef568d32" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019b2f96-6b20-7b0a-add3-d1df7994e2a5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019b2f63-77e7-7fea-944f-738428d15727" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfitLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019b2f63-77e7-729c-a68c-78fadaf8337a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ProfitLoss_019b2f63-77e7-7fea-944f-738428d15727" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019b2f63-77e7-729c-a68c-78fadaf8337a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019b2f63-77e7-75d5-98c1-b9589da4d438" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ProfitLoss_019b2f63-77e7-7fea-944f-738428d15727" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019b2f63-77e7-75d5-98c1-b9589da4d438" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019b2f63-77e7-7de8-afd2-2cd401816299" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019b2f63-77e7-7867-b848-e3f23729c783" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfitLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019b2f63-77e7-7de8-afd2-2cd401816299" xlink:to="loc_us-gaap_ProfitLoss_019b2f63-77e7-7867-b848-e3f23729c783" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_019b2f63-77e7-78ff-b1b5-29d4604a8ca4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019b2f63-77e7-7de8-afd2-2cd401816299" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_019b2f63-77e7-78ff-b1b5-29d4604a8ca4" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/ConsolidatedStatementsofCashFlows" xlink:type="simple" xlink:href="dec-20251231.xsd#ConsolidatedStatementsofCashFlows"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/ConsolidatedStatementsofCashFlows" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019c2626-a531-7cf8-9302-a4106716b33c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_019c2626-a531-7259-9c42-0447592e8ac7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019c2626-a531-7cf8-9302-a4106716b33c" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_019c2626-a531-7259-9c42-0447592e8ac7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_019c2626-a531-7467-93b1-94feee5ada47" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceOfLongTermDebt"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019c2626-a531-7cf8-9302-a4106716b33c" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_019c2626-a531-7467-93b1-94feee5ada47" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_PaymentOnEarlyRetirementOfDebt_019c2626-a531-76d7-9351-fcac864f408f" xlink:href="dec-20251231.xsd#dec_PaymentOnEarlyRetirementOfDebt"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019c2626-a531-7cf8-9302-a4106716b33c" xlink:to="loc_dec_PaymentOnEarlyRetirementOfDebt_019c2626-a531-76d7-9351-fcac864f408f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDebtIssuanceCosts_019c2626-a531-76a4-8738-313732cd3ee8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsOfDebtIssuanceCosts"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019c2626-a531-7cf8-9302-a4106716b33c" xlink:to="loc_us-gaap_PaymentsOfDebtIssuanceCosts_019c2626-a531-76a4-8738-313732cd3ee8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_DerivativeInstrumentsModificationsFinancing_019c2626-a531-77ab-a66e-8ff37b54deb9" xlink:href="dec-20251231.xsd#dec_DerivativeInstrumentsModificationsFinancing"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019c2626-a531-7cf8-9302-a4106716b33c" xlink:to="loc_dec_DerivativeInstrumentsModificationsFinancing_019c2626-a531-77ab-a66e-8ff37b54deb9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_019c2626-a531-7474-a083-9caa1ebf484b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceOrSaleOfEquity"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019c2626-a531-7cf8-9302-a4106716b33c" xlink:to="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_019c2626-a531-7474-a083-9caa1ebf484b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_ProceedsFromLeaseModifications_019c2626-a531-79bf-baf3-fdec20c42154" xlink:href="dec-20251231.xsd#dec_ProceedsFromLeaseModifications"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019c2626-a531-7cf8-9302-a4106716b33c" xlink:to="loc_dec_ProceedsFromLeaseModifications_019c2626-a531-79bf-baf3-fdec20c42154" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeasePrincipalPayments_019c2626-a531-7d48-a123-4fb680c20683" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeasePrincipalPayments"/>
    <link:calculationArc order="8" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019c2626-a531-7cf8-9302-a4106716b33c" xlink:to="loc_us-gaap_FinanceLeasePrincipalPayments_019c2626-a531-7d48-a123-4fb680c20683" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDividendsCommonStock_019c2626-a531-7eea-b858-56acdc0c3516" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsOfDividendsCommonStock"/>
    <link:calculationArc order="9" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019c2626-a531-7cf8-9302-a4106716b33c" xlink:to="loc_us-gaap_PaymentsOfDividendsCommonStock_019c2626-a531-7eea-b858-56acdc0c3516" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToMinorityShareholders_019c6cd3-278d-7af8-b3a0-9527e531b28c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToMinorityShareholders"/>
    <link:calculationArc order="10" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019c2626-a531-7cf8-9302-a4106716b33c" xlink:to="loc_us-gaap_PaymentsToMinorityShareholders_019c6cd3-278d-7af8-b3a0-9527e531b28c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_PaymentsForRepurchaseOfCommonStockStockRepurchaseProgram_019c6cd3-278d-78e0-b10c-1bc352234ee1" xlink:href="dec-20251231.xsd#dec_PaymentsForRepurchaseOfCommonStockStockRepurchaseProgram"/>
    <link:calculationArc order="11" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019c2626-a531-7cf8-9302-a4106716b33c" xlink:to="loc_dec_PaymentsForRepurchaseOfCommonStockStockRepurchaseProgram_019c6cd3-278d-78e0-b10c-1bc352234ee1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_PaymentsForRepurchaseOfCommonStockEmployeeBenefitTrust_019c7bde-3eb3-7c50-a5bc-74f020e39996" xlink:href="dec-20251231.xsd#dec_PaymentsForRepurchaseOfCommonStockEmployeeBenefitTrust"/>
    <link:calculationArc order="12" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019c2626-a531-7cf8-9302-a4106716b33c" xlink:to="loc_dec_PaymentsForRepurchaseOfCommonStockEmployeeBenefitTrust_019c7bde-3eb3-7c50-a5bc-74f020e39996" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019c2625-3792-7df2-9389-f5f2259077cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019c2625-3793-7921-ad37-95c97ca4a433" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019c2625-3792-7df2-9389-f5f2259077cb" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019c2625-3793-7921-ad37-95c97ca4a433" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_PaymentsForAssetAcquisitionsNetOfCashAcquired_019c2625-3793-71ca-8968-4187060ab2f1" xlink:href="dec-20251231.xsd#dec_PaymentsForAssetAcquisitionsNetOfCashAcquired"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019c2625-3792-7df2-9389-f5f2259077cb" xlink:to="loc_dec_PaymentsForAssetAcquisitionsNetOfCashAcquired_019c2625-3793-71ca-8968-4187060ab2f1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_019c2625-3793-7eba-8376-b6a9b1652d18" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromDivestitureOfBusinesses"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019c2625-3792-7df2-9389-f5f2259077cb" xlink:to="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_019c2625-3793-7eba-8376-b6a9b1652d18" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_019c2625-3793-796f-91a8-feaf7b4eb58d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019c2625-3792-7df2-9389-f5f2259077cb" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_019c2625-3793-796f-91a8-feaf7b4eb58d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentForContingentConsiderationLiabilityInvestingActivities_019c9030-62a2-79cc-b8d7-0969f64050a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentForContingentConsiderationLiabilityInvestingActivities"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019c2625-3792-7df2-9389-f5f2259077cb" xlink:to="loc_us-gaap_PaymentForContingentConsiderationLiabilityInvestingActivities_019c9030-62a2-79cc-b8d7-0969f64050a6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019b3680-14d7-70ab-9894-8e8a7b4d40be" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019b3680-14d7-7452-9b82-c3ebea357448" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019b3680-14d7-70ab-9894-8e8a7b4d40be" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019b3680-14d7-7452-9b82-c3ebea357448" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019b3680-14d7-7eab-af99-40e8c50528a5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019b3680-14d7-70ab-9894-8e8a7b4d40be" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019b3680-14d7-7eab-af99-40e8c50528a5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019b3680-14d7-7a91-9400-bf6867ad9df0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019b3680-14d7-70ab-9894-8e8a7b4d40be" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019b3680-14d7-7a91-9400-bf6867ad9df0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019c3727-7caa-7516-ae6b-0e5743e90821" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019c3727-7caa-7bc5-841d-3ab4e39ea17a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019c3727-7caa-7516-ae6b-0e5743e90821" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019c3727-7caa-7bc5-841d-3ab4e39ea17a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCash_019c3727-7caa-743b-98af-bfe5ead29ad6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedCash"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019c3727-7caa-7516-ae6b-0e5743e90821" xlink:to="loc_us-gaap_RestrictedCash_019c3727-7caa-743b-98af-bfe5ead29ad6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019c2624-10e3-7466-83a2-de819d930088" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfitLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:to="loc_us-gaap_ProfitLoss_019c2624-10e3-7466-83a2-de819d930088" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_019c2624-10e3-75fd-b8fe-87d39afd77e1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_019c2624-10e3-75fd-b8fe-87d39afd77e1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetRetirementObligationAccretionExpense_019c2624-10e3-7ec5-8d81-cd37dc8accc4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetRetirementObligationAccretionExpense"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:to="loc_us-gaap_AssetRetirementObligationAccretionExpense_019c2624-10e3-7ec5-8d81-cd37dc8accc4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019c2624-10e3-75b0-bf25-e71fa78f68b3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019c2624-10e3-75b0-bf25-e71fa78f68b3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019c2624-10e3-767f-9a20-408e55d4c50e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019c2624-10e3-767f-9a20-408e55d4c50e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_CashProceedsPaymentsOnSettlementOfDerivatives_019c2624-10e3-7c9c-9145-758b302dbc33" xlink:href="dec-20251231.xsd#dec_CashProceedsPaymentsOnSettlementOfDerivatives"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:to="loc_dec_CashProceedsPaymentsOnSettlementOfDerivatives_019c2624-10e3-7c9c-9145-758b302dbc33" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_AssetRetirementObligationsSettlements_019c2624-10e3-70ba-bf4a-b2336b335e46" xlink:href="dec-20251231.xsd#dec_AssetRetirementObligationsSettlements"/>
    <link:calculationArc order="7" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:to="loc_dec_AssetRetirementObligationsSettlements_019c2624-10e3-70ba-bf4a-b2336b335e46" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfOilAndGasProperty_019c2624-10e3-7818-bb9c-d26747a61a0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnSaleOfOilAndGasProperty"/>
    <link:calculationArc order="8" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:to="loc_us-gaap_GainLossOnSaleOfOilAndGasProperty_019c2624-10e3-7818-bb9c-d26747a61a0b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiRealizedGainLoss_019c2624-10e3-7f9c-8493-6fdf149e6002" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquitySecuritiesFvNiRealizedGainLoss"/>
    <link:calculationArc order="9" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:to="loc_us-gaap_EquitySecuritiesFvNiRealizedGainLoss_019c2624-10e3-7f9c-8493-6fdf149e6002" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019c2624-10e3-74c6-8356-793e41f79e06" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:calculationArc order="10" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019c2624-10e3-74c6-8356-793e41f79e06" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_DerivativeInstrumentsModificationsOperating_019c2624-10e3-74c6-89af-8bbd8987ee95" xlink:href="dec-20251231.xsd#dec_DerivativeInstrumentsModificationsOperating"/>
    <link:calculationArc order="11" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:to="loc_dec_DerivativeInstrumentsModificationsOperating_019c2624-10e3-74c6-89af-8bbd8987ee95" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_019c2624-10e3-794b-9342-c2c8694abbe8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensation"/>
    <link:calculationArc order="12" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:to="loc_us-gaap_ShareBasedCompensation_019c2624-10e3-794b-9342-c2c8694abbe8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncashIncomeExpense_019c2624-10e3-7bba-8f7a-400f0477fd53" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNoncashIncomeExpense"/>
    <link:calculationArc order="13" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:to="loc_us-gaap_OtherNoncashIncomeExpense_019c2624-10e3-7bba-8f7a-400f0477fd53" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_019c2624-10e3-7475-b521-5540480b9d6c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:calculationArc order="14" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_019c2624-10e3-7475-b521-5540480b9d6c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_019c2624-10e3-7d27-a56a-810d07404bb9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets"/>
    <link:calculationArc order="15" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_019c2624-10e3-7d27-a56a-810d07404bb9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_019c2624-10e3-7bd8-82df-34a54769336a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccountsPayable"/>
    <link:calculationArc order="16" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_019c2624-10e3-7bd8-82df-34a54769336a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_019c2624-10e3-7d27-bb62-1f25be905287" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities"/>
    <link:calculationArc order="17" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019c2624-10e3-724e-a809-3aab2a5bb001" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_019c2624-10e3-7d27-bb62-1f25be905287" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/SummaryofSignificantAccountingPoliciesScheduleofRestrictedCashDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#SummaryofSignificantAccountingPoliciesScheduleofRestrictedCashDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/SummaryofSignificantAccountingPoliciesScheduleofRestrictedCashDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCash_019b0f5d-bb10-7f69-b492-cfc9e3e52c92" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedCash"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashCurrent_019b0f5d-bb10-7bfe-9be5-94c7320fc8a5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedCashCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_RestrictedCash_019b0f5d-bb10-7f69-b492-cfc9e3e52c92" xlink:to="loc_us-gaap_RestrictedCashCurrent_019b0f5d-bb10-7bfe-9be5-94c7320fc8a5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashNoncurrent_019b0f5d-bb10-7bff-be6a-c2684f645064" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedCashNoncurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_RestrictedCash_019b0f5d-bb10-7f69-b492-cfc9e3e52c92" xlink:to="loc_us-gaap_RestrictedCashNoncurrent_019b0f5d-bb10-7bff-be6a-c2684f645064" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/AcquisitionsDivestituresScheduleofAssetAcquisitionDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#AcquisitionsDivestituresScheduleofAssetAcquisitionDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/AcquisitionsDivestituresScheduleofAssetAcquisitionDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionConsiderationTransferred_019b26c9-43b6-70af-b481-c22bcda05c76" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetAcquisitionConsiderationTransferred"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_PaymentsForAssetAcquisitions_019b26c9-43b6-7268-922d-deee79fe95b3" xlink:href="dec-20251231.xsd#dec_PaymentsForAssetAcquisitions"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetAcquisitionConsiderationTransferred_019b26c9-43b6-70af-b481-c22bcda05c76" xlink:to="loc_dec_PaymentsForAssetAcquisitions_019b26c9-43b6-7268-922d-deee79fe95b3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionConsiderationTransferredEquityInterestIssuedAndIssuable_019b9d68-8660-7720-8c05-359c8b7cc6ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetAcquisitionConsiderationTransferredEquityInterestIssuedAndIssuable"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetAcquisitionConsiderationTransferred_019b26c9-43b6-70af-b481-c22bcda05c76" xlink:to="loc_us-gaap_AssetAcquisitionConsiderationTransferredEquityInterestIssuedAndIssuable_019b9d68-8660-7720-8c05-359c8b7cc6ee" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLinesOfCredit_019b9d68-c811-7b21-ab8f-3427e17fc45c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RepaymentsOfLinesOfCredit"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetAcquisitionConsiderationTransferred_019b26c9-43b6-70af-b481-c22bcda05c76" xlink:to="loc_us-gaap_RepaymentsOfLinesOfCredit_019b9d68-c811-7b21-ab8f-3427e17fc45c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_AssetAcquisitionAssetsAcquiredAndLiabilitiesAssumedNet_019b265e-f98b-7e18-9d9a-bee2dc3e636e" xlink:href="dec-20251231.xsd#dec_AssetAcquisitionAssetsAcquiredAndLiabilitiesAssumedNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_AssetAcquisitionCashandEquivalents_019b265e-f98b-7da0-a7a8-f1e489b5c141" xlink:href="dec-20251231.xsd#dec_AssetAcquisitionCashandEquivalents"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_AssetAcquisitionAssetsAcquiredAndLiabilitiesAssumedNet_019b265e-f98b-7e18-9d9a-bee2dc3e636e" xlink:to="loc_dec_AssetAcquisitionCashandEquivalents_019b265e-f98b-7da0-a7a8-f1e489b5c141" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_AssetAcquisitionNaturalGasAndOilProperties_019b265e-f98b-72d2-a08c-3f02ed2ef504" xlink:href="dec-20251231.xsd#dec_AssetAcquisitionNaturalGasAndOilProperties"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_AssetAcquisitionAssetsAcquiredAndLiabilitiesAssumedNet_019b265e-f98b-7e18-9d9a-bee2dc3e636e" xlink:to="loc_dec_AssetAcquisitionNaturalGasAndOilProperties_019b265e-f98b-72d2-a08c-3f02ed2ef504" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAdditions_019b265e-f98b-71cf-88e0-64543123be69" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentAdditions"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_AssetAcquisitionAssetsAcquiredAndLiabilitiesAssumedNet_019b265e-f98b-7e18-9d9a-bee2dc3e636e" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAdditions_019b265e-f98b-71cf-88e0-64543123be69" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_AssetAcquisitionOtherAssetsNoncurrent_019b9d64-452a-795b-955a-4c6b086fea24" xlink:href="dec-20251231.xsd#dec_AssetAcquisitionOtherAssetsNoncurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_AssetAcquisitionAssetsAcquiredAndLiabilitiesAssumedNet_019b265e-f98b-7e18-9d9a-bee2dc3e636e" xlink:to="loc_dec_AssetAcquisitionOtherAssetsNoncurrent_019b9d64-452a-795b-955a-4c6b086fea24" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_AssetAcquisitionAccountsReceivableNet_019b265e-f98b-7d95-8802-cf5b87adb7b3" xlink:href="dec-20251231.xsd#dec_AssetAcquisitionAccountsReceivableNet"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_AssetAcquisitionAssetsAcquiredAndLiabilitiesAssumedNet_019b265e-f98b-7e18-9d9a-bee2dc3e636e" xlink:to="loc_dec_AssetAcquisitionAccountsReceivableNet_019b265e-f98b-7d95-8802-cf5b87adb7b3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_AssetAcquisitionOtherAssetsCurrent_019b270f-d022-7b15-b0dd-79a16333575a" xlink:href="dec-20251231.xsd#dec_AssetAcquisitionOtherAssetsCurrent"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_AssetAcquisitionAssetsAcquiredAndLiabilitiesAssumedNet_019b265e-f98b-7e18-9d9a-bee2dc3e636e" xlink:to="loc_dec_AssetAcquisitionOtherAssetsCurrent_019b270f-d022-7b15-b0dd-79a16333575a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetRetirementObligationLiabilitiesIncurred_019b9d68-04fe-7124-8520-d98ed3c35df5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetRetirementObligationLiabilitiesIncurred"/>
    <link:calculationArc order="7" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_AssetAcquisitionAssetsAcquiredAndLiabilitiesAssumedNet_019b265e-f98b-7e18-9d9a-bee2dc3e636e" xlink:to="loc_us-gaap_AssetRetirementObligationLiabilitiesIncurred_019b9d68-04fe-7124-8520-d98ed3c35df5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_AssetAcquisitionDeferredIncomeTaxLiability_019b270f-d022-7baa-8d5a-fc1ad194920c" xlink:href="dec-20251231.xsd#dec_AssetAcquisitionDeferredIncomeTaxLiability"/>
    <link:calculationArc order="8" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_AssetAcquisitionAssetsAcquiredAndLiabilitiesAssumedNet_019b265e-f98b-7e18-9d9a-bee2dc3e636e" xlink:to="loc_dec_AssetAcquisitionDeferredIncomeTaxLiability_019b270f-d022-7baa-8d5a-fc1ad194920c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_AssetAcquisitionOtherLiabilitiesNoncurrent_019b270f-d022-7305-8349-8e48b4a3715f" xlink:href="dec-20251231.xsd#dec_AssetAcquisitionOtherLiabilitiesNoncurrent"/>
    <link:calculationArc order="9" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_AssetAcquisitionAssetsAcquiredAndLiabilitiesAssumedNet_019b265e-f98b-7e18-9d9a-bee2dc3e636e" xlink:to="loc_dec_AssetAcquisitionOtherLiabilitiesNoncurrent_019b270f-d022-7305-8349-8e48b4a3715f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_AssetAcquisitionAccountsPayableCurrent_019c4e0f-9dbe-70b0-9177-af37eb017a96" xlink:href="dec-20251231.xsd#dec_AssetAcquisitionAccountsPayableCurrent"/>
    <link:calculationArc order="10" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_AssetAcquisitionAssetsAcquiredAndLiabilitiesAssumedNet_019b265e-f98b-7e18-9d9a-bee2dc3e636e" xlink:to="loc_dec_AssetAcquisitionAccountsPayableCurrent_019c4e0f-9dbe-70b0-9177-af37eb017a96" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_AssetAcquisitionOtherCurrentLiabilities_019c4e0f-9dbe-7198-ac8c-e24f3722ac78" xlink:href="dec-20251231.xsd#dec_AssetAcquisitionOtherCurrentLiabilities"/>
    <link:calculationArc order="11" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_AssetAcquisitionAssetsAcquiredAndLiabilitiesAssumedNet_019b265e-f98b-7e18-9d9a-bee2dc3e636e" xlink:to="loc_dec_AssetAcquisitionOtherCurrentLiabilities_019c4e0f-9dbe-7198-ac8c-e24f3722ac78" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/AcquisitionsDivestituresScheduleofBusinessAcquisitionsDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#AcquisitionsDivestituresScheduleofBusinessAcquisitionsDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/AcquisitionsDivestituresScheduleofBusinessAcquisitionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b264a-3b79-7e42-84ee-dd8968413dd0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_019b264a-3b79-7c06-a519-56927f9a37ea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b264a-3b79-7e42-84ee-dd8968413dd0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_019b264a-3b79-7c06-a519-56927f9a37ea" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_BusinessCombinationRecognizedAssetAcquiredNaturalGasAndOilProperties_019b264a-3b79-76e7-aedc-b216db3b9f66" xlink:href="dec-20251231.xsd#dec_BusinessCombinationRecognizedAssetAcquiredNaturalGasAndOilProperties"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b264a-3b79-7e42-84ee-dd8968413dd0" xlink:to="loc_dec_BusinessCombinationRecognizedAssetAcquiredNaturalGasAndOilProperties_019b264a-3b79-76e7-aedc-b216db3b9f66" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_019b264a-3b79-7284-9267-dfffa5f3d077" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b264a-3b79-7e42-84ee-dd8968413dd0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_019b264a-3b79-7284-9267-dfffa5f3d077" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_BusinessCombinationRecognizedAssetAcquiredRestrictedCash_019b264a-3b79-7000-929a-907bc00f3242" xlink:href="dec-20251231.xsd#dec_BusinessCombinationRecognizedAssetAcquiredRestrictedCash"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b264a-3b79-7e42-84ee-dd8968413dd0" xlink:to="loc_dec_BusinessCombinationRecognizedAssetAcquiredRestrictedCash_019b264a-3b79-7000-929a-907bc00f3242" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_019b264a-3b79-7c64-bc42-b2fa9dcc829a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b264a-3b79-7e42-84ee-dd8968413dd0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_019b264a-3b79-7c64-bc42-b2fa9dcc829a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_BusinessCombinationRecognizedAssetAcquiredDerivativeAssets_019b264a-3b79-7c57-bf38-934957f5248f" xlink:href="dec-20251231.xsd#dec_BusinessCombinationRecognizedAssetAcquiredDerivativeAssets"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b264a-3b79-7e42-84ee-dd8968413dd0" xlink:to="loc_dec_BusinessCombinationRecognizedAssetAcquiredDerivativeAssets_019b264a-3b79-7c57-bf38-934957f5248f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_019b264a-3b79-73ee-80b9-6aa219af56d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b264a-3b79-7e42-84ee-dd8968413dd0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_019b264a-3b79-73ee-80b9-6aa219af56d9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther_019b264a-3b79-73c2-8165-fcbfaca9ecf4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b264a-3b79-7e42-84ee-dd8968413dd0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther_019b264a-3b79-73c2-8165-fcbfaca9ecf4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_BusinessCombinationRecognizedAssetAcquiredAssetRetirementObligationsLiabilityPortion_019b264a-3b79-75b7-9ff9-2636edf15ca2" xlink:href="dec-20251231.xsd#dec_BusinessCombinationRecognizedAssetAcquiredAssetRetirementObligationsLiabilityPortion"/>
    <link:calculationArc order="9" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b264a-3b79-7e42-84ee-dd8968413dd0" xlink:to="loc_dec_BusinessCombinationRecognizedAssetAcquiredAssetRetirementObligationsLiabilityPortion_019b264a-3b79-75b7-9ff9-2636edf15ca2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt_019b264a-3b79-7ab4-a3b2-29b492b0b357" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt"/>
    <link:calculationArc order="10" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b264a-3b79-7e42-84ee-dd8968413dd0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt_019b264a-3b79-7ab4-a3b2-29b492b0b357" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_019b264a-3b79-7fbb-9359-ddb4991a8a27" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther"/>
    <link:calculationArc order="11" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b264a-3b79-7e42-84ee-dd8968413dd0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_019b264a-3b79-7fbb-9359-ddb4991a8a27" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_019b264a-3b79-700a-b14d-4a4a5ee0ed0f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable"/>
    <link:calculationArc order="12" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b264a-3b79-7e42-84ee-dd8968413dd0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_019b264a-3b79-700a-b14d-4a4a5ee0ed0f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_BusinessCombinationRecognizedLiabilityAssumedAccruedExpenseCurrent_019bdfc4-3e20-7b15-b8f6-f1c1d938f2de" xlink:href="dec-20251231.xsd#dec_BusinessCombinationRecognizedLiabilityAssumedAccruedExpenseCurrent"/>
    <link:calculationArc order="13" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b264a-3b79-7e42-84ee-dd8968413dd0" xlink:to="loc_dec_BusinessCombinationRecognizedLiabilityAssumedAccruedExpenseCurrent_019bdfc4-3e20-7b15-b8f6-f1c1d938f2de" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_BusinessCombinationRecognizedLiabilityAssumedRevenuePayable_019c0a81-c8ff-78f9-855f-aa393734938b" xlink:href="dec-20251231.xsd#dec_BusinessCombinationRecognizedLiabilityAssumedRevenuePayable"/>
    <link:calculationArc order="14" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b264a-3b79-7e42-84ee-dd8968413dd0" xlink:to="loc_dec_BusinessCombinationRecognizedLiabilityAssumedRevenuePayable_019c0a81-c8ff-78f9-855f-aa393734938b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_019c0a83-1806-7b3a-ad80-0195d1c080ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther"/>
    <link:calculationArc order="15" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019b264a-3b79-7e42-84ee-dd8968413dd0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_019c0a83-1806-7b3a-ad80-0195d1c080ce" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_019b2628-0dde-7b56-bec5-655f1e570201" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_019b2628-0dde-71bb-af7f-c4fcd386d384" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferred1_019b2628-0dde-7b56-bec5-655f1e570201" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_019b2628-0dde-71bb-af7f-c4fcd386d384" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_019b2628-0dde-74f8-81ea-d37e3982ecd8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferred1_019b2628-0dde-7b56-bec5-655f1e570201" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_019b2628-0dde-74f8-81ea-d37e3982ecd8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLinesOfCredit_019b2628-0dde-7535-ae13-ef2b04a857c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RepaymentsOfLinesOfCredit"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferred1_019b2628-0dde-7b56-bec5-655f1e570201" xlink:to="loc_us-gaap_RepaymentsOfLinesOfCredit_019b2628-0dde-7535-ae13-ef2b04a857c5" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/IncomeTaxScheduleofProvisionforIncomeTaxesDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#IncomeTaxScheduleofProvisionforIncomeTaxesDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/IncomeTaxScheduleofProvisionforIncomeTaxesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019b217e-447d-706c-88cc-16f7f5e33383" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFederalIncomeTaxExpenseBenefit_019b217e-447d-75d1-b99a-4daa3b72a804" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredFederalIncomeTaxExpenseBenefit"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019b217e-447d-706c-88cc-16f7f5e33383" xlink:to="loc_us-gaap_DeferredFederalIncomeTaxExpenseBenefit_019b217e-447d-75d1-b99a-4daa3b72a804" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit_019b217e-447d-7378-acc7-8e439c10e908" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019b217e-447d-706c-88cc-16f7f5e33383" xlink:to="loc_us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit_019b217e-447d-7378-acc7-8e439c10e908" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredForeignIncomeTaxExpenseBenefit_019b217e-447d-7269-bfeb-24f2718fc5a2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredForeignIncomeTaxExpenseBenefit"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019b217e-447d-706c-88cc-16f7f5e33383" xlink:to="loc_us-gaap_DeferredForeignIncomeTaxExpenseBenefit_019b217e-447d-7269-bfeb-24f2718fc5a2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_019b217e-2c61-7929-94e8-2f09b56e0a59" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CurrentIncomeTaxExpenseBenefit"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrentFederalTaxExpenseBenefit_019b217e-2c61-752d-89b8-ad94cb85bebd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CurrentFederalTaxExpenseBenefit"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_019b217e-2c61-7929-94e8-2f09b56e0a59" xlink:to="loc_us-gaap_CurrentFederalTaxExpenseBenefit_019b217e-2c61-752d-89b8-ad94cb85bebd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrentStateAndLocalTaxExpenseBenefit_019b217e-2c61-72bd-bcac-0cfcebb5803c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CurrentStateAndLocalTaxExpenseBenefit"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_019b217e-2c61-7929-94e8-2f09b56e0a59" xlink:to="loc_us-gaap_CurrentStateAndLocalTaxExpenseBenefit_019b217e-2c61-72bd-bcac-0cfcebb5803c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrentForeignTaxExpenseBenefit_019b217e-2c61-74a8-990f-226f7030a8ec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CurrentForeignTaxExpenseBenefit"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_019b217e-2c61-7929-94e8-2f09b56e0a59" xlink:to="loc_us-gaap_CurrentForeignTaxExpenseBenefit_019b217e-2c61-74a8-990f-226f7030a8ec" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019b217e-67c6-7677-bc23-7edb03f3f95a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_019b217e-67c6-792b-b4a8-f23e71a34b7a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CurrentIncomeTaxExpenseBenefit"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019b217e-67c6-7677-bc23-7edb03f3f95a" xlink:to="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_019b217e-67c6-792b-b4a8-f23e71a34b7a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019b217e-67c6-724c-bc93-b97271087caf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019b217e-67c6-7677-bc23-7edb03f3f95a" xlink:to="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019b217e-67c6-724c-bc93-b97271087caf" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/IncomeTaxScheduleofDifferencesBetweentheStatutoryUSFederalIncomeTaxRateandtheEffectiveTaxRatesDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#IncomeTaxScheduleofDifferencesBetweentheStatutoryUSFederalIncomeTaxRateandtheEffectiveTaxRatesDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/IncomeTaxScheduleofDifferencesBetweentheStatutoryUSFederalIncomeTaxRateandtheEffectiveTaxRatesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c4d08-e274-727c-9448-a40c6d8a9d5e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_019c4d08-e274-7d5e-b0e8-f9254a937232" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c4d08-e274-727c-9448-a40c6d8a9d5e" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_019c4d08-e274-7d5e-b0e8-f9254a937232" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes_019c4d08-e274-704a-8ddc-003c4e8db9a8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c4d08-e274-727c-9448-a40c6d8a9d5e" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes_019c4d08-e274-704a-8ddc-003c4e8db9a8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential_019c4d08-e274-7318-80c3-734ed63c8fec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c4d08-e274-727c-9448-a40c6d8a9d5e" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential_019c4d08-e274-7318-80c3-734ed63c8fec" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_EffectiveIncomeTaxRateReconciliationEquityInEarningsForeignSubsidiaryPercent_019c4d08-e274-729d-99de-b758014ccba0" xlink:href="dec-20251231.xsd#dec_EffectiveIncomeTaxRateReconciliationEquityInEarningsForeignSubsidiaryPercent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c4d08-e274-727c-9448-a40c6d8a9d5e" xlink:to="loc_dec_EffectiveIncomeTaxRateReconciliationEquityInEarningsForeignSubsidiaryPercent_019c4d08-e274-729d-99de-b758014ccba0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxExemptIncome_019c4d08-e274-7ab1-b0cf-904511cc5507" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationTaxExemptIncome"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c4d08-e274-727c-9448-a40c6d8a9d5e" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxExemptIncome_019c4d08-e274-7ab1-b0cf-904511cc5507" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxCredits_019c4d08-e274-747d-8061-b2705def6b69" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationTaxCredits"/>
    <link:calculationArc order="6" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c4d08-e274-727c-9448-a40c6d8a9d5e" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxCredits_019c4d08-e274-747d-8061-b2705def6b69" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance_019c4d08-e274-7733-ad1e-d28260b8c48b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c4d08-e274-727c-9448-a40c6d8a9d5e" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance_019c4d08-e274-7733-ad1e-d28260b8c48b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseOther_019c4d08-e274-793f-a19b-ebff498cc4cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseOther"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c4d08-e274-727c-9448-a40c6d8a9d5e" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseOther_019c4d08-e274-793f-a19b-ebff498cc4cf" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments_019c4d08-e274-7440-b8f0-67ec56589305" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments"/>
    <link:calculationArc order="9" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019c4d08-e274-727c-9448-a40c6d8a9d5e" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments_019c4d08-e274-7440-b8f0-67ec56589305" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019c7720-e6a3-70a6-8e34-0fe279ec8c4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate_019c7720-e6a3-7d51-b7f3-77fb6ddf13cd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c7720-e6a3-70a6-8e34-0fe279ec8c4d" xlink:to="loc_us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate_019c7720-e6a3-7d51-b7f3-77fb6ddf13cd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes_019c7720-e6a3-792c-bd0c-f76acdcd44f5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c7720-e6a3-70a6-8e34-0fe279ec8c4d" xlink:to="loc_us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes_019c7720-e6a3-792c-bd0c-f76acdcd44f5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationForeignIncomeTaxRateDifferential_019c7720-e6a3-75b6-af39-a01cbf353ea9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationForeignIncomeTaxRateDifferential"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c7720-e6a3-70a6-8e34-0fe279ec8c4d" xlink:to="loc_us-gaap_IncomeTaxReconciliationForeignIncomeTaxRateDifferential_019c7720-e6a3-75b6-af39-a01cbf353ea9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_EffectiveIncomeTaxRateReconciliationEquityInEarningsForeignSubsidiaryAmount_019c7720-e6a3-7c4a-9240-a9214ef719dc" xlink:href="dec-20251231.xsd#dec_EffectiveIncomeTaxRateReconciliationEquityInEarningsForeignSubsidiaryAmount"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c7720-e6a3-70a6-8e34-0fe279ec8c4d" xlink:to="loc_dec_EffectiveIncomeTaxRateReconciliationEquityInEarningsForeignSubsidiaryAmount_019c7720-e6a3-7c4a-9240-a9214ef719dc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationTaxExemptIncome_019c7720-e6a3-746a-b652-cceaee7a0f6e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationTaxExemptIncome"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c7720-e6a3-70a6-8e34-0fe279ec8c4d" xlink:to="loc_us-gaap_IncomeTaxReconciliationTaxExemptIncome_019c7720-e6a3-746a-b652-cceaee7a0f6e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationTaxCredits_019c7720-e6a3-7003-869b-a172c2d6b9c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationTaxCredits"/>
    <link:calculationArc order="6" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c7720-e6a3-70a6-8e34-0fe279ec8c4d" xlink:to="loc_us-gaap_IncomeTaxReconciliationTaxCredits_019c7720-e6a3-7003-869b-a172c2d6b9c8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance_019c7720-e6a3-7f76-946e-9a65b5c858c7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c7720-e6a3-70a6-8e34-0fe279ec8c4d" xlink:to="loc_us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance_019c7720-e6a3-7f76-946e-9a65b5c858c7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationNondeductibleExpenseOther_019c7720-e6a3-7bbc-a616-318d788acaf0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationNondeductibleExpenseOther"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c7720-e6a3-70a6-8e34-0fe279ec8c4d" xlink:to="loc_us-gaap_IncomeTaxReconciliationNondeductibleExpenseOther_019c7720-e6a3-7bbc-a616-318d788acaf0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationOtherAdjustments_019c7720-e6a3-73ad-b72d-c8d772917d6d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationOtherAdjustments"/>
    <link:calculationArc order="9" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_019c7720-e6a3-70a6-8e34-0fe279ec8c4d" xlink:to="loc_us-gaap_IncomeTaxReconciliationOtherAdjustments_019c7720-e6a3-73ad-b72d-c8d772917d6d" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/IncomeTaxScheduleofDeferredTaxAssetsandLiabilitiesDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#IncomeTaxScheduleofDeferredTaxAssetsandLiabilitiesDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/IncomeTaxScheduleofDeferredTaxAssetsandLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsLiabilitiesNet_019b9904-d84f-7b95-9350-8b2241133eb7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsLiabilitiesNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_019b9904-d84f-7942-bfda-eacf29351bc0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsLiabilitiesNet_019b9904-d84f-7b95-9350-8b2241133eb7" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_019b9904-d84f-7942-bfda-eacf29351bc0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_019b9904-d84f-7f3b-adec-16a920fac9c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsLiabilitiesNet_019b9904-d84f-7b95-9350-8b2241133eb7" xlink:to="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_019b9904-d84f-7f3b-adec-16a920fac9c3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsNet_019b21ba-81fa-7f6a-8725-5f8915756e09" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAssetRetirementObligations_019b21ba-81fa-7c81-b993-6cdea94a533a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAssetRetirementObligations"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_019b21ba-81fa-7f6a-8725-5f8915756e09" xlink:to="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAssetRetirementObligations_019b21ba-81fa-7c81-b993-6cdea94a533a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsDerivativeInstruments_019b21ba-81fa-79ca-8f92-dfdc8c5932e5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsDerivativeInstruments"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_019b21ba-81fa-7f6a-8725-5f8915756e09" xlink:to="loc_us-gaap_DeferredTaxAssetsDerivativeInstruments_019b21ba-81fa-79ca-8f92-dfdc8c5932e5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts_019b21ba-81fa-743c-95b0-73ccf16f0570" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_019b21ba-81fa-7f6a-8725-5f8915756e09" xlink:to="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts_019b21ba-81fa-743c-95b0-73ccf16f0570" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic_019b21ba-81fa-79a1-9089-5f2cc77d5645" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_019b21ba-81fa-7f6a-8725-5f8915756e09" xlink:to="loc_us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic_019b21ba-81fa-79a1-9089-5f2cc77d5645" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsValuationAllowance_019c6482-24bb-7195-a77a-3c041ee4346a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsValuationAllowance"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_019b21ba-81fa-7f6a-8725-5f8915756e09" xlink:to="loc_us-gaap_DeferredTaxAssetsValuationAllowance_019c6482-24bb-7195-a77a-3c041ee4346a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsTaxCreditCarryforwards_019b21ba-81fa-73ff-8574-d029e523e974" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsTaxCreditCarryforwards"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_019b21ba-81fa-7f6a-8725-5f8915756e09" xlink:to="loc_us-gaap_DeferredTaxAssetsTaxCreditCarryforwards_019b21ba-81fa-73ff-8574-d029e523e974" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_DeferredTaxAssetsInvestmentsInPartnerships_019b21ba-81fa-7c8b-855b-682be98f3125" xlink:href="dec-20251231.xsd#dec_DeferredTaxAssetsInvestmentsInPartnerships"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_019b21ba-81fa-7f6a-8725-5f8915756e09" xlink:to="loc_dec_DeferredTaxAssetsInvestmentsInPartnerships_019b21ba-81fa-7c8b-855b-682be98f3125" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetInterestCarryforward_019b21ba-81fa-76aa-9797-44d8102af0ab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetInterestCarryforward"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_019b21ba-81fa-7f6a-8725-5f8915756e09" xlink:to="loc_us-gaap_DeferredTaxAssetInterestCarryforward_019b21ba-81fa-76aa-9797-44d8102af0ab" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsOther_019c7bac-1708-7d8d-ba35-cc8054230025" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsOther"/>
    <link:calculationArc order="9" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_019b21ba-81fa-7f6a-8725-5f8915756e09" xlink:to="loc_us-gaap_DeferredTaxAssetsOther_019c7bac-1708-7d8d-ba35-cc8054230025" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxLiabilities_019b21ba-aa3c-7ece-9c79-f329c8792cf1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxLiabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment_019b21ba-aa3c-725d-86d1-30eeba9a425d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxLiabilities_019b21ba-aa3c-7ece-9c79-f329c8792cf1" xlink:to="loc_us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment_019b21ba-aa3c-725d-86d1-30eeba9a425d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_DeferredTaxLiabilitiesInvestmentInPartnerships_019b21ba-aa3c-7efc-8a39-a746ddff02ee" xlink:href="dec-20251231.xsd#dec_DeferredTaxLiabilitiesInvestmentInPartnerships"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxLiabilities_019b21ba-aa3c-7ece-9c79-f329c8792cf1" xlink:to="loc_dec_DeferredTaxLiabilitiesInvestmentInPartnerships_019b21ba-aa3c-7efc-8a39-a746ddff02ee" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxLiabilitiesOther_019b21ba-aa3c-75de-a146-367bff2f4a44" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxLiabilitiesOther"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxLiabilities_019b21ba-aa3c-7ece-9c79-f329c8792cf1" xlink:to="loc_us-gaap_DeferredTaxLiabilitiesOther_019b21ba-aa3c-75de-a146-367bff2f4a44" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/IncomeTaxCashPaidforIncomeTaxesDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#IncomeTaxCashPaidforIncomeTaxesDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/IncomeTaxCashPaidforIncomeTaxesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxesPaidNet_019c71b4-6b5c-7bd0-85d5-7f828128dc5e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxesPaidNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxPaidFederalAfterRefundReceived_019c71b4-6b5c-71b0-8c75-53fba739bc3f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxPaidFederalAfterRefundReceived"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxesPaidNet_019c71b4-6b5c-7bd0-85d5-7f828128dc5e" xlink:to="loc_us-gaap_IncomeTaxPaidFederalAfterRefundReceived_019c71b4-6b5c-71b0-8c75-53fba739bc3f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxPaidStateAndLocalAfterRefundReceived_019c71b4-6b5c-78a9-ab89-c055a446ea33" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxPaidStateAndLocalAfterRefundReceived"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxesPaidNet_019c71b4-6b5c-7bd0-85d5-7f828128dc5e" xlink:to="loc_us-gaap_IncomeTaxPaidStateAndLocalAfterRefundReceived_019c71b4-6b5c-78a9-ab89-c055a446ea33" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/EarningsLossPerShareDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#EarningsLossPerShareDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/EarningsLossPerShareDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019b8ff6-0053-74e6-a773-a7b7222ed4a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019b8ff6-0053-7edb-b848-5f61b4130ce1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019b8ff6-0053-74e6-a773-a7b7222ed4a4" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019b8ff6-0053-7edb-b848-5f61b4130ce1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_019b8ff6-0053-7c2c-aafc-43bc2e072901" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019b8ff6-0053-74e6-a773-a7b7222ed4a4" xlink:to="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_019b8ff6-0053-7c2c-aafc-43bc2e072901" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/NaturalGasOilPropertiesDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#NaturalGasOilPropertiesDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/NaturalGasOilPropertiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OilAndGasPropertySuccessfulEffortMethodNet_019b8fda-16fa-7f3d-b616-455ed8a7ab49" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OilAndGasPropertySuccessfulEffortMethodNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OilAndGasPropertySuccessfulEffortMethodGross_019b8fda-16fa-7122-91fd-a5df45f7d2c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OilAndGasPropertySuccessfulEffortMethodGross"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OilAndGasPropertySuccessfulEffortMethodNet_019b8fda-16fa-7f3d-b616-455ed8a7ab49" xlink:to="loc_us-gaap_OilAndGasPropertySuccessfulEffortMethodGross_019b8fda-16fa-7122-91fd-a5df45f7d2c5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OilAndGasPropertySuccessfulEffortMethodAccumulatedDepreciationDepletionAmortizationAndImpairment_019b8fda-16fa-7eee-8cd8-8d6c434843e2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OilAndGasPropertySuccessfulEffortMethodAccumulatedDepreciationDepletionAmortizationAndImpairment"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OilAndGasPropertySuccessfulEffortMethodNet_019b8fda-16fa-7f3d-b616-455ed8a7ab49" xlink:to="loc_us-gaap_OilAndGasPropertySuccessfulEffortMethodAccumulatedDepreciationDepletionAmortizationAndImpairment_019b8fda-16fa-7eee-8cd8-8d6c434843e2" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/PropertyPlantEquipmentScheduleofPropertyPlantandEquipmentDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#PropertyPlantEquipmentScheduleofPropertyPlantandEquipmentDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/PropertyPlantEquipmentScheduleofPropertyPlantandEquipmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_019c4e63-28f5-74e4-995b-8b012ecfe8d0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_019c4e63-28f5-7825-b046-3cd35e0548e4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentNet_019c4e63-28f5-74e4-995b-8b012ecfe8d0" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_019c4e63-28f5-7825-b046-3cd35e0548e4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_019c4e63-28f5-7549-94e4-9ee5bb780c94" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentNet_019c4e63-28f5-74e4-995b-8b012ecfe8d0" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_019c4e63-28f5-7549-94e4-9ee5bb780c94" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/DerivativesScheduleofNetDerivativesDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#DerivativesScheduleofNetDerivativesDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/DerivativesScheduleofNetDerivativesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_019b2869-bb53-7c53-a1fb-6a60b9d23874" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssets"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsNoncurrent_019b2869-bb53-7067-b01e-2e38ef443cff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetsNoncurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeAssets_019b2869-bb53-7c53-a1fb-6a60b9d23874" xlink:to="loc_us-gaap_DerivativeAssetsNoncurrent_019b2869-bb53-7067-b01e-2e38ef443cff" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsCurrent_019b2869-bb53-7311-bd89-91780749ff82" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetsCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeAssets_019b2869-bb53-7c53-a1fb-6a60b9d23874" xlink:to="loc_us-gaap_DerivativeAssetsCurrent_019b2869-bb53-7311-bd89-91780749ff82" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_019b286a-5153-709a-b9bf-bfaecefa77c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesNoncurrent_019b286a-5153-7f40-ac13-a7b03cb5e674" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilitiesNoncurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeLiabilities_019b286a-5153-709a-b9bf-bfaecefa77c3" xlink:to="loc_us-gaap_DerivativeLiabilitiesNoncurrent_019b286a-5153-7f40-ac13-a7b03cb5e674" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesCurrent_019b286a-5153-7c61-8456-9dfd24b45344" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilitiesCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeLiabilities_019b286a-5153-709a-b9bf-bfaecefa77c3" xlink:to="loc_us-gaap_DerivativeLiabilitiesCurrent_019b286a-5153-7c61-8456-9dfd24b45344" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_DerivativeAssetLiabilityCurrent_019b8f8b-9ff5-7054-8d12-aa570ee48cd0" xlink:href="dec-20251231.xsd#dec_DerivativeAssetLiabilityCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsCurrent_019b8f8b-9ff5-79f6-89dd-6da0f65f0235" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetsCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_DerivativeAssetLiabilityCurrent_019b8f8b-9ff5-7054-8d12-aa570ee48cd0" xlink:to="loc_us-gaap_DerivativeAssetsCurrent_019b8f8b-9ff5-79f6-89dd-6da0f65f0235" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesCurrent_019b8f8b-9ff5-76ee-a976-5aa72192ff53" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilitiesCurrent"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_DerivativeAssetLiabilityCurrent_019b8f8b-9ff5-7054-8d12-aa570ee48cd0" xlink:to="loc_us-gaap_DerivativeLiabilitiesCurrent_019b8f8b-9ff5-76ee-a976-5aa72192ff53" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeNet_019b8f8b-c12f-7e88-82fd-2759ef5e6e97" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_019b8f8b-c12f-79b4-81cb-c43cf3587d2b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssets"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeFairValueOfDerivativeNet_019b8f8b-c12f-7e88-82fd-2759ef5e6e97" xlink:to="loc_us-gaap_DerivativeAssets_019b8f8b-c12f-79b4-81cb-c43cf3587d2b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_019b8f8b-c12f-7242-96b3-fa0ec6aaabff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilities"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeFairValueOfDerivativeNet_019b8f8b-c12f-7e88-82fd-2759ef5e6e97" xlink:to="loc_us-gaap_DerivativeLiabilities_019b8f8b-c12f-7242-96b3-fa0ec6aaabff" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_DerivativeAssetLiabilityNoncurrent_019b8f8b-7f4b-7267-912b-1c6e632e93d9" xlink:href="dec-20251231.xsd#dec_DerivativeAssetLiabilityNoncurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsNoncurrent_019b8f8b-7f4b-73f9-9c44-2f52c7852dbc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetsNoncurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_DerivativeAssetLiabilityNoncurrent_019b8f8b-7f4b-7267-912b-1c6e632e93d9" xlink:to="loc_us-gaap_DerivativeAssetsNoncurrent_019b8f8b-7f4b-73f9-9c44-2f52c7852dbc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesNoncurrent_019b8f8b-7f4b-7428-a332-fdffe57dedf5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilitiesNoncurrent"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_DerivativeAssetLiabilityNoncurrent_019b8f8b-7f4b-7267-912b-1c6e632e93d9" xlink:to="loc_us-gaap_DerivativeLiabilitiesNoncurrent_019b8f8b-7f4b-7428-a332-fdffe57dedf5" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/DerivativesScheduleofNetDerivativesDetails_1" xlink:type="simple" xlink:href="dec-20251231.xsd#DerivativesScheduleofNetDerivativesDetails_1"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/DerivativesScheduleofNetDerivativesDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeNet_019b286f-382b-7ead-9df8-94f7a48265ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_DerivativeAssetLiabilityNoncurrent_019b286f-382b-7a5f-96f2-6d2a3da2b4ea" xlink:href="dec-20251231.xsd#dec_DerivativeAssetLiabilityNoncurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeFairValueOfDerivativeNet_019b286f-382b-7ead-9df8-94f7a48265ee" xlink:to="loc_dec_DerivativeAssetLiabilityNoncurrent_019b286f-382b-7a5f-96f2-6d2a3da2b4ea" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_DerivativeAssetLiabilityCurrent_019b286f-382b-7774-a31e-1965db7cbae9" xlink:href="dec-20251231.xsd#dec_DerivativeAssetLiabilityCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeFairValueOfDerivativeNet_019b286f-382b-7ead-9df8-94f7a48265ee" xlink:to="loc_dec_DerivativeAssetLiabilityCurrent_019b286f-382b-7774-a31e-1965db7cbae9" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/DerivativesScheduleofCompanysRecognizedAssetsandLiabilitiesDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#DerivativesScheduleofCompanysRecognizedAssetsandLiabilitiesDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/DerivativesScheduleofCompanysRecognizedAssetsandLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_019c7bb5-af60-7469-b014-47bff4a5b6d4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssets"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019c7bb5-af60-7eeb-aa52-7c535e675c73" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeAssets_019c7bb5-af60-7469-b014-47bff4a5b6d4" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019c7bb5-af60-7eeb-aa52-7c535e675c73" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetFairValueGrossLiability_019c7bb5-af60-7a36-b3f8-66e29db8571e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetFairValueGrossLiability"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeAssets_019c7bb5-af60-7469-b014-47bff4a5b6d4" xlink:to="loc_us-gaap_DerivativeAssetFairValueGrossLiability_019c7bb5-af60-7a36-b3f8-66e29db8571e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_019c4e81-e20d-76c4-9f4c-01b47112c0fd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019c4e81-e20d-79ae-99eb-e440c21b6811" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeLiabilities_019c4e81-e20d-76c4-9f4c-01b47112c0fd" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019c4e81-e20d-79ae-99eb-e440c21b6811" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityFairValueGrossAsset_019c4e81-e20d-7315-a0b4-d674c761db2d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilityFairValueGrossAsset"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeLiabilities_019c4e81-e20d-76c4-9f4c-01b47112c0fd" xlink:to="loc_us-gaap_DerivativeLiabilityFairValueGrossAsset_019c4e81-e20d-7315-a0b4-d674c761db2d" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/DerivativesScheduleofGainsLossesonDerivativeFinancialInstrumentsDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#DerivativesScheduleofGainsLossesonDerivativeFinancialInstrumentsDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/DerivativesScheduleofGainsLossesonDerivativeFinancialInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019b8fab-7d0d-7828-be24-556c3ffab3f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfDerivatives_019b8fab-7d0d-78f2-a5df-a1a007641592" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnSaleOfDerivatives"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019b8fab-7d0d-7828-be24-556c3ffab3f3" xlink:to="loc_us-gaap_GainLossOnSaleOfDerivatives_019b8fab-7d0d-78f2-a5df-a1a007641592" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnDerivatives_019b8fab-7d0d-745a-8cf5-88ad7e7fafe8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnrealizedGainLossOnDerivatives"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019b8fab-7d0d-7828-be24-556c3ffab3f3" xlink:to="loc_us-gaap_UnrealizedGainLossOnDerivatives_019b8fab-7d0d-745a-8cf5-88ad7e7fafe8" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/AccountsReceivableDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#AccountsReceivableDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/AccountsReceivableDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_019b0162-3ab3-75fc-8893-29df80dd366a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableGrossCurrent_019b0162-3ab3-7421-8ce2-c8b91523eff2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableGrossCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsReceivableNetCurrent_019b0162-3ab3-75fc-8893-29df80dd366a" xlink:to="loc_us-gaap_AccountsReceivableGrossCurrent_019b0162-3ab3-7421-8ce2-c8b91523eff2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_019b0162-3ab3-755e-8c88-de7b7db1a0f4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsReceivableNetCurrent_019b0162-3ab3-75fc-8893-29df80dd366a" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_019b0162-3ab3-755e-8c88-de7b7db1a0f4" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/OtherAssetsDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#OtherAssetsDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/OtherAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_019b017f-5219-71e6-b513-25395744d80f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseCurrent_019b017f-5219-7798-b7c4-ec0c29f9035b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrepaidExpenseCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_019b017f-5219-71e6-b513-25395744d80f" xlink:to="loc_us-gaap_PrepaidExpenseCurrent_019b017f-5219-7798-b7c4-ec0c29f9035b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_019c0aa3-e306-792e-be3b-54f9f9279fb3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryNet"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_019b017f-5219-71e6-b513-25395744d80f" xlink:to="loc_us-gaap_InventoryNet_019c0aa3-e306-792e-be3b-54f9f9279fb3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_019b0180-9750-7f24-9b63-f25692a62f77" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019b0f32-a159-76c3-b90e-ef05bbda8b59" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherAssetsNoncurrent_019b0180-9750-7f24-9b63-f25692a62f77" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019b0f32-a159-76c3-b90e-ef05bbda8b59" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_019b0f32-a159-7f4d-b76c-71f8c7381f27" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherAssetsNoncurrent_019b0180-9750-7f24-9b63-f25692a62f77" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_019b0f32-a159-7f4d-b76c-71f8c7381f27" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseRightOfUseAsset_019b0180-9750-7dc2-b042-00de2d81e792" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseRightOfUseAsset"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherAssetsNoncurrent_019b0180-9750-7f24-9b63-f25692a62f77" xlink:to="loc_us-gaap_FinanceLeaseRightOfUseAsset_019b0180-9750-7dc2-b042-00de2d81e792" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsNoncurrent_019c0aa3-6058-79da-bcfb-487c3b0b72cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetsNoncurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherAssetsNoncurrent_019b0180-9750-7f24-9b63-f25692a62f77" xlink:to="loc_us-gaap_DerivativeAssetsNoncurrent_019c0aa3-6058-79da-bcfb-487c3b0b72cf" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsMiscellaneousNoncurrent_019c0aa3-6058-7ec2-b6db-c749cf755257" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsMiscellaneousNoncurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherAssetsNoncurrent_019b0180-9750-7f24-9b63-f25692a62f77" xlink:to="loc_us-gaap_OtherAssetsMiscellaneousNoncurrent_019c0aa3-6058-7ec2-b6db-c749cf755257" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/LeasesScheduleofComponentsofLeaseCostsandOtherInformationRelatedtoLeasesDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#LeasesScheduleofComponentsofLeaseCostsandOtherInformationRelatedtoLeasesDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/LeasesScheduleofComponentsofLeaseCostsandOtherInformationRelatedtoLeasesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseCost_019b0290-0863-79e9-baf3-728ba5e965a8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LeaseCost"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseCost_019b0290-0863-7d34-a051-8f67d5dddf96" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseCost"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LeaseCost_019b0290-0863-79e9-baf3-728ba5e965a8" xlink:to="loc_us-gaap_OperatingLeaseCost_019b0290-0863-7d34-a051-8f67d5dddf96" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseRightOfUseAssetAmortization_019b0290-0863-79b9-bb67-99d596da015d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseRightOfUseAssetAmortization"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LeaseCost_019b0290-0863-79e9-baf3-728ba5e965a8" xlink:to="loc_us-gaap_FinanceLeaseRightOfUseAssetAmortization_019b0290-0863-79b9-bb67-99d596da015d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseInterestExpense_019b0290-0863-7155-b18e-e017eb36d832" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseInterestExpense"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LeaseCost_019b0290-0863-79e9-baf3-728ba5e965a8" xlink:to="loc_us-gaap_FinanceLeaseInterestExpense_019b0290-0863-7155-b18e-e017eb36d832" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermLeaseCost_019b0290-0863-71f3-9fd9-86f26278679e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermLeaseCost"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LeaseCost_019b0290-0863-79e9-baf3-728ba5e965a8" xlink:to="loc_us-gaap_ShortTermLeaseCost_019b0290-0863-71f3-9fd9-86f26278679e" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/LeasesScheduleofMaturitiesofOperatingandFinancingLeaseLiabilitiesDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#LeasesScheduleofMaturitiesofOperatingandFinancingLeaseLiabilitiesDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/LeasesScheduleofMaturitiesofOperatingandFinancingLeaseLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b029d-ef6f-7935-89e1-073d40291bc7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_019b029d-ef6f-70ee-a829-8a08bcb352f2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b029d-ef6f-7935-89e1-073d40291bc7" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_019b029d-ef6f-70ee-a829-8a08bcb352f2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_019b029d-ef6f-7f4c-916b-bf3b3705d173" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b029d-ef6f-7935-89e1-073d40291bc7" xlink:to="loc_us-gaap_OperatingLeaseLiability_019b029d-ef6f-7f4c-916b-bf3b3705d173" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019b02a2-e268-70b5-8011-39607cdf27ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount_019b02a2-e268-72ec-b01c-a7107dbc8c1b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019b02a2-e268-70b5-8011-39607cdf27ee" xlink:to="loc_us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount_019b02a2-e268-72ec-b01c-a7107dbc8c1b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiability_019b02a2-e268-746b-bda5-237e86904cbf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiability"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019b02a2-e268-70b5-8011-39607cdf27ee" xlink:to="loc_us-gaap_FinanceLeaseLiability_019b02a2-e268-746b-bda5-237e86904cbf" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/LeasesScheduleofMaturitiesofOperatingandFinancingLeaseLiabilitiesDetails_1" xlink:type="simple" xlink:href="dec-20251231.xsd#LeasesScheduleofMaturitiesofOperatingandFinancingLeaseLiabilitiesDetails_1"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/LeasesScheduleofMaturitiesofOperatingandFinancingLeaseLiabilitiesDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019b02a2-c574-71d3-9017-ff4188bed031" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths_019b02a2-c574-7ffa-b5bb-95f03d0c9fcb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019b02a2-c574-71d3-9017-ff4188bed031" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths_019b02a2-c574-7ffa-b5bb-95f03d0c9fcb" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo_019b02a2-c574-7527-ba5b-5b9a85501f7b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019b02a2-c574-71d3-9017-ff4188bed031" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo_019b02a2-c574-7527-ba5b-5b9a85501f7b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree_019b02a2-c574-7157-9cf8-1276ff7349c1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019b02a2-c574-71d3-9017-ff4188bed031" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree_019b02a2-c574-7157-9cf8-1276ff7349c1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour_019b02a2-c574-7743-9b99-9fdf6ccd9097" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019b02a2-c574-71d3-9017-ff4188bed031" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour_019b02a2-c574-7743-9b99-9fdf6ccd9097" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive_019b02a2-c574-785f-afdd-58f62806f3cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019b02a2-c574-71d3-9017-ff4188bed031" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive_019b02a2-c574-785f-afdd-58f62806f3cf" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive_019b02a2-c574-721c-8b49-a33d286b2f9d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019b02a2-c574-71d3-9017-ff4188bed031" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive_019b02a2-c574-721c-8b49-a33d286b2f9d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b029d-c870-7635-9fc6-ce4c10137d66" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_019b029d-c870-70e9-a6c3-6d111aa2caf2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b029d-c870-7635-9fc6-ce4c10137d66" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_019b029d-c870-70e9-a6c3-6d111aa2caf2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_019b029d-c870-763d-8f06-f44f410fbe64" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b029d-c870-7635-9fc6-ce4c10137d66" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_019b029d-c870-763d-8f06-f44f410fbe64" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_019b029d-c870-7314-9866-c521785e4406" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b029d-c870-7635-9fc6-ce4c10137d66" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_019b029d-c870-7314-9866-c521785e4406" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_019b029d-c870-7140-9e1e-f626e924ca76" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b029d-c870-7635-9fc6-ce4c10137d66" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_019b029d-c870-7140-9e1e-f626e924ca76" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_019b029d-c870-71e6-a2f2-3ecf80155590" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b029d-c870-7635-9fc6-ce4c10137d66" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_019b029d-c870-71e6-a2f2-3ecf80155590" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_019b029d-c870-7382-a273-c058b8eccac9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019b029d-c870-7635-9fc6-ce4c10137d66" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_019b029d-c870-7382-a273-c058b8eccac9" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/BorrowingsScheduleofFutureMaturitiesofTotalBorrowingsDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#BorrowingsScheduleofFutureMaturitiesofTotalBorrowingsDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/BorrowingsScheduleofFutureMaturitiesofTotalBorrowingsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019b0185-29cf-75c9-b7c8-d2a5889209db" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_019b0185-29cf-7f4f-b715-2146efcb0b33" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019b0185-29cf-75c9-b7c8-d2a5889209db" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_019b0185-29cf-7f4f-b715-2146efcb0b33" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_019b0185-29cf-763e-a5bb-a3b4e6b60b2c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019b0185-29cf-75c9-b7c8-d2a5889209db" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_019b0185-29cf-763e-a5bb-a3b4e6b60b2c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_019b0185-29cf-7dd9-8fbb-dde3acb0b4d5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019b0185-29cf-75c9-b7c8-d2a5889209db" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_019b0185-29cf-7dd9-8fbb-dde3acb0b4d5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_019b0185-29cf-70cc-beb2-62006ad9f7a1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019b0185-29cf-75c9-b7c8-d2a5889209db" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_019b0185-29cf-70cc-beb2-62006ad9f7a1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive_019b0185-29cf-7edf-a160-d2070a4f6146" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019b0185-29cf-75c9-b7c8-d2a5889209db" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive_019b0185-29cf-7edf-a160-d2070a4f6146" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive_019b0185-29cf-71d3-8a3a-538657b37776" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019b0185-29cf-75c9-b7c8-d2a5889209db" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive_019b0185-29cf-71d3-8a3a-538657b37776" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/BorrowingsScheduleofInterestExpenseDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#BorrowingsScheduleofInterestExpenseDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/BorrowingsScheduleofInterestExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_019b0187-ce1c-7e7a-b739-d3c35a0091a8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseDebt"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebtExcludingAmortization_019b0187-ce1c-7246-ba06-69b05f477eb2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseDebtExcludingAmortization"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InterestExpenseDebt_019b0187-ce1c-7e7a-b739-d3c35a0091a8" xlink:to="loc_us-gaap_InterestExpenseDebtExcludingAmortization_019b0187-ce1c-7246-ba06-69b05f477eb2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_InterestExpenseDebtMiscellaneous_019b0187-ce1c-7a54-b858-d181642d20d0" xlink:href="dec-20251231.xsd#dec_InterestExpenseDebtMiscellaneous"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InterestExpenseDebt_019b0187-ce1c-7e7a-b739-d3c35a0091a8" xlink:to="loc_dec_InterestExpenseDebtMiscellaneous_019b0187-ce1c-7a54-b858-d181642d20d0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseNonoperating_019b0ed7-85aa-7552-ae65-2e2ab242bb73" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseNonoperating"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_019b0ed7-85aa-7cc0-a892-de1545c01b3f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseDebt"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InterestExpenseNonoperating_019b0ed7-85aa-7552-ae65-2e2ab242bb73" xlink:to="loc_us-gaap_InterestExpenseDebt_019b0ed7-85aa-7cc0-a892-de1545c01b3f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestCostsCapitalizedAdjustment_019b0ed7-85aa-7f0d-9e19-cf7f659b07bb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestCostsCapitalizedAdjustment"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InterestExpenseNonoperating_019b0ed7-85aa-7552-ae65-2e2ab242bb73" xlink:to="loc_us-gaap_InterestCostsCapitalizedAdjustment_019b0ed7-85aa-7f0d-9e19-cf7f659b07bb" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/AccountsPayableAccruedLiabilitiesDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#AccountsPayableAccruedLiabilitiesDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/AccountsPayableAccruedLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_019b2681-c5ab-734d-b9ce-2e614e59bfea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_019b2681-c5ab-74f8-9e67-5282aeb399b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_019b2681-c5ab-734d-b9ce-2e614e59bfea" xlink:to="loc_us-gaap_AccountsPayableCurrent_019b2681-c5ab-74f8-9e67-5282aeb399b4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_AccruedOperatingExpense_019b2681-c5ab-7b5f-a69f-51f7ba4a2114" xlink:href="dec-20251231.xsd#dec_AccruedOperatingExpense"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_019b2681-c5ab-734d-b9ce-2e614e59bfea" xlink:to="loc_dec_AccruedOperatingExpense_019b2681-c5ab-7b5f-a69f-51f7ba4a2114" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_019b2681-c5ab-7d33-8099-f405b3977f35" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_019b2681-c5ab-734d-b9ce-2e614e59bfea" xlink:to="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_019b2681-c5ab-7d33-8099-f405b3977f35" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_AccruedCapitalExpendituresCurrent_019b2681-c5ab-7b1c-8f1a-ebb65f145719" xlink:href="dec-20251231.xsd#dec_AccruedCapitalExpendituresCurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_019b2681-c5ab-734d-b9ce-2e614e59bfea" xlink:to="loc_dec_AccruedCapitalExpendituresCurrent_019b2681-c5ab-7b1c-8f1a-ebb65f145719" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019b2681-c5ab-7bd0-89df-66cd35394506" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAccruedLiabilitiesCurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_019b2681-c5ab-734d-b9ce-2e614e59bfea" xlink:to="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019b2681-c5ab-7bd0-89df-66cd35394506" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/OtherLiabilitiesDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#OtherLiabilitiesDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/OtherLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_019b35b9-7585-7d79-982d-2819925022ed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityNoncurrent_019c0ab2-4733-7f85-9622-871e8639f970" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityNoncurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesNoncurrent_019b35b9-7585-7d79-982d-2819925022ed" xlink:to="loc_us-gaap_FinanceLeaseLiabilityNoncurrent_019c0ab2-4733-7f85-9622-871e8639f970" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_019c0ab2-4733-7ce5-8dd9-4adb5c5114b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesNoncurrent_019b35b9-7585-7d79-982d-2819925022ed" xlink:to="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_019c0ab2-4733-7ce5-8dd9-4adb5c5114b5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherSundryLiabilitiesNoncurrent_019c0ab2-4733-7cbc-acf4-49b6a84f80e9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherSundryLiabilitiesNoncurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesNoncurrent_019b35b9-7585-7d79-982d-2819925022ed" xlink:to="loc_us-gaap_OtherSundryLiabilitiesNoncurrent_019c0ab2-4733-7cbc-acf4-49b6a84f80e9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019b35b9-7585-789b-86ee-ca9b3fff28db" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesNoncurrent_019b35b9-7585-7d79-982d-2819925022ed" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019b35b9-7585-789b-86ee-ca9b3fff28db" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesCurrent_019b35a6-e62f-7217-99be-6d29ee7ab773" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherLiabilitiesCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxesPayableCurrent_019b35a6-e62f-78c2-b976-d99a39594698" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxesPayableCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesCurrent_019b35a6-e62f-7217-99be-6d29ee7ab773" xlink:to="loc_us-gaap_TaxesPayableCurrent_019b35a6-e62f-78c2-b976-d99a39594698" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_019b35a6-e62f-7ff4-9234-ee4016b775cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesCurrent_019b35a6-e62f-7217-99be-6d29ee7ab773" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_019b35a6-e62f-7ff4-9234-ee4016b775cb" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityCurrent_019b35a6-e62f-79f1-bfcc-28e59d05e6c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityCurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesCurrent_019b35a6-e62f-7217-99be-6d29ee7ab773" xlink:to="loc_us-gaap_FinanceLeaseLiabilityCurrent_019b35a6-e62f-79f1-bfcc-28e59d05e6c4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetRetirementObligationCurrent_019c0ab2-736d-7a2a-8a03-cc9066f8e576" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetRetirementObligationCurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesCurrent_019b35a6-e62f-7217-99be-6d29ee7ab773" xlink:to="loc_us-gaap_AssetRetirementObligationCurrent_019c0ab2-736d-7a2a-8a03-cc9066f8e576" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherSundryLiabilitiesCurrent_019c0ab2-736d-7615-b95b-598719a72aa0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherSundryLiabilitiesCurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesCurrent_019b35a6-e62f-7217-99be-6d29ee7ab773" xlink:to="loc_us-gaap_OtherSundryLiabilitiesCurrent_019c0ab2-736d-7615-b95b-598719a72aa0" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/FairValueDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#FairValueDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/FairValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetAssetLiability_019b01f8-fb91-765f-9b71-abd40606f465" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueNetAssetLiability"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_019b01f8-fb91-7b97-81a1-f716873113d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssets"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FairValueNetAssetLiability_019b01f8-fb91-765f-9b71-abd40606f465" xlink:to="loc_us-gaap_DerivativeAssets_019b01f8-fb91-7b97-81a1-f716873113d8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_019b01f8-fb91-7cc9-998a-9765bcc91067" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilities"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FairValueNetAssetLiability_019b01f8-fb91-765f-9b71-abd40606f465" xlink:to="loc_us-gaap_DerivativeLiabilities_019b01f8-fb91-7cc9-998a-9765bcc91067" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.div.energy/role/CommitmentsContingenciesDetails" xlink:type="simple" xlink:href="dec-20251231.xsd#CommitmentsContingenciesDetails"/>
  <link:calculationLink xlink:role="http://www.div.energy/role/CommitmentsContingenciesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dec_SupplyCommitmentRemainingAmountCommittedQuantity_019b01c5-67e1-7e2e-8c28-3286740380d6" xlink:href="dec-20251231.xsd#dec_SupplyCommitmentRemainingAmountCommittedQuantity"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_SupplyCommitmentQuantityDueNextTwelveMonths_019b01c5-67e1-7776-8b5f-e6ae401287d8" xlink:href="dec-20251231.xsd#dec_SupplyCommitmentQuantityDueNextTwelveMonths"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_SupplyCommitmentRemainingAmountCommittedQuantity_019b01c5-67e1-7e2e-8c28-3286740380d6" xlink:to="loc_dec_SupplyCommitmentQuantityDueNextTwelveMonths_019b01c5-67e1-7776-8b5f-e6ae401287d8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_SupplyCommitmentQuantityDueYearTwo_019b01c5-67e1-7e20-b44d-78a20412cc92" xlink:href="dec-20251231.xsd#dec_SupplyCommitmentQuantityDueYearTwo"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_SupplyCommitmentRemainingAmountCommittedQuantity_019b01c5-67e1-7e2e-8c28-3286740380d6" xlink:to="loc_dec_SupplyCommitmentQuantityDueYearTwo_019b01c5-67e1-7e20-b44d-78a20412cc92" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_SupplyCommitmentQuantityDueYearThree_019b01c5-67e1-7e2d-b5b5-a2c20ca9ce67" xlink:href="dec-20251231.xsd#dec_SupplyCommitmentQuantityDueYearThree"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_SupplyCommitmentRemainingAmountCommittedQuantity_019b01c5-67e1-7e2e-8c28-3286740380d6" xlink:to="loc_dec_SupplyCommitmentQuantityDueYearThree_019b01c5-67e1-7e2d-b5b5-a2c20ca9ce67" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_SupplyCommitmentQuantityDueYearFour_019b01c5-67e1-7890-b6a2-d85a4ee57ba5" xlink:href="dec-20251231.xsd#dec_SupplyCommitmentQuantityDueYearFour"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_SupplyCommitmentRemainingAmountCommittedQuantity_019b01c5-67e1-7e2e-8c28-3286740380d6" xlink:to="loc_dec_SupplyCommitmentQuantityDueYearFour_019b01c5-67e1-7890-b6a2-d85a4ee57ba5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_SupplyCommitmentQuantityDueYearFive_019b01c5-67e1-76d4-b761-0fd408b456bb" xlink:href="dec-20251231.xsd#dec_SupplyCommitmentQuantityDueYearFive"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_SupplyCommitmentRemainingAmountCommittedQuantity_019b01c5-67e1-7e2e-8c28-3286740380d6" xlink:to="loc_dec_SupplyCommitmentQuantityDueYearFive_019b01c5-67e1-76d4-b761-0fd408b456bb" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_dec_SupplyCommitmentQuantityAfterYearFive_019b01c5-67e1-73df-a91c-a8e9e16238eb" xlink:href="dec-20251231.xsd#dec_SupplyCommitmentQuantityAfterYearFive"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_dec_SupplyCommitmentRemainingAmountCommittedQuantity_019b01c5-67e1-7e2e-8c28-3286740380d6" xlink:to="loc_dec_SupplyCommitmentQuantityAfterYearFive_019b01c5-67e1-73df-a91c-a8e9e16238eb" xlink:type="arc"/>
  </link:calculationLink>
</link:linkbase>
