Marketing expense. Marketing expense decreased from $148 million for the six months ended June 30, 2023 to $131 million for the six months ended June 30, 2024, a decrease of $17 million, or 11%. Marketing expense includes the cost of third-party purchased natural gas, NGLs and oil as well as firm transportation costs, including costs related to current excess firm capacity. The cost of third-party natural gas purchases decreased $39 million, partially offset by oil and NGLs purchases increase of $31 million and $3 million, respectively. The total cost of third-party commodity purchases decreased primarily due to lower natural gas marketing volumes and prices between periods, partially offset by higher oil prices and marketing volumes during the six months ended June 30, 2024. Firm transportation costs decreased $12 million from $55 million for the six months ended June 30, 2023 to $43 million for the six months ended June 30, 2024, due to the reduction in firm transportation commitments between periods.
Contract termination, loss contingency and other operating expenses. Contract termination, loss contingency and other operating expenses attributable to our marketing segment for the six months ended June 30, 2023, relate to a $24 million payment for the early termination of our firm transportation commitment of 200,000 MMBtu per day on the Equitrans pipeline. Our marketing segment did not incur any contract termination, loss contingency and other operating expenses for the six months ended June 30, 2024.
Antero Midstream Segment
Antero Midstream revenue. Revenue from the Antero Midstream segment increased from $518 million for the six months ended June 30, 2023 to $549 million for the six months ended June 30, 2024, an increase of $31 million. This increase is primarily due to higher gathering and processing revenues of $46 million, partially offset by lower water handling revenues of $15 million. The increased gathering and processing revenues between periods is primarily a result of the expiration of the growth incentive fee rebate program on December 31, 2023, increased throughput and annual CPI-based gathering and compression rate adjustments between periods. The decreased water handling revenues between periods is primarily due to lower fresh water delivery volumes and lower water handling volumes that are billed at cost plus 3%, partially offset by higher blending volumes and an increased fresh water delivery rate due to an annual CPI-based adjustment during the six months ended June 30, 2024.
Antero Midstream operating expense. Total operating expense related to the Antero Midstream segment increased from $224 million for the six months ended June 30, 2023 to $230 million for the six months ended June 30, 2024, an increase of $6 million. This increase is primarily due to higher equity-based compensation expense and depreciation expense between periods, partially offset by lower interest expense during the six months ended June 30, 2024.
Items Not Allocated to Segments
Interest expense. Interest expense increased from $54 million for the six months ended June 30, 2023 to $63 million for the six months ended June 30, 2024, an increase of $9 million or 17%, primarily due to higher average Prior Credit Facility borrowings between periods and higher benchmark interest rates during the six months ended June 30, 2024.
Income tax expense (benefit). For the six months ended June 30, 2023, we had income tax expense of $32 million, with an effective tax rate of 14%, related to our income before income taxes of $226 million. For the six months ended June 30, 2024, we had an income tax benefit of $3 million, with an effective tax rate of 21%, related to our loss before income taxes of $15 million. The increase in the effective tax rate between periods was primarily due to the effects of noncontrolling interests and our income (loss) before income taxes.
Capital Resources and Liquidity
Sources and Uses of Cash
Our primary sources of liquidity have been through net cash provided by operating activities, borrowings under our Credit Facility, issuances of debt and equity securities and additional contributions from our asset sales, including our drilling partnership. Our primary use of cash has been for the exploration, development and acquisition of oil and natural gas properties. As we develop our reserves, we continually monitor what capital resources, including equity and debt financings, are available to meet our future financial obligations, planned capital expenditure activities and liquidity requirements. Our future success in developing our proved reserves and production will be highly dependent on net cash provided by operating activities and the capital resources available to us.
Based on strip prices as of June 30, 2024, we believe that net cash provided by operating activities and available borrowings under the Credit Facility will be sufficient to meet our cash requirements, including normal operating needs, debt service obligations, capital expenditures and commitments and contingencies for at least the next 12 months.