General and administrative expenses. General and administrative expenses (excluding equity-based compensation expense) increased from $6 million for the nine months ended September 30, 2018 to $32 million for the nine months ended September 30, 2019. The increase was primarily due to the inclusion of general and administrative expenses of Antero Midstream Partners after the completion of the Transactions on March 12, 2019. Equity-based compensation increased from $26 million for the nine months ended September 30, 2018 to $53 million for the nine months ended September 30, 2019 due to the Series B Exchange and the adoption of the AMC LTIP as result of the Transactions.
Impairment of property and equipment expense. Impairment of property and equipment expense of $408 million for the nine months ended September 30, 2019 was primarily due to the idling of the Clearwater Facility in September 2019.
Impairment of goodwill expense. Impairment of goodwill expense of $44 million for the nine months ended September 30, 2019 reflects an impairment of the goodwill that was associated with the Clearwater Facility.
Impairment of customer relationships expense. Impairment of customer relationships expense of $6 million for the nine months ended September 30, 2019 reflects an impairment of the customer relationships that were associated with the Clearwater Facility.
Depreciation expense. Depreciation expense increased from none for the nine months ended September 30, 2018 to $69 million for the nine months ended September 30, 2019 as a result of our acquisition of Antero Midstream Partners on March 12, 2019.
Accretion and change in fair value of contingent acquisition consideration. Accretion expenses increased from none for the nine months ended September 30, 2018 to $5 million for the nine months ended September 30, 2019 as a result of our acquisition of Antero Midstream Partners on March 12, 2019.
Interest expense. Interest expense increased from $82 thousand for the nine months ended September 30, 2018 to $74 million for the nine months ended September 30, 2019 as a result of the acquisition of Antero Midstream Partners, which included the assumption of approximately $2.4 billion of debt.
Operating loss. Total operating loss increased from a loss of $32 million for the nine months ended September 30, 2018 to $206 million for the nine months ended September 30, 2019. The increase was due to net operating revenues and expenses as a result of the acquisition of Antero Midstream Partners on March 12, 2019 and impairments to property and equipment, goodwill and customer relationships of approximately $408 million, $44 million and $6 million, respectively.
Equity in earnings of unconsolidated affiliates. Equity in earnings of unconsolidated affiliates for the nine months ended September 30, 2018 represents Antero Midstream GP LP’s equity investment in Antero Midstream Partners. Equity in earnings of unconsolidated affiliates for the nine months ended September 30, 2019 represents Antero Midstream GP LP’s equity investment in Antero Midstream Partners from January 1, 2019 through March 12, 2019 and the portion of the net income from Antero Midstream Partners’ investments in Stonewall and the Joint Venture, which is allocated to us based on our equity interests for the period from March 13, 2019 through September 30, 2019.
Income tax benefit (expense). Income tax benefit (expense) changed from an income tax expense of $22 million for the nine months ended September 30, 2018 to a benefit of $34 million for the nine months ended September 30, 2019 primarily due to the loss before taxes for the nine months ended September 30, 2019.
Pro Forma Results of Operations
Unless the context otherwise requires, references in this “Pro Forma Segment Results of Operations” to the “Company,” “we,” “us” or “our” refer to, and the results of operations discussed below relate to, the combined results of Antero Midstream Corporation and Antero Midstream Partners as if the Transactions had occurred on January 1, 2018.
The pro forma segment results of operations and the pro forma operations data for the three and nine months ended September 30, 2018 and for the nine months ended September 30, 2019 have been prepared to give pro forma effect to the Transactions as if they had occurred on January 1, 2018. For the three months ended September 30, 2019, actual segment results of operations and operations data has been presented. The pro forma adjustments are based on currently available information and certain estimates and assumptions, including preliminary purchase price allocation for the acquisition of Antero Midstream Partners,