Oil sales. Revenues from sales of oil increased from $57 million for the three months ended September 30, 2021 to $67 million for the three months ended September 30, 2022, an increase of $10 million, or 18%. Higher oil prices, excluding the effects of derivative settlements, accounted for an approximate $18 million increase in year-over-year oil revenues (calculated as the change in the year-to-year average price times current year production volumes). Lower oil production volumes during the three months ended September 30, 2022 accounted for an approximate $8 million decrease in year-over-year oil revenues (calculated as the change in year-to-year volumes times the prior year average price).
Commodity derivative fair value losses. To achieve more predictable cash flows, and to reduce our exposure to price fluctuations, we enter into fixed for variable price swap contracts, swaptions, basis swap contracts and collar contracts when we believe that favorable future sales prices for our production can be secured. Because we do not designate these derivatives as accounting hedges, they do not receive hedge accounting treatment. Consequently, all mark-to-market gains or losses, as well as cash receipts or payments on settled derivative instruments, are recognized in our statements of operations. For the three months ended September 30, 2021 and 2022, our commodity hedges resulted in derivative fair value losses of $1.3 billion and $531 million, respectively. For the three months ended September 30, 2021 and 2022, commodity derivative fair value losses included $416 million and $640 million, respectively, of cash payments for settled commodity derivatives.
Commodity derivative fair value gains or losses vary based on future commodity prices and have no cash flow impact until the derivative contracts are settled or monetized prior to settlement. Derivative asset or liability positions at the end of any accounting period may reverse to the extent future commodity prices increase or decrease from their levels at the end of the accounting period, or as gains or losses are realized through settlement. We expect continued volatility in commodity prices and the related fair value of our derivative instruments in the future.
Amortization of deferred revenue, VPP. Amortization of deferred revenues associated with the VPP decreased from $11 million for the three months ended September 30, 2021 to $9 million for the three months ended September 30, 2022, a decrease of $2 million, or 17%, primarily due to lower production volumes between periods. Under the terms of the agreement, the production volumes are delivered at approximately $1.61 per MMBtu over the contractual term.
Lease operating expense. Lease operating expense increased from $25 million, or $0.08 per Mcfe, for the three months ended September 30, 2021 to $27 million, or $0.09 per Mcfe, for the three months ended September 30, 2022, an increase of $2 million, or $0.01 per Mcfe, primarily due to higher oilfield service costs and water disposal costs.
Gathering, compression, processing and transportation expense. Gathering, compression, processing and transportation expense increased from $628 million for the three months ended September 30, 2021 to $716 million for the three months ended September 30, 2022, an increase of $88 million, or 14%. Gathering and compression costs increased from $0.73 per Mcfe for the three months ended September 30, 2021 to $0.81 per Mcfe for the three months ended September 30, 2022, primarily due to higher compressor fuel costs as a result of higher commodity prices and an annual CPI-based adjustment between periods, partially offset by $12 million in incentive fee rebates earned from Antero Midstream during the three months ended September 30, 2022 that were not earned during the three months ended September 30, 2021. Processing costs increased from $0.69 per Mcfe for the three months ended September 30, 2021 to $0.82 per Mcfe for the three months ended September 30, 2022, primarily due to increased costs for NGL processing, which includes an annual CPI-based adjustment during the first quarter of 2022, and higher NGL transportation fees. Transportation costs increased from $0.68 per Mcfe for the three months ended September 30, 2021 to $0.80 per Mcfe for the three months ended September 30, 2022 primarily due to higher fuel costs as a result of higher commodity prices and demand fees between periods.
Production and ad valorem tax expense. Total production and ad valorem taxes increased from $52 million for the three months ended September 30, 2021 to $93 million for the three months ended September 30, 2022, an increase of $41 million, or 78%, primarily due to higher commodity prices between periods. Production and ad valorem taxes as a percentage of natural gas revenues remained relatively consistent at 6% and 5% for the three months ended September 30, 2021 and 2022, respectively.
General and administrative expense. General and administrative expense (excluding equity-based compensation expense) increased from $27 million for the three months ended September 30, 2021 to $33 million for the three months ended September 30, 2022, an increase of $6 million, or 20%, primarily due to higher salary and wage expense, professional service fees and software license costs between periods. We had 506 and 554 employees as of September 30, 2021 and 2022, respectively. The higher general and administrative expense excluding equity-based compensation together with lower production volumes between periods resulted in per unit costs of $0.09 per Mcfe and $0.11 per Mcfe for the three months ended September 30, 2021 and 2022, respectively.
Equity-based compensation expense. Noncash equity-based compensation expense increased from $5 million for the three months ended September 30, 2021 to $10 million for the three months ended September 30, 2022, an increase of $5 million, or 96%,