Services reported operating income of $5.3 million for the third quarter of 2022 compared to an operating loss of $55 thousand for the third quarter of 2021.
Cost of revenues. Cost of revenues increased 81.6 percent to $309.8 million for the three months ended September 30, 2022 compared to $170.6 million for the three months ended September 30, 2021. Cost of revenues increased primarily due to increases in expenses consistent with higher activity levels, such as materials and supplies expenses, maintenance and repairs expenses, employment costs and fuel costs. In addition, these costs increased due to higher market prices for materials and supplies, fuel and other raw materials. Cost of revenues, as a percentage of revenues, decreased from 75.7 percent in the third quarter of 2021 to 67.4 percent in the third quarter of 2022 primarily due to improved pricing for our services and leverage of employment costs.
Selling, general and administrative expenses. Selling, general and administrative expenses increased to $38.2 million for the three months ended September 30, 2022 compared to $31.4 million for the three months ended September 30, 2021, primarily due to increases in variable incentive compensation costs consistent with improved operating results. Selling, general and administrative expenses, as a percentage of revenues, decreased from 14.0 percent in the third quarter of 2021 to 8.3 percent in the third quarter of 2022 due to leverage of costs that are relatively fixed during the short term over higher revenues.
Depreciation and amortization. Depreciation and amortization increased 15.7 percent to $20.9 million for the three months ended September 30, 2022, compared to $18.1 million for the three months ended September 30, 2021. Depreciation and amortization increased due to capital expenditures in the past year.
Gain on disposition of assets, net. Gain on disposition of assets, net was $1.5 million for the three months ended September 30, 2022 compared to a gain on disposition of assets, net of $2.8 million for the three months ended September 30, 2021. The gain on disposition of assets, net is generally comprised of gains and losses related to various property and equipment dispositions or sales to customers of lost or damaged rental equipment.
Other (expense) income, net. Other expense, net was $67 thousand for the three months ended September 30, 2022 compared to other income, net of $448 thousand for the same period in the prior year.
Interest expense. Interest expense was $143 thousand for the three months ended September 30, 2022 compared to $1.3 million for the three months ended September 30, 2021. The decrease in interest expense is primarily due to interest expense related to the settlement of a legal dispute with a supplier in the third quarter of 2021. Interest expense also includes facility fees on the unused portion of the credit facility and the amortization of loan costs.
Income tax provision. Income tax provision was $22.9 million during the three months ended September 30, 2022 compared to $1.9 million tax provision for the same period in 2021. The effective tax rate was 24.9 percent for the three months ended September 30, 2022 compared to a 26.4 percent effective benefit rate for the three months ended September 30, 2021. The increase in income tax provision is mainly related to an increase in pretax income for the quarter ended September 30, 2022. In addition, this is what created a decrease in the effective tax rate by diluting the impact the unfavorable permanent and discrete adjustments had on the rate.
NINE MONTHS ENDED SEPTEMBER 30, 2022 COMPARED TO NINE MONTHS ENDED SEPTEMBER 30, 2021
Revenues. Revenues of $1.1 billion for the nine months ended September 30, 2022 increased 87.7 percent compared to the nine months ended September 30, 2021. Domestic revenues of $1.1 billion increased 87.7 percent for the nine months ended September 30, 2022 compared to the same period in the prior year. The increase in revenues was due to higher customer activity levels, pricing improvements and a larger fleet of pressure pumping equipment in service. International revenues of $25.2 million increased 2.8 percent for the nine months ended September 30, 2022 compared to the same period in the prior year.
During the first nine months of 2022, the average price of oil was 52.1 percent higher and the average price of natural gas was 84.3 percent higher, both as compared to the same period in the prior year. Oil and gas prices are higher due to continued strong demand as well as supply constraints worldwide due to the Russian invasion of Ukraine during the first quarter of 2022. The average domestic rig count during the first nine months of 2022 was 56.7 percent higher than the same period in 2021.
The Technical Services segment revenues for the first nine months of 2022 increased by 88.8 percent compared to the same period of the prior year due to higher activity levels and improved pricing. Technical Services reported operating income of $171.1 million during the first nine months of 2022 compared to operating income of $3.9 million during the first nine months of 2021. The Support Services segment revenues for the first nine months of 2022 increased by 70.5 percent compared to the same period in the