quarter of 2021. Adjusted net income (non-GAAP) for the twelve months ending December 31, 2021 was $535 million, or $13.49 per share. The primary difference between net income and adjusted net income for all periods is non-cash expense related to the change in the value of the Company’s hedging portfolio. The third quarter was also affected by the gain on sale of properties related to a previously announced divestiture.
The Company’s adjusted EBITDAX (non-GAAP) for the fourth quarter of 2021 was $226 million compared to $201 million for the third quarter of 2021. Net cash provided by operating activities was $214 million in the fourth quarter and adjusted free cash flow (non-GAAP) was $156 million. Adjusted EBITDAX (non-GAAP) for the twelve months ended December 31, 2021 was $774 million. Net cash provided by operating activities was $740 million and adjusted free cash flow (non-GAAP) was $504 million for the twelve months ended December 31, 2021.
Adjusted net income, adjusted net income per share, adjusted EBITDAX and adjusted free cash flow are non-GAAP financial measures. Please refer to the end of this release for disclosures and reconciliations regarding these measures.
Production for the fourth quarter averaged 92.8 thousand barrels of oil equivalent per day (MBOE/d) which was consistent with the previous quarter of 92.1 MBOE/d. Oil production averaged 52.9 thousand barrels of oil per day (MBO/d) compared to 51.8 MBO/d in the third quarter 2021.
Capital expenditures in the fourth quarter of 2021 were $66 million compared to the third quarter 2021 spend of $67 million. During the quarter, the Company drilled 17 gross/10.4 net operated wells and turned in line 16 gross/12.0 net operated wells. As of December 31, 2021, the Company has 34 gross (20.2 net) drilled uncompleted wells.
Lease operating expense (LOE) for the fourth quarter of 2021 was $62 million compared to $57 million in the third quarter of 2021. The increase was primarily due to more operated expense workovers and the effects of higher production. General and administrative expenses in the fourth quarter of 2021 were $15 million compared to $12 million in the third quarter 2021. Both quarters included approximately $3 million of non-cash stock compensation costs.
Liquidity
As of December 31, 2021, the Company had a borrowing base of $750 million on its revolving credit facility, no borrowings and unrestricted cash of $41 million, resulting in total liquidity of $790 million, net of outstanding letters of credit. Whiting expects to continue to fund its 2022 operations and its dividend fully within operating cash flow.
Proved Reserves
During 2021, the Company added 20.3 million barrels of oil equivalent (MMBOE) of reserves primarily due to successful drilling in the Williston Basin. Additionally, 15.9 MMBOE was added from acquisitions during the year, which was partially offset by a decrease of 10.7 MMBOE primarily due to the disposition of the Redtail field located in Colorado. As of December 31, 2021, the Company’s estimated proved reserves totaled 326.0 MMBOE. The Standardized Measure of those reserves was $3,679 million and the pre-tax PV10% of those reserves was $4,381 million, in each case using SEC pricing as noted below.