Aggregate principal amount of current and long-term debt

EOG RESOURCES, INC.NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS – (Continued) (Unaudited)  
When circumstances indicate that proved oil and gas properties may be impaired, EOG compares expected undiscounted future cash flows at a depreciation, depletion and amortization group level to the unamortized capitalized cost of the asset. If the expected undiscounted future cash flows, based on EOG's estimate of (and assumptions regarding) significant Level 3 inputs, including future crude oil, natural gas liquids (NGLs) and natural gas prices, operating costs, development expenditures, anticipated production from proved reserves and other relevant data, are lower than the unamortized capitalized cost, the capitalized cost is reduced to fair value. Fair value is generally calculated using the Income Approach described in the FASB's Fair Value Measurement Topic of the Accounting Standards Codification. In certain instances, EOG utilizes accepted offers from third-party purchasers as the basis for determining fair value.  
EOG utilized average prices per acre from comparable market transactions and estimated discounted cash flows as the basis for determining the fair value of unproved and proved properties, respectively, received in non-cash property exchanges. See Note 4.  
Fair Value Disclosures. EOG's financial instruments, other than financial commodity derivative contracts, consist of cash and cash equivalents, accounts receivable, accounts payable and current and long-term debt. The carrying values of cash and cash equivalents, accounts receivable and accounts payable approximate fair value.  
At both September 30, 2022 and December 31, 2021, EOG had outstanding $4,890 million aggregate principal amount of senior notes, which had estimated fair values at such dates of approximately $4,667 million and $5,577 million, respectively. The estimated fair value of debt was based upon quoted market prices and, where such prices were not available, other observable (Level 2) inputs regarding interest rates available to EOG at the end of each respective period.  
-18-
