KOSMOS ENERGY LTD. Notes to Consolidated Financial Statements (Continued) 2. Accounting Policies (Continued) Derivative Instruments and Hedging Activities We utilize oil derivative contracts to mitigate our exposure to commodity price risk associated with our anticipated future oil production. These derivative contracts consist of collars, put options, call options and swaps. We also use interest rate derivative contracts to mitigate our exposure to interest rate fluctuations related to our long-term debt. Our derivative financial instruments are recorded on the balance sheet as either assets or liabilities and are measured at fair value. We do not apply hedge accounting to our derivative contracts. As of December 31, 2016 all instruments previously designated as hedges have settled and there is no balance remaining in AOCI. See Note 9—Derivative Financial Instruments. Estimates of Proved Oil and Natural Gas Reserves Reserve quantities and the related estimates of future net cash flows affect our periodic calculations of depletion and assessment of impairment of our oil and natural gas properties. Proved oil and natural gas reserves are the estimated quantities of crude oil, natural gas and natural gas liquids that geological and engineering data demonstrate with reasonable certainty to be recoverable in future periods from known reservoirs under existing economic and operating conditions. As additional proved reserves are discovered, reserve quantities and future cash flows will be estimated by independent petroleum consultants and prepared in accordance with guidelines established by the Securities and Exchange Commission (‘‘SEC’’) and the Financial Accounting Standards Board (‘‘FASB’’). The accuracy of these reserve estimates is a function of: • the engineering and geological interpretation of available data; • estimates of the amount and timing of future operating cost, production taxes, development cost and workover cost; • the accuracy of various mandated economic assumptions; and • the judgments of the persons preparing the estimates. Revenue Recognition We use the sales method of accounting for oil and gas revenues. Under this method, we recognize revenues on the volumes sold based on the provisional sales prices. The volumes sold may be more or less than the volumes to which we are entitled based on our ownership interest in the property. These differences result in a condition known in the industry as a production imbalance. A receivable or liability is recognized only to the extent that we have an imbalance on a specific property greater than the expected remaining proved reserves on such property. As of December 31, 2017 and 2016, we had no oil and gas imbalances recorded in our consolidated financial statements. Our oil and gas revenues are based on provisional price contracts which contain an embedded derivative that is required to be separated from the host contract for accounting purposes. The host contract is the receivable from oil sales at the spot price on the date of sale. The embedded derivative, which is not designated as a hedge, is marked to market through oil and gas revenue each period until the final settlement occurs, which generally is limited to the month after the sale. 116