b'KOSMOS ENERGY LTD.Notes to Consolidated Financial Statements (Continued)2. Accounting Policies (Continued)Revenue RecognitionWe use the sales method of accounting for oil and gas revenues. Under this method, we recognizerevenues on the volumes sold. The volumes sold may be more or less than the volumes to which we areentitled based on our ownership interest in the property. These differences result in a condition knownin the industry as a production imbalance. A receivable or liability is recognized only to the extent thatwe have an imbalance on a specific property greater than the expected remaining proved reserves onsuch property. As of December 31, 2018 and 2017, we had no oil and gas imbalances recorded in ourconsolidated financial statements.Our oil and gas revenues are recognized when production has been sold to a purchaser at a fixedor determinable price, title has transferred and collectability is probable. Certain revenues are based onprovisional price contracts which contain an embedded derivative that is required to be separated fromthe host contract for accounting purposes. The host contract is the receivable from oil sales at the spotprice on the date of sale. The embedded derivative, which is not designated as a hedge, is marked tomarket through oil and gas revenue each period until the final settlement occurs, which generally islimited to the month after the sale.Oil and gas revenue is composed of the following:Years Ended December 31,2018 2017 2016Revenues from contracts with customersGhana . . . . . . . . . . . . . . . $741,033 $590,642 $307,837Revenues from contracts with customersU.S. Gulf of Mexico . . . . . 147,596Provisional oil sales contracts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (1,963) (12,503) 2,540Oil and gas revenue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $886,666 $578,139 $310,377Equity-based CompensationFor equity-based compensation awards, compensation expense is recognized in the Companysfinancial statements over the awards vesting periods based on their grant date fair value. The Companyutilizes (i) the closing stock price on the date of grant to determine the fair value of service vestingrestricted stock awards and restricted stock units and (ii) a Monte Carlo simulation to determine thefair value of restricted stock awards and restricted stock units with a combination of market and servicevesting criteria. Forfeitures are recognized in the period in which they occur.Treasury StockWe record treasury stock purchases at cost. Our treasury stock purchases are from our employeesthat surrendered shares to the Company to satisfy their statutory tax withholding requirements and arenot part of a formal stock repurchase plan. In November 2018, Kosmos repurchased 35 million sharesof our common stock from funds affiliated with Warburg Pincus LLC in a privately negotiatedtransaction at a price per share of $5.38. The total aggregate purchase price for the share repurchasewas approximately $188 million. The remainder of our treasury stock is forfeited restricted stock awardsgranted under our long-term incentive plan.115'