b'KOSMOS ENERGY LTD.Notes to Consolidated Financial Statements (Continued)6. Suspended Well Costs (Continued)well costs associated with the Mahogany and Teak fields were reclassified to proved property as theywere unitized into the Jubilee Unit as part of the Greater Jubilee Full Field Development Plan.Years Ended December 31,2018 2017 2016(In thousands)Beginning balance . . . . . . . . . . . . . . . . . . . . . . . . $410,113 $ 734,463 $426,881Additions to capitalized exploratory well costspending the determination of proved reserves . . 10,518 69,567 307,582Additions associated with the acquisition of DGE . 26,224Reclassification due to determination of provedreserves(1). . . . . . . . . . . . . . . . . . . . . . . . . . . . (26,224) (176,881) Divestitures(2) . . . . . . . . . . . . . . . . . . . . . . . . . .(206,400) Contribution of oil and gas property to equitymethod investmentKBSL . . . . . . . . . . . . . . . .(131,764) Dissolution of equity method investmentKBSL .121,128 Capitalized exploratory well costs charged toexpense(3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . (52,966)Ending balance . . . . . . . . . . . . . . . . . . . . . . . . . . $367,665 $ 410,113 $734,463(1) Represents the reclassification of Nearly Headless Nick well costs associated with theDGE acquisition in 2018 and inclusion of the Mahogany and Teak discoveries in theJubilee Unit in 2017.(2) Represents the reduction in basis of suspended well costs associated with the Mauritaniaand Senegal transactions with BP(3) Primarily related to Akasa and Wawa as we wrote off $38.1 million and $13.6 million,respectively, of previously capitalized costs exploratory well costs to exploration expenseduring the third quarter of 2018. These impairments are included in our Ghana segment.The following table provides aging of capitalized exploratory well costs based on the date drillingwas completed and the number of projects for which exploratory well costs have been capitalized formore than one year since the completion of drilling:Years Ended December 31,2018 2017 2016(In thousands, except well counts)Exploratory well costs capitalized for a period of one year or less . . . $$ 67,159 $279,809Exploratory well costs capitalized for a period of one to two years . . . 299,253 291,252 244,804Exploratory well costs capitalized for a period of three years orlonger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68,412 51,702 209,850Ending balance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $367,665 $410,113 $734,463Number of projects that have exploratory well costs that have beencapitalized for a period greater than one year . . . . . . . . . . . . . . . . 3 5 5124'