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 they were unitized into the Jubilee Unit as part of the Greater Jubilee Full Field Development Plan. Years Ended December 31, 2017 2016 2015 (In thousands) Beginning balance . . . . . . . . . . . . . . . . . . . . . . . . $ 734,463 $426,881 $226,714 Additions to capitalized exploratory well costs pending the determination of proved reserves . . 69,567 307,582 223,542 Reclassification due to unitization of Mahogany and Teak discoveries . . . . . . . . . . . . . . . . . . . . (176,881) — — Divestitures(1) . . . . . . . . . . . . . . . . . . . . . . . . . . (206,400) — — Contribution of oil and gas property to equity method investment . . . . . . . . . . . . . . . . . . . . . . (131,764) — — Dissolution of equity method investment . . . . . . . 121,128 — — Capitalized exploratory well costs charged to expense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . — — (23,375) Ending balance . . . . . . . . . . . . . . . . . . . . . . . . . . $ 410,113 $734,463 $426,881 (1) Represents the reduction in basis of suspended well costs associated with the Mauritania and Senegal transactions with BP. The following table provides aging of capitalized exploratory well costs based on the date drilling was completed and the number of projects for which exploratory well costs have been capitalized for more than one year since the completion of drilling: Years Ended December 31, 2017 2016 2015 (In thousands, except well counts) Exploratory well costs capitalized for a period of one year or less . . . $ 67,159 $279,809 $199,486 Exploratory well costs capitalized for a period of one to two years . . . 291,252 244,804 17,702 Exploratory well costs capitalized for a period of three to six years . . 51,702 209,850 209,693 Ending balance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $410,113 $734,463 $426,881 Number of projects that have exploratory well costs that have been capitalized for a period greater than one year . . . . . . . . . . . . . . . . 5 5 3 As of December 31, 2017, the projects with exploratory well costs capitalized for more than one year since the completion of drilling are related to the Akasa discovery in the West Cape Three Points (‘‘WCTP’’) Block and the Wawa discovery in the DT Block, which are located offshore Ghana, the Greater Tortue discovery which crosses the Mauritania and Senegal maritime border, the BirAllah discovery (formerly known as the Marsouin discovery) in Block C8 offshore Mauritania and the Teranga discovery in the Cayar Offshore Profond block offshore Senegal. Akasa Discovery—We are currently in discussions with the government of Ghana regarding additional technical studies and evaluation that we want to conduct before we are able to make a 124