KOSMOS ENERGY LTD. Supplemental Oil and Gas Data (Unaudited) Net proved oil and gas reserve estimates presented were prepared by Ryder Scott Company, L.P. (‘‘RSC’’) for the years ended December 31, 2017, 2016 and 2015. RSC are independent petroleum engineers located in Houston, Texas. RSC has prepared the reserve estimates presented herein and meet the requirements regarding qualifications, independence, objectivity and confidentiality set forth in the Standards Pertaining to the Estimating and Auditing of Oil and Gas Reserves Information promulgated by the Society of Petroleum Engineers. We maintain an internal staff of petroleum engineers and geoscience professionals who work closely with our independent reserve engineers to ensure the integrity, accuracy and timeliness of data furnished to independent reserve engineers for their reserves estimation process. Net Proved Developed and Undeveloped Reserves The following table is a summary of net proved developed and undeveloped oil and gas reserves to Kosmos’ interest in the Jubilee and TEN fields in Ghana and our equity method investment. Equity Method Investment— Kosmos Entities Equatorial Guinea Oil Gas Total Oil Gas Total Total (MMBbl) (Bcf) (MMBoe) (MMBbl) (Bcf) (MMBoe) (MMBoe) Net proved developed and undeveloped reserves at December 31, 2014(1) . . . . . 73 14 75 — — — 75 Production . . . . . . . . . . . . (9) (1) (9) — — — (9) Revision in estimate(3) . . . . . 10 1 10 — — — 10 Net proved developed and undeveloped reserves at December 31, 2015(1) . . . . . 74 14 76 — — — 76 Production . . . . . . . . . . . . (7) (1) (7) — — — (7) Revision in estimate(4) . . . . . 7 2 8 — — — 8 Net proved developed and undeveloped reserves at December 31, 2016(1) . . . . . 74 15 77 — — — 77 Extensions and discoveries . . 1 — 1 — — — 1 Production . . . . . . . . . . . . (11) (1) (11) (1) — (1) (12) Revision in estimate(5) . . . . . 18 35 24 — — — 24 Purchases of minerals-in-place(6) . . . . . — — — 20 13 21 21 Net proved developed and undeveloped reserves at December 31, 2017(1) . . . . . 82 49 89 19 13 21 110 Proved developed reserves(1) December 31, 2015 . . . . . . . 50 10 52 — — — 52 December 31, 2016 . . . . . . . 64 13 66 — — — 66 December 31, 2017 . . . . . . . 59 38 65 18 13 20 85 Proved undeveloped reserves(1) December 31, 2015 . . . . . . . 24 4 25 — — — 25 December 31, 2016 . . . . . . . 10 2 11 — — — 11 December 31, 2017 . . . . . . . 23 11 24 1 — 1 25 (1) The sum of proved developed reserves and proved undeveloped reserves may not add to net proved developed and undeveloped reserves as a result of rounding. (2) Discoveries are related to the TEN fields being moved from unproved to proved during 2014. 149