KOSMOS ENERGY LTD. Notes to Consolidated Financial Statements (Continued) 11. Asset Retirement Obligations (Continued) The Ghanaian legal and regulatory regime regarding oil field abandonment and other environmental matters is evolving. Currently, no Ghanaian environmental regulations expressly require that companies abandon or remove offshore assets. Under the Environmental Permit for the Jubilee Field, a decommissioning plan will be prepared and submitted to the Ghana Environmental Protection Agency. ASC 410—Asset Retirement and Environmental Obligations requires the Company to recognize this liability in the period in which the liability was incurred. The TEN fields commenced production during the third quarter of 2016 and an asset retirement obligation was recorded for the facilities and wells that came online during 2016. Additional asset retirement obligations will be recorded in the period in which additional wells within our producing fields are commissioned. 12. Equity-based Compensation Restricted Stock Awards and Restricted Stock Units Prior to our corporate reorganization in May 2011, Kosmos Energy Holdings issued common units designated as profit units with a threshold value ranging from $0.85 to $90 to employees, management and directors. Profit units were equity awards that were measured on the grant date and expensed over a vesting period of four years. Founding management and directors vested 20% as of the date of issuance and an additional 20% on the anniversary date for each of the next four years. Profit units issued to employees vested 50% on the second and fourth anniversaries of the issuance date. As part of the corporate reorganization in May 2011, vested profit units were exchanged for 31.7 million common shares of Kosmos Energy Ltd., unvested profit units were exchanged for 10.0 million restricted stock awards and the $90 profit units were cancelled. These restricted stock awards ultimately vested during 2015. Based on the terms and conditions of the corporate reorganization, the exchange of profit units for common shares of Kosmos Energy Ltd. resulted in no incremental compensation costs. In April 2011, the Board of Directors approved the LTIP, which provides for the granting of incentive awards in the form of stock options, stock appreciation rights, restricted stock awards, restricted stock units, among other award types. In January 2015, the board of directors approved an amendment to the plan to add 15.0 million shares to the plan which was approved at the Annual General Meeting in June 2015. The LTIP provides for the issuance of 39.5 million shares pursuant to awards under the plan, in addition to the 10.0 million restricted stock awards exchanged for unvested profit units. As of December 31, 2017, the Company had approximately 3.4 million shares that remain available for issuance under the LTIP. The Company adopted ASU 2016-9, ‘‘Improvements to Employee Share-based Payment Accounting’’ during the second quarter of 2016 using an effective date of January 1, 2016. Prior period compensation expense disclosed below includes estimated forfeitures and has not been adjusted. We record equity-based compensation expense equal to the fair value of share-based payments over the vesting periods of the LTIP awards. We recorded compensation expense from awards granted under our LTIP of $40.0 million, $40.1 million and $75.1 million during the years ended December 31, 2017, 2016 and 2015, respectively. The total tax benefit for the years ended December 31, 2017, 2016 and 2015 was $13.2 million, $13.0 million and $25.7 million, respectively. Additionally, we expensed a tax shortfall related to equity-based compensation of $3.1 million, $5.5 million and $18.6 million for the years ended December 31, 2017, 2016 and 2015, respectively. The fair value of awards vested during 138