KOSMOS ENERGY LTD. Notes to Consolidated Financial Statements (Continued) 3. Acquisitions and Divestitures (Continued) 2015 Transactions In March 2015, we closed a farm-in agreement with Repsol Exploracion, S.A. (‘‘Repsol’’), acquiring a non-operated interest in the Camarao, Ameijoa, Mexilhao and Ostra blocks in the Peniche Basin offshore Portugal. As part of the agreement, we reimbursed a portion of Repsol’s previously incurred exploration costs, as well as partially carried Repsol’s share of the costs of a planned 3D seismic program. After giving effect to the farm-in agreement, our participating interest was 31% in each of the blocks. In January 2017, we provided to our co-venturers a notice of withdrawal from the Ameijoa, Camarao, Mexilhao and Ostra Blocks offshore Portugal. In March 2015, we closed a farm-out agreement with Chevron Corporation (‘‘Chevron’’) covering the C8, C12 and C13 petroleum contracts offshore Mauritania. As partial consideration for the farm-out, Chevron paid a disproportionate share of the costs of one exploration well, the Marsouin-1 exploration well, as well as its proportionate share of certain previously incurred exploration costs. The final allocation resulted in sales proceeds of $28.7 million, which exceeded our book basis in the assets, resulting in a $24.7 million gain on the transaction. As a further component of the consideration for the farm-out, Chevron was required to make an election by February 1, 2016, to either farm-in to the Tortue-1 exploration well by paying a disproportionate share of the costs incurred in drilling of the well or, alternatively elect to not farm-in to the Tortue-1 exploration well and pay a disproportionate share of the costs of a second contingent exploration or appraisal well in the contract areas, subject to maximum expenditure caps. Chevron failed to make this mandatory election by the required date. Consequently, pursuant to the terms of the farm-out agreement, Chevron has withdrawn from our Mauritania blocks. Chevron’s 30% non-operated participating interest was reassigned to us. In September 2015, we notified the government of Ireland and our partners that we are withdrawing from all of our blocks offshore Ireland. These blocks were acquired during 2013. In October 2015, we closed a sale and purchase agreement with ERHC Energy EEZ, LDA, whereby we acquired an 85% participating interest and operatorship in Block 11 offshore Sao Tome and Principe. The National Petroleum Agency, Agencia Nacional Do Petroleo De Sao Tome E Pr´ ıncipe (‘‘ANP STP’’), has a 15% carried interest. In November 2015, we closed a farm-in agreement with Galp Energia Sao Tome E Principe, Unipessoal, LDA (‘‘Galp’’), a wholly owned subsidiary of Petrogal, S.A. to acquire a 45% non-operated participating interest in Block 6 offshore Sao Tome and Principe. 4. Joint Interest Billings The Company’s joint interest billings consist of receivables from partners with interests in common oil and gas properties operated by the us. Joint interest billings are classified on the face of the consolidated balance sheets as current and long-term receivables based on when collection is expected to occur. In 2014, the Ghana National Petroleum Corporation (‘‘GNPC’’) notified us and our block partners of its request for the contractor group to pay GNPC’s 5% share of the Tweneboa, Enyenra and Ntomme (‘‘TEN’’) development costs. The block partners will be reimbursed for such costs plus interest out of a portion of GNPC’s TEN production revenues. As of December 31, 2017 and 2016, the current portion of the joint interest billing receivables due from GNPC for the TEN fields development costs were $15.2 million and zero, respectively, and the long-term portion is $31.6 million and $44.0 million. 122