In late October 2019, operator Kosmos Energy Ltd (Kosmos) has hit a 39-m net oil pay in its S-5 exploration well in Block S, offshore Rio Muni Basin. The well (AKA G-13 ILX for Infrastructure-Led Exploration), was spudded on 20 September with the âMaersk Voyagerâ drillship and drilled to a total depth of 4,400 m, before the rig was demobilized around 13 November. The company explained that oil was encountered in good-quality Santonian reservoir (Upper Cretaceous). With this success, Kosmos sees a potential for an accelerated development through the existing nearby infrastructures (Ceiba and Okume Complexes). First oil for G-13 is therefore expected around 2021.   S-5 is considered as an appraisal well by IHS Markit, as it is located in the center of G-13 oil discovery made in 2002 by Triton Energy. It targeted the G-13 main reservoir fairway (prospecting resources estimated at 50 MMboe).  Kosmos mobilized the âMaersk Voyagerâ drillship on 18 September. This well is part of a five-well programme for Kosmos, including one basin-opener in Mauritania, and three exploration wells in the Gulf of Mexico, all to be drilled in 2019. Of note, Kosmos is believed to have a good understanding of the regional geology of Rio Muni Basin, as Kosmos was formed in 2003 from Triton people, who discovered Ceiba in 1999.  As of February 2019, Kosmos Energy was estimating the G-13 oil discovery recoverable reserves around 56 MMboe. Three outposts were drilled after the discovery (two in 2003 and one in 2014), but the development of the field was never made possible because of the failure to clearly identify the Senonian main fairway. Recent new seismic material apparently helped the company to image it.
Kosmos Energy Ltd found Cretaceous oil in S-5 (G-13 ILX) explo well, in Block S