Located approximately 285km southwest of Nouakchott in 2,700m of water, the well has been drilled to the planned total depth of approximately 5,250m aimed to test the Tortue West prospect.
The prospect is a part of the Greater Tortue Complex, in Block C-8.
The company identified a single gas pool in the primary Lower Cenomanian objective which includes three multi-Darcy reservoirs totaling 88m in thickness over a gross hydrocarbon bearing interval of 160m.
Within the secondary Upper Cenomanian target, a fourth zone 19m thick was penetrated over a gross hydrocarbon bearing interval of 150m.
Kosmos Energy chairman and CEO Andrew Inglis said: "Volumetrically, the Tortue-1 well has far exceeded our pre-drill expectations and has discovered a large scale gas resource.
"Our seismic imaging indicates the areal extent of Tortue West could cover approximately 90 square kilometers that will be better defined with appraisal drilling. Importantly, given the results and excellent well-to-seismic calibration, the Tortue-1 well has significantly de-risked our large and under-explored 27,000 square kilometer deepwater position in Mauritania.
"Our acreage offers substantial follow-on prospectivity including a diverse range of Cenomanian as well as deeper Cretaceous plays and fairways with strong dependency."
The company is planning an appraisal program to delineate the Tortue West discover.