Kosmos Energy has made a major gas discovery at its Guembeul-1 exploration well located in the northern part of the St Louis Offshore Profond license area in Senegal.

The well, which is located about 5km south of the basin-opening Tortue-1 gas discovery in water depths of 2,700m, was drilled to a total depth of 5,245m using the Atwood Achiever drillship.

The well encountered 101m of net gas pay in two quality reservoirs, including 56m in the Lower Cenomanian as well as 45m in the underlying Albian.

Guembeul-1 has de-risked adjacent prospectivity and proved that quality reservoirs exist in the Albian.

"Guembeul-1 confirms the presence of a world class gas resource that extends into both Senegal and Mauritania."

Kosmos Energy said that its mean gross resource estimate for the Tortue West structure has increased to 11 trillion cubic feet (Tcf) from 8 Tcf based on the integration of the Guembeul-1 well results.

The gross resource estimate for the Greater Tortue Complex has also increased to 17 Tcf from 14 Tcf.

Kosmos Energy chairman and CEO Andrew Inglis said: "Guembeul-1 confirms the presence of a world class gas resource that extends into both Senegal and Mauritania.

"The Guembeul-1 well continues our 100% success rate in the outboard Cretaceous petroleum system offshore Senegal and Mauritania, which we believe is a strategically important new oil and gas province and we are focused on unlocking the basin’s full potential."

The drillship delivered by Daewoo Shipbuilding and Marine Engineering will now proceed to Mauritania and drill the Ahmeyim-2 delineation well in the southern part of Mauritania’s Block C-8 to test the downdip limits of the field.

Kosmos owns a 60% interest in the Guembeul-1 well, along with Timis (30%) and Petrosen (10%).