By Toyin Akinosho
One failed due to charge access, another for lack of trap, the third being evaluated….
Kosmos has encountered another dry hole in its campaign to find oil (and some gas) in the sequences outboard of its gas discoveries in the NW Africa margin.
The prospect, Requin Tigre-1 (Tiger Shark), in Senegal’s Saint Louis Offshore Profond block “was fully tested but did not encounter hydrocarbons”, the company declared on Monday, February 5, 2018.
Requin Tigre-1 was the fourth of a four well drilling programme which featured Yaakar-1, Hipoccampe-1, and Lamantin-1. This particular well was targeted at finding gas, and extending the 15-25Tcf Tortue play.
The well drilled to a total depth of 5,200 meters and was designed to evaluate Cenomanian and Albian reservoirs in a structural-stratigraphic trap, charged from an underlying Neocomian-Valanginian source kitchen. “Post-well analysis is currently ongoing to determine the reasons it was unsuccessful”, Kosmos lamented.
The four prospects are all located in combination strat/structural plays, with Cenomanian-Turonian and Albian oil source kitchen “with increased probability for liquids”.
But Yaakar-1 was the only one that was successful and even then, what it encountered was gas, which wasn’t the primary objective.
Kosmos had encountered tanker loads of natural gas in the Northwest African margin and was hoping to find oil in prospects located outboard of these gas tanks.
Hippocampe-1, drilled in approximately 2,600 meters of water in Block C-8, offshore Mauritania, “encountered well-developed reservoirs in both exploration targets but these proved to be water bearing”. Kosmos’ earth scientists believe that this prospect failed due to a lack of charge access in this part of the play fairway.
Lamantin-1 also came up water wet. Located in Block C-12 offshore Mauritania in approximately 2,200 meters of water, it was drilled to a total depth of 5,150 meters and was designed to evaluate a previously untested Lower Campanian base of slope fan supplied from the Nouakchott River system, trapped in a combination structural-stratigraphic feature, and charged from underlying, oil-prone Cenomanian/Turonian and Albian source rocks. But the Campanian reservoir objective was water bearing with some residual hydrocarbons due to, Kosmos believes, “a lack of trap, related to a combination of up-dip sand pinch-out and top / base seal effectiveness”.
Kosmos, a passionate exploration company, looks on the bright side: “With each exploration well drilled, we deepen our understanding of this newly emerging basin, further refining our geologic model and geophysical tools. Requin Tigre was the last well in our second phase of exploration of the deepwater Cretaceous petroleum systems offshore Mauritania and Senegal targeting large basin floor fan structures.
We have delivered one success (Yakaar) in four wells in this second phase programme, following three successes in three wells (Tortue, Marsouin, Teranga) in the first phase programme targeting inboard structures on the slope. Overall we have discovered gross resource of 40 trillion cubic feet, at a net cost of $0.20 per barrel of oil equivalent benefiting from the partner carry, and have created the potential for two world scale LNG hubs. We will rigorously evaluate our large inventory of prospects across Mauritania and Senegal ahead of the next phase of exploration offshore the two countries.”
