Exploration interest is growing off central West Africa with recent announcement of a significant oil discovery off Equatorial Guinea's Rio Muni enclave.
The discovery by Triton Energy Ltd. on Block G about 22 miles off the coast flowed 12,400 bo/d from one zone. The operator said the M'bini well, in 2,200 ft of water, might go on line at more than 20,000 bo/d (OGJ, Oct. 11, Newsletter).
Analysis of wireline logs and core data indicated a 742-ft gross oil column with 314 ft of net oil-bearing pay in four zones.
Triton and Energy Africa Ltd., which last month took a 15% interest with Triton in blocks G and F, plan to start appraisal drilling in fourth quarter 1999 and acquire a 740,000 acre 3D seismic survey to define the field and evaluate other exploration prospects on the licenses. The two blocks cover a combined 1.3 million acres.
Early estimates of recovery were several hundred million barrels of oil.
Assessing significance
In addition to the high potential of the field, designated La Ceiba, the discovery is significant because it proves a hitherto untested play fairway within the Gulf of Guinea West African margin, incorporating a mature oil prone source rock and high quality reservoir units, said Exploration Consultants Ltd., Henley, U.K.
ECL believes the find lies on trend with areas of large-scale gravity sliding within the Cretaceous "drift" section associated with the mid-Cretaceous "Senonian" unconformity (OGJ, Feb. 1, 1999, p. 67). The consultant believes that the trend continues northward through open Rio Muni acreage and that it can be linked with a zone of similar gravity slide features that can be followed on seismic data through the offshore-Cameroon area towards the Kribi-Sanaga Sud discoveries.
Raymond Joyes, author of a 1998 report on the area published by IHS Energy Group's Petroconsultants unit, said La Ceiba (silk tree) indicates a new productive province running from Cameroon to northern Gabon that easily could be as important as the Campos basin and Congo fan. The find heralds more discoveries to come in even deeper waters extending seaward from Rio Muni, Joyes said.
ECL is engaged in continuing studies to investigate the evolution of the hydrocarbon system on the Gulf of Guinea Atlantic margin, which looks set to stage the next chapter in the development of the prolific West African oil province.
Triton's acreage lies between open blocks recently offered in Equatorial Guinea's deepwater licensing round and 50 km south of the nearest acreage open in Cameroon's third round.
The discovery might have exploration implications for Brazil. Joyes said oil charge for the Rio Muni basin comes from prolific Late Cretaceous source rocks deposited in anoxic conditions in the deep waters. These source rocks are proven in Gabon and also across the Atlantic from Rio Muni in the Sergipe-Alagoas basin.
