The Rio Muni basin of Equatorial Guinea; a new hydrocarbon province

Dailly, Paul and Kenny Goh, Triton Energy, Dallas, TX; Phil Lowry and Gene Monson

Abstract

The Rio Muni basin underlies the continental shelf of the West African Republic of Equatorial Guinea, located between Gabon and Cameroon. The basin is located above a zone dominated by a northeast-southwest trending oceanic fracture zone and its continental extension. This constitutes the boundary between the equatorial Atlantic margin and the West African salt basin. Despite its location between the prolific hydrocarbon provinces of the Niger delta to the north and the Gabon coastal basin to the south, the Rio Muni basin has been overlooked by the industry for much of the last decade. Previous wells proved a viable source rock, but no accumulations. Triton Energy licensed Blocks F and G in 1997 and drilled the Ceiba 1 discovery well in 1999, proving a new hydrocarbon system in the deep water, Late Cretaceous post- rift sequence. Deformation by Santonian-Coniacian transpression caused uplift of the shelfal area and deposition of a thick, slope fan sequence. Contemporaneous salt deformation of rafted deposits and the development of a base of slope compressional belt are also evident. The resultant turbidite sequences form the reservoirs in the Ceiba discovery, which was tested at 12,400 BOPD. Both Late Cretaceous and Tertiary turbidite reservoirs form exploration targets in the basin, these may be charged by a deepwater source kitchen from which earlier, shelfal wells were shadowed.