Exploration and development of Ceiba Field, Rio Muni Basin, Southern Equatorial Guinea

Abstract

Ceiba Field, offshore Equatorial Guinea approximately 75 km southwest of the port of Bata and 275 km south of the city of Malabo, was discovered with the drilling of Ceiba-1 in September 1999. The first appraisal well, Ceiba-2, was drilled in November 1999 approximately 1.6 km southwest of Ceiba-1. Both wells were based on interpretation of 2D seismic data acquired between 1984 and 1999. Open-hole logs, cores, pressure data, and a drill stem test of Ceiba-1 (maximum flow rate of 12 400 b/d) indicated that both wells contained Cretaceous sands of very high quality, capable of high rates of oil production. Despite being between two prolific hydrocarbon provinces—Niger delta to the north and the Gabon coastal basin to the south (Figure 1)—Rio Muni Basin was essentially overlooked by the industry until the late 1990s. Six wells were drilled between 1968 and 1991 in the shelfal and onshore areas of the basin. These focused on Albian and Aptian aged objectives and, although they proved the presence of a viable source rock, the early wells did not result in the discovery of any oil accumulations. Figure 1. Ceiba Field is offshore Equatorial Guinea approximately 75 km southwest of the port of Bata and 275 km south of the city of Malabo. In 1997, following a review of the West African margin, Triton Energy identified a number of aspects of Rio Muni Basin that suggested an unexplored deepwater play. These included an immature oil-prone source in shelfal wells, which had the potential to be more deeply buried in the outboard part of the basin, and evidence for base of slope structuring on the margins of the shelf in the 2D data. The presence of shelfal canyons suggested that bypassed clastics could potentially be deposited in deepwater. The presence, in the Sergipe-Alagoas Basin of Brazil, of …