Control of salt structures on hydrocarbons in the passive continental margin of West Africa

Abstract

Salt basins along the passive continental margin of West Africa are becoming one of the most attractive areas for hydrocarbon exploration. The oil and gas discovered recently are related to salt structures. The salt structures are widespread in Anglo-Cameroon, the thickness of salt is up to 1 500 m and the average width is 300 km. These basins can be divided into two parts in horizontal direction: extensional zone and compressional zone, which extend 100–150 km and 100–200 km respectively. The extensional zone includes sealed titled zone, growth fault zone and diapir zone, and is characterized by tilted block, rollover structure and turtle structure anticline. The compressional zone is characterized by salt sheet, salt tongue, thrust fault and small folds. Oil and gas are distributed in both zones, oil and gas reserves in the extensional zone are a little larger than reserves in the compressional zone. Several types of salt related traps can be recognized, such as salt anticline, salt diapir and fault related trap, unconformity and structural-lithologic traps. Salt anticlines are the most potential exploration targets. Key words: West Africa, passive continental margin, salt structure, extensional zone, compressional zone