Role of the large-scale strike-slip transform zone in controlling the differential hydrocarbon distribution: A case of the Côte d'Ivoire Basin in West Africa

Abstract

Objective The Côte d'Ivoire Basin, which is located in the equatorial section of West Africa and features large-scale strike-slip transform zones, is a typical transformed passive continental margin basin. This area is currently a hot spot for oil and gas exploration and has great exploration potential but has an uneven distribution of hydrocarbons both horizontally and vertically. Methods Based on previous results, well data, seismic data and new discoveries, this paper focuses on the differential controls of hydrocarbon distribution from two perspectives: structure and sedimentation. Results The results show that the basin has experienced three main tectonic-sedimentary evolution stages, namely, intracontinental rift, ocean-continent transition, and passive margin, forming the "narrow west-wide east" axe structure. The basin has a narrow and steep transform margin in the west, a wide and gentle divergent margin in the east, and a transitional margin in the central region, which controls the overall oil and gas distribution of "less in the west and more in the east" in macro-scale. The main response area of the strike-slip transformation stress in the central transitional margin and the central uplift developed many structural traps, which were sourced from both the northern and southern depression and ultimately controlled the distribution of the Albian oil and gas reservoirs. Conclusion The palaeomorphology formed by the strike-slip transform zone plays an important role in controlling the spatial distribution of both the Upper Albian-Cenomanian reservoirs in the early stage and the Turonian reservoirs in the late stage. The stepped or intra-slope ponds on slopes formed by strike-slip transform zone are often the most favourable sand-rich places and benefit stratigraphic-lithologic traps. Additionally, the distribution of oil and gas reservoirs has good consistency with the distribution of sedimentary systems; that is, the transformation controls the reservoirs, and the distribution controls the oil and gas reservoirs.

Keywords

• côte d'ivoire basin
• transformed passive continental margin basin
• strike-slip transform zone
• transform margin
• divergent margin
• transitional margin