Offshore Côte d’Ivoire: Stratigraphic and Basin Modelling for Petroleum Evaluation

Gauly, Gbomea Marcelle ²; N'Da, Jacques ²; Bléoué, N'Zalassé ²; Murat, Bruno ¹; Wojciak, Patrick ¹; Jermannaud, Paul ¹; Roure, Sébastien ¹
(1) Beicip-Franlab, Rueil-Malmaison, France. (2) PETROCI, Abidjan, Cote d'Ivoire.

The Côte d'Ivoire sedimentary basin is a typical transform passive margin, with a complex tectonic history including pre-, syn and post-transform stages. The onshore expression of the Côte d’Ivoire basin is limited, but the sedimentary section expands dramatically south of the east-west trending Lagunes fault on the eastern Abidjan margin, and south of the northeast-southwest trending Saint Paul fault in its western San Pedro margin.

A seismic stratigraphy exercise was performed for the Upper Cretaceous and Tertiary sediments on a series of seismic cross-sections, in order to capture the key stratigraphic features of the margin. They were built by combining 2D regional sections connected to 3D seismic surveys and well-logs for lithological calibration. Detailed biostratigraphic data performed on the Cretaceous section enabled the correlation of packages and paleoenvironments, and major timelines were defined as guides for sequence and seismic stratigraphy.

A stratigraphic modelling was then performed in order to better understand the 3D sedimentary architecture of the basin, and to quantify the sedimentary volumes at basin scale. It also allowed the facies prediction in prospective areas, especially for the Upper Cretaceous section. It took into account the importance of the key erosion episodes by assessing the eroded thicknesses.

The results of stratigraphic modelling were fully integrated to the basin modelling, with a sequence of 1D modelling for the determination and calibration of thermal history, followed by 2D modelling performed on selected cross-sections, and by a 3D modelling on the full margin allowing the source rock parameters to be fully integrated and understood, together with hydrocarbon expulsion timing.

Facies maps were extracted for the relevant stratigraphic intervals, combining lithologies and paleoenvironmental data. They show in particular the distribution of the Post Albian flooding and onset of marine gravity driven complexes in the Cenomanian, the transgressive/flooding silty shales of the Turonian, the occurrence of turbiditic channel complexes in the Lower Senonian, and the onset of a starved passive margin to the west during the Campanian.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.