Regional Geological Study and Potential Prediction of the Rio Del Rey Basin (RDR), Offshore Cameroon

Abstract

ABSTRACT Located in the eastern end of Niger delta; the Rio Del Rey (RDR) basin has a unique, complex multi-staged geological features and different types of Structures. This study has aimed to better understand the different structural and stratigraphic setting of the fields within the RDR basin and the way they control the hydrocarbon occurrences. To do that, an integrated 2D and 3D seismic interpretation was done targeting the toe thrust boundary, the upper Cretaceous unconformity and four key horizons of different depth levels in the Tertiary formations. Twelve regional profiles of contrastive orientations that cover the whole basin were interpreted to identify the regional structures; well correlation was done to identify the shallower tertiary settings while additional detailed grids of interpretation at the northeastern and southwestern corners and the seismic facies analysis of the whole RDR study area were used to classify the stratigraphic setting at the deeper regions. The results have revealed that the RDR basin is mainly controlled by thrusting, diapirism and detachment fault structures. The major toe thrust zone is found southern of Ngosso and trends in the northeast-southwestern direction. Gravitational tectonism becomes the primary deformation process shaping the structures as the sediments accumulation increases to the south and consequently, several shale ridges were formed. These ridges and their lateral movement from North to South along with the whole sediments increasing have caused a slope instability of the lower ductile Akata shale formation; what caused the forming of the detachment faults zone in the Northern and middle parts of the RDR basin. The Oongue Turbidites of Eocene were deposited in the northeastern part of the basin in deep water fans by the main sediments supply from the North and the East with various sand thicknesses due to the structural system. The hydrocarbon potential accumulations are found in the mid to upper Tertiary formations and the deeper Upper Cretaceous, but most of the oil and gas fields are located in shallower deltaic reservoirs associated with fault-bounded traps related to shale ridges and diapir structures. Considerable amounts of hydrocarbons were also found within the turbidites sands of Oongue (NE) and Isongo (SE).