Evaluation of basement topography and structures in the Dahomey Basin and surrounding environs of Southwestern Nigeria, using satellite gravity data

摘要

Attempts at regional gravity studies of the southwest Nigerian geologic terrain have been limited due to sparse distribution of gravity stations and prohibitive costs of gravity measurements. The use of satellite-based global gravity data provides a reliable and cost-effective means of regional-scale studies, and the WGM2012 gravity data was employed to evaluate the basement topography and structures. The aim of the work is to map regions in the Nigerian sector of the Dahomey Basin with suitable sediments thickness and fracture systems, capable of hydrocarbon generation and preservation. The Bouguer anomaly data was subjected to series of processing and anomaly enhancement, using the Oasis Montaj software. Observations of anomaly distributions reveal division of the study area into three geologic zones, namely, basement terrain, Dahomey Basin and Niger Delta Basin. The basement structures trend in a general north–south directions, but approximate orientations vary significantly, with abundance of sub-parallel and discordant alignments. The depths to basement range from <2000 to >5000 m, with the southwest being the deepest part of the study area. The results establish the Dahomey Basin as containing the minimum required sedimentary thickness of 3000 m and suitable structures necessary for hydrocarbon generation and accumulation.