Structural characterization of the Nigerian sector of Benin Basin using geopotential field attributes

Abstract

The structural dispositions of the Nigerian sector of the Benin Basin have been investigated using attributes of geomagnetic and gravimetric fields. Aeromagnetic anomalies were reduced to the equator to improve the correspondence of the anomalies with the causative bodies. The residual, upward continued, tilt and horizontal derivatives, and pseudogravity attributes and forward models of both geomagnetic and gravimetric anomalies were computed to accentuate geological features including shallow and regional faults, fracture network, basement block pattern and depth to magnetic basement. Three generations of sinistral faults were identified. The oldest generation of faults (F1) is the NE-SW trend corresponding to the oceanic fracture zones trend. The F1 is truncated by the second generation of faults (F2) with E-W trends. The third generation of faults (F3) assumes NW-SE trend and is offset by F2. Shallow and deep regional faults and fractures envisaged to play major role in migration and entrapment of hydrocarbons and localization of mineral resources in this area were imaged. The coastline, Lagos and Lekki Lagoons surface geometry showed high degree of similarity with their underlying basement block pattern, thus implying that these surface features are structurally controlled. The basement morphology is not flat but of horst and graben architecture in which sediment thickness attained about 4 km within the graben. Hence, the graben has significant hydrocarbon potential. This study has shown the capabilities of geopotential field attributes in providing information about the structural architecture of frontier basin. Such knowledge will aid the understanding of the geology of the basin and its resources.