Magnetic anomaly patterns, fault-block tectonism and hydrocarbon related structural features in the Niger Delta basin

Abstract

Gridded airborne magnetic data, 3D magnetic forward models in combination with filtered maps and derivative techniques such as analytic signal and directional derivatives were used to reveal basement structure and architecture of the study area in offshore Niger Delta. The generating mechanisms of the magnetic anomalies are boundaries (fault) of basement blocks of different compositions having different physical properties (susceptibilities and remanence) and horst/graben structures with associated normal faults and extensions. The intrabasement sources exhibit anisotropic susceptibilities and depth to basement (sedimentary thickness) is between 4000m to over 10,000m indicating deep depocenters. All these factors combined to influence magnetic anomaly patterns which have implications in hydrocarbon prospect target. The regional structural characteristics of the basement interpreted from the regional magnetic data sets show clear relationship between inferred rift-related basement structures and oil fields. Oil and gas discoveries appear to be located on the flanks of steep/faulted basement and on top of basement structural highs and lows. This study, therefore, is significant in understanding the petroleum system, contributes to basin modelling and can unravel areas of identical structural development in less well-explored sectors of the basin.