Structural Interpretations Inferred from a High Resolution Aeromagnetic (HRAM) Data over Parts of Onshore Niger Delta, Nigeria

Bello Rasaq

doi:10.11648/j.ijhep.20170403.11

Abstract

Aeromagnetic data acquired by the Nigerian Geological Survey Agency (NGSA) and which covers about 3025 square kilometer of some parts of onshore Niger Delta, Nigeria, was processed and interpreted with the purpose of highlighting the structural lineaments with their corresponding trend patterns and then inferring the effect of the structures as it relates to the hydrocarbon potential and tectonic history of the area using the qualitative approach. Using polynomial fitting of degree two (2), regional - residual separation was carried out on the Composite Total Magnetic Intensity (CTMI) map, lying geographically within longitude 6°30'E-7°0'0''E and latitude 4°30'N-5°0'0'', and this generated the regional and residual maps. Some enhancement techniques applied upon the residual map gave rise to some directional gradient maps that depicted structural lineaments trending in the E - W, NE - SW, NW - SE and N - S directions. These lineaments influence the tectonics of the area and as such created faults and fractures that fostered the migration and entrapment of hydrocarbon, and perhaps mineral, within the area under review.

Highlights

The aim of magnetic survey is to investigate subsurface geology on the basis of magnetic anomalies in the earth’s magnetic field resulting from the magnetic properties of the underlying rocks [1]
Changes in the earth’s magnetic are caused by variations in rock magnetism, which is mostly controlled by a physical property called magnetic susceptibility [4]. [6] pointed out that this variation in the magnetic susceptibility can cause small magnetic variation in the magnetic fields of rocks measured on the surface
To achieve the purpose of this research which is aimed at identifying structures within the study area, the following enhancement techniques were applied on the aeromagnetic data obtained in spread sheet file format: Regional - Residual Separation [12] stated that magnetic data obtained during a magnetometer survey is a sum total of the magnetic effect from the underground sources and that the usual targets in a magnetic survey are the high wave number components buried at shallow depths

Summary

Introduction

The aim of magnetic survey is to investigate subsurface geology on the basis of magnetic anomalies in the earth’s magnetic field resulting from the magnetic properties of the underlying rocks [1]. Magnetic survey can be performed on land, at sea and in air. [5] stated that the speed of operation and low number of field personnel’s make magnetic surveys performed either on land, at sea and in the air, very attractive. They further explained that the main objective has been to assist in mineral and hydrocarbon exploration through improved geologic mapping. Changes in the earth’s magnetic are caused by variations in rock magnetism, which is mostly controlled by a physical property called magnetic susceptibility [4]. The shape, dimensions and amplitude of an induced magnetic anomaly is a function of the orientation, geometry, size, Bello Rasaq and OfohaChimezie Charles: Structural Interpretations Inferred from a High Resolution

Methods

Results

Discussion

Conclusion