Spectral re-evaluation of sediment thickness within Afikpo Basin and environs, southeastern Nigeria, using high resolution aeromagnetic dataset

Stephen Stephen Onyejiuwaka Ibe,Kevin Uche Iduma

doi:10.14419/ijag.v9i1.31258

Stephen Stephen Onyejiuwaka Ibe, Kevin Uche Iduma

Open Access

https://doi.org/10.14419/ijag.v9i1.31258

Copy DOI

Abstract

The discovery of hydrocarbon in the areas bordering Afikpo Basin prompted the re-evaluation of the sedimentary thickness within the basin with high resolution geophysical data. Depth to magnetic sources, sediment thickness, basement topography and structures within it were investigated using spectral analysis, analytic signal and tilt derivative of aeromagnetic data. The results show that the depth to the basement varies between 1.52 and 3.15 km; depth to intermediate magnetic anomaly sources ranges from 0.40 to 1.05 km and depth to the shallow sources varies from 0.10 to 0.34 km. Structures within the basin predominantly have NE-SW trend and the boundary between Afikpo Basin and Southwestern Basement Massif is characterised by NE-SW trending dykes with the longest dyke extending from Amasiri to Abba Omege. The results show that the basin is greatly undulated and the deformation that led to its undulation resulted in the formation of structures which could serve as traps for hydrocarbon accumulation. Sediment thickness greater than 2.3 km associated with some locations within the basin prompted the classification of the places as viable for hydrocarbon formation, if other conditions necessary for its generation are favourable. These places were recommended for further studies for hydrocarbon prospecting on the bases of their sediment structural complexities and thicknesses.Â Â

Highlights

The Afikpo basin is located in the Southern Benue Trough
The Benue Trough is a continental-large scale intraplate tectonic mega structure, which is part of the Mid-African Rift system initiated in the Latest Jurassic to Early Cretaceous and it is related to the opening of Central and South Atlantic Ocean (Benkhelil, 1989)
Ehinola et al (2005) carried out the analysis of one of the basin’s strata, the Nkporo Shale, to assess its petroleum potential by sedimentological analysis and Rock-Eval pyrolysis and the results show that the Total Organic Carbon (TOC) range exceeds the minimum value usually required for potential petroleum source rocks

Summary

Introduction

The Afikpo basin is located in the Southern Benue Trough. The Benue Trough is a continental-large scale intraplate tectonic mega structure, which is part of the Mid-African Rift system initiated in the Latest Jurassic to Early Cretaceous and it is related to the opening of Central and South Atlantic Ocean (Benkhelil, 1989). Previous geophysical studies on the study area (Onwuemesi 1995; 1997; Ugbor and Okeke 2010; Onuba et al 2013; Opara et al 2014; Obi and Obeten 2017) dwelt more on the sediment thickness and petroleum potentials, using forward and inverse modelling technique, spectral analysis or half width method These studies made use of obsolete method, low resolution airborne magnetic data, one-dimensional profiles for depth modelling or high spectral grid cell size to generate results. This study used high resolution aeromagnetic dataset and a smaller spectral grid cell size to appraise the hydrocarbon potential of the study area This was accomplished by the determination of the depth to magnetic sources, sediment thickness, basement topography and structures within the basin

Methods

Results

Conclusion