Iranian Journal of Geophysics

Iranian Journal of Geophysics

Structural and depth to basment evaluation of parts of Brass and Olobiri, Bayelsa STATE, Nigeria, using airborne magnetic data

Document Type : Research Article

Authors
Cyril Nwankwo 1
Charles Ofoha 2
Joy Egbune 3
1 Professor, Department of Physics, University of Port Harcourt, Rivers State, Nigeria
2 Ph.D., Deparment of Physical Sciences, Edwin Clark University, Kiagbodo, Delta State, Nigeria
3 M.Sc., Department of Physics, University of Port Harcourt, Rivers State, Nigeria
10.30499/ijg.2023.420210.1545
Abstract
The usage of potential field data in studying basins has gained recently despite being a reconnaissance tool. High-resolution aeromagnetic data from Niger Delta's Brass and Oloibiri regions were used in this study to qualitatively and quantitatively: examine structures, identify the extension/occurrence of the chain and oceanic fracture zone traversing from the Gulf of Guinea, delineate basement morphology, delineate basement lineament/tectonic trends and then determine depth to basement. On the aeromagnetic map, geomagnetic and diurnal corrections were applied by the Nigerian Geological Survey Agency to remove the effects other than that due to local geology. A project file was created as the gridded data was imported into the Oasis Montaj environment in X (x-coordinate), Y (y-coordinate), and Z (main) channels. Regional-residual separation was initiated on the Z channel for signature decomposition into anomalies of regional and residual extent. Subtlest structural signatures were revealed as the residual was filtered further.  This resulted in other field channels from which qualitative maps were generated. Various qualitative grid maps were generated. Faults, folds, dykes, and fracture zones in the ENE-WSW and E-W directions were visible on the qualitative maps. These lineaments hugely affect the area as they act as conduits, synclines, and anticlines, possibly improving economic viability. Fast Fourier Transform (FFT) was applied. This discriminated the signal into its energy and wavenumber component. Consequently, the Log of energy against wavenumber was plotted, and then a line was visually fit unto the high and low spectral energy curves. This art called 2D spectral depth estimate modeled two structural depth sources, Da and Db. The depth to deeper sources, Da, varies from 3 km to 6.8 km, with a 4.5 km average depth, actually the shallow sources are found between 1.5 km and 3.2 km, but with a 2.2 km average depth. Da was imported into Surfer 20 for the depth to the basement map to be generated. The basement map depicts undulations linked to the area. The average depth of 4.5 km emanating from the deeply seated sources is the sedimentary thickness value of the region. The NE-SW and NW-SE lineaments indicate extended Chain/Charcot fracture zones towards the Nigerian Niger Delta region.  Due to the appropriate sedimentary thickness discovered and the recessive, NE-SW and NW-SE lineaments traversing from the Biafra Bight towards the region, this suggests that the area still holds a promise and thus hydrocarbon exploration can still be fostered if other conditions are met.
 
Keywords
Fracture zones
lineament
Fast Fourier Transform (FFT)
anomalies

Subjects

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Iranian Journal of Geophysics
Volume 18, Issue 3
July and August 2024
Pages 85-104