Interpretation of Regional Magnetic Field Data Offshore Niger Delta Reveals Relationship between Deep Basement Architecture and Hydrocarbon Target

Abstract

Directional horizontal derivatives, analytic signal, filtering of magnetic data sets and 3D magnetic modelling incorporating induced and remanent magnetization were performed on low resolution aeromagnetic data to unravel the basement structure and its relationship with hydrocarbon target offshore Niger Delta basin. Forward modelling of the residual magnetic data gave discrete depth values that were exploited to compile the depth to basement (thickness of the sedimentary section) map which highlighted deep depocenters, high blocks and major sedimentary fairways in the study area. The uplifted blocks created the arches while downdropped ones produced the depocenters. The depth to the basement map revealed basement paleotopography which resulted from movement along fault zones. The transformed/enhanced data revealed three potential stress regimes trending NE-SW, N-S and E-W. The NE-SW lineaments are shear zones, more dominant and indicate possible extensions within the African continent of Charcot and Chain oceanic fracture zones. The E-W lineaments are revealed not only in the enhanced maps but also in the total magnetic intensity and residual data sets because they are associated with dykes. The N-S structures are very subtle and are therefore highlighted only in the transformed data. In combination with the E-W structures they are brittle and reactivated structures associated with faults and have significant implications for the tectonic evolution of the Niger Delta and its basin extensions. The transformed data sets, depth to basement map and residual data strongly suggest that jostling of the basement blocks has influenced deposition in the Niger Delta basin. The structural highs (basement highs), basement lows (structural lows) and steep/faulted basement flanks are attractive sites for oil and gas accumulation.

Basin Framework and Basement Structuring of Lower Benue Trough, West Africa based on Regional Magnetic Field Data: Tectonic and Hydrocarbon Implications

“…The magnetic susceptibility values resulting from the residual field modelling may be useful in locating hydrocarbon deposits in the study area as in the case of Barinas Apure basin, Venezuala, where high magnetic susceptibilities were observed to coincide to the top of the sedimentary units corresponding to reservoir and source rocks of oil-producing wells (Perez-Perez, D"onofrio, Bosch & Zapata, 2011). This relationship between magnetic anomalies and hydrocarbon fields has also been established in cement oil field Oklahoma (Reynolds, Webring, Grauch &Tuttle, 1990) and in the Niger delta basin (Okiwelu, Ofrey-Kulo & Ude, 2013). Shelf sandstones members of the Cretaceous aged Asu River group and shallow marine Ezu Aku formations, as well as Nkporo and Ajali (Maastrichtian) [ Figure 3] are proven petroleum reservoirs in the study area.…”

Investigation of gravity anomalies in parts of Niger Delta Region in Nigeria using aerogravity data

“…The towns covered in the study were Olobirin, Degema, Patani and Ahoada. Niger Delta has an area of about 300,000 km 2 , sediment thickness of over 10,000 km and Ekpa et al 55 sediment volume of 500,000 km 3 (Okiwelu et al, 2013). Niger Delta is located between latitudes 3°30' and 4°30'N, longitude 6°00' and 7°00'E.…”

“…Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License fluids within materials affect density contrast. Gravity data can be used in many ways to solve different exploration problems, depending on the geologic setting and rock parameters (Ezekiel et al, 2013;Okiwelu et al, 2013;Obiora et al, 2016), the data when analyzed provide insight to elements of petroleum exploration and production (Johnson, 1998;Obiora et al, 2016). The density contrasts presented by the juxtaposition of sediments with shales make detailed gravity modeling in this region a valuable exercise.…”

Modeling Magnetic Basement in Relationship to Hydrocarbon Habitats in the Central Niger Delta, Nigeria

“…So far, aeromagnetic studies have been done by studying magnetic profiles on regional data sets and some parts of offshore Niger Delta [6,7,8]. The onshore Nigeria Delta has not been modeled in details using magnetics to unravel the deepseated hydrocarbon habitats.…”