Reservoir Characterization of the NKO Field, Onshore Niger Delta Basin Using Multi-Seismic Attribute Algorithms

Abstract

This study presents a comprehensive reservoir characterization of the NKO Field onshore Niger Delta Basin using multi seismic attributes algorithms. The study is aimed at delineating the lithofacies stratigraphic framework using well-logs, characterizing the reservoirs and evaluate their petrophysical properties, build a robust structural and tectonostratigraphic framework of the NKO Field well-log and seismic data, generate volume and surface attributes for prospect identification and analysis as it will enhance adequate reservoir characterization. The integration well logs and seismic data enabled the delineation of lithofacies, characterization of the reservoirs and evaluation of the petrophysical properties. A multi-attribute seismic analysis used increased the reliability of the subsurface predictions. The results reveal six distinct reservoirs with varying petrophysical properties, including porosity, permeability, and hydrocarbon saturation. Also, seismic attribute analysis which include, sweetness attribute, RMS amplitude, and variance edge, helped in identifying potential Hydrocarbon bearing zones. The variance (edge) attribute clearly shows the faults within the field that were not evident in the original seismic data. The reservoir interval exhibited a total porosity range of 0.16 to 0.29, indicating a moderate to good storage capacity, while the effective porosity, which is a critical parameter for hydrocarbon flow, was computed to range from 0.16 to 0.29, suggesting a potentially significant proportion of interconnected pore spaces. The volume of shale within the reservoir interval varies between 0.12 and 0.23, which is relatively consistent with the lithology expected in this geological setting, and the net-to-gross ratio ranges from 0.75 to 0.89, indicating a relatively high proportion of reservoir-quality rock. Permeability, a key factor controlling fluid flow, ranges from 589mD to 987mD, suggesting a moderate to good flow potential. Hydrocarbon saturation within the Res_2 reservoir interval is estimated to range from 0.62 to 0.71, indicating a significant presence of hydrocarbons and potentially commercial quantities. The well tie analysis reveals that the top of the targeted reservoirs corresponds to the peak, indicating that they are consisting of high-impedance sands overlain by low-impedance shale layers. A total of 42 faults were identified and mapped, with three major faults causing significant displacement in the region. The depth map exhibits a substantial depth range of 5014 Ft (9093-4079 Ft), with a structural high reaching as shallow as -4079 ft. and structural lows plunging to 9093 ft. The integration of structural attributes with fault interpretation enabled a more accurate understanding of the subsurface geology and the role of faults in controlling hydrocarbon accumulation. This study provides valuable insights into the reservoir structure and stratigraphy, informing development strategies.