Rock Physics and Gassman Fluid Substitution Analysis for Reservoir Characterization: A Case Study of Ky Field Chad Basin North-Eastern Nigeria.
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Abstract: This study investigates the application of rock physics and Gassmann fluid substitution analysis for reservoir characterization in the KY Field of the Chad Basin, Northeastern Nigeria. The primary objective is to evaluate the impact of fluid saturation on seismic elastic properties, such as P-wave and S-wave velocities, and density, to better understand reservoir potential and fluid distribution. The research utilizes 3D seismic data and well log suites, including gamma ray, density neutron, resistivity, and sonic logs, from four wells (XY-1, XY-2, XY-3 and XY-4). Gassmann's equations are employed to model fluid effects on rock velocity and density, enabling the identification and quantification of fluid types and saturations within the reservoir. The study highlights the challenges of estimating water saturation from seismic data and emphasizes the importance of rock physics modeling in interpreting seismic amplitude anomalies. Results from crossplots of Acoustic Impedance (AI) versus Vp/Vs and LambdaRho versus MuRho reveal distinct lithological and fluid trends, with hydrocarbon-bearing sands showing significant deviations from brine-saturated sands. Fluid substitution analysis demonstrates that changes in fluid saturation, particularly gas content, significantly affect seismic responses, indicating partially gas-saturated reservoirs with patchy distributions. The findings provide valuable insights into the reservoir's elastic properties and fluid dynamics, offering a robust framework for future exploration and development in the KY Field. This research underscores the critical role of rock physics and fluid substitution in enhancing seismic interpretation and reservoir characterization in complex sedimentary basins.
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