ROCK PHYSICS AND FLUID SUBSTITUTION FOR RESERVIOR CHARACTERISATION IN ‘IBB’ FIELD, NIGER DELTA.
Abstract
Reservoir characterization in the Niger Delta is hindered by the inherent complexity of heterogeneous formations and the limitations of traditional rock physics models. These models often fail to accurately predict seismic responses due to simplistic assumptions about pore geometry and fluid distribution, leading to significant uncertainties in identifying hydrocarbonbearing zones and optimizing extraction strategies.
This study employed an integrated workflow to characterize reservoirs in the 'IBB' field. Well log data from three wells were analyzed to perform a detailed petrophysical evaluation, identifying reservoir zones and calculating key parameters (porosity, saturation, permeability). Rock physics template (RPT) diagnostics were then applied through cross-plot analysis of elastic properties like Acoustic Impedance (AI) and Vp/Vs ratio for lithology and fluid discrimination. Finally, Gassmann's fluid substitution theory was used to model the changes in seismic velocities (Vp, Vs) and impedance under different fluid saturation scenarios (100% brine vs. 100% gas).
Two viable reservoirs were delineated, with Reservoir 1 showing superior average properties (23% porosity, 71% hydrocarbon saturation, 2136 mD permeability). Cross-plots of AI vs. Vp/Vs and Lambda-Rho vs. Mu-Rho effectively discriminated sand from shale and hydrocarbon-saturated sands from brine-filled zones. Fluid substitution results confirmed the theoretical response: brine saturation increased density and P-wave velocity (Vp) while leaving S-wave velocity (Vs) unchanged, whereas gas saturation decreased density and Vp but increased Vs. This behavior provides a clear seismic signature for fluid identification.
The research successfully established a robust relationship between rock physics and petrophysical parameters for the Agbada Formation. The developed calibrated rock physics model provides a reliable framework for interpreting seismic data to directly map fluid saturation, thereby reducing interpretation risk and offering a valuable tool for future exploration and development decisions in the Niger Delta basin.
Full-Text Access Notice
In accordance with the NERD Policy on promoting peer-reviewed publication, public access to the full text of a project, thesis or dissertation is restricted for three years, allowing the author and supervisors sufficient time to pursue peer-reviewed publication.
During this period, researchers with legitimate academic or research purposes may request authorisation directly from the author to enable NERD to release the indexed full texts of the work using the form below.