TITLE:
Subsurface Reservoir Properties Assessment and Fluids Discrimination from Rock Physics and Seismic Inversion in Termit Basin, Niger
AUTHORS:
Amadou Hassane, Chukwuemeka Ngozi Ehirim, Tamunonengiyeofori Dagogo
KEYWORDS:
Crossplots, Rock Physics Template, Elastic Parameters, Seismic Inversion, Seismic Attributes, Reservoir Characterization, Reservoir Properties Prediction
JOURNAL NAME:
International Journal of Geosciences,
Vol.16 No.4,
April
30,
2025
ABSTRACT: Sokor Formation reservoir intervals are intrinsically anisotropic, heterogeneous and with a characteristic of Low Contrast Low Resistivity (LCLR) log responses in parts of the Termit basin. Discriminating sands from shales/mudstones and hydrocarbon sands from brine sands as well as accurately evaluating the distribution of relevant reservoir properties using conventional seismic interpretation are complicated, and undermines reservoir characterization in such reservoirs. To enhance reservoir evaluation and reduce development planning and production risks, rock physics analysis was intergrated into the petrophysical workflow, which fed higher fidelity inputs into a post stack seismic inversion workflow. Rock Physics Diagnostics (RPD) analysis revealed that the reservoir interval of interest has grain size distribution of different lithologies, which is related to the environment of deposition and burial history, and could be best described by the constant cement sand model. The rock physics analyses revealed that facies were most effectively discriminated based on their Vp/Vs ratios and acoustic impedance. Particularly, hydrocarbon saturated sandstones, brine saturated shaly sandstones and shales/mudstones which exhibit similar acoustic impedance characteristics, were clearly discriminated by their Vp/Vs. The inverted seismic attributes as well as Seismic Based-Rock Physics Templates (RPT), clearly delineated the hydrocarbon fields, predicted new prospects beyond the existing well locations, which could be considered for field appraisal or development opportunities in the basin. These results demonstrate the value of the robust application of rock physics diagnostic modeling and seismic inversion in quantitative reservoir characterization and may be quite useful in undrilled locations in the basins and fields with similar geology.