Quantitative Seismic Interpretation Framework for Unconventional Shale Gas Exploration in the Benue Trough

This study develops an original quantitative seismic interpretation framework for unconventional shale gas exploration in the Benue Trough, North Central Nigeria, representing the first systematic geophysical evaluation of Nigeria's shale gas potential. While Nigeria's conventional hydrocarbon endowment in the Niger Delta is well characterised, the country's unconventional gas resources in carbonaceous shale sequences remain almost completely unevaluated. The Asu River Group and Eze-Aku shale formations of the Benue Trough contain organic-rich marine shales comparable in geological setting to productive shale gas plays in North Africa and the East African rift. This study develops a quantitative interpretation framework that addresses the specific seismic signatures of organic-rich shales in the Benue Trough geological context, including low-frequency shadows below gas-charged intervals, brittleness prediction from seismic attributes, and natural fracture characterisation from azimuthal seismic analysis. Seismic inversion produces acoustic and elastic impedance volumes that are converted to brittleness index using published empirical relationships calibrated to Benue Trough core samples. Rock physics modelling predicts the seismic response of shale gas scenarios for different TOC and maturity levels. Geomechanical analysis from existing regional stress data evaluates hydraulic fracture orientation potential. Findings reveal acoustic impedance anomalies in the Asu River Group consistent with organic-rich shale facies at depths of 2 to 4 kilometres where maturity modelling suggests the gas generation window. Brittleness index values of 0.45 to 0.65 in the identified intervals indicate moderate fracability. The study provides an original geophysical exploration model for Benue Trough shale gas and recommends a dedicated shale gas exploration programme.

Keywords: shale gas, quantitative seismic interpretation, Benue Trough, unconventional resources, brittleness.