Assessment of Crude Oil Spill Impacts on Soil Permeability and Reservoir Analogue Properties in Imo State, South East Nigeria

Crude oil spills in the South East geopolitical zone of Nigeria have caused significant environmental contamination, and their effect on the geomechanical and petrophysical properties of shallow soil formations with reservoir analogue characteristics merits systematic investigation. This study assesses the impact of historical crude oil spills on soil porosity, permeability, and grain structure in selected contaminated sites in Imo State. Soil core samples were collected from three contaminated and three uncontaminated reference sites across Ohaji-Egbema local government area, and subjected to standard core analysis including helium porosity measurement, air permeameter tests, and thin-section petrographic analysis. Scanning electron microscopy was employed to characterise pore-blocking mechanisms resulting from bituminous residue deposition within pore throats. Results indicate a mean permeability reduction of 62 percent in contaminated samples compared to reference cores, accompanied by pore throat occlusion by polymerised hydrocarbon residues. These findings have direct implications for bioremediation strategy design and for the characterisation of shallow aquitards in hydrocarbon-producing zones. The study adopts Darcy's Law as the foundational framework for permeability estimation and the Kozeny-Carman model for porosity-permeability correlation analysis. Recommendations are made for soil remediation approaches that can restore hydrological functionality in affected areas, with broader lessons for environmental baseline assessments in South East exploration licences. Keywords: crude oil spill, soil permeability, Imo State, petrophysical analysis, reservoir analogue.