Empirical Investigation of Multiscale Permeability Heterogeneity and Its Influence on Waterflood Pattern Efficiency in Agbada Formation Point Bar Deposits, OML 40, Rivers State

Point bar fluvial deposits within the Agbada Formation constitute some of the most laterally heterogeneous reservoir bodies in the Niger Delta, and their multiscale permeability structure, spanning log-scale beds to pore-scale lamination, has a profound influence on waterflood displacement efficiency. This study empirically investigates multiscale permeability heterogeneity in point bar reservoir bodies of OML 40, Rivers State, and quantifies its influence on waterflood pattern performance. Permeability data from 847 core plug measurements, wireline log-derived permeability profiles from twelve wells, and horizontal-to-vertical permeability anisotropy measurements were integrated to characterise the permeability architecture across four spatial scales. Dykstra-Parsons permeability variation coefficients computed at core scale (0.84) versus log scale (0.71) indicate progressive scale-dependent heterogeneity reduction consistent with core-to-log upscaling effects. Representative elementary volume analysis confirms that log-scale permeability volumes adequately represent flow at the well-to-well inter-well scale. Streamline simulation using Frontsim was applied to a fine-scale heterogeneous reservoir model to evaluate sweep efficiency under four waterflood patterns: line drive, nine-spot, seven-spot, and staggered line drive. Geological heterogeneity effects on volumetric sweep were quantified by comparing pattern performance between realisations spanning the P10 to P90 permeability uncertainty range. Results confirm that the staggered line drive pattern provides the most robust sweep efficiency across the full permeability uncertainty range due to its tolerance to cross-flow between injection rows. Keywords: permeability heterogeneity, waterflood efficiency, point bar, OML 40, Rivers State.