Fluid replacement dynamics: evolving reservoir properties during hydrocarbon production in X-field, Niger Delta, Nigeria

During hydrocarbon recovery, fluid replacement takes place in reservoirs, affecting the reservoir properties and consequently altering the production model and forecast. These attributes were utilized to refine fluid replacement modeling (FRM). This research aims to generate geological models capable of serving as predictive tools for reservoir monitoring. The FRM was carried out using rock-physics analysis of the wells of X-field, onshore Niger Delta, while the reservoirs’ stress state was determined using Dynamic Rock-Physics Template (RPT). Rock-physics modeling was used to characterize the reservoirs dynamically and estimate their geomechanical responses due to fluid replacement. As hydrocarbons were replaced by brine, the FRM showed a consistent increase in density (ρ) attributed to a gradual rise in bulk and shear moduli. Gas dissolution resulted from the unusual reduction of compressional wave velocity (Vp) from 3.92 to 3.86 km/s in reservoir D of well A1. As hydrocarbon is replaced by water, the reservoir's shearing strength decreases. Reservoir B of well A2 has comparatively low resistance to deformation and rock strength of 18.40 GPa and 77.70 MPa, while 34.29 GPa and 142.85 MPa were recorded for reservoir D (well A1), while 34.29 GPa and 142.85 MPa were recorded for reservoir D (well A1), respectively, at 100% Sw. The increase in young modulus and strength (138.86–142.85 MPa) in reservoir D (well A1) implied mechanical and well-bored stability. Pore pressure depletion in reservoir B (well A2) from RPT could induce well instability. This study highlights tailored production strategies to mitigate destabilizing effects, stressing the relationship between pore pressure depletion, stress redistribution, and fluid migration for sustainable hydrocarbon exploitation and well integrity.