Voidage Replacement Ratio and Pressure Stability: An Analytical Assessment of Volumetric Control in Waterflooding

Voidage Replacement Ratio (VRR) is widely used in water injection management as a volumetric performance indicator; however, its role in ensuring environmentally safe reservoir pressure control remains insufficiently quantified. This study presents an analytical assessment of VRR as a stability-governing parameter linking cumulative volumetric imbalance to reservoir pressure evolution. A conceptual homogeneous reservoir model based on classical material balance principles was developed to evaluate under-injection (VRR < 1), balanced injection (VRR = 1), and over-injection (VRR > 1) regimes under constant-rate conditions. Results demonstrate that sustained deviation from unity VRR produces linear cumulative imbalance and systematic pressure drift. Under-injection leads to progressive pressure depletion, whereas over-injection generates continuous pressure build-up, potentially increasing risks of caprock stress alteration, fracture propagation, and unintended fluid migration. Sensitivity analysis indicates that even moderate deviation (±0.05–0.1) may cause measurable long-term instability. The findings support interpretation of VRR not merely as an operational metric but as a dynamic stability control parameter contributing to environmentally responsible reservoir management. Maintaining VRR within a narrow tolerance range minimizes cumulative imbalance growth and supports safe pressure maintenance. The analytical framework provides a transparent basis for integrating volumetric stability criteria into sustainable water injection strategies