Application of the modified capacitance-resistance method to model reservoir pressure maintenance

A pressure maintenance strategy is crucial in reservoir management, especially in single-phase oil reservoirs, to keep the reservoir pressure above the bubble point. Water injection is a common way to prevent pressure decline due to production. Water may be injected into oil zone and/or aquifer. Analytical and semi-analytical methods are applied to analyze the reservoir response and pressure alteration during the water injection and pressure maintenance operation. Capacitance- Resistance Model (CRM) is a well-known semi-analytical method to predict oil production by water flooding. In this work, Static Capacitance- Resistance Model (SCRM) in which time constant parameter is unique value in whole matching duration has been applied to estimate water injection in the reservoirs with charging aquifer; in addition to, our aim is analytical investigation of water injection performance in the aquifer zone. As a matter of fact, SCRM has been coupled for the reservoir and aquifer in which SCRM has been written for a reservoir and an aquifer zone as two independent porous medium. Consequently, SCRM has been developed to estimate pressure maintenance performance in the cases of charging aquifer; moreover, new parameter is defined as pressure difference between aquifer and reservoir transition zone (DP) is added to SCRM tuning parameters that can indicate flow and reverse flow between reservoir and aquifer. This parameter is a water saturation-dependent function considered as another tuning parameter. Two synthetic reservoirs were simulated in this work, including homogenous and streak cases with nine spot patterns. The developed SCRM has shown acceptable accuracy, of which 6.1% of total absolute error was obtained for the homogenous case and 7.5% for the streak case.