Sensitivity Analysis of the Critical Gas Saturation on Water Injection

Reservoir simulations are widely used in the oil and gas industry to study, understand and develop new fields to forecast production, make important investment decisions and ultimately increase recovery. To achieve ultimate recovery, pressure in the reservoir must always be maintained and one of the effective ways to maintain reservoir pressure is by water flooding/injection. Water flooding is an Enhanced Oil Recovery method which deals with high pressure injection of water into the reservoir to sweep or displace the residual oil, pushing it closer to producer wells. The effect of critical gas saturation on this water injection process is thoroughly studied through sensitivity analysis, which essentially deals with altering the critical gas saturation values in the reservoir model and investigating the outcome as a function of the overall recovery of oil, gas produced, water produced and the field pressure among others. In gas reservoirs, saturation of associated gas increases in the gas cap as reservoir pressure decreases below the bubble point. The continuous increase creates a saturation which is immobile until the critical saturation point is reached.