Effect of Reservoir Heterogeneity on Immiscible Foam Enhanced Oil Recovery

Gas flooding is a widely used improved and enhanced oil recovery (IOR/EOR) method. However, due to low density and high mobility of gas compared to oil and water, gas tends to segregate to the top of the reservoir and overrides both oil and water. In heterogeneous and layered reservoirs gas also tends to channel through high permeability streaks. Hence in gas flooding the sweep efficiency is generally poor which leads to low incremental oil recovery factor. The development of foam leads to lowering the gas mobility and thus can help overcome the above disadvantages and improve the reservoir sweep efficiency. Many experimental and modeling studies have been devoted to describe foam in the last decade, but questions remain about foam performance in EOR. In particular there are still some important questions regarding foam stability and propagation in reservoirs containing oil and the effect of reservoir heterogeneity. Recent experiments done at the Delft University of Technology have demonstrated that adequately selected surfactants produce foams that are stable in presence of oil. However, if oil saturation is too large there is still a risk that foam will not be sufficiently strong to achieve the desired high recovery factor. In this study we investigate the effect reservoir heterogeneity on the performance of immiscible foam EOR. The study addresses four different types of reservoir models, homogeneous reservoir, stochastic permeability reservoir, layered reservoir and layered stochastic reservoir. We adopt six different recovery methods starting with water flooding and NFA as a base case, surfactant flooding, gas flooding, foam co-injection, SAG processes and WAG processes. The simulation results show that foam co-injection has the best sweep efficiency and highest oil recovery. Foam front propagation rate is found to be lower in heterogeneous reservoirs compare with homogenous case and therefore more injection time is needed to reach the same recovery as in the homogeneous case. In all the injection scenarios, the oil recovery in heterogeneous reservoirs is lower.Petroleum Engineering and GeosciencesCivil Engineering and Geoscience