Optimasi Kinerja Injeksi Air Pola Inverted Five-Spot pada Reservoir Laminated Shaly Sand

Abstract

Laminated shaly sand reservoirs exhibit high heterogeneity due to the presence of shale laminations, resulting in uneven permeability distribution and reduced sweep efficiency during waterflooding operations. Therefore, an optimization strategy is required to improve oil recovery. This study aims to evaluate the effect of Zonal Selective Perforation (ZSP) and injection rate variation on waterflooding performance using the Inverted Five Spot well pattern. Reservoir simulation was conducted using CMG IMEX (Black Oil Simulator) on a synthetic reservoir model. The perforation interval was limited to Layers 4–10 based on reservoir characteristics, while water injection rates were varied at 500, 600, and 700 BWPD. The performance of each scenario was evaluated using oil saturation distribution, oil production rate, water breakthrough, water cut, cumulative oil production, and recovery factor. The simulation results indicate that increasing the injection rate improves reservoir pressure maintenance, leading to higher cumulative oil production and recovery factor. However, a higher injection rate also accelerates water breakthrough and increases water cut at an earlier stage of production. Among the evaluated scenarios, the 500 BWPD injection rate achieved the highest recovery factor and cumulative oil production, although the production wells reached the 90% water cut limit sooner than in the other scenarios. Overall, the results demonstrate that the combination of Zonal Selective Perforation and injection rate optimization can improve the effectiveness of waterflooding in laminated shaly sand reservoirs and may serve as a reference for developing water injection strategies in heterogeneous reservoirs.