Optimizing oil recovery from thin oil rims having gas cap and aquifer

Abstract

The goal in any oil field development is to accelerate the hydrocarbon production and optimize the oil recovery at lowest cost possible. This objective becomes very challenging when managing thin oil rim reservoirs where a thin column of oil is overlain by a large gas cap and underlain by a strong aquifer. Early gas breakthrough and water coning can cause serious problems to production and hence jeopardize oil recovery. In this type of reservoir, it is very critical to control the movement of GOC and OWC. Keeping a force balance between gas cap expansion and aquifer movement is the key for maximum oil recovery. A successful project may entail plans to maintain the reservoir energy through water injection or produced gas re-injection to maintain reservoir pressure and enhance oil recovery. This study presents evaluation of a thin oil rim from Gulf of Thailand (GOT) offshore reservoir to estimate the optimum recovery factor based on dynamic flow properties. An experimental design and optimization workflow is adopted to study the effect of different flow dynamic parameters on overall recovery of a thin oil rim reservoir. Secondary recovery options (water/gas injection) are also evaluated to see their impact on incremental recovery. In this study, the impact of changing the force balance on oil recovery by horizontal well drilling is evaluated. The effect of horizontal well lateral length and distance from OWC and GOC on oil recovery is also studied. The results show a potential of improving oil recovery factor by drilling horizontal wells in thin oil rims that are farther from GOC and closer to OWC.