An oil rim reservoir is a saturated reservoir with an oil column of limited thickness, less than 90 feet, overlain by a gas cap and underlain by an aquifer. Among the various challenges encountered in producing oil rim reservoirs, water and/or gas coning and breakthrough is the most prominent. Water and gas breakthrough occurs majorly due to heel-toe effect and reservoir permeability variations. Inflow control devices (ICDs) were deployed to mitigate the heel-toe effect thereby delaying the water and gas breakthrough.
The reservoir is a typical onshore Niger Delta oil rim reservoir of 30 feet oil column thickness. A long horizontal well of 4250 feet was completed in the oil column. ECLIPSE 100 reservoir simulator was used in modeling the reservoir. To assess the performance of ICDs, two case scenarios were simulated: conventional horizontal well without ICD completion and horizontal well with ICD completion. Modeling of ICDs in ECLIPSE was achieved by the Multi-segment Well model. A multi-segment well model is an advanced well modeling that allows accurate modeling of multi-phase flow and pressure variations in wells with a reservoir simulation model. The well was divided into 25 segments.
This project highlights the benefit of ICDs in mitigating the heel-toe problem faced in oil rim reservoir development. Results obtained from the simulation showed that for the case without ICDs, PLT plot indicated that only about 15% of the well length was contributing to flow. The heel-toe effect resulted in early water and gas coning, and a low oil recovery of 21%. Deployment of ICDs yielded a more uniform fluid inflow (100%) along the entire length of the well; delayed water and gas breakthrough for about one year; increased well productive life by one year; and increased oil recovery by an extra 22% (3.65 MMSTB).