Exploitation of thin oil rims with large associated gas cap

Abstract

Thin oil rims are reservoirs with thin oil column sandwich between water and gas layers, it occurs in reservoirs with high compacts sand, high porosity, high permeability and contain light crude. However, with this favourable reservoir conditions, maximising oil production is a challenge. Even with good practices, a significant amount of oil column about 10+ ft is left at abandonment. This research investigates the use of horizontal well with different completion scenarios to maximise oil recovery under the reservoir's prevailing natural energy. The research was based on extensive simulation studies conducted for several hypothetical cases, with varied petrophysical data. Oil recovery greater than 19% of the OOIP, with a high gas production of about 95% GIIP, and low water production of 8% was observed. Applying the Levenberg-Marquardt algorithm in the statistical data analysis, a recovery factor correlation was developed as a simple tool to evaluate the performance of thin oil rims, the recovery factor correlation was validated with publish data. Thus, it can be concluded from this hypothetical study that, the oil recovery from a thin oil rim reservoir with a large associated gas cap increases as the horizontal permeability increases and decreases as the oil rate and horizontal well length increases. Moreover, the simulation studies also reveal that placing horizontal wells near the gas-oil contact is most likely the optimum production strategy for increasing oil recovery.