Dual Benefit of CO2 Sequestration: Storage and Enhanced Oil Recovery

Abstract

Carbon dioxide (CO2) sequestration is usually implied in geological formations because; they can provide the pore volumes needed to store large amount of CO2; they have adequate permeability required for efficient injection; and they are widely distributed geographically. They also possess the seal (Cap rock) needed to keep the stored CO2 in place. Of all the sedimentary formations, saline aquifers have the largest global sequestration capacity. Saline aquifers might exist at the bottom of an oil reservoir that acting as a pressure support to the oil reservoir. CO2 can be sequestered in saline aquifers underlying oil reservoirs or in saline aquifers that are located away from the oil reservoirs. In this study the dual benefit of CO2 sequestration will be introduced in which the CO2 will be injected in saline aquifers underlying oil reservoirs. The CO2 will be injected in the aquifer at the bottom part using different well schemes (horizontal and vertical wells). Numerical reservoir simulation software was used to build the reservoir and aquifer models and to carry out the CO2 injection and oil recovery. The injected CO2 will migrate from the aquifer to the oil zone and the oil will be produced through oil producers. Different combination between CO2 injectors and oil producers will be used to maximize the amount of stored CO2 and the oil recovery. The simulation results showed that CO2 can be stored in saline aquifers underlying oil reservoirs. The saline aquifer will start releasing CO2 to the oil zone after it gets saturated with CO2. The aquifer dissolved 5% of its volume CO2 and after this saturation whatever CO2 injected migrated to the oil zone and reduced the viscosity of oil and increased the oil recovery. Horizontal well gave better storage capacity and also gave better recovery compared to vertical wells. The oil recovery increased by 75 % of the residual oil using this method after seawater injection.