Pressure maintenance and improving oil recovery with immiscible CO2 injection in thin heavy oil reservoirs

Techniques have been developed to experimentally and numerically evaluate performance of CO2 injection in heavy oil reservoirs for pressure maintenance purpose. More specifically, a three-dimensional (3D) physical model consisting of five vertical wells and three horizontal wells is used to examine the effect of well configurations on pressure maintenance and oil recovery with CO2 injection in heavy oil reservoirs. The initial oil saturation, oil production rate, water cut, gas-oil ratio, ultimate oil recovery, and distribution of residual oil saturation are examined under three well configurations, which can be optimized to maximize heavy oil recovery when CO2 injection is employed for pressure maintenance purpose. Subsequently, numerical simulation has been performed to match the experimental measurements. It has been found that pressure maintenance with CO2 injection is beneficial for oil recovery in heavy oil reservoirs. Compared with the conventional five-spot well configuration, the well configurations associated with horizontal well(s) are found to achieve a better performance, while the well configuration of two horizontal wells (Scenario ♯3) yields the highest oil recovery. The oil recovery of Scenario ♯3 is experimentally determined to be 38.6% of original oil in place (OOIP) after CO2 injection.