Practical Approach for Formation Damage Control in CO2 Gas Flooding in Asphaltenic Crude Systems

CO2 flooding has become a strategic tool for enhanced oil recovery and reservoir management in mature fields. This technique, however, is rarely utilized in asphaltenic crude oil systems, due to the likely occurrence of high asphaltene precipitation. The effect of asphaltene concentrations and CO2 injection pressures has mostly been the focus of studies in determining asphaltene precipitation rates. However, asphaltene precipitation is not the only direct factor to be considered in predicting the extent of damage in an asphaltenic crude oil system. In this study, a compositional reservoir simulation was conducted using Eclipse 300 to investigate the injection pressure at which asphaltene-induced formation damage can be avoided during both miscible and immiscible CO2 flooding in an asphaltenic crude system. Simulation results indicate that asphaltene-induced permeability reduction exceeded 35% in most affected zones, with a corresponding drop in injectivity of 28%. Cumulative oil recovery improved by 19% compared to base cases without CO2 injection, achieving peak recovery after approximately 4200 days of simulation time. As CO2 was injected below the minimum miscibility pressure of 2079.2 psi, a significantly lower asphaltene precipitation was observed near the injector. This could be attributed to the stripping of lighter hydrocarbon components (C2–C7+) occurring in the transition zone at the gas–oil interface. Injecting CO2 at pressures above the minimum miscibility pressure resulted in precipitation occurring throughout the entire reservoir at 3200 psia and 1000 bbls per day injection rates. An increase in the injection rate at pressures above the minimum miscibility pressure increased the rate of precipitation. However, a further increase in the injection rate from 1000 bbl per day to 4200 bbl per day resulted in a decrease in asphaltene. The pressure drop in the water phase caused by pore throat increase demonstrated that water injection was effective in removing asphaltene deposits and restoring permeability. This work provides critical insights into optimizing CO2 injection strategies to enhance oil recovery while minimizing asphaltene-induced formation damage in heavy oil reservoirs.