Laboratory investigation of the gradual asphaltene precipitation and mineral re-deposition from injection to production spot during varying concentration of CO₂ injection in an Iranian carbonate reservoir: A novel insight into CO₂ enhanced oil recove

This study investigates the effects of CO₂ and flue gas injection on asphaltene deposition and mineral dissolution in an Iranian carbonate reservoir with an initial pressure of 4100.0 psi and a temperature of 74.0°C. Four representative carbonate core plugs were used in flooding experiments—first as a composite core and then individually—to evaluate asphaltene precipitation from the injection to production points. Static dissolution effects were analyzed using SEM imaging, while dynamic impacts were assessed through gas flooding tests in the presence of formation water. Slim-tube simulations (PVTi in ECLIPSE software) determined the minimum miscibility pressure (MMP) for different injectants: CO₂ (3134.0 psi), Flue Gas 1 (20.00 % CO₂/80.00 % N₂; 6190.0 psi), Flue Gas 2 (40.00 % CO₂/60.00 % N₂; 5420.0 psi), and Flue Gas 3 (60.00 % CO₂/40.00 % N₂; 4740.0 psi). SEM analysis and gas mobility trends confirmed significant rock dissolution under reservoir conditions, indicating that permeability impairment during flooding resulted exclusively from asphaltene deposition. Damage severity was quantified via cyclohexane mobility, showing permeability reductions of 30.79% (CO₂), 7.64 % (Flue Gas 1), 10.13 % (Flue Gas 2), and 18.08 % (Flue Gas 3), with higher CO₂ concentrations correlating to greater asphaltene deposition. Individual plug assessments using the residual resistance factor (RRF) revealed higher asphaltene accumulation near injection points due to direct gas-oil contact, while production-end oil flowed without significant deposition. Despite stronger asphaltene effects during CO₂ injection, it achieved superior oil recovery (64.00 %) compared to Flue Gas 1 (33.00%), 2 (41.00%), and 3 (54.00 %). This is attributed to CO₂’s ability to reduce oil viscosity, lower interfacial tension, and enhance oil swelling.