Experimental study of asphaltene deposition as well as heavy oil recovery via CO ₂ flooding

Asphaltene deposition during CO 2 flooding and its effects on oil recovery were experimentally investigated using a high-pressure microscopic porous test cell at reservoir temperature of 80°C and pressures of 2 MPa, 6 MPa, and 10 MPa. CO 2 flooding led to significant asphaltene deposition under higher pressures (6 MPa and 10 MPa), while no deposition occurred at 2 MPa. The amount, outset, and particle sizes of deposition were greater under higher pressure. In addition, the significant dynamics of oil/gas interfaces and the simultaneous deposition experimentally indicated that the deposition was closely related to CO 2 dissolution. Concerning the oil production, it was pointed out that 48%, 64%, and 38% of the initially existing oil volume have been produced at pressures of 2 MPa, 6 MPa, and 10 MPa, respectively. Sufficient dissolution between oil and gas enhances oil recovery. However, severe asphaltene deposition clogs throats and reduces sweep efficiency and oil recovery. Therefore, oil recovery was positively and negatively impacted by CO 2 dissolution and asphaltene deposition, respectively.