CO2 injection for boosting pressure and displacing oil has become a potential method with which to enhance the recovery. Crude oil extraction and displacement experiments by CO2 injection were conducted to study the CO2-crude oil interaction and displacement effect. Additionally, numerical simulations were performed to optimize and predict its in-situ efficacy. Results show that CO2 is superior to hydrocarbon gases in terms of the extraction capacity for crude oil and its volumetric extraction ratio reaches 85.2%; however, if there is no CO2-crude oil convection, the efficacy decreases significantly. In heterogeneous cores, oil displacement efficiency of CO2 reaches 85.2%, which is higher than those of hydrocarbon gases; in spite of this, CO2 does not readily displace crude oil from the matrix in the matrix-fracture model and the crude oil recovery is only 20.0% after continuous CO2 injection-soaking; CO2 puff-n-huff can leverage the mass transfer effect between CO2 and crude oil in the fractures, which further enhances the recovery by 69.2% and results in a total recovery of 89.2%; the larger the differential pressure, the higher the oil extraction efficiency through CO2 puff-n-huff. After applying CO2 puff-n-huff and displacement in oilfield A, the recovery is expected to increase by 20.0%.
Hu et al. (Sat,) studied this question.
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