CO2-based cyclic solvent injection (CSI) process has shown great potential in enhancing heavy oil recovery while sequestrating CO2 in heavy oil reservoirs. However, the effects of gravity on the CO2-based CSI process have not been comprehensively studied yet. In this work, five groups of CO2-based CSI experiments were implemented using the 1D sand-pack model. Gravity effects were simulated by increasing the angles of the model from 0 to 45 degrees counterclockwise. The experimental results suggest that oil recovery factor decreases with increasing cycle number in all groups. However, in the groups with higher angles, more cycles and higher recovery factors are observed since the decrease rate of oil recovery is slower with increasing cycles. As the angles of the model increase from 0 to 45 degrees, the cycle number in the CO2-based CSI process gradually increases from 5 to 13, and the recovery factor dramatically rises from 29.89% to 76.74%. Moreover, the production stage is divided into three sections: initial rapid GOR decrease section, steady production section, and high GOR section. Experiments with larger angles have a longer steady production section. The main reason for these phenomena is that higher angles bring a more significant gravity effect, which can enlarge the CO2 swept area and drive crude oil in the unswept area to flow to the producer. The experimental results show that the change in model angles does not have an obvious impact on CO2 storage. Analytical models were developed for the prediction of oil recovery considering the effect of gravity in the CO2-based CSI process. This work is the first work to quantitatively characterize the effect of gravity on the EOR potential and the CO2 storage capacity of the CO2-based CSI process. The findings and innovations in this study can provide better references for field development.
Keywords Gravity, EOR, CO2-based cyclic solvent injection, heavy oil, CO2 storage, analytical model