Numerical simulation of foamy-oil flow in a cyclic solvent injection process

Abstract

Cyclic solvent injection (CSI) has emerged as a promising and environment-friendly heavy oil production process. One of its main recovery mechanisms is foamy-oil flow. This study first experimentally observes the foamy-oil flow under reservoir conditions in a sand-packed CSI test, and then theoretically interpret the flow pattern through mathematical modeling. Finally, the oil recovery mechanisms of CSI are investigated. Results show that foamy oil flows in an intermittent instead of continuous manner during the production period. Multiple waves of foamy oil start from the transition zone and push oil toward the producer. This is well predicted by our newly developed theoretical model: the oil and gas productions increase stepwise during a production period. Besides, the foamy-oil flow occurred 2–4 times, which is because the position of equilibrium state in the transition zone keeps changing during the pressure drawdown process. Moreover, larger diffusivity, higher initial solvent content, slower pressure depletion, and slower formation rate of free gas leads to more waves of foamy-oil flow and higher oil production. This study provides some meaningful insights into foamy-oil flow process, as well as cleaner recovery of heavy oil reserves through solvent-based technique.