Use of Air with Methane in Cyclic Solvent Injection Applications for Improved Foam Stability and Cost Effective Heavy Oil Recovery

摘要

The cornerstone of foamy oil behavior during cyclic solvent injection (CSI) is its stability, of which depends on parameters such as oil viscosity, temperature, dissolved gas ratio, pressure decline rate, and dissolved gas (solvent) composition. Although the process has been investigated and analyzed for different parameters in the literature, the optimal conditions for an effective and more economical process (mainly foamy oil stability) has not been thoroughly understood, especially for secondary recovery conditions. In this study, air has been used as an ameliorative to improve foamy oil stability during CSI. Four pressure-depletion tests were performed, each of them consisting of five consecutive cycles. It was observed that increasing pressure-depletion rates increased the formation of foamy oil; however, when pressure-depletion rates were too high, it may have caused a negative effect in the final oil recovery factor by CSI. Injecting air into the sandpack caused an increase in the viscosity of heavy oil, and the subsequent injection of methane as a solvent became more effective in generating a more stable foamy oil, which resulted in obtaining a higher oil recovery factor.