CO 2 huff and puff for heavy oil recovery after primary production

In this study, micromodel tests were performed to investigate the microscopic flow behavior during primary production and the subsequent CO 2 huff and puff. A series of 12 tests was conducted in sandpacks to evaluate the effects of the injection and production parameters on the displacement efficiency of the CO 2 huff and puff. The micromodel tests and sandpack tests showed that the flow characteristics of CO 2 huff‐and‐puff process was significantly affected by the pressure of converting the solution gas drive to the subsequent CO 2 huff and puff. A foamy oil flow could be more easily formed in the production period of the CO 2 huff and puff with a higher conversion pressure. Foamy oil can reduce the mobility of gas and provide tremendous energy to the system, thereby improving the performance of the CO 2 huff and puff. The sandpack flood results show that the oil recovery of the solution gas drive decreased as the conversion pressure increased, whereas the oil recovery of the CO 2 huff and puff increased as the conversion pressure increased. The highest total oil recovery was obtained at the pseudo‐bubblepoint pressure. The oil recovery of the CO 2 huff and puff increased as the CO 2 injection pressure and pressure decline rate increased. The oil recovery of CO 2 huff and puff increased with the soaking time, and it exhibits a significant change when the soaking time ranges from 10 h to 24 h; above this value, the increase become slight. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd