Experimental evaluation of carbonated waterflooding: A practical process for enhanced oil recovery and geological CO2 storage

The rapid escalation of anthropogenic CO2 emissions at the same time as the growth in energy demand has brought the importance of CO2 enhanced oil recovery (EOR) into the spotlight. Nevertheless, fundamental problems with conventional CO2 injection have paved the way for practicing other strategies, such as carbonated waterflooding (CWF), i.e., flooding of CO2 dissolved in flood water through the reservoir. In this work, performance of CWF as a joint method of EOR and CO2 storage in an Iranian oil field is examined through sets of coreflooding experiments, conducted at a specified pressure and temperature condition on two different reservoir oil (light and heavy) and rock (carbonate and sandstone) samples from the investigated oil field. In summary, CWF improved the oil recovery as compared to waterflooding (WF). Average recovery factors (RFs) for CWG ranged from 6.4% to 13.6% when implemented as a secondary recovery technique and 4.2% to 4.8% when used as a tertiary recovery technique. This improvement was also higher in the carbonate rock than in the sandstone one, slightly higher with light oil than with heavy oil, and lower when a more saline brine was used for carbonated water preparation. CWF also showed to be more effective when implemented in a mixed-wet system than in a water-wet one. Moreover, considerable amounts (about 42‒60%) of the CO2 injected through the flooding brine were ultimately stored in the porous media. Finally, a co-optimizing function was used as a standard for coupling CO2 EOR and storage. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd.