Experimental study on the expansion of foamy bitumen for CO2 huff-n-puff process

This study investigates the feasibility of cold in-situ bitumen recovery using a CO 2 huff-n-puff process, focusing on foam swelling and expansion under reservoir conditions. Experiments simulate CO 2 injection into Canadian bitumen at pressures of 2–4 MPa and temperatures of 5–55 °C to obtain swelling factors in the huff stage and expansion factors in the puff stage. Additional tests using a 1:1 M CO 2 -N 2 mixture, pure N 2 , and pure O 2 at 4 MPa and 25 °C provide comparative insights. Gas solubility in bitumen is assessed using PROPATH, the Peng–Robinson equation of state (EOS), and the Soave–Redlich–Kwong EOS. Results indicate that foam expansion is the dominant recovery mechanism, particularly at 4 MPa at 25 °C and 3–4 MPa at 5–15 °C, where expansion factors range from 9.7 to 10.7, independent of CO 2 solubility anomalies. CO 2 huff-n-puff also outperforms other gases, with expansion increasing proportionally to CO 2 concentration. With bitumen expansion exceeding 10 times its initial volume, an estimated 66.7–88.9 % of the bitumen in place is expelled from the reservoir's pore space, enhancing recovery efficiency. The findings validate the feasibility of cold production techniques, demonstrating that optimal temperature and pressure conditions can be naturally achieved in Canada. This makes CO 2 huff-n-puff a practical and efficient method for improving bitumen extraction, offering a promising alternative or complement to conventional thermal recovery processes. • Carbon dioxide dissolves better in bitumen at high pressure and low temperature. • Three models effectively estimate gas solubility in bitumen. • Bitumen expands most with cooler temperatures; pressure has a smaller effect. • A specific pressure-temperature range gives a peak expansion of 9.7–10.7 times. • Carbon dioxide recovers up to 89 % of bitumen, better than nitrogen or oxygen.