Preliminary Investigation on Impacts of Temperature, Pressure, Viscosity, and Solubility on Expansion of CO₂-Based Foamy Bitumen

The current thermal recovery processes of bitumen consume tremendous amounts of water and energy and even emit greenhouse gases (GHGs). As a solution, this study proposes a cold bitumen recovery that adapts the CO₂ huff-n-puff process combined with horizontal wells and gravity drainage on the premise that CO₂ gas is more soluble in bitumen at lower temperatures. This process generates CO₂-based foamy bitumen, introduces swelling phenomenon in the huff stage due to CO₂ dissolution in the bitumen phase, and provides foam expansion in the puff stage because of CO₂ liberation. Due to pressure differences, gravity, and foam expansion, foamy bitumen is drained into the production well. Therefore, the current study aims to evaluate the potential of this method after the impacts of important parameters on the foam expansion such as temperature, pressure, viscosity, and solubility are investigated. The studied conditions are 2, 3, and 4 MPa of CO₂ injection pressure under temperatures of 25, 35, 45, and 55 °C. The results from the adapted CO₂ huff-n-puff experiment show that the solubility of CO₂ in bitumen increases at higher injecting pressures and lower temperatures. The highest expansion factors which are about 9 were obtained at the highest injecting pressure at 25 and 35 °C followed by the expansion from 3 MPa injecting pressure at 45 and 55 °C. The third place is shared by the injecting pressure of 3 MPa at 25 and 35 °C and injecting pressure of 4 MPa at 45 and 55 °C. The lowest expansion factor was obtained at the lowest injecting pressure at the highest temperature. These peculiar results indicate that temperature, pressure, viscosity, and solubility possess unique roles and strongly influence each other in a certain manner that can either benefit or hinder the foam expansion. It also depicts that with a harmonious and optimal combination of all these parameters, a high expansion of CO₂-based foamy bitumen is achievable. Besides, the current highest expansion factor of this study proves that this cold production is theoretically capable of driving bitumen out of the pore spaces even without the assistance of gravity drainage or any form of heating.