Propane-Bitumen Interactions during Cyclic Solvent InjectionA Cold Lake Case Study

Common bitumen recovery processes, such as steam-assistedgravitydrainage (SAGD) and vapor extraction (VAPEX), are not suitable forthin reservoirs due to the heavy consumption of water and heat andthe lack of a gravity drainage mechanism. As an alternative, cyclicsolvent injection (CSI) at low temperatures has been developed asa more sustainable and energy-efficient technique for bitumen recoveryfrom oil-sand reservoirs. This study aims to conduct specific CSIexperiments to address the following questions: (1) How does the propanephase affect bitumen recovery? (2) What mechanisms control bitumenrecovery at different propane phases? We synthesized core plugs fromin situ oil-sand and bitumen samples of the Clearwater Formation atCold Lake. Three CSI experiments were conducted by liquid propane(C-3,C-L), two-phase propane (C-3,C-V-L), andvapor propane (C-3,C-V) in a state-of-the-art visualizationcell equipped with a camera and a digital pressure transducer. Wecalculated the bitumen recovery factor (RFb) by the weight-balancemethod and analyzed the pressure profiles and images from the coreface during the three experiments. The results show that RFb by C-3,C-V is higher than that by C-3,C-L. In addition,we observed that when CSI is conducted by C-3,C-L, the coreface is plugged by asphaltene deposition. Furthermore, in CSI by C-3,C-L, limited bitumen recovery occurs when pressure is droppedbelow the saturation pressure of propane during depletion. The resultsalso suggest that the combination of asphaltene deposition, solutiongas drive, oil extraction, and production under wormhole support arethe mechanisms controlling bitumen recovery from oil-sand cores.