Vapor extraction (VAPEX) has been proposed as an alternative for heavy-oil recovery in reservoirs where thermal methods face technical and economic problems. In VAPEX, a pair of horizontal injector-producer wells is employed. The gaseous hydrocarbon solvent (normally propane or a mixture of methane-propane or propanebutane) is injected from the top well and the diluted oil drains downward by gravity to the bottom producer. Recently, the idea of incorporation of CO 2 into the gaseous hydrocarbon

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... mixture has emerged. Incorporation of CO 2 is believed to make the process more economical and environmentally and technically attractive. CO 2 is cheaper than the hydrocarbon gases and has higher solubility into the heavy oil than most of the hydrocarbon gases. It also adds value to the environmental side of the process as CO 2 can be sequestered while improving the VAPEX performance at the same time. Moreover, the addition of CO 2 to the injected gas increases the dew point of the solvent mixture, and solvent mixtures with higher dew point can be used in heavy-oil reservoirs with higher pressure in which the mixture of hydrocarbon gases may partly condense, which decreases the VAPEX efficacy. Thus, the advantage of incorporating CO 2 into the injected solvent is threefold. The objective of this work, therefore, is to simulate the performance of the VAPEX process when different solvent mixtures, including hydrocarbon gases and CO 2 , are incorporated with the aim of improving its performance. The design and the major results of the simulation for the CO 2 -based VAPEX process are discussed.