Experimental Investigation of CO2 Utilization as an Injection Solvent in Vapour Extraction (VAPEX) Process

Abstract

Abstract In this research, an extensive experimental investigation is carried out to evaluate the utilization of CO 2 as an injection solvent for VAPEX process. To accomplish this goal, two large, visual rectangular, sand-packed VAPEX models with 24.5 cm and 47.5 cm heights were employed to run the experiments using Plover Lake heavy oil (5650 cP) with a low permeability (6∼9 D) sand pack. Propane, CO 2 and propane/CO 2 mixture were considered as respective solvents for the experiments, and a total of 6 tests were carried out. The heavy oil production rate and the produced gas-oil ratio were measured periodically. Moreover, separate experiments were carried out at the end of each VAPEX experiment to measure the asphaltene precipitation at various locations of the VAPEX models. To observe the drainage height effect in more details, a comprehensive image analysis was performed during the solvent chamber evolution. As a result, it was determined that drainage height has a significant impact on production rate and heavy oil recovery. The results prove the complexity of the effect of drainage height and the up- scaling issues with the VAPEX process. Furthermore, in terms of solvents, propane showed the highest recovery factor of 75% of original oil in place due to its favourable low vapour pressure and high solubility. Ultimately, the promising recovery performance after introducing CO 2 as a carrier gas was observed, the recovery factor of 55% of original oil in place was achieved when the mixture of propane/CO 2 was used as the solvent. After conducting asphaltene measurement tests, it was observed that more asphaltene precipitation occurred close to the injection points and at the oil/solvent interface. Furthermore, the image analysis revealed that the highest sweep efficiency was observed to be 0.86 after injecting propane, followed by propane/CO 2 mixture, and pure CO 2 .