Performance enhancement of VAPEX by temporal variation of solvent injection pressure

Vapor extraction (VAPEX) is a solvent-based process for the recovery of oil sands. The objective of this work was to investigate on the enhancement of oil recovery in the VAPEX process by varying the solvent injection pressure with time. To that end, lab-scale experiments were designed and carried out to investigate this concept. Three different simulated mediums with permeabilities of 204, 102 and 51 Darcy; two heavy oils with viscosities of 14,500 mPa s and 20,000 mPa s; and two physical reservoir model heights of 25 and 45 cm were considered. Butane at four different injection pressures close to the dew point was injected for 6–7 h. It was found that the temporal variation of solvent injection pressure enhanced the extraction process significantly; resulting in an increase in live oil production by 20–30%. Pulse changes in pressure were found to be more effective in increasing the production in comparison with other pressure versus time policies. These results demonstrate that the solvent pressure variations potentially enhance the oil recovery process in VAPEX.