Investigation of the Vapex Process Using CT Scanning and Numerical Simulation

摘要

The “Vapex” process, a solvent analogue of Steam-rnAssisted Gravity Drainage, has attracted considerablernattention as a recovery method for heavy oil. However,rnto date, there are still many questions about the naturernand magnitude of basic process mechanisms, andrnwhether the process can produce economic oil rates. Thernexperiments discussed in this paper were aimed atrnquantifying some of the basic mechanisms, in particularrnthe dispersive mixing mechanism. We have performed arnseries of top-down solvent injection experiments underrnvarying conditions, utilizing a CT scanner to monitorrnfluid movements. All of the displacements we havernobserved are gravity-unstable in the early stages, andrncharacterized by viscous fingering of the solvent into thern5,500 cP oil. After solvent breakthrough, therndisplacements become stable, dominated by a singlernsolvent finger which has many of the features of a Vapexrnsolvent chamber. The “mixing parameter” we infer forrnthese experiments using the Butler/Mokrys analytic modelrnis higher than that reported for Hele-Shaw Vapexrnexperiments. An analysis of localized fluid velocities inrnthe experiments using numerical simulation shows thatrnthe enhanced mixing parameter can be understood as arnconsequence of convective dispersion in the porousrnmedium. By adjusting the amount of physical dispersion,rnthe simulations can match breakthrough time, postbreakthroughrnoil rates, and the general character of thernfingering. A novel type of “quasi-pore-scale” simulationrngrid appears to provide advantages in simulating thernunstable period at the beginning of the displacements.