Abstract
A need for a reduction in energy intensity and greenhouse gas emissions of bitumen and heavy oil recovery processes has led to the invention of several methods where mass-transfer-based recovery processes in terms of cold or heated solvent injection are used to reduce bitumen viscosity rather than steam injection. Despite the extensive numerical and experimental investigations, the field results are not always aligned to what is predicted unless several history matches are done. These discrepancies can be explained by investigating the mechanisms involved in mass transfer and corresponding viscosity reduction at the pore level. A two-phase multicomponent pore-scale simulator is developed to be used for realistic porous media simulation. The simulator developed predicts the chamber front velocity and chamber propagation in agreement with 2D experimental data in the literature. The simulator is specifically used for vapor extraction (VAPEX) modelling in a 2D porous medium. It was found that the solvent cannot reach its equilibrium value everywhere in the oleic phase confirming the non-equilibrium phase behavior in VAPEX. The equilibrium assumption is found to be invalid for VAPEX processes even at a small scale. The model developed can be used for further investigation of mass transfer-based processes in porous media.
Highlights
Vapor extraction (VAPEX) is the solvent variant of the steam-assisted gravity drainage (SAGD) process which is driven by the solvent diffusion/dispersion mass transfer
The model developed is used for investigating VAPEX process in a 2D porous media as described in the methodology section
A pore-scale simulator was developed for mass transfer in the porous media
Summary
Vapor extraction (VAPEX) is the solvent variant of the steam-assisted gravity drainage (SAGD) process (steam is replaced by solvent) which is driven by the solvent diffusion/dispersion mass transfer In this process, the solvent is injected into a horizontal well at a pressure close to its dew point, and bitumen viscosity is reduced by solvent diffusion/dispersion. The VAPEX process is analogous to SAGD but requires much less energy and is aimed at reducing energy input and greenhouse gas emissions, assuming it is as effective for oil production as steam. It reduces or eliminates the water treatment needed for the SAGD process; this would result in a significant reduction in capital investment and operational cost. VAPEX is beneficial in reservoirs with a gas cap, bottom water, low thermal conductivity, high water saturation, clay swelling, and formation damage [6]
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