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Using a pore-network simulator we study pattern formation in reverse filtration combustion in porous media. The two-dimensional pore network includes all relevant pore-level mechanisms, including heat transfer through the pore space and the solid matrix, fluid and mass transfer through the pore space, and reaction kinetics of a solid fuel embedded in the pores. Both adiabatic and nonadiabatic cases are considered, the latter modeled with the inclusion of heat losses from the pore network to the ambient. The simulation results show the development of unstable, fingered patterns of the burned fuel, similar to previously reported in the literature in the related problem of reverse combustion in a Hele-Shaw cell. We study the sensitivity of the patterns obtained on a number of parameters, including the Peclet number. The results on finger spacing and finger width are analyzed in terms of a selection principle, similar to that used in the theory for unstable Laplacian growth.

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Summary In this study, the effects of viscosity-reducer (VR) concentration, salinity, water/oil ratio (WOR), and temperature on the performance of emulsions are examined on the basis of the selected VR. Different VR-injection scenarios, including single-VR injection and coinjection of steam and VR, are conducted after steamflooding by use of single-sandpack models. The results show that high VR concentration, high WOR, and low salinity are beneficial to form stable oil/water emulsions. The oil recoveries of steamflooding for bitumen and heavy oil are approximately 31 and 52%, respectively. The subsequent VR flooding gives an incremental oil recovery of 5.2 and 6.4% for bitumen and heavy oil, respectively. Flooding by steam/VR induces an additional oil recovery of 8.4–11.0% for bitumen and 12.1% for heavy oil. High-temperature steam favors the peeling off of oil and improving its fluidity, as well as the in-situ emulsions. VR solution is beneficial for the oil dispersion and further viscosity reduction. The coinjection of high-temperature steam and VR is much more effective for additional oil production in viscous-oil reservoirs.

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