Abstract

The goal of solvent-steam-flooding is enhancing bitumen recovery by the simultaneous development of miscibility and reduction of oil viscosity. Though this strategy reduces greenhouse gas emissions, solvents are expensive. Additionally, bitumen recovery performance is affected by oil/solvent/clay/asphaltene interactions on pore-scale. The solvent dose and type must be optimized to maximize recovery, while minimizing environmental impacts and operational costs. To investigate the performance of solvent-steam processes, six core flooding experiments were conducted on a Canadian bitumen sample with 8.8°API and 54,000 cP. Propane-steam flooding was tested and compared to steam-flooding. The effect of reservoir clays is studied by repeating experiments without clay addition. Three propane flowrates were tested to examine the impact of solvent dosages. After the experiments, asphaltene, clay, viscosity, and water content in produced oil were measured. Propane-steam flooding increased recovery factors, accelerated production, and had higher quality oil than steam-flooding. The lowest propane flowrate (1:9 vol/vol) improved oil recovery by 23%, indicating that higher solvent concentration may not be needed. This work reveals that bitumen microscopic displacement efficiency is enhanced by up to 88% with the addition of solvent to steam flooding. It is proposed that pore-scale interactions, solvent flowrate, and clays also highly influence produced oil quality and oil recovery rates.

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