MECHANICS AND UP SCALING OF HEAVY OIL BITUMEN RECOVERY BY STEAM OVER SOLVENT INJECTION IN FRACTURED RESERVOIRS (SOS FR) METHOD

Recently, steam‑over‑solvent injection in fractured reservoirs (SOS‑FR) method was proposed to be a potential solution for efficient heavy‑oil/bitumen recovery. The method is based on injection steam initially followed by solvent. In the third cycle, steam is injected again to recover more oil. Solvent retrieval during the third cycle was observed to be very fast if the temperature is around the boiling point of solvent. This process is controlled by efficient matrix recovery and the mechanisms and the physics of the process are needed clarifications to further determine the efficient application conditions for given matrix and oil characteristics. Single matrix behavior during the process was numerically modeled for static and dynamic conditions and the results were matched with the experimental observations for different matrix wettability, oil viscosity, solvent type, and matrix boundary conditions (co‑ or counter‑current transfer). The physics of the recovery mechanism was analyzed through visual inspection of saturation, temperature, and concentration profiles during each cycle. Then, an efficiency analysis was performed by determining the optimal heating time, solvent soaking period, solvent retrieval time for different matrix characteristics, most importantly matrix size, to maximize the recovery time and minimize matrix residual oil saturation. Next, an up‑scaling analysis was performed. The initial matrix size was 1.5x3 inch for verification of the model with the same size experimental core. The critical parameters that control the matrix‑fracture transfer of heat, solvent, and water were determined at different scales (for different matrix sizes) and up‑scaling parameters (diffusion and dispersion coefficients for heat, mass and volume transfer) were determined. This work provides practical information (especially the amount of injectant needed and time required to recover targeted oil) for field scale application of heavy‑oil/bitumen recovery from fractured reservoirs, especially oil‑wet carbonates.