Technical Paper: Mechanics of Heavy Oil and Bitumen Recovery by Hot Solvent Injection

Society: SPE
Paper Number: 144546
Presentation Date: 2011
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In our earlier works (Pathak et al. 2010; 2011), we presented the initial results for heavy oil and bitumen recovery using heated solvent vapours. The heavy oil and bitumen saturated sand pack samples of different heights were exposed to heated vapours of butane or propane at a constant temperature and pressure for an extended duration of time. The produced oil was analyzed for recovery, asphaltene content, viscosity, composition and refractive index. Recovery was found to be very sensitive to temperature and pressure.

The current work was undertaken to better understand the physics of the process and to explain the observations of the earlier experiments using additional experiments on tighter samples of different sizes, numerical simulation and visualization experiments. The effects of temperature and pressure on the recovery were studied using a commercial reservoir simulator. Propane and butane were used as solvents. Asphaltene precipitation was also modeled. A qualitative history match with the experiments on different porous media types was achieved by mainly considering the permeability reduction due to asphaltene precipitation, pore plugging, the extent of interaction between solvent and oil phase, and the parameters like model height, vertical permeability and gravity.

To investigate the phenomenon further, visualization experiments were performed. 2-D Hele-Shaw models were constructed by joining two plexiglass sheets from three sides, leaving some space in between to accommodate oil. The models were saturated with heavy-oil and left open from one side and were exposed to different types of solvents from this side. The setup was continuously monitored to observe fluid fronts and asphaltene precipitation.

Using this analysis, the mechanics of the process was clarified from the effect of solvent type on the recovery process. The optimum operating temperature for the hot solvent process and the dominant mechanisms were identified.

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