EFFECT OF SOLVENT TYPE AND DRAINAGE HEIGHT ON ASPHALTENE PRECIPITATION FOR THE SOLVENT PERCOLATING GRAVITY DRAINAGE MECHANISM IN THE VAPOR EXTRACTION PROCESS

摘要

The problems associated with highly viscous heavy oil reservoirs, excessive heat loss to the surrounding formations, low permeability carbonate reservoirs, and the large amount of CO_2 emitted during thermal processes have made solvent-based heavy oil recovery methods more attractive than thermal methods. In this study, an extensive experimental investigation was carried out to evaluate the effect of solvent type and drainage height, as the key parameters in vapor extraction, on asphaltene precipitation. Two large visual rectangular sand-packed physical models with heights of 24 and 47 cm were employed to conduct the experimental studies. Propane, methane, and a propane/CO_2 mixture were considered as the respective solvents in the experiments. Also, separate experiments were carried out to measure the asphaltene precipitation at different locations in the models. The results show that for almost all of the different solvents used in this study more asphaltene precipitation was observed close to the injection points and at the oil/solvent interface. Comparing the textures of the asphaltene precipitants from different locations in the models, it was found that the precipitants close to the injection points were more brittle, while the precipitants close to the production points were more ductile. After comparing the asphaltene precipitation in the small and large models when various solvents were used, it was observed that in the case of propane injection more asphaltene precipitation was observed at different locations in the physical models.