A new environmentally friendly aqueous solution was developed to enhance recovery of bitumen from oil sands. The new solvent is water-based fluid with surfactants as the main component. The solvent can reduce the interfacial tension and change the wettability of the rock surface, which improves the efficiency and production of heavy oil recovery.
Extraction tests were conducted to evaluate the performance of the solution by soaking the oil sands with the solvent at different temperatures and times. Meanwhile, the composition of the new solvent was continuously adjusted to enhance recovery. Then, coreflood tests were conducted to evaluate the new solvent on recovery of heavy crude oil from Canada. Berea sandstone cores, with an initial permeability of 60 md, were used to conduct the coreflood tests. The cores were 6-inch length and 1.5-inch diameter. When the cores were fully saturated with heavy oil, the whole setup was placed in the oven at the designated temperature and heated for 24 hours to reach equilibrium. Then the cores were flushed with various fluids at a flow rate of 5 cm3/min. Core effluent samples were collected and the amount of crude oil was determined through the extraction method.
For the bitumen extraction tests, the first generation of the new solvent can only extract about 80% of the total bitumen at 70°C after 5 minutes soaking. About 90% of recovery was achieved at 90°C with the same solvent. The final generation of the solvent could extract 99% of the total bitumen at 70°C. For the coreflood tests, the new solvent recovered almost 90% of the heavy oil at 90°C and nearly 95% at 170°C. Meanwhile, the recovery factor was only 75% by flushing with 5 wt% KCl at 90°C.
This paper will summarize the results obtained and address the methodology of using the new solvent in the field.