Study On Canadian SAGD Oil Sands Emulsion Dehydration Process

The development of Canadian oil sands has two technical options open-pit mining and in-situ thermal. SAGD technology is less destructive and environmental friendly, thus it is widely used in Canada. SAGD emulsion is multiple emulsion. Due to high viscosity, low density difference and strong stability, demulsification of such emulsion is difficult.Based on the viscosity-temperature curve, the feasible treatment temperature of 120℃ is deduced so as to reduce diluent loss and recover more thermal energy. And, dilution experiments have proved that n-heptane and naphtha have different dehydration mechanism. For n-heptane dilution a solvent/bitumen ratio about 1.8 is enough to settle all water and sands. However, the sediment is likely to block the equipment. Hence, it is not used in SAGD operation. While a dilution ration of 20% naphtha is enough to reduce the viscosity and increase the density difference to facilitate dehydration. Thus, diluent and dilution ratio is determined for SAGD emulsion processing.Large amounts of demulsifier selection experiments have proved that the collected demulsifiers at home and abroad are not suitable for SAGD emulsion treatment. Thus, if thermo-chemical settling dehydration process is applied effective demulsifiers and reverse demulsifers need to be developed to improve dehydration efficiency.Electrostatic dehydration experiments have proved electrostatic coalescence is effective for small droplet coalescence. It is found that DC electrostatic field is more efficient than AC. And, with 1000V/cm DC electrostatic field strength and 90 min retention time, the water content can be lowered to 0.5%.Thus, based on experiment research a dehydration process is proposed: Demulsifying at wellhead, degassing at the inlet of central processing plant while diluting 20% naphtha at the outlet of degasser. Then, with reverse demulsifier addition emulsion is directed to FWKO operating at 120℃ with 20-30 retention time. Electrostatic treater is applied after FWKO with 1000V/cm DC electrostatic field strength and 90 min retention time.