Quick starting technology of solvent assisted SAGD for oil sand production

Double-horizontal well SAGD technology is a main oil sand production method. To solve the problem that the SAGD preheating starting time is long, the mode of solvent injection before steam cycle is adopted to shorten the preheating time and improve the steam utilization efficiency. The viscosity reducing efficiency after the mixing of solvent and crude oil was tested. Then, the solvent injection performance was studied using the one-dimensional sand pack model. In addition, the different preheating starting modes were experimentally studied using the three-dimensional physical model, to analyze the change laws of temperature field and pressure field over the time in different SAGD starting modes. Finally, SAGD starting mode and technological parameter optimization were carried out on the Canadian oil sand. It is indicated that the solvent can reduce the oil viscosity greatly and solvent pre-injection can improve the steam injection capacity. The steam-solvent combined cycle starting time along the way is reduced by 15% on average and the steam injection volume is reduced by 21.4%. The comparative study by means of the numerical reservoir simulation method shows that after the injection of solvent, it takes 90 d which is 50% shorter to reach the interwell temperature of 80 ℃. In conclusion, the application of the steam-solvent combined cycle starting technology can effectively improve the starting efficiency of Canadian oil sand production and reduce the costs greatly.