Study On The Production Mechanism Of Flue Gas–Solvent Assisted SAGD

Steam assisted gravity drainage(SAGD) is with high steam injection intensity, excessive thermal energy losses and low oil to steam ratio, the improved technology includes Steam and Gas Push technology(SAGP) and Expanding Solvent Assisted SAGD technology(ES-SAGD). The fommer one can reduce the thermal losses, decrease steam intensity and improve oil to steam ratio, howewer its ability to increase oil production is limited. The latter one can increase oil production rate, enhance oil displacement efficiency and improve oil to steam ratio, however, there are some issues related to the serious overlap phenomenon of steam and excessive thermal energy losses. Therefore, the feasibility, production mechanism and injection–production parameters are investigated in this paper further to provide theory basis for pilot test and promotion.The property between flue gas/ solvent and Xinjiang super heavy oil is investigated by laboratory experiment. The results show that under experimental temperature and pressure, the maximum volume factor of crude oil with flue gas is 1.04, the maximum viscosity reduction rate is 54.14%. The effect of solvent concentration and temperature on viscosity reduction are researched, at last, the optimized solvent is n–hexane. Compared with flue gas, n-hexane reduces surface tension significantly. It showes that in SAGD process, added proper amount of solvent can enhance the gravity drainage process effect. Steam flooding, flue gas assisted steam flooding, solvent assisted flooding and flue gas-solvent assisted steam flooding are taken place to research the displacement pressure difference, oil displacement efficiency, oil displacement velocity and componet variation of collected oil and sand residual oil. The results show that with added flue gas and solvent, the light component content of produed oil increases, meanwhile heavy componet decreases. The oil displacement effect of flue gas-solvent assisted steam flooding is better than steam flooding, flue gas assisted steam flooding and solvent assisted flooding. Flue gas has smaller impact on the componet of crude oil, wheares, solvent is the opposite. Under similar compatible principle, dissolved solvent can change the structure of colloid and asphaltene, make the asphaltene molecules together, therefore asphaltene weight inecreases and its flow ability decreases. At last, fluid phase behavior is matched by CMG’s Winprop module, which provides basic property parameters for flue gas-solvent assisted SAGD numerical simulation. Combined with the reservoir rock and fluid property parameters of SAGD pilot zone Zhong 32 area in Xinjiang oilfield, the numerical simulation model of flue gas-solvent assisted SAGD is created. After analyzed the effect of added flue gas and solvent on steam chamber expansion, it showes that along the horizontal cross section is divided into six zones, they are steam zone, steam condensation zone, non-condensable zone, solvent-rich zone, mobile oil zone and immobile oil zone. In order to optimize injection-production parameters, the profit function is established. Considering the production performance and economic profit, the optimization results are: solvent concentration(volume fraction) is 10%, production-injection ratio is 1.2, total fluid injection rate is 200m3/d, injection time of solvent is 8 years after preheating period, injection volume of flue gas is 0.3 pore volume and injection time of flue gas is after preheating period.