Study On Multistage Profile Control In Steam Stimulation At High Water Cut Stage

During steam stimulation, high permeability zones will change into strong gas suction ones and the amount of gas intake in low permeability zones will be little and even none, under the influence of the maldevelopment of barriers, permeability contrast between layers and steam overriding and so on. With the increase of steam stimulation rounds, the effect of steam stimulation will decline because of the further influence of the phenomenon of gas breakthrough and well interference. However the most effective method is employing high-temperature chemical plugging agent to block high permeability zones and gas breakthrough channels, adjust the gas intake profile of oil zones; tap the potential of low permeability zones and at last to improve the effect of steam stimulation.Through foam static evaluation tests in the laboratory, a foam agent named DHG-1 that can resist high temperature and high salt is optimized among manifold ones. And an optimized prescription of tannin extract system is got through performance appraisal experiments. Then a new type of composite plugging agent that can resist high temperature– tannin extract and foam system will be got with the blend of the two systems.Through static evaluation tests in the laboratory, the effect of component concentration, salinity, temperature etc. on the new type composite plugging agent is studied. Then the rules of the system flows in the porous media are studied, the effect of gas liquid ratio, permeability, injection regime on the system's blocking ability and the influence of different permeability contrast, oil saturation on the system's profile controlling and diversion are analyzed through physical model tests. The blocking ability is the best when employing the system under continuous injection pattern and 1:1 for gas liquid ratio, and the system's ability of profile controlling and diversion will decline with the increase of permeability contrast. Though crude oil will play a negative role in the system's ability of profile controlling and diversion, the system still have effective effect on profile controlling and diversion under the same condition through comparative experiments. In addition, with respect to single foam system, the tannin extract in the tannin extract and foam system will lead to secondary blocking after it generates, and this will certainly enhance the system's effect on diversion and profile controlling.Finally, through comparative experiments on the ability of blocking, we can draw a conclusion that tannin extract and foam system is the optimized plugging agent when temperature ranges from 150℃to 250℃, and tannin extract system is the best one when temperature is greater than 250℃. According to the characteristics of tannin extract system and tannin extract & foam systems, field plans of multistage profile controlling are designed.