X油田CO_2辅助蒸汽吞吐技术提高采收率研究

Study on improvement of oil recovery of X oilfield by CO_2-assisted steam stimulation technology

X油田九区齐古组浅层油藏由于原油黏度高、非均质性强、地层能量低,导致油藏投产以来蒸汽吞吐效果一直较差。针对在蒸汽吞吐开发过程中出现的蒸汽超覆及汽窜等现象,采用了CO_2辅助蒸汽吞吐采油技术。通过PVT高压物性试验,研究了CO_2的作用机理,结果表明:注入CO_2可以增加原油膨胀能、降低原油黏度、降低油水界面张力、调整注气剖面,因此蒸汽伴注CO_2较单纯的蒸汽吞吐效果好。对该区块进行了CO_2辅助蒸汽吞吐技术矿场试验,试验井组单周期累计增油量为8 792 t,措施井平均含水率降低了20%,生产天数延长90 d。试验结果说明CO_2辅助蒸汽吞吐技术可以提高该区块采收率,增产效果较为明显。

The shallow oil reservoir of Qigu group in nine-block,X oilfield has high crude oil viscosity,great heterogeneity and low producing energy,which makes the recovery factor of steam stimulation low. Aiming at the steam overlap and steam channeling occurred in steam stimulation,CO_2-assistant steam stimulation is applied to enhance oil recovery. The mechanism of CO_2 action is studied through PVT lab test,and the results show that CO_2 injection can increase the oil expansion energy,reduce the viscosity of crude oil,decrease the oil-water interfacial tension and adjust the profile of gas injection,therefore,the effect of CO_2-assistant steam stimulation is superior to that of simple steam stimulation. The field experiments of CO_2-assistant steam stimulation have been carried out at this block. The accumulative oil increment of test well group is up to 8 792 tones and the average water content of the measure well is reduced by 20%,the production day extends 90 days which indicate that the CO_2-assistant steam stimulation technology can enhance oil recovery in this area and the yield increasing effect is obvious.