压力对二氧化碳驱油效果影响的实验研究

Experimental Research on the Effect of Pressure on CO_2 Oil Displacement Efficiency

为研究CO_2注入压力对驱油效果的影响规律,在模拟大庆扶杨油层及恒定注采压差条件下,利用细管法进行CO_2驱油实验。研究结果表明:扶杨油层原油与CO_2的最小混相压力为22.5 MPa,注气压力越高,CO_2突破时注气量及采收率、累计采收率、生产气油比及注入能力越大;达到混相驱后,注气压力对CO_2驱油效果影响非常小,但生产气油比明显高于非混相驱。因此,CO_2非混相驱油时,为取得好的驱油效果,应尽可能提高注入压力;混相驱油时,提高注气压力对增加采收率效果不大。CO_2突破后不宜继续进行CO_2驱,应改用其他的开采方式。该项研究在相同注采压差条件下注入压力对驱油效果影响方面取得了突破。

In order to investigate the influence rule of CO2 injection pressure on displacement efficiency, slime tube method was used for CO2 oil displacement experiment to simulate Fuyang oil zone in Daqing oil field under constant injection production pressure difference. The research results show that the minimum miscibility pressure for oil in Fuyang oil zone and CO2 was 22.5 MPa and that higher gas injection pressure resulted in larger gas injection volume, recovery, cumulative recovery, produced gas oil ratio and injectability when CO2 broke through. After miscible displacement began, gas injection pressure had very small influence on oil displacement efficiency of CO2 , but produced gas oil ratio was significantly higher than that during immiscible displacement. Therefore, injection pressure should be increased as much as possible during immiscible CO2 displacement, in order to obtain better oil displacement efficiency. During miscible displacement, increasing gas injection pressure has little influence on recovery ineremem. After breakthrough of CO2 , it is not recommended to continue CO2 displacement but other development method should be used. This research achieved breakthrough in the effect of injection pressure on oil displacement efficiency under the same injection production pressure difference.