页岩油CO_(2)非混相吞吐与埋存实验及影响因素

Experiment and influencing factors of CO_(2)immiscible huff-and-puff and sequestration for shale oil

将CO_(2)注入页岩,不但能提高页岩油采收率,还能达到埋存CO_(2)的目的,但CO_(2)吞吐和埋存的影响因素较多且相互作用。为搞清楚页岩油CO_(2)非混相吞吐与埋存特征,通过开展页岩岩心CO_(2)吞吐、吸附实验,定量评价了CO_(2)注入压力、CO_(2)相态类型、储层温度、闷井时间、裂缝、吞吐次数对CO_(2)吞吐效果以及颗粒直径、CO_(2)注入压力、储层温度对CO_(2)埋存效果的影响程度。研究表明:增大注入压力不但有利于CO_(2)吞吐,还能增大吸附量;增加注入压力会诱导天然微裂缝的扩展、延伸,有利于扩大CO_(2)波及面积,减小原油渗流阻力;当储层温度小于50℃时,温度升高有利于提高吞吐采收率,但会降低CO_(2)吸附量;当温度大于等于50℃时,温度升高不利于CO_(2)吞吐和埋存;在超临界条件(7.4 MPa、31℃)下CO_(2)吞吐采收率最大,最佳闷井时间为10 h左右;裂缝扩展有助于提高吞吐采收率,CO_(2)吸附量受页岩颗粒直径影响很小。研究成果可为鄂尔多斯盆地页岩油CO_(2)吞吐及埋存提供借鉴。

CO_(2)injection into shale can not only improve the recovery of shale oil,but also achieve the purpose of CO_(2)storage.However,there are many and interactive factors affecting CO_(2)huff-and-puff and CO_(2)storage effect of shale oil.Through CO_(2)huff-and-puff and adsorption experiments of shale core,the influence of CO_(2)injection pressure,phase type,reservoir temperature,soaking time,fracture and huff-and-puff times on CO_(2)huff-and-puff effect,as well as the influence of particle diameter,CO_(2)injection pressure and temperature on CO_(2)sequestration effect are evaluated quantitatively.The results show that increasing CO_(2)injection pressure not only is conducive to CO_(2)huffand-puff,but also can increase CO_(2)adsorption.Increasing injection pressure may induce the propagation and extension of natural microfractures,which is conducive to expanding CO_(2)sweep area and reducing oil flow resistance.When reservoir temperature is<50℃,the increase of temperature is conducive to increasing recovery of CO_(2)huffand-puff but decreases adsorption capacity,while when the temperature is≥50℃,the increase of temperature is not conducive to CO_(2)huff-and-puff and sequestration.Under supercritical conditions(7.4 MPa,31℃),the recovery rate of CO_(2)huff-and-puff is the highest,and the optimal soaking time is about 10 h.Fractures propagation is helpful for improving recovery rate of huff-and-puff.CO_(2)adsorption capacity is little affected by diameter of shale particles.The research provides reference for CO_(2)huff-and-puff and sequestration of shale oil in Ordos Basin.