天然气藏CO_2驱及地质埋存技术研究进展

Research progress of CO_2 flooding and geological storage in gas reservoirs

目前,随着CO_2排放量的增加,全球温室效应日趋显著,CO_2的处理问题显得愈加重要。中国现阶段的CO_2埋存点均为油藏或盐水层,将干气藏CO_2驱与其埋存相结合的研究甚少,现场试验更是没有。为此,调研了大量国外的相关研究,综述了目前已有的衰竭干气藏CO_2驱及地质埋存示范工程,并结合已发表的气藏CO_2驱室内实验与数值模拟研究成果,分析了影响CO_2驱提高气藏采收率(EGR)的各个因素,CO_2驱的优缺点及发展方向,以及今后在低渗致密气藏CO_2驱方面应做的工作。结果表明:CO_2埋存于干气藏中安全可靠、存储量大、成本低,同时可采出部分剩余天然气;束缚水可减弱储层非均质性对干气藏CO_2驱的影响;在中高渗气藏中,与气态CO_2驱相比,液态或超临界态CO_2驱效果更好;进行气态CO_2驱开注时气藏压力越小,注入压力和注入速度越大,其提高采收率效果越好。

Nowadays,with the increase of CO_2 emissions,the global greenhouse effect has become increasingly significant,so the disposal of CO_2 become more and more important.While in China all of the projects of CO_2 storage are conducted in oil reservoir or saline formation,there is no project of CO_2 flooding plus CO_2 capture and storage（CCS） in gas reservoirs and little studies about it.By reviewing a large number of studies about this topic,and the existing projects of CO_2 flooding and geological storage projects of depleted gas reservoirs,as well as CO_2 flooding simulation studies,this paper analyzed the affecting factors,the advantages and disadvantages of enhanced gas recovery（EGR） by CO_2 flooding in gas reservoirs,and pointed out that the works should be done when applying it to tight gas reservoirs.The result shows that CO_2 storage in depleted gas reservoirs is reliable,with large storage capacity and low cost,and has some additional economic benefits.Irreducible water can reduce the impact of heterogeneity on EGR.Comparing with the results of gaseous CO_2 flooding in moderate or high permeability gas reservoirs,the effect of liquid or supercritical CO_2 flooding is better.Moreover,the later the start time of CO_2 flooding is or the higher the injection pressure and rate is,the higher the gas recovery factor will be.