摘要
向页岩储层中注入超临界CO_(2)能够在提高页岩气采收率的同时实现CO_(2)地质封存,但CO_(2)—水—页岩会发生相互作用,导致储层孔隙结构及物理特性发生变化,进而影响井壁稳定性及页岩气产量,亟需开展相关机理基础研究。为此,以四川盆地长宁地区下志留统龙马溪组页岩为研究对象,基于矿物组分测试、扫描电镜、超声波透射等室内实验,系统分析了超临界CO_(2)—水—岩相互作用对页岩物理特性的影响,进而建立了页岩储层井壁稳定性评价模型,定量评价了超临界CO_(2)—水—岩相互作用对井壁稳定性的影响。研究结果表明:①黏土矿物水化作用及超临界CO_(2)—水—岩相互作用均导致页岩孔隙度及渗透率增加、声波能量损失及力学强度下降,页岩在超临界CO_(2)—水环境中,声波信号呈现高频向低频迁移特征,声波速度降幅为去离子水环境的2.53倍,孔隙度与渗透率增幅分别为其1.57倍和2.60倍,力学参数平均劣化程度为去离子水环境的2.12倍;②去离子水环境主要引发黏土矿物水化膨胀和分散,而超临界CO_(2)—水环境则通过碳酸盐溶解与黏土水化协同作用,加剧孔隙结构演化;③相较于原状地层,黏土矿物水化作用、超临界CO_(2)—水—岩相互作用分别使临界坍塌压力当量密度提升20.9%和42.7%。结论认为:①井壁稳定评价模型预测的坍塌压力当量密度为1.57 g/cm^(3),与现场实测数据(平均值为1.53 g/cm^(3))吻合良好(平均误差为2.61%),验证了井壁稳定性评价模型的可靠性;②研究成果有助于认识超临界CO_(2)—水—岩相互作用下页岩物理特性演化机理,为页岩气安全高效开发提供理论支撑。
Injecting supercritical CO_(2)(scCO_(2))into shale reservoirs can enhance the recovery factor of shale gas while realizing CO_(2)geological storage,but the interaction of CO_(2),water and shale leads to changes in pore structures and physical properties of shale reservoirs,thereby influencing wellbore stability and the shale gas production rate.Therefore,it is urgent to study the related basic mechanisms.Taking the Lower Silurian Longmaxi Formation shale in the Changning block of the Sichuan Basin as an example,this paper systematically analyzes the influence of scCO_(2)–water–rock interaction on the physical properties of shale by means of laboratory experiments such as mineral composition test,scanning electron microscopy and ultrasonic transmission.Then,a model for evaluating the wellbore stability in shale reservoir is established,and the influence of scCO_(2)–water–rock interaction on wellbore stability is quantitatively evaluated.The following research results are obtained.First,the hydration of clay minerals and the interaction of scCO_(2),water and rock lead to an increase in shale porosity and permeability,a loss in acoustic wavy energy and a decrease in mechanical strength.When shale is in the CO_(2)–water environment,its acoustic signals present the characteristics of migrating from high frequency to low frequency,and its acoustic wave velocity reduction,porosity increase,permeability increase,and average degradation degree of mechanical parameters are respectively 2.53,1.57,2.60,and 2.12 times that in the deionized water environment.Second,deionized water environment primarily causes hydration,swelling and dispersion of clay minerals,while scCO_(2)–water environment intensifies the evolution of pore structures through the synergetic effect of carbonate dissolution and clay hydration.Third,the hydration of clay minerals and the interaction of scCO_(2),water and rock increase the equivalent density of critical collapse pressure by 20.9%and 42.7%,respectively,compared with the original strata.In conclusion,the equivalent density of collapse pressure predicted by the wellbore stability evaluation model is 1.57 g/cm is in agreement with field measurements(average 1.53 g/cm^(3)),with an average error of 2.61%,verifying the reliability of the wellbore 3,which stability evaluation model.The research results help understand the evolution mechanisms of shale physical properties under scCO₂–water–rock interaction,and provide theoretical support for the safe and efficient development of shale gas.
作者
雷刚
任建飞
刘佰衢
熊健
刘向君
程万
梁利喜
黎子阳
LEI Gang;REN Jianfei;LIU Baiqu;XIONG Jian;LIU Xiangjun;CHENG Wan;LIANG Lixi;LI Ziyang(College of Engineering,China University of Geosciences-Wuhan,Wuhan,Hubei 430074,China;Southwest Geosteering&Logging Company,Sinopec Matrix Corporation,Chengdu,Sichuan 610100,China;State Key Laboratory of Oil&Gas Reservoir Geology and Exploitation//Southwest Petroleum University,Chengdu,Sichuan 610500,China)
出处
《天然气工业》
北大核心
2025年第5期136-149,共14页
Natural Gas Industry
基金
岩土钻掘与防护教育部工程研究中心开放基金项目“水化—高温耦合效应对页岩渗透率及力学性质演化规律研究”(编号:202406)。
关键词
龙马溪组页岩
安全高效开发
超临界CO_(2)—水—岩相互作用
室内实验
物理特性
演化机理
井壁稳定评价
Longmaxi Formation shale
Safe and efficient development
scCO_(2)-water-rock interaction
Laboratory experiment
Physical properties
Evolution mechanism
Wellbore stability evaluation
