致密砂岩气藏注CO_(2)提高天然气采收率微观机理  

Microscopic mechanism of CO_(2) injection to enhance gas recovery in tight sandstone gas reservoirs

作　　者：朱清源 吴克柳[1] 张晟庭 程诗颖 王田多奕 刘琦琦 李靖[1] 陈掌星 ZHU Qingyuan;WU Keliu;ZHANG Shengting;CHENG Shiying;WANG Tianduoyi;LIU Qiqi;LI Jing;CHEN Zhangxing(State Key Laboratory of Petroleum Resources and Prospecting//China University of Petroleum-Beijing,Beijing 102249,China;Department of Chemical and Petroleum Engineering,University of Calgary,Alberta T2N 1N4,Canada)

机构地区：[1]油气资源与探测国家重点实验室•中国石油大学(北京) [2]卡尔加里大学化学与石油工程系

出　　处：《天然气工业》2024年第4期135-145,共11页Natural Gas Industry

基　　金：国家自然科学基金项目“非常规储层纳米孔中水驱气动态润湿机理与传输特性”(编号:52174041);“页岩储层压裂液侵入/返排/滞留机理及其对气井产能影响规律研究”(编号:52104051);“页岩气有效储渗孔隙跨尺度耦合渗流及产出规律研究”(编号:51874319);北京市自然科学基金项目“非常规储层纳米孔水传输研究”(编号:3232029)。

摘　　要：中国致密砂岩气藏资源储量丰富,复杂的气水渗流关系和气水同产特征制约了单井产能的发挥和天然气采收率提高,注CO_(2)是提高气藏采收率(EGR)和实现碳埋存的双赢途径。为明确致密砂岩气藏CO_(2)驱替微观渗流和提高天然气采收率机理,指导致密砂岩气藏CO_(2)-EGR方案设计,基于格子玻尔兹曼方法(LBM)建立了孔隙尺度多相多组分流动模型,揭示了致密砂岩气藏储层微观气水分布特征和CO_(2)-EGR的微观渗流机理,并明确了CO_(2)-EGR的主控因素。研究结果表明:①驱动压差显著影响了致密砂岩气藏的气水微观分布和水锁程度,使得气水流动能力和气水相对渗透率特征不同;②CO_(2)-EGR微观渗流过程包括气水两相的非混相驱替和CO_(2)-CH_(4)的混相驱替,对应EGR机理为分别受生产压差和地层压力控制的黏性驱替和混相扩散;③注入的CO_(2)可有效缓解水锁现象和贾敏效应,与CH_(4)良好的混相能力能促进沟通分散气泡,微观驱气效率可达42%~94%;④含水饱和度、孔隙结构和驱动压差显著影响微观驱气的作用机制和驱气效率的改善幅度。结论认为,在进行致密砂岩气CO_(2)-EGR的方案设计时,可优先考虑中—低含水饱和度的区块作为试验靶区,并根据靶区储层孔隙结构特征,优化不同注气阶段的注采参数,可充分发挥CO_(2)对CH_(4)的黏性驱替和混相扩散作用。Tight sandstone gas reservoirs in China have abundant natural gas reserves,but the complex gas-water flow relationships and the co-production of gas and water restrict the exertion of single well productivity and the improvement of natural gas recovery factor.CO_(2) injection is a promising dual-benefit approach to enhancing gas recovery(EGR)and achieving carbon storage.In order to clarify the microscopic flow and EGR mechanisms of CO_(2) flooding in tight sandstone gas reservoirs and guide the design of tight sandstone gas CO_(2)-EGR scheme,this paper establishes a pore-scale multiphase and multicomponent flow model based on lattice Boltzmann method(LBM),reveals the microscopic gas and water distribution characteristics of tight sandstone gas reservoirs and the microscopic flow mechanisms of CO_(2)-EGR,and finally clarifies the main control factors of CO_(2)-EGR.And the following research results are obtained.First,the displacement pressure difference significantly affects the microscopic gas and water distribution and water blocking degree in tight sandstone gas reservoirs,resulting in various gas and water flow capabilities and relative permeability characteristics.Second,the microscopic flow process of CO_(2)-EGR includes gas-water immiscible displacement and CO_(2)-CH_(4) miscible displacement,whose corresponding EGR mechanisms are viscous displacement and miscible diffusion,controlled by production pressure difference and formation pressure respectively.Third,the injected CO_(2) can effectively alleviate water blocking and Jamin effect,and its good miscibility with CH_(4) promotes the communication of dispersed gas bubbles,which results in a microscopic gas displacement efficiency of 42%to 94%.Fourth,water saturation,pore structure and displacement pressure difference significantly affect the mechanism and performance of microscopic gas displacement efficiency.In conclusion,when designing the CO_(2)-EGR scheme for tight sandstone gas,priority shall be given to the reservoir with low to medium water saturati

关 键 词：致密砂岩气藏 注CO_(2)提高气藏采收率 格子玻尔兹曼 微观驱气效率 孔隙尺度 多相多组分 

分 类 号：TE377[石油与天然气工程—油气田开发工程]