咸水层毛管力圈闭机制及对非纯CO_(2)封存效率的影响  

Local capillary entrapment and its effect on sequestration efficiencies during impure CO_(2) injection into saline aquifers

作　　者：崔国栋 胡哲 宁伏龙[1] 王延永 焦玉勇 CUI Guodong;HU Zhe;NING Fulong;WANG Yanyong;JIAO Yuyong(Faculty of Engineering,China University of Geosciences,Wuhan430074,China;College of Energy Resources,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]中国地质大学(武汉)工程学院,湖北武汉430074 [2]成都理工大学能源学院,四川成都610059

出　　处：《煤炭学报》2023年第7期2791-2801,共11页Journal of China Coal Society

基　　金：国家自然科学基金资助项目(42202349,42227805);湖北省自然科学基金资助项目(2021CFB189)。

摘　　要：实际咸水层呈垂向多层分布,物性差异大,毛管力非均质性严重。非纯CO_(2)气体封存过程中,毛管力不仅会圈闭CO_(2),更会圈闭伴随的杂质气体,影响CO_(2)运移和封存。但是,垂向多层系下毛管力的圈闭机制还不清楚,其对非纯CO_(2)气体封存效率的影响亟待分析。为此结合随机统计地质建模和非纯CO_(2)-盐水两相渗流模型,建立了垂向多层系咸水层非纯CO_(2)封存运移模型;研究了毛管力作用下CO_(2)和杂质气体的运移过程及其羽流发育规律,并对非纯CO_(2)气体垂向运移速率和毛管力圈闭能力进行了量化计算;最后通过敏感性分析,阐明了毛管力大小、非均质程度、杂质体积分数等因素对非纯CO_(2)气体封存效率的影响。研究结果表明,非均质毛管力可有效圈闭非纯CO_(2)气体,增加非纯CO_(2)气体在横向上的波及体积;随着毛管力大小和非均质程度增加,毛管力圈闭量升高,毛管力封存系数增大,但CO_(2)垂向运移速率降幅明显,与杂质气体垂向运移速率的差异幅度增加。毛管力自上而下递减时,底部毛管力圈闭减少,更多的非纯CO_(2)气体将运移到地层上部的各个区域,使得非纯CO_(2)气体毛管力封存系数增加,非纯CO_(2)气体残余封存系数减少,CO_(2)垂向运移速率增大,与杂质气体垂向运移速率的差异幅度减小;随着杂质气体体积分数增加,非纯CO_(2)气体浮力增加,垂向运移速率增大,更多非纯CO_(2)气体运移到地层顶部,非纯CO_(2)气体毛管力封存系数降低,残余封存系数增加。因此为保证封存安全性,应尽可能选择含杂质少的非纯CO_(2)气体注入毛管力大、非均质性强以及垂向毛管力自上而下先递增后递减的咸水层。The actual saline aquifers is vertically distributed in multiple layers,with large differences in physical properties and serious heterogeneity of capillary pressure.During the sequestration of impure CO_(2),the capillary pressure will not only trap CO_(2) but also trap the accompanying impurity gas,affecting CO_(2) migration and sequestration.However,the entrapment of local capillary under the vertical multi-layer system is still unclear,and its impact on the sequestration efficiency of impure CO_(2) needs to be analyzed urgently.For this reason,stochastic statistical geological modeling and impure CO_(2)-brine two-phase seepage model are combined to establish a vertical multi-layer impure CO_(2) sequestration and migration model in saline aquifers.Under the action of capillary pressure,the migration process and its plume development law are studied and the vertical migration rate of impure CO_(2) and the capillary pressure trapping ability are calculated quantitatively.Finally,through the sensitivity analysis,the capillary pressure,the influence of capillary pressure,heterogeneity,and impurity volume fraction on CO_(2) sequestration efficiency is clarified.The research results show that heterogeneous capillary pressure can effectively trap impure CO_(2) and increase the swept volume of impure CO_(2) in the lateral direction.With the increase of capillary pressure and its heterogeneity,local capillary trap volume and local capillary sequestration coefficient increase.However,the vertical migration rate of CO_(2) decreases significantly,and the difference between the vertical migration rate of impurity gas increases.When the capillary pressure decreases from top to bottom,the local capillary entrapment at the bottom decreases,and more impure CO_(2) will migrate to various areas in the upper part of the formation,which makes the local capillary sequestration coefficient of impure CO_(2) increase,and the residual sequestration coefficient of impure CO_(2) decrease.What's more,it makes the vertical migration rate of

关 键 词：非纯CO_(2)气体 咸水层 毛管力圈闭 封存效率 杂质气体 

分 类 号：X141[环境科学与工程—环境科学] P342[天文地球—水文科学]