煤中超临界CO_(2)解吸滞后机理及其对地质封存启示  

Hysteresis mechanism of supercritical CO_(2) desorption in coal and its implication for carbon geo-sequestration

作　　者：刘操[1,2,3,4,5] 闫江伟 赵春辉[1] 钟福平 贾天让 刘小磊[1,2] 张航[1] LIU Cao;YAN Jiangwei;ZHAO Chunhui;ZHONG Fuping;JIA Tianrang;LIU Xiaolei;ZHANG Hang(School of Safety Science and Engineering,Henan Polytechnic University,Jiaozuo 454003,China;State Key Laboratory Cultivation Base for Gas Geo-logy and Gas Control,Henan Polytechnic University,Jiaozuo 454000,China;National Coal Field Engineering Research Center for Gas Geology and Gas Control(P.R.C),Jiaozuo 454003,China;Collaborative Innovation Center of Coalbed Methane and Shale Gas for Central Plains Economic Region,Jiaozuo 454000,China;Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization,Jiaozuo 454000,China)

机构地区：[1]河南理工大学安全科学与工程学院,河南焦作454003 [2]河南理工大学河南省瓦斯地质与瓦斯治理重点实验室−省部共建国家重点实验室培育基地,河南焦作454000 [3]全国煤炭行业瓦斯地质与瓦斯防治工程研究中心,河南焦作454003 [4]中原经济区煤层(页岩)气河南省协同创新中心,河南焦作454000 [5]煤炭安全生产与清洁高效利用省部共建协同创新中心,河南焦作454000

出　　处：《煤炭学报》2024年第7期3154-3166,共13页Journal of China Coal Society

基　　金：河南省高校基本科研业务费专项资金资助项目(NSFRF240301);河南省科技攻关资助项目(222102320154);河南省高校重点科研资助项目(22A610009)。

摘　　要：将CO_(2)注入不可采煤层地质封存既是降低温室气体效应最理想选择之一,也是煤炭工业降低CO_(2)排放、实现低碳化可持续发展的必由之路,然而,煤层CO_(2)地质封存悬而未决的关键问题是:“注入煤层中的CO_(2)到底能否长期停留而安全封存?”。鉴于此,在弄清煤体CO_(2)解吸滞后规律的基础上,揭示超临界CO_(2)解吸滞后机理,建立煤层CO_(2)地质封存量化模型,探讨利用解吸滞后实现煤层CO_(2)长期安全封存。研究表明:煤中超临界态CO_(2)解吸滞后程度大于亚临界态CO_(2),在超临界阶段,吸附与解吸等温线形成近似“平行线”的稳定滞后特征;解吸滞后的本质原因是煤中微纳米级亲水性孔隙形成弯液面、产生强大毛细压力、渗吸液态水、截断并固定超临界CO_(2)流体、最终形成了CO_(2)残余封存,例如,煤中直径40~10 nm圆柱形无机孔隙可产生7.30~29.12 MPa毛细压力,足以封堵超临界态CO_(2);以九里山煤样解吸等温线数据为例,采用基于煤层CO_(2)解吸滞后的地质封存量化模型,评估出900~1500 m深部二1煤层封存总量稳定在35~37 m^(3)/t,其中,吸附封存约占80%,残余封存约占15%,而结构封存仅占5%;解吸滞后启示应尽可能采取措施提高煤层残余封存CO_(2)比例,原因是毛细堵塞的残余封存CO_(2)较围岩密封的游离和吸附CO_(2)更安全且没有泄露风险,煤层灰分、水分、孔隙尺寸和形貌等物性参数是影响残余封存效率的主要因素。Sequestration of CO_(2) in the unmineable coal seams is not only one of the most ideal options for reducing green-house gas effects,but also the only way for the coal industry to reduce CO_(2) emissions and achieve low carbonization sus-tainable development.However,the key unresolved issues regarding the CO_(2) geo-sequestration in coal seams is:“how long does CO_(2) injected into a coal seam remain in the seam?”.In this regard,on the basis of clarifying the hysteresis law of CO_(2) desorption in coals,this paper reveals the mechanism of supercritical CO_(2) desorption hysteresis,establishes a quantitative model for the geological storage of CO_(2),and explores the use of desorption hysteresis to achieve a long-term safe storage of CO_(2) in coal seams.The study results shows that the degree of desorption hysteresis of supercritical CO_(2) in coal is greater than that of subcritical CO_(2),and a stable hysteresis characteristic similar to a“parallel line”in the supercrit-ical phase is formed between the adsorption and desorption isotherm.The fundamental reason for the desorption hyster-esis is that the micro and nano sized pores in coal form curved surfaces due to their hydrophilicity,which generate strong capillary pressure following the Laplace’s equation,absorb liquid water,truncate and fix the supercritical CO_(2) fluid,and ultimately form CO_(2) residual trapping.For example,the cylindrical inorganic pores with a diameter of 40-10 nm in coal can generate a capillary pressure of 7.30-29.12 MPa,which is sufficient to block supercritical CO_(2).Taking the desorption isotherm of Jiulishan coal as an example,using the quantitative model for the geological storage of CO_(2) established in this study,it has been estimated that the total trapping capacity of the No.21 coal seam at depths of 900-1500 m is stable at 35-37 m^(3)/t.Among them,the adsorption trapping capacity accounts for about 80%,residual trapping capacity accounts for about 15%,and structural trapping capacity only accounts for 5%.Desorption

关 键 词：CO_(2)地质封存 超临界CO_(2) 解吸滞后 残余封存 毛细压力 地质封存量化模型 

分 类 号：P618.11[天文地球—矿床学]