SCCO_(2)作用下不同含水性煤孔裂隙结构变化机制  

Effect of Supercritical Carbon Dioxide(SCCO_(2))on the mechanism of change in pore and fracture structure of coal with different moisture content

作　　者：张小东[1] 靳沙沙 张瑜 张硕[1] 韩磊 ZHANG Xiaodong;JIN Shasha;ZHANG Yu;ZHANG Shuo;HAN Lei(School of Energy Science and Engineering,Henan Polytechnic University,Jiaozuo 454000,China;The First Institute of Resources and Environment Investigation of Henan Province,Zhengzhou 450000,China)

机构地区：[1]河南理工大学能源科学与工程学院,河南焦作454000 [2]河南省资源环境调查一院,河南郑州450000

出　　处：《煤炭学报》2024年第7期3143-3153,共11页Journal of China Coal Society

基　　金：国家自然科学基金资助项目(42172198,42202210);河南省科技攻关计划资助项目(232102320336)。

摘　　要：深部煤层封存CO_(2)增产CH_(4)产出过程中,处于超临界状态的CO_(2)(SCCO_(2))与煤中矿物质发生反应,改变煤的孔隙性,进而影响煤层封存CO_(2)的效果和甲烷增产效果。为发现SCCO_(2)–H_(2)O–煤岩作用对煤中孔隙的影响特征,以焦煤为研究对象,开展了不同含水条件下的超临界CO_(2)改造煤实验,基于矿物组成和孔隙性测定结果,对比煤中主要矿物质和不同尺度的孔裂隙变化的差异,探讨了不同含水状态下SCCO_(2)流体对孔裂隙性的作用机制。研究表明:①SCCO_(2)作用后,煤体表面粗糙、疏松,且由于矿物溶蚀使得一些裂隙得到贯通,微裂隙连通性增强。②SCCO_(2)流体对煤具有“扩孔”作用,表现为微、小孔含量下降,中、大孔占比升高,也即微、小孔隙向大孔隙的转化,且孔隙连通性改善;进一步发现,萃余煤吸附孔的分形维数稍微增加,粗糙度增大,而渗流孔的分形维数显著降低,复杂性和非均质性降低。③SCCO_(2)对煤中碳酸盐类矿物的溶解性最好,其次是黏土矿物,且随着含水率增加,萃余煤中的碳酸盐矿物占比先增加后减小。SCCO_(2)使干燥基态、饱和水态煤样中碳酸盐矿物显著溶解,有效改善了孔隙结构,且对饱和水态煤样作用效果更好。空气干燥基态煤样经SCCO_(2)作用后,新生成的白云石矿物聚集在孔喉中造成堵孔效应,缩小原有大孔隙尺寸,是引起不同含水性煤孔隙差异性变化的主要原因。When the CO_(2) in a supercritical state(SCCO_(2))is released from deep coal seams,it reacts with minerals in coal,changing the porosity of coal,which in turn affects the effect of CO_(2) sequestration in coal seams and the effect of increas-ing methane production.In order to discover the influence characteristics of SCCO_(2)-H_(2)O-coal rock interaction on the porosity in coal,the experiments on the supercritical CO_(2) reforming coal under different water content conditions were carried out with coking coal as the research object.Based on the results of mineral composition and porosity measure-ments,the differences between the main minerals and the changes in pore cleavage at various scales in coal were com-pared,and the action mechanism of the SCCO_(2) fluid on the pore cleavage properties under various water content states was explored.The results show that:①After the SCCO_(2) treatment,the surface of the coal body is rough and loose,some fissures are penetrated as a result of mineral dissolution,and the connectivity of micro fissure is improved.②The SCCO_(2) fluid has a“pore-expanding”effect on coal,which is manifested by a decrease of the content of micro-and small pores,and an increase of the proportion of medium-and large pores,i.e.,the conversion of micro-and small-sized pores to large pores,as well as the improvement of pore connectivity.Furthermore,it is discovered that the fractal dimension of the ad-sorption pores of the coal samples increases slightly in size and roughness,while the fractal dimension of the seepage pores decreases significantly,and the complexity and non-homogeneity are reduced.③The SCCO_(2) fluid has the best sol-ubility on the carbonate minerals in coal,followed by clay minerals,and with the increase of water content,the proportion of carbonate minerals in the extracted coal first increases and then decreases.The SCCO_(2) fluid makes the carbonate miner-als in the coal samples of the dry basal state and saturated water state dissolve significantly,which effectively impro

关 键 词：焦煤 孔裂隙结构 含水性 超临界状态的CO_(2) CO_(2)封存 

分 类 号：TQ531[化学工程—煤化学工程]