摘要
CO_(2)提高煤层气采收率(CO_(2)-ECBM)技术能够在封存CO_(2)的同时增产煤层气,兼具碳减排和能源开发的双重效益。在深部储层高温、高压、含水状态下,超临界CO_(2)(ScCO_(2))-H_(2)O-煤体系会发生一系列的地球化学作用,进而导致煤储层矿物与孔裂隙结构发生显著变化,并直接影响CO_(2)-ECBM的有效性。通过室内物模实验,充分利用全自动矿物分析系统(AM)具有提供大尺寸高分辨率背散射图像的优势,实现了原位观测,并结合图像处理方法,对反应前后矿物和孔裂隙的参数变化进行定量分析,由此揭示了不同尺度矿物和孔裂隙在数量、面积及分形维数上的变化规律,形成了研究ScCO_(2)-H_(2)O-煤地球化学作用下矿物变化对孔裂隙影响机理的新方法。研究结果表明:①ScCO_(2)-H_(2)O对煤中碳酸盐矿物的溶解作用最为显著,而对长石、磷灰石和黏土矿物的影响相对较弱;②碳酸盐矿物的溶解和煤体的溶胀作用促进了新的孔裂隙和裂缝的形成,尤其是在直径大于10μm的孔裂隙;③碳酸盐矿物部分溶解可增加孔裂隙形态的复杂性,而晶胞型充填碳酸盐的完全溶解则会降低孔裂隙的分形维数。结论认为,该研究方法可更直观和科学地揭示ScCO_(2)-H_(2)O-煤地球化学作用下,矿物变化对孔裂隙的影响机理,还可应用于其他研究背景中储层物性原位改造的机理分析,如压裂液作用、微生物作用、酸化作用等。
s:CO_(2)enhanced coalbed methane recovery(CO_(2)-ECBM)technology can store CO_(2)while enhancing CBM recovery,and can achieve the dual benefit of carbon emission reduction and energy development as well.In the deep reservoirs with high temperature,high pressure and water,a series of geochemical processes occur in the supercritical CO_(2)(ScCO_(2))-H_(2)O-coal system,leading to a significant change in mineral compositions and in pore and fracture structures.These changes directly impact the effectiveness of CO_(2)-ECBM.By means of laboratory physical simulation experiment,this paper establishes a theoretical calculation model of fractal dimension by making full use of the advantage of automated mineralogy(AM)to provide large-sized and high-resolution backscattering images.By virtue of this model,in-situ observation was realized,combined with image processing method,the parameter changes of minerals and pores before and after the reaction were quantitatively analyzed,revealing the variation patterns of minerals and pores at different scales in terms of quantity,area,and fractal dimension.Thus,a new method of investigating the influence of mineral alterations on pores and fractures under the ScCO_(2)-H_(2)O-coal geochemical reaction is formed.And the following research results are obtained.First,ScCO_(2)-H_(2)O has the strongest dissolution effect on carbonate minerals in coal,but relatively weak effect on feldspar,apatite,and clay minerals.Second,the dissolution of carbonate minerals and the swelling of coal body promote the formation of new pores and fractures,particularly those with diameter larger than 10μm.Third,partial dissolution of carbonate minerals enhances the complexity of pore morphology,whereas the complete dissolution of cellular-filled carbonate reduces the fractal dimension of pores.In conclusion,this research method enables a more intuitive and scientific understanding of the influence of mineral alterations on pores and fractures under ScCO_(2)-H_(2)O-coal geochemical reaction,and it can be also applied to the mechanism analysis of in-situ modification of reservoir physical properties in other research backgrounds,such as fracturing fluid,microbial,and acidizing processes.
作者
杜艺
吕春阳
严世杰
付常青
徐伟丰
桑树勋
DU Yi;LYU Chunyang;YAN Shijie;FU Changqing;XU Weifeng;SANG Shuxun(Department of Geology,Northwest University,Xi'an,Shaanxi 710069,China;National and Local Joint Engineering Research Center of Carbon Capture and Storage Technology,Xi'an,Shaanxi 710127,China;State Key Laboratory of Continental Dynamics//Northwest University,Xi'an,Shaanxi 710069,China;College of Geology and Environment,Xi'an University of Science and Technology,Xi'an,Shaanxi 710054,China;Carbon Neutrality Institute,China University of Mining and Technology,Xuzhou,Jiangsu 221116,China)
出处
《天然气工业》
EI
CAS
CSCD
北大核心
2024年第10期93-104,共12页
Natural Gas Industry
基金
国家自然科学基金面上项目“深部煤系复合储层注CO_(2)的热—流—固耦合作用与地球化学效应研究”(编号:42372188)
中国科协第九届青年人才托举工程(编号:2023QNRC001)。
