林魂,梅晶,贾赛楠,黄俊和,董明达
LIN Hun,MEI Jing,JIA Sainan,HUANG Junhe,DONG Mingda

• 1:重庆科技大学安全工程学院

摘要(Abstract)：

为明确注CO_2提高页岩气开采过程中CO_2与水作用后对页岩微观孔隙结构的影响，采用X射线衍射、低温N_2吸附和低场核磁共振等实验方法，研究了原始页岩及纯盐水、注入压力为6和12 MPa的CO_2水溶液浸泡后页岩的矿物组成、孔径分布和微观孔隙结构变化特征，并结合分形理论，获取了孔表面和孔体积的分形特征，明确了页岩中吸附孔隙和渗流孔隙的变化特征。结果表明：CO_2水溶液浸泡后，页岩中石英含量增大，黏土矿物和碳酸盐含量降低；随着CO_2注入压力的增加，微孔比表面积和总比表面积减小，平均孔径、核磁孔隙度和大孔孔体积比例增大，表明在CO_2水溶液的溶解作用下微孔和介孔逐渐向大孔转化；低温N2吸附和核磁共振（NMR）获得的分形维数均随CO_2注入压力的增加逐渐降低，表明页岩在CO_2水溶液浸泡后孔隙结构的非均质性和复杂性降低；孔表面分形维数DL1、DN1和孔体积分形维数DL2、DN2与总比表面积和总孔质量体积呈正相关性，这2个指标可分别用于表征页岩中的吸附孔隙和渗流孔隙特征，能够有效评价页岩气体吸附与渗流能力。研究成果为注CO_2高效开发页岩气提供了参考和依据。
To clarify the effect of CO_2 injection on micro-pore structure of shale gas after interaction of CO_2 with water during the process of shale gas production, experimental methods of XRD, low-temperature N_2 adsorption and low-field NMR are used to study mineral composition, pore size distribution and micro-pore structure variation of shale after immersing in original shale and pure saline water, 6 and 12 MPa(injection pressures) CO_2 aqueous solutions. Combined with fractal theory, the fractal characteristics of pore surface and pore volume are obtained, determining variation characteristics of adsorption pores and flow pores in shale. The results show that after immersing in CO_2 injection aqueous solution, quartz content in shale increases, while clay mineral and carbonate contents decrease. As CO_2 pressure increases, specific surface area of micro-pores and total specific surface area decrease, while average pore size, nuclear magnetic porosity and proportion of macro-pore volume increase, indicating a trend of gradual transformation from micro-pores and meso-pores to macro-pores effected by dissolution of CO_2 aqueous solution. Fractal dimension obtained by low-temperature N2 adsorption and NMR decreases gradually with CO_2 injection pressure increase, indicating that heterogeneity and complexity of pore structure of shale are gradually reduced after immersion in CO_2 aqueous solution. Pore surface fractal dimension DL1 and DN1 and pore volume fractal dimension DL2 and DN2 are positively correlated with total specific surface area and total pore volume. These 2 indicators can be used to characterize the adsorption pores and flow pores in shale, respectively, and can effectively evaluate gas adsorption and flow capacity of shale, providing reference and basis for efficient development of shale gas by CO_2 injection.

关键词(KeyWords)： 页岩;孔隙结构;CO_2;分形维数;核磁共振;N_2吸附;孔径分布
shale;pore structure;CO_2;fractal dimension;nuclear magnetic resonance(NMR);N_2 adsorption;pore size distribution

Abstract:

Keywords:

基金项目(Foundation): 重庆市教委科学技术研究项目“致密油藏CO_2吞吐排驱机理及影响因素研究”（KJQN202001508）;; 重庆市大学生创新训练计划项目“页岩储层地质封存CO_2的力学可靠性分析”（S202211551010）;; 重庆科技大学研究生科技创新项目“CO_2地质封存中碳酸盐岩溶蚀效率影响因素研究”（YKJCX2220711）

作者(Author): 林魂,梅晶,贾赛楠,黄俊和,董明达
LIN Hun,MEI Jing,JIA Sainan,HUANG Junhe,DONG Mingda

DOI: 10.19597/J.ISSN.1000-3754.202305017

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