Inner Mongolia Coal Geological Exploration (Group)153 Co., Ltd.
Institute of Unconventional Oil & Gas, Northeast Petroleum University
College of Mining and Engineering, Taiyuan University of Technology
School of Earth Sciences, Northeast Petroleum University

超临界CO2(SCCO2)流体对含水煤层纳米孔隙结构的改变将显著影响目标煤层的CO2封存能力；为此，基于流体地球化学反应装置，以长焰煤、气煤和无烟煤为研究对象，模拟了SCCO2-H2O混合流体(温度45℃、压力12 MPa)与3类煤阶煤的地球化学反应；在此基础上，采用小角X射线散射(SAXS)研究了纳米孔隙结构及其非均质性对SCCO2-H2O流体的响应。结果表明：SCCO2-H2O作用重塑了煤的纳米孔隙结构，但不同煤阶煤的纳米孔隙对混合流体的响应有所差异；SCCO2-H2O流体作用后，长焰煤孔隙度、比表面积和小于5 nm的孔隙含量降低，但大于5 nm的中孔含量增大；气煤微孔含量减小，但中孔含量和比表面积显著增大；无烟煤孔隙度和比表面积均提高；煤基质溶胀、SCCO2流体萃取、矿物的溶解和迁移的综合作用造成煤纳米孔隙的差异演化；SCCO2-H2O流体增强了低中阶烟煤孔隙分布的非均质性，以气煤尤为显著，但降低了所有煤样孔隙表面的不规则性。

The change in nanopore structure of coal with the presence of water due to supercritical CO2 (SCCO2) exposure could significantly affects CO2 storage in target coal seams. Thus, the interaction of SCCO2-H2O mixture fluid with long flame coal, gas coal and anthracite was simulated on a fluid geo-reaction system. All the samples were exposed to fluid at 45 ℃ and 12 MPa. The small angle X-ray scattering (SAXS) was used to address the response of nanopore structure and heterogeneity of coal samples to SCCO2-H2O exposure. The results indicate that SCCO2-H2O exposure reconstructs nanopore structure of coal samples. However, the responses of nanopores of different rank coals to the exposure are different. After the exposure, the porosity, specific surface area (SSA) and microporous content with diameter below 5 nm of long flame coal decrease, while mesoporous content with diameter greater than 5 nm increases. For gas coal after the exposure, a reduction in microporous content is recorded, but remarkable increases occur in mesoporous content and SSA. The increase in both porosity and SSA is found for anthracite. The multiple effects of coal matrix swelling, extraction effect due to SCCO2 exposure, and dissolution and mobilization of mineral matters account for the different variation in coal nanopores. SCCO2-H2O fluid enhances the heterogeneity of pore size distribution of low-medium bituminous coal samples with the remarkable change in gas coal, while decreases the irregularity of pore surfaces of all the coal samples.

国家自然科学基金资助项目（41902176）；黑龙江省优秀青年基金资助项目（YQ2021D005）；黑龙江省博士后基金资助项目（LBH-Z19121）；

1 样品与实验
1.1 煤样特征
1.2 SCCO2-H2O-煤地球化学反应实验
1.3 SAXS实验
2 SAXS孔隙参数计算方法
3 结果与讨论
3.1 SAXS散射曲线
3.2 比表面积及孔径分布
3.3 分形特征
4 结语

SU Junsheng, LI Bin, LI Wei, et al. Influence of supercritical CO2-H2O fluid on nanopore structure of coal based on small angle X-ray scattering[J]. Safety in Coal Mines, 2023, 54（11）: 9−17.