Microstructure Evolution of Bituminous Coal Modified by High-Pressure CO2 Foam Fracturing Fluid with Different Treatment Times

被引:16
作者
Zheng, Yangfeng [1 ,2 ,3 ]
Zhai, Cheng [1 ,2 ,3 ]
Chen, Aikun [1 ,2 ,3 ]
Sun, Yong [4 ]
Cong, Yuzhou [1 ,2 ,3 ]
Tang, Wei [1 ,2 ,3 ]
Xu, Jizhao [1 ,2 ,3 ]
Yu, Xu [1 ,2 ,3 ]
Zhu, Xinyu [1 ,2 ,3 ]
Li, Yujie [1 ,2 ,3 ]
机构
[1] China Univ Min & Technol, Sch Safety Engn, Xuzhou 221116, Jiangsu, Peoples R China
[2] China Univ Min & Technol, Key Lab Gas & Fire Control Coal Mines, Minist Educ, Xuzhou 221116, Jiangsu, Peoples R China
[3] China Univ Min & Technol, Natl Engn Res Ctr Coal Gas Control, Xuzhou 221116, Jiangsu, Peoples R China
[4] China Univ Min & Technol, Sch Low Carbon Energy & Power Engn, Xuzhou, Jiangsu, Peoples R China
基金
中国国家自然科学基金; 中国博士后科学基金; 美国国家科学基金会;
关键词
Coalbed methane; CO2 foam fracturing fluid; Bituminous coal; Different treatment times; Microstructure evolution; SUPERCRITICAL CO2; CARBON-DIOXIDE; PORE STRUCTURE; CBM PRODUCTION; METHANE; WATER; SEQUESTRATION; PERMEABILITY; ADSORPTION;
D O I
10.1007/s11053-023-10179-3
中图分类号
P [天文学、地球科学];
学科分类号
07 ;
摘要
The microstructure of bituminous coal can be changed significantly due to injection of CO2 foam fracturing fluid into the coal seam, affecting CBM production efficiency. To investigate the microstructural change characteristics of bituminous coal treated with high-pressure CO2 foam fracturing fluid at different treatment times (0-24 h), medium-rank bituminous coal was selected as the research object. X-ray diffraction, Fourier transform infrared spectroscopy, and low-temperature N-2 adsorption tests were carried out to study the changes in mineral components, functional groups, micropore structure, respectively. It was found that the pore structure of bituminous coal can be changed by CO2 foam fracturing fluid. With increase in modification time, the proportion of macropore (> 50 nm) volume of bituminous coal increased gradually, while the proportion of pore (2-5 nm) volume showed a trend of "increase rapidly-decrease rapidly-decrease slowly." When the modification time was within 6-24 h, the average pore size showed a quadratic polynomial positive correlation with treatment time, the seepage pore fractal dimension (D-1) decreased linearly with increase in modification time, and the adsorption pore fractal dimension (D-2) showed the opposite trend. Moreover, with increase in modification time, the infrared peak area of oxygen-containing functional groups and aromatic, aliphatic, and hydroxyl structures of bituminous coal showed a trend of "decrease rapidly-decrease slowly," the aromaticity and degree of aromatic ring condensation showed "decreasing-increasing-decreasing" trends, and the aliphatic chain length and oxygen-containing functional groups fluctuated and increased. CO2 foam fracturing fluids significantly dissolve clay and carbonate minerals in bituminous coal. Coal microstructure can be changed by CO2 foam fracturing fluid through hydrocarbon extraction and transport, differential swelling, and mineral dissolution. The findings showed that 18-24 h was the optimal time range for fracturing fluid flowback after performing CO2 foam fracturing measurements. The research results are significant for selecting CO2 foam fracturing fluid flowback time and improving CBM recovery.
引用
收藏
页码:1319 / 1338
页数:20
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