Mining College, Guizhou University
Institute of Gas DisasterPrevention and Coalbed Methane Development, Guizhou University
Hongyang Second Coal Mine, Shenyang Coking Coal Co Ltd

超声波辅助压裂增透技术具有水力压裂大范围增透、压裂液改造微孔隙、超声波促进瓦斯解吸抽采等优点,可有效改善瓦斯抽采效率,具有广阔的应用前景。为研究超声波作用时间对清洁压裂液改造煤岩效果的影响,对沈阳某矿煤样开展了不同超声波作用时间下清洁压裂液浸泡试验,并通过扫描电镜结合能谱(SEM-EDS)和压汞法(MIP)联合表征煤样孔隙结构,利用傅立叶变换红外光谱(FTIR)分析煤的化学结构。结果表明:超声波作用下压裂液与矿物杂质产生化学反应,改善了孔隙结构特征和孔隙连通性,且增长趋势先急后缓,拐点约为5h,此时煤岩总孔容、孔隙分形维数和渗透率相较原煤分别增加了22.60%,5.25%和73.95%,迂曲度降低了17.93%;超声波和压裂液共同作用可增加煤的芳香度,有利于瓦斯解吸,且增加趋势为先缓后急再缓,拐点分别约为3h和8h,芳香度分别增加了0.98%和16.23%;受能垒及分子结构等影响,煤分子结构改造难度大于矿物质化学反应,芳香结构参数的变化较孔隙结构滞后约3h;煤样孔隙结构和芳香度的变化表明该技术可有效改善煤孔隙结构、促进瓦斯解吸,且该条件下的有效作用时间为8h。研究结果丰富了瓦斯抽采理论体系,可为该技术的现场实践提供理论指导。

Ultrasonic-assisted fracturing permeability enhancement technology offers several advantages, including large-scale permeability enhancement of hydraulic fracturing, transformation of micro-pores by fracturing fluid, and ultrasonic promotion of gas desorption and extraction. It can effectively improve the efficiency of coalbed methane extraction and used in general. To investigate the effect of ultrasonic action time on the impact of clean fracturing fluid on coal transformation, soaking experiments are conducted on coal samples from a mine in Shenyang. The pore structure of the coal samples is characterized withenergy dispersive spectroscopy ( SEM-EDS) and mercury intrusion porosimetry ( MIP), while the chemical structure of the coal is analyzed with Fourier transform infrared spectroscopy (FTIR). The re- sults indicate that under the influence of ultrasonic action, the chemical reaction,which occurs between fracturing fluid and mineral impurities, improves the pore structure characteristics and pore connectivity of the coal. The growth trend follows a rapid-to-slow pattern, with an inflection point occurring at ap- proximately 5 hours. At this point, the total pore volume, pore fractal dimension, and permeability of the coal rock increase by 22.60% , 5.25% , and 73.95% , respectively, while the tortuosity decrease by 17.93% . The combination of ultrasonic waves and fracturing fluid can increase the aromaticity of the coal, which benefits gas desorption. The rate of increasing initially rises slowly, then accelerates, and fi- nally slows down. The inflection points occur at around 3 hours and 8 hours, resulting in aromaticity in- creases of 0.98% and 16.23% , respectively. Due to the influence of energy barriers and molecular struc- ture, the modification of the coal's molecular structure is more challenging than that of the chemical re- action with minerals, resulting in a time lag of approximately 3 hours between changes in aromatic struc- ture and pore structure parameters. The changes observed in the pore structure and aromaticity of the coal samples demonstrate that this technology can effectively improve the coal's pore structure and promote gas desorption. The optimal duration for efficient action under these conditions is 8 hours. The research results enrich the theoretical system of coalbed methane drainage, and can provide theoretical guidance for application of this technology.

贵州省省级科技计划项目(黔科合基础-ZK〔2022〕一般163,黔科合重大专项字〔2021〕3001,黔科中引地〔2021〕4005,黔科合支撑〔2022〕一般016);贵州大学引进人才科研项目(贵大人基合字〔2020〕57号)