Effect of ultrasonic action time on coal transformation by clean fracturing fluid
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 with energy 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.
ultrasonicfracturing fluidpore structurechemical constitutionfunctional groupscoal-bed gas desorption
万方数据
维普
