Characteristics of microseismic waveforms induced by hydraulic fracturing in coal seam for coal rock dynamic disasters prevention. (June 2019)

• Record Type: Journal Article
• Authors: Li, Nan; Huang, Bingxiang; Zhang, Xin; Yuyang, Tan; Li, Baolin
• Is Part Of: Safety science. Volume 115(2019)
• Page Start: 188
• Page End: 198
• Publication Date: 2019-06
• Subjects: Mine safety -- Coal rock dynamic disasters prevention -- Hydraulic fracturing -- Microseismic monitoring -- Waveform analysis; Industrial accidents -- Periodicals; Accident Prevention -- Periodicals; Safety -- Periodicals; Travail -- Accidents -- Périodiques; 363.11
• DOI: 10.1016/j.ssci.2019.01.024
• Languages: English
• ISSNs: 0925-7535

Abstract

Highlights: Coal rock dynamic disasters have been a persistent threat to mine safety. In recent years, hydraulic fracturing (HF) technique has been proved to be an effective method for preventing coal rock dynamic disasters. But there has been no effective monitoring tool for the hydraulic cracks, which has severely influenced the safety, optimization and effectiveness of HF in coal mines. In this manuscript, microseismic(MS) technique is introduced to study the distribution of hydraulic cracks induced by HF in coal seam. The highly accurate MS data acquisition apparatus and sensitive sensors were elaborately selected for the field coal seam HF test. And then lots of effective and weak MS waveforms induced by HF are successfully recorded during the field test. The characteristics of HF induced MS waveforms are studied systematically for the first time. Three sensitive characteristic parameters, the peak frequency, duration time and peak following attenuation, are proposed to distinguish three typical kinds of induced MS waveforms. The conclusions are the theoretical basis of locating the cracks and monitoring the effect of HF in coal seams by MS technique, which is of great significance to coal rock dynamic disasters prevention by HF technique. The manuscript has been reviewed by two anonymous reviewers, and both of them gave positive comments on the manuscript. They both recommend the publication of this paper after modifying the manuscript based on their comments. We have responded to all of the comments point by point. We also made the modifications after studying the comments very carefully. Abstract: Coal rock dynamic disasters have been a persistent threat to mine safety. Hydraulic fracturing(HF) technique has been proved to be an effective method for preventing coal rock dynamic disasters in underground coal mines. In order to monitor the crack extent of HF in coal seam, highly precision microseismic(MS) data acquisition apparatus and sensitive sensors are employed to monitor the cracks induced by coal seam HF in Xieqiao Coal Mine. Lots of effective and weak MS waveforms induced by HF are successfully recorded. Some useful methods such as wavelet transformation, Hilbert-Huang transformation, envelope analysis and curve fitting method help to make comprehensive insights into the amplitude-frequency, time-frequency, duration and peak following attenuation characteristics of these HF induced MS waveforms. The frequency, duration time and peak following attenuation characteristics of MS waveforms induced by mining, blast and coal seam HF are statistically studied. The results show that these characteristic parameters, peak frequency, duration time and peak following attenuation, are very sensitive to distinguish these three typical kinds of induced MS waveforms. Further study shows that the principles of fractures' propagation influenced by the pressurized water and the backfill effect of pores by large volume of pressurized water injection and the pressurized water itself are the key factors influencing the characteristics of MS waveforms. The conclusions are the theoretical basis of locating the cracks and monitoring the effect of HF in coal seams by using MS technique, which can provide the basis reference for designing optimized, safe and effective HF program to prevent the coal rock dynamic disasters, and will be of great significance to coal mine safety.