Acoustic emission characteristics in hydraulic fracturing of stratified rocks: A laboratory study

• Published in: Powder technology Vol. 371; pp. 267 - 276
• Main Authors: Jiang, Zhizhong, Li, Quangui, Hu, Qianting, Liang, Yunpei, Xu, Yangcheng, Liu, Le, Wu, Xiaobing, Li, Xuelong, Wang, Xiaoguang, Hu, Liangping, Ling, Faping
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 30-06-2020; Elsevier BV
• Subjects: Acoustic emission; Axial stress; Coalbed methane; Emission analysis; Energy distribution; Frequency response; Gas production; Hydraulic fracturing; Natural gas; Oil and gas production; Peak frequency; Rocks; Acoustic emission; Peak frequency; Hydraulic fracturing; Coalbed methane
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2020.05.050

Acoustic emission (AE) is a popular technique to monitor the process of rock failure during hydraulic fracturing for unconventional natural gas production. It contains abundant information that will be useful to study in-depth the nature of hydraulic fracturing. In this study, we focused on the AE count, energy, peak frequency, crack classification, and location recorded from four rock specimens subjected to a specific triaxial stress condition. We found the multi-frequency-response phenomenon of AE, and proposed the multi-frequency-response index to indicate the moment of the macrohydraulic crack formation. Furthermore, it was found that the power law distribution index of AE energy of non-stratified specimen was bigger than that of stratified specimens during hydraulic fracturing. The tensile crack dominated in all hydraulic fracturing tests. Our results are of significance for understanding hydraulic fracturing in stratified rocks.
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•Multi acoustic emission characteristics were combined to explain the rock failure of hydraulic fracturing.•A stratified formation was particularly studied comparing with the single stratum.•The multi-frequency-response index was proposed to indicated the macrohydraulic crack formation.•The type of ruptured stratum was diagnosed with the statistics of acoustic emission energy.