Title: Pulse hydraulic fracturing technology and its application in coalbed methane extraction

Authors: Jizhao Xu; Cheng Zhai; Lei Qin; Shimin Liu

Addresses: Key Laboratory of Coal-based CO₂ Capture and Geological Storage, China University of Mining and Technology, Xuzhou, Jiangsu, 221008, China; Laboratory of Coal Methane and Fire Control, Ministry of Education, China University of Mining and Technology, Xuzhou, 221116, China; School of Safety Engineering, China University of Mining and Technology, Xuzhou, 221116, China ' Key Laboratory of Coal-based CO₂ Capture and Geological Storage, China University of Mining and Technology, Xuzhou, Jiangsu, 221008, China; Laboratory of Coal Methane and Fire Control, Ministry of Education, China University of Mining and Technology, Xuzhou, 221116, China; School of Safety Engineering, China University of Mining and Technology, Xuzhou, 221116, China ' Key Laboratory of Coal-based CO₂ Capture and Geological Storage, China University of Mining and Technology, Xuzhou, Jiangsu, 221008, Chinal; Laboratory of Coal Methane and Fire Control, Ministry of Education, China University of Mining and Technology, Xuzhou, 221116, China ' Department of Energy and Mineral Engineering, G3 Center and Energy Institute, Pennsylvania State University, University Park, PA 16802, USA

Abstract: The sealing and operating procedures of pulse hydraulic fracturing (PHF) were systematically introduced to increase the methane reservoir permeability. The results of a pilot application conducted at Sv719 working face in Daxing coal mine, China, shown that both the sealing and cracking were successfully operated. The injection time and water quantity were positively correlated with the fracturing initiation pressure. The fracturing mechanism of PHF was theoretically analysed, and the relationship between fatigue-loaded coal strength and injecting frequency was studied. A criterion for determining the fracture pressure was established. Compared to conventional hydraulic fracturing and deep-hole blasting, PHF technology is superior in gas-extraction performance, with a relatively high extraction concentration and less gas attenuation. Moreover, the content and pressure of residual gas in the fractured coal seams were reduced below the regulatory limits, with decrease of 46.15-83.67% and 61.61%, respectively. [Received: January 22, 2016; Accepted: May 17, 2017]

Keywords: pulse hydraulic fracturing; coalbed methane; CBM; permeability; injecting frequency; extraction concentration; gas attenuation.

DOI: 10.1504/IJOGCT.2018.093962

International Journal of Oil, Gas and Coal Technology, 2018 Vol.19 No.1, pp.115 - 133

Received: 22 Jan 2016
Accepted: 17 May 2017
Published online: 10 Aug 2018 *

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