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Article

Episodes 2019; 42(3): 213-223

Published online September 1, 2019

https://doi.org/10.18814/epiiugs/2019/019017

Copyright © International Union of Geological Sciences.

Laboratory-scale fracturing of cement and rock specimen by plasma blasting

Heesung Riu1, Hyun-Sic Jang1, Bong Ju Lee2, Chuangzhou Wu1, and Bo-An Jang1*

1 Department of Geophysics, Kangwon National University, 1 Kangwondaehakgil Chuncheon Gangwon-do 24341, Korea
2Graduate School of Advanced Green Energy & Environment, Handong Global University, 558 Handong-Ro Pohang Gyung-buk 37554, Korea; *Corresponding author: E-mail: bajang@kangwon.ac.kr

Correspondence to:E-mail: bajang@kangwon.ac.kr

Received: June 5, 2019; Revised: July 23, 2019; Accepted: July 23, 2019

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Although hydraulic fracturing is the most commonly used method for fracturing of shale-gas-bearing rock, there are some problems with this method. As plasma blasting can fracture rock without these problems, laboratory-scale fracturing of cement and rock specimens by plasma blasting was performed to investigate the possibility of using this method in shale gas development. Specimens were fractured by plasma blasting under various stress conditions. First, specimens were fractured under uniform pressure, and the discharge energies required for fracturing and fracture development were investigated. As uniform pressure increased, the energy increased as a parabolic curve. Fewer fractures were developed as uniform pressure increased for the same discharge energy. Second, plasma blasting was performed for specimens subjected to three different stresses. Fractures both perpendicular and oblique to the minor stress direction were developed with a differential stress of 3 MPa; however, only fractures perpendicular to the direction of the minor stress were developed with an 8 MPa differential stress. More fractures with diverse directions were developed with the same stress conditions but higher energy. Several long fractures were developed by multiple low-energy blasts, the same result as for one high-energy blast. Proppants were injected effectively into fractures by plasma blasting, resulting in a hydraulic conductivity increase. In sandstone, the geological structure controlled the direction and characteristics of fracture development by plasma blasting. All these results indicate that plasma blasting can be a possible method for fracturing shale gas formation. However, more researches are necessary to apply this method in shale gas development in field.