Characterisation and evaluation of shockwave generation in water conditions for coal fracturing

Ren, Fei and Ge, Lei and Stelmashuk, Vitaliy and Rufford, Thomas E. and Xing, Huilin and Rudolph, Victor (2019) Characterisation and evaluation of shockwave generation in water conditions for coal fracturing. Journal of Natural Gas Science and Engineering, 66. pp. 255-264. ISSN 1875-5100

Abstract

We investigated the effect of circuit parameters on shockwaves generated by electrohydraulic discharge (EHD), and the application of EHD to stimulation of coal seam gas reservoirs. The discharge circuit analyses indicate that the deposited electrical energy used for shockwave generation is not simply determined by charging voltage or capacitance. The discharge efficiency is also affected by mutual interactions among inductance, resistance and capacitance as well as real-time current change. Furthermore, the relation between charging voltage and peak pressure strength revealed that voltage at breakdown point, ranging from 9 kV to 28 kV, was more closely associated to shock strength rather than the initial charge voltage. Generally, a higher breakdown voltage tends to lead to a stronger shockwave. Finally the EHD fracturing stimulation conducted on coal cubes showed the coal was effectively fractured with enormous cracks and voids. By using three-dimension computed-tomography (CT), the fracture extension and propagation in the coals are found to be obvious and extensive. Though the existing fracture greatly affects the new fracture development in vertical direction, the horizontal fractures parallel with the bedding plane direction are more likely to occur and even expand across the entire tested coal core. The dramatic coal permeability improvement (over a hundred times) after EHD also validates the cutting-through fractures, as does the enhancement of pore and porosity observed by morphology and structural characterisation via scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP).


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version cannot be displayed due to copyright restrictions.
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Future Materials (1 Jan 2017 -)
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Future Materials (1 Jan 2017 -)
Date Deposited: 28 Aug 2019 03:23
Last Modified: 25 Sep 2019 05:18
Uncontrolled Keywords: electrohydraulic discharge; discharge efficiency; peak pressure strength; breakdown voltage; fracture extension
Fields of Research : 09 Engineering > 0914 Resources Engineering and Extractive Metallurgy > 091406 Petroleum and Reservoir Engineering
Socio-Economic Objective: B Economic Development > 85 Energy > 8501 Energy Exploration > 850103 Oil and Gas Exploration
Identification Number or DOI: 10.1016/j.jngse.2019.04.005
URI: http://eprints.usq.edu.au/id/eprint/36481

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