Study on Breakdown Pressure in Hydraulic Fracturing Process of Hard Rock Based on Numerical Simulation
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ORIGINAL PAPER
Study on Breakdown Pressure in Hydraulic Fracturing Process of Hard Rock Based on Numerical Simulation Wen Li . Yuming Liu . Xin Yao . Jinwang Chu . Xiaowei Chen . Zhuoying Tan
Received: 28 May 2019 / Accepted: 24 August 2020 Ó Springer Nature Switzerland AG 2020
Abstract Pre-conditioning by hydraulic fracturing is a vital work in block caving mining of hard-rock metal mine, and breakdown pressure is one of the important parameters in rock hydraulic fracturing process, which determines the equipment selection and job-parameter control. Based on numerical simulation method, a pre-holed cylindrical hard rock sample was built for simulation of hydraulic fracturing process to investigate the effect of stress condition, rock properties and water injection rate on breakdown pressure. The results show that the breakdown pressure is increased with the confining stress, and the breakdown pressure is 2.28 times confining stress based on rock tension strength. The variation of rock tension strength affects the breakdown pressure and a positive linear relation exists. Pre-formed notch could obviously reduce the breakdown pressure and control the orientation of hydraulic fracture. And the borehole
W. Li China Nonferrous Metal Engineering Corporation, Beijing 100038, China e-mail: [email protected] W. Li Z. Tan School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China Y. Liu (&) X. Yao J. Chu X. Chen China ENFI Engineering Corporation, Beijing 100038, China e-mail: [email protected]
diameter has a reverse influence on rock breakdown pressure. Keywords Breakdown pressure Hydraulic fracturing Pre-conditioning Pre-holed rock sample Block caving mining
1 Introduction Pre-conditioning by hydraulic fracturing is an important part in block caving mining of hard rock metal mine. It plays an important role in the improvement of caveability and control of fragmentation (Liu et al. 2018a). Block caving mining method, as a highefficiency, low-cost mining method with simple structure and continuous mining, has received more and more attention and is the preferred method for large-scale underground mines (Orellana et al. 2017). The caveability of rock mass is the key to determining the success of block caving application, which is influenced by natural factors such as rock joints and artificial engineering (Rafiee et al. 2016). As a kind of artificial engineering technology, hydraulic fracturing has been widely used in stress measurement of deep rock, development of unconventional oil and gas reservoir and roof pressure relief and anti-reflection of coal mine. This technology has also been introduced into the field of metal mine and some block caving mines abroad have explored the usage of hydraulic
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Geotech Geol Eng
fracturing in preconditioning hardrock mass, but some uncertain knowledge still exists on the mechanism of cracking, processing parameters and evaluation of fracturing effect. Breakdow
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