Experimental study on the mechanical properties of coal-like materials for hydraulic fracturing simulation

Authors

ZHAI Cheng, School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, China; National Engineering Research Center for Coal Gas Control, China University of Mining and Technology, Xuzhou 221116, China; Key Laboratory of Gas and Fire Control for Coal Mines, Ministry of Education, China University of Mining and Technology, Xuzhou 221116, ChinaFollow
ZHENG Yangfeng, School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, China
YU Xu, School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, China; National Engineering Research Center for Coal Gas Control, China University of Mining and Technology, Xuzhou 221116, China; Key Laboratory of Gas and Fire Control for Coal Mines, Ministry of Education, China University of Mining and Technology, Xuzhou 221116, China
XU Jizhao, School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, China; National Engineering Research Center for Coal Gas Control, China University of Mining and Technology, Xuzhou 221116, China; Key Laboratory of Gas and Fire Control for Coal Mines, Ministry of Education, China University of Mining and Technology, Xuzhou 221116, China
SUN Yong, School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, China
CONG Yuzhou, School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, China
TANG Wei, School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, China
LI Yujie, School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, China
ZHU Xinyu, School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, China
CHEN Aikun, School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, China

Abstract

Simulation experiments on hydraulic fracturing of the coal seam in the laboratory are an effective method to study the mechanism of fracturing and enhancing permeability of coal-rock mass by hydraulic fracturing in coal mines. However, the technology in-situ sampling for large-size coal mass is immature, and the existing large-size coal samples are mostly taken from the stress-relaxation area, which can be further damaged in the transportation and preparation processes, causing large dispersion in test results. Therefore, The use of coal-like materials is a viable option to replace large-size raw coal for hydraulic fracturing simulation experiments. The mechanical properties of coal-like specimens are the most important factor affecting the effectiveness of hydraulic fracturing. In this paper, in order to accurately characterize “the basic mechanical properties of coal-like materials”, coal powder, cement, gypsum, and sand are used to make coal-like samples with seven ratios for examining the coupling response law of ultrasonic and mechanical properties. The experiments results include: The ultrasonic wave velocity (P-and S-waves) and strength (uniaxial compressive and tensile strength) of coal-like samples increase with increasing density and decrease with increasing porosity. The effect of similar materials on ultrasonic wave velocity, strength, and density increments, cement > sand > gypsum, with the opposite porosity. Cement and gypsum play a major role in regulating the strength and deformation characteristics of coal-like samples, respectively. The strength of coal-like samples can be predicted in advance by measuring ultrasonic P-wave velocity based on the quadratic polynomial mathematical model between ultrasonic P-wave velocity and strength. The mechanical properties of the coal-like material can be adjusted in a wide range. Various properties of coal-like samples can be adjusted to simulate coal-rock mass accurately by changing the ratio of similar materials, and the sample can be made simply. This study provides a basis for a similar design of mechanical properties of coal-like materials for hydraulic fracturing simulation, which can promote the development of mine gas prevention technology and has high application value.

Keywords

coal-like material, mechanical properties, hydraulic fracturing, ultrasonic wave velocity, mine gas prevention and control

DOI

10.12363/issn.1001-1986.22.04.0272

Recommended Citation

ZHAI Cheng, ZHENG Yangfeng, YU Xu, et al. (2022) "Experimental study on the mechanical properties of coal-like materials for hydraulic fracturing simulation," Coal Geology & Exploration: Vol. 50: Iss. 8, Article 3.
DOI: 10.12363/issn.1001-1986.22.04.0272
Available at: https://cge.researchcommons.org/journal/vol50/iss8/3

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