University of Oulu

Zhuang D-D, Yin T-B, Zhang Z-X, Aladejare A, Wu Y, Qiao Y. An Innovative Method to Analyze the Hydraulic Fracture Reopening Pressure of Hot Dry Rock. Materials. 2023; 16(3):1118.

An innovative method to analyze the hydraulic fracture reopening pressure of hot dry rock

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Author: Zhuang, Deng-Deng1,2; Yin, Tu-Bing1; Zhang, Zong-Xian2;
Organizations: 1School of Resources and Safety Engineering, Central South University, Changsha 410083, China
2Oulu Mining School, University of Oulu, 90015 Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 35.7 MB)
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Language: English
Published: Multidisciplinary Digital Publishing Institute, 2023
Publish Date: 2023-07-13


This paper focuses on a new test method and theoretical model for measuring and evaluating the reopening pressure during hot dry rock hydraulic fracturing. Firstly, rock blocks of four lithologies were collected from the hot dry rock strata. Hydraulic fracturing tests at high temperatures in real-time were conducted using drilled cubic specimens and drilled cubic specimens with a pre-crack. Breakdown pressure, reopening pressure, and fracture toughness were measured, respectively. In addition, Brazilian splitting tests at high temperatures in real-time were performed using Brazilian disc specimens to measure tensile strength. Secondly, an empirical equation for evaluating the reopening pressure during hot dry rock secondary fracturing was developed based on fracture mechanics and hydraulic fracturing theory. Third, the values calculated by the new equation, considering breakdown pressure, fracture toughness, and tensile strength, were compared to the values determined by the classical equation and to measurement results. It was found that the new equation predicted closer reopening pressure to the measurement results, regardless of the lithology of the hot dry rock. Moreover, with increasing temperature in the specimens, the error between the value calculated by the new equation and the measurement value remained low. In contrast, the difference between the classical equation predictions and the measurement results was widened. In addition, the reopening pressure was positively correlated with tensile strength and fracture toughness. Variations in lithology and temperature affected tensile strength and fracture toughness, which then changed the hot dry rock reopening pressure.

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Series: Materials
ISSN: 1996-1944
ISSN-E: 1996-1944
ISSN-L: 1996-1944
Volume: 16
Issue: 3
Article number: 1118
DOI: 10.3390/ma16031118
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Funding: This research was funded by the Postgraduate Scientific Research Innovation Project of Hunan Province, under Grant No. CX20220126, Fundamental Research Funds for the Central Universities of Central South University, under Grant No. 2022ZZTS0034, and National Natural Science Foundation of China, under Grant No. 41972283.
Copyright information: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (