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Fluid-driven micro-cracking behaviour of crystalline rock using a coupled hydro-grain-based discrete element method

Kong, Lie and Ranjith, Pathegama Gamage and Li, Bing Qiuyi (2021) Fluid-driven micro-cracking behaviour of crystalline rock using a coupled hydro-grain-based discrete element method. International Journal of Rock Mechanics and Mining Sciences, 144 . Art. No. 104766. ISSN 1365-1609. doi:10.1016/j.ijrmms.2021.104766. https://resolver.caltech.edu/CaltechAUTHORS:20210623-144901805

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Abstract

The grain-scale heterogeneity of rock has been found to greatly affect the cracking behaviour in mechanical tests. However, the heterogeneity has been insufficiently considered in hydraulic fracturing. To fill the gap, this paper proposes a coupled hydro-grain-based discrete element model and explores the fluid-driven micro-cracking of crystalline rock. The micro-heterogeneity of the rock is represented by a grain-based model. Three laboratory-scale fracturing cases over granite under different in-situ stresses are simulated. First, typical micro behaviour and hydro/hydro-mechanical responses are presented and interpreted. Next, sensitivity analysis of in-situ stress conditions is carried out. It is found that hydraulic fracturing of crystalline rock involves many unique behaviours on grain-scale such as non-symmetrical propagation, “zipper mode” initiation time order, generations of isolated and branching cracks, and re-closure of the cracks earlier initiated. Cracks can be induced in mineral grains and along the grain interfaces. The cracking mode is dominated by tension failure, with a small proportion in shear (between 3.5% and 1.5%). The interplays among orientation, aperture and number of different types of crack show that: 1. The inclination of cracks to the direction of maximum confining stress may occupy the entire range from 0° to 180°; 2. The aperture of cracks decreases statistically with their orientations turning to the direction of the minimum confining stress (σ₃); 3. Increases in σ₃ suppress the generation of total cracks and tend to force cracks to propagate in mineral grains; 4. A small in-situ stress difference results in fewer branching and isolated cracks. In this paper, evolutions of injection pressure and rock deformation during hydraulic fracturing are also discussed.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.ijrmms.2021.104766DOIArticle
ORCID:
AuthorORCID
Ranjith, Pathegama Gamage0000-0003-0094-7141
Li, Bing Qiuyi0000-0002-4158-4941
Additional Information:Crown Copyright © 2021 Published by Elsevier Ltd. Received 24 August 2020, Revised 21 March 2021, Accepted 5 April 2021, Available online 16 June 2021. This work is funded by the China Scholarship Council (CSC)-Monash University Postgraduate Scholarship [grant number. CSC201708150112]; and Monash University Faculty of Engineering Graduate Research International Exchange Award (to L. Kong). We thank Prof. Herbert Einstein at MIT for the valuable suggestions on the work. Sincere appreciation also goes to Dr. Kai Liu at the University of Oxford and Mr. Jing Li at Monash University for the extensive discussion. The comments from the editors and the reviewers are appreciated. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funders:
Funding AgencyGrant Number
China Scholarship CouncilCSC201708150112
Monash UniversityUNSPECIFIED
Subject Keywords:Hydraulic fracturing; Grain-based method; Micro-structure; Heterogeneity; Coupled scheme; Sustainability
DOI:10.1016/j.ijrmms.2021.104766
Record Number:CaltechAUTHORS:20210623-144901805
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20210623-144901805
Official Citation:Lie Kong, Pathegama Gamage Ranjith, Bing Qiuyi Li, Fluid-driven micro-cracking behaviour of crystalline rock using a coupled hydro-grain-based discrete element method, International Journal of Rock Mechanics and Mining Sciences, Volume 144, 2021, 104766, ISSN 1365-1609, https://doi.org/10.1016/j.ijrmms.2021.104766. (https://www.sciencedirect.com/science/article/pii/S1365160921001519)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109546
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:23 Jun 2021 18:32
Last Modified:23 Jun 2021 18:32

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