Thermal Effect of Cold Fluid Injection on Fracture Integrity of Host Rock: A Microscale Analysis of Single Asperity

Abstract

When relatively cold fluid is injected to hot host rock featured with fractures, the fluid-rock temperature difference induces cooling of the self-propping fractures and could cause the failure of the asperity. Although fracture sustainability has been extensively studied, little research has focused on thermal effects on asperity failure. A finite-element analysis is conducted to investigate the effect of fluid-rock temperature differences on the asperity failure. In the analysis, rock mechanical properties are coupled with the temperature and stress states of the host rock. The thermally-induced tensile cracks initiate at the junction of asperity and rock matrix and also start at rim of contact tip at higher temperature difference. When the temperature difference is high enough to propagate tensile cracks, two groups of tensile cracks would coalesce and lead to asperity failure. The critical threshold to initiate two groups of tensile cracks is identified in this study. This asperity failure could also result in the closure of fractures and change the fracture network distribution in the rock. Further, the comparison with fracture wall with no asperity addresses the effect of the asperity on the growth pattern of secondary thermal cracks.

Department(s)

Civil, Architectural and Environmental Engineering

Second Department

Mathematics and Statistics

Research Center/Lab(s)

Center for High Performance Computing Research

Keywords and Phrases

Enhanced Geothermal Systems; Fracture Asperity; Thermo-Mechanical Analysis

International Standard Serial Number (ISSN)

0375-6505

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2021 Elsevier, All rights reserved.

Publication Date

01 Sep 2020

Link to Full Text

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