Unstable crack growth in hydraulic fracturing: The combined effects of pressure and shear stress for a power-law fluid

Wenhao Shen, Fuqian Yang, Ya Pu Zhao

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

The underlying mechanisms of hydraulic fracturing remain elusive, and the optimization of the related processes for rocks of low permeability is challenging. There exists local crack closure induced by shear stress, which is one of the crack instabilities for a straight crack. In this study, we develop a full-stress model, which includes the combined effects of hydrodynamic pressure and shear stress on the crack surfaces. The hydrodynamic pressure is a driving force, while the shear stress is a resistance force. A novel criterion for crack propagation is derived based on the asymptotic solution of shear stress. The asymptotic solution, which is derived using perturbation analysis in the toughness-dominant regime, reveals the existence of the crack-closure phenomenon and shear-stress-dominant regime. The necessary condition for the crack closure is obtained according to numerical calculations. An energy analysis is conducted to discuss the difference between the shear-stress-dominant and the viscosity-dominant regimes. The existence of the crack closure is shown to be independent of two assumptions, lubrication theory and no-fluid-lag zone. The results presented in this study are useful for the simulation and design of hydraulic fracturing.

Original languageEnglish
Article number106245
JournalEngineering Fracture Mechanics
Volume225
DOIs
StatePublished - Feb 15 2020

Bibliographical note

Publisher Copyright:
© 2018 Elsevier Ltd

Keywords

  • Crack-closure criterion
  • Full-stress model
  • Hydraulic fracturing
  • Shear stress
  • Unstable crack

ASJC Scopus subject areas

  • General Materials Science
  • Mechanics of Materials
  • Mechanical Engineering

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