Discrete micro-physics interactions determine fracture apertures

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Abstract

An important question arises in relation to a rock-mass that is disrupted by an array of fractures, namely: how to quantify the evolving spatial arrangement of fracture apertures that are a major factor in bulk fluid flow processes. The approach herein employs a discrete micro-physics model of the rock texture, enabling the formulation of analytical expressions that explicitly define the fluids//geomechanics interactions that occur at the micro-scale. The resulting macro-scale responses of the model define the stress, bulk strain, and pressure states that characterise the porous rock. Via extending the discrete model by introducing a planar discontinuity, the fracture-normal bulk strain determines the status of the fracture aperture, as a consequence of the movement of the rock//fracture interface. The micro-physics model shows that a closed fracture cannot change to an open fracture by pressure changes alone; instead, bulk strain must elongate the porous rock in a direction normal to the fracture. Once opened, fracture apertures respond to changes in fluid pressure. A realistic context, within which the required bulk strain occurs, is the discontinuum geomechanics of fractured rock-mass systems, for which previous simulations exhibit a range of emergent local states that relate to the conditions, identified via the micro-physics, as being the essential controls on aperture evolution.

Article highlights:

- Discrete rock-texture model underpins micro-physics expressions that lead to macro-scale material response of matrix//fracture

- Closed fracture cannot open without local elongation normal to fracture; high pressure alone does not open fracture

- Open fracture changes aperture with changing pressure.

Original languageEnglish
Article number170
JournalGeomechanics and Geophysics for Geo-Energy and Geo-Resources
Volume8
Issue number5
DOIs
Publication statusPublished - 5 Oct 2022

Keywords

  • Effective stress
  • Fluid–solid interaction
  • Fracture aperture
  • Micro-physics
  • Micro-to-macro

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology
  • Geophysics
  • Energy(all)
  • Economic Geology

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