Quantifying Patterns of Brittle Damage in Fractured Rock

Lead Research Organisation: University of Aberdeen
Department Name: School of Geosciences

Abstract

Cracks control the flow of fluids in the Earth's crust - this is critical for producing hydrocarbons, for planning subsurface waste storage and for understanding earthquakes. The strength or weakness of fractured rock depends on the pressure of the fluid in the cracks and the pattern of those cracks. In the simplest case, in a rock with spherical fluid-filled pores, changes in pore fluid pressure are felt equally in all directions. This is known as isotropic poroelasticity. However, fractured rocks are known to contain arrays of narrow cracks, many of which are oriented in a similar direction. This suggests that changes in pore fluid pressure will *not* be felt equally in all directions, and this has been described by a theory of anisotropic poroelasticity. This project aims to test the hypothesis of anisotropic poroelasticity: chiefly, that changes in stress in a fluid saturated rock depend on the pattern of cracks in that rock. To date, there has been no systematic assessment of this theory based on measured data from deformed rocks. This project will collect quantitative data on crack patterns from fractured rocks and then predict changes in stress with changes in fluid pressure. These predictions will be compared to the commonly used isotropic case, and the discrepancy will be quantified. The research described in this proposal will significantly improve our mechanical models of fluid-saturated fractured rock, leading to more efficient management of subsurface resources and better assessment of seismic hazards and risks of waste facility failure.

Publications

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Farrell N (2014) Anisotropy of permeability in faulted porous sandstones in Journal of Structural Geology

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Healy D (2012) Anisotropic poroelasticity and the response of faulted rock to changes in pore-fluid pressure in Geological Society, London, Special Publications

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Healy D (2015) Polymodal faulting: Time for a new angle on shear failure in Journal of Structural Geology

 
Description We have developed software tools to quantify fracture patterns in 2D and 3D.
Exploitation Route Geologists in industry and academia can use our published code to quantify fracture patterns using published methods.
Sectors Energy,Environment

URL https://uk.mathworks.com/matlabcentral/fileexchange/58860-davehealy-aberdeen-fracpaq
 
Description We have used the findings in a JIP with industry to explore the geomechanical risks of pressure changes around subsurface faults.
First Year Of Impact 2012
Sector Energy,Environment
Impact Types Economic

 
Title FracPaQ - Quantification of Fracture Patterns 
Description The code enables the user to quantify patterns of fractures in rocks (or other materials) from 2D maps of the fracture traces. 
Type Of Technology Software 
Year Produced 2017 
Open Source License? Yes  
Impact We have published two papers from this work already; and more are in the pipeline. 
URL https://uk.mathworks.com/matlabcentral/fileexchange/58860-davehealy-aberdeen-fracpaq