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Spatial mapping of fracture aperture changes with shear displacement using X-ray computerized tomography

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Title: Spatial mapping of fracture aperture changes with shear displacement using X-ray computerized tomography
Authors: Wenning, QC
Madonna, C
Kurotori, T
Pini, R
Item Type: Journal Article
Abstract: The shearing of fractures can be a significant source of permeability change by altering the distribution of void space within the fracture itself. Common methods to estimate the effects of shearing on properties, such as aperture, roughness, and connectivity are incapable of providing these observations in‐situ. Laboratory protocols are needed that enable measurements of the spatial structure of the fracture aperture field in the medium, non‐invasively. Here, we investigate changes in rough‐walled Brazilian‐induced tensile fracture aperture distribution with progressive shear displacement in Westerly granite and Carrara marble using a novel X‐ray transparent core‐holder. The so‐called calibration‐free missing attenuation method is applied to reconstruct highly‐resolved (sub‐millimeter) fracture aperture maps as a function of displacement (0 to 5.75 mm) in induced fractures. We observe that shearing increases the core‐averaged fracture aperture and significantly broadens the distribution of local values, mostly towards higher apertures. These effects are particularly strong in Westerly granite and may be the result of the higher initial roughness of its fracture surfaces. Also, while the correlation length of the aperture field increases in both parallel and perpendicular directions, significant anisotropy is developed in both samples with the progression of shearing. The results on Westerly granite provide a direct indication that fracture aperture remains largely unaffected until 1~mm of displacement is achieved, which is important when estimating permeability enhancement due to natural and induced shear displacement in faults.
Issue Date: 1-Jul-2019
Date of Acceptance: 18-Jun-2019
URI: http://hdl.handle.net/10044/1/70975
DOI: 10.1029/2019jb017301
ISSN: 2169-9313
Publisher: American Geophysical Union
Start Page: 7320
End Page: 7340
Journal / Book Title: Journal of Geophysical Research: Solid Earth
Volume: 124
Issue: 7
Copyright Statement: ©2018 American Geophysical Union. All rights reserved.
Sponsor/Funder: BEIS - Department for Business, Energy and Industrial Strategy
Funder's Grant Number: 415000025679
Keywords: Science & Technology
Physical Sciences
Geochemistry & Geophysics
fracture aperture
shear displacement
computed tomography (CT)
fluid flow
FLUID-FLOW
HYDRAULIC CHARACTERISTICS
WESTERLY GRANITE
ROUGH FRACTURES
ROCK FRACTURE
CT
TEMPERATURE
PRESSURE
PERMEABILITY
DEFORMATION
Publication Status: Published
Embargo Date: 2019-12-22
Online Publication Date: 2019-06-22
Appears in Collections:Faculty of Engineering
Chemical Engineering



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