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Evaluation of local porosity changes in limestone samples under triaxial stress field by using X-ray computed tomography

By
C. O. Karacan
C. O. Karacan
The Pennsylvania State University, 403 Academic Activities Building, University Park, PA 16802, USA (e-mail: karacan@pnge.psu.edu)
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A. S. Grader
A. S. Grader
The Pennsylvania State University, 403 Academic Activities Building, University Park, PA 16802, USA (e-mail: karacan@pnge.psu.edu)
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P. M. Halleck
P. M. Halleck
The Pennsylvania State University, 403 Academic Activities Building, University Park, PA 16802, USA (e-mail: karacan@pnge.psu.edu)
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Published:
January 01, 2003

Abstract

The character of reservoir rocks is uncertain and variable at the depths where they are subjected to different tectonic forces and pressure changes due to drilling, well stimulation and production operations. The stress- and time-dependent deformation of the porous structure is expected to change the behaviour of the most important properties of the rock, such as porosity and permeability, which in turn changes the reservoir production predictions.

In this study, we demonstrate the use of X-ray computed tomography (CT) to investigate the porosity and permeability changes of Cordova Limestone samples during deformation in a triaxial cell. The experiments were performed in a specially designed X-ray transparent triaxial test cell, which enables applying stress as well as making flow measurements. Because the presence and value of confining pressure changes the deformation behaviour of the rock, different constant confining stresses were applied to the samples to change the deformation regime. As the axial load was increased, samples were scanned at different locations to determine the stress-dependent local changes in porosity. Absolute permeability during the deformation was also measured.

Results show that the stress condition applied to the porous medium changes the rock and fluid transport properties, compared to measurements taken without stressing the sample. X-ray CT enabled the local porosity changes to be quantified, to locate compaction bands and places where shear location occurs, and to evaluate how the inner structure of the rock changes during different modes of deformation.

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Contents

Geological Society, London, Special Publications

Applications of X-ray Computed Tomography in the Geosciences

F. Mees
F. Mees
Ghent University, Belgium
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R. Swennen
R. Swennen
Physico-chemical Geology, K. U. Leuven, Belgium
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M. Van Geet
M. Van Geet
SCK-CEN, Belgium
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P. Jacobs
P. Jacobs
Ghent University, Belgium
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Geological Society of London
Volume
215
ISBN electronic:
9781862394636
Publication date:
January 01, 2003

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