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Permanent link (DOI): https://doi.org/10.7939/R38D3M

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Three-dimensional Numerical Models of Drilling Induced Core Fractures Open Access

Descriptions

Other title
Subject/Keyword
core fracture
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Zhang, Lei
Supervisor and department
Currie, Claire (Physics)
Examining committee member and department
Currie, Claire (Physics)
Moussa, Walied (Mechanical Engineering)
Schmitt, Douglas R. (Physics)
Dumberry, Mathieu (Physics)
Department
Department of Electrical and Computer Engineering
Specialization

Date accepted
2011-08-30T20:53:27Z
Graduation date
2011-11
Degree
Master of Science
Degree level
Master's
Abstract
Drilling-induced fractures in borehole cores have distinct morphologies (e.g., petal, petal-centreline, saddle, and disk) and are produced under pure tensional stress, although most in-situ stresses are compressive. 3D numerical models show that tensile stress concentrations occur near the bottom of a vertical borehole. A new algorithm is developed to trace 3D tensile fractures for a range of crustal stress conditions. In a normal fault regime, fractures change from petal/petal-centreline to saddle to disk with increasing minimum horizontal stress (Sh). In a strike-slip regime, saddle fractures occur, except where Sh is much less than the vertical stress and petal centre-line fractures are found. In a thrust fault regime, saddle and disk fractures occur at low and high Sh, respectively. The results demonstrate that in-situ stress is the dominant control on fracture morphology; variations in Poisson’s ratio and core stub length primarily affect the magnitude of tensile stress.
Language
English
DOI
doi:10.7939/R38D3M
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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