Gas Well Stimulation Studies
The research described here is part of a program funded by Morgantown Energy Technology Center under the Eastern Gas Shale Program to determine if tailored pulse loading (TPL) offers a viable means for stimulating Devonian Shale Wells. This technique (TPL
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ROCK
FRACTURE MECHANICS
EDITED BY
H.P. ROSSMANITH TECHNICAL UNIVERSITY OF VIENNA
SPRINGER-VERLAG WIEN GMBH
This work is sub;ect to copyright. AII rights are reserved, whether the whole or part of the material is concemed specifically those of translation, reprinting, re-use of illustrations, broadcasting, reproduction by photocopying machine or similar means, and storage in data banks.
©
1983 by Springer-Verlag Wien
Originally publisbed by Springer Verlag Wien-New York in '1983
ISBN 978-3-211-81747-6 DOI 10.1007/978-3-7091-2750-6
ISBN 978-3-7091-2750-6 (eBook)
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CONTENTS
PREFACE
I. BAs I CS
OF RocK FRACTURE MEeHAN I CS (R.A.Sahmidt - H.P.Rossmanith)
1
1. Introduction
2. Linear Elastic Fracture Mechanics (LEFM) 2.1. The Stress Intensity Factor 2.2. Fracture Criteria 2.3. Fracture Toughness 2.4. Crack Tip Zone of Micro-Cracking in Rock 2.5. Subcritical Crack Growth 3. Development of Fracture Toughness Testing 3.1. CT-Specimen and 3PB-Specimen Testing 3.2. Anisotropy 3.3. Effects of Hydrostatic Compression 4. Closure 5. References
II
I
ANALYSIS OF CRACKS RELATED TO ROCK FRAG"ENTATION
3 5 10 11 12 17 19 21 25 25 26 27
31
(F. Ouahter•lony)
1. Introduction to Blasting Configurations
2. Idealized Crack Systems 3. Complex Representation and Conformal Mapping 3. 1• ~1ethod 3.2. Results 3.3. Formal Approach to Uniform Growth 4. Path-Independent Integrals 4.1. Method 4.2. Results and Applications 5. References
31 32 37 37 40 52 57 57 61 66
IV
Contents
III. FRACTURE TOUGHNESS TESTING OF ROCK (F.Ouahter:>Zony)
1. Review of Toughness Testing 1.1. On Specimen Geometries 1.2. Specific Work of Fracture 1.3. Griffith's Balance of Energy Rates 1.4. Fracture Toughness 1.4.1. Validity of Metals Testing Criteria 1.4.2. Other Aspects 1.5. J-Integral Resistance 1.5.1. Applicability of JicTest Practice for Metals to Rock 1.5.2. J 1 ~-Measurements on Rock 1.6. Anisotropy Effects 1.6.1. Material Description 1.6.2. Crack Growth Resistance Values 1. 7. Cone 1us ions 2. Development of Core Bend Specimens 2.1. Single-Edqe-Crack-Round-Bar in Bending (SECRBB) 2.1.1. Experimental Procedure 2.1.2. Results 2.1.3. Further Fracture Mechanics Formulas 2.2. Chevron-Edge-Notch-Round-Bar in Bending (CENRBB) 3. Crack Resistance Measurements on Core Specimens 3.1. SimpleR-Curve Approach to SECRBB Testing 3.1.1. Prediction Formulas 3.1.2. Energy Rate Crack Pesistance Data 3.1.3. Conclusions 3.2. Direct R-Curve Measurements on SECRBB Specimens 3.2.1. R-Curves from Complete Failure Curves 3.2.2. R-Curves from Sub-Critical Failure Cycles 3.2.3. Conclusions 3.3. Conclusions from Core Toughness Data 4. References
IV
I
69 69 70 70
72
74 75
79
82
83 85
90 91 92 96 98 98
101
105 107
110 114
115
115 118
121
121
122 131
141
141 145
Nll'fRICAL l"t..DELLING OF FRACTURE ~OPAGATION (A. R. Ingr:>affea)
151
1. Introduction
151
2. The Nature of Fracture Propagation in Rock 3. Stress Intensity Factor Computation 3.1. A
