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subcritical crack index

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<b>Subcritical</b> <b>crack</b> <b>index</b> measurements compiled for six shales. These are plo...
Published: 01 November 2014
Figure 8 Subcritical crack index measurements compiled for six shales. These are plotted by depth, although there is no depth correlation. New Albany Shale data from Fidler ( 2011 ); Barnett data from Gale and Holder ( 2008 , 2010 ).
Journal Article
Journal: AAPG Bulletin
Published: 01 April 2007
AAPG Bulletin (2007) 91 (4): 603-622.
... of orientation, size, and sealing properties. We measured a mechanical rock property, the subcritical crack index, which governs fracture pattern development. Natural fractures are common, narrow (<0.05 mm; <0.002 in.), sealed with calcite, and present in en echelon arrays. Individual fractures have high...
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Journal Article
Journal: Geology
Published: 25 September 2018
Geology (2018)
... also measured the subcritical cracking index (n), Charles’s law velocity constant (A), and fracture toughness (KIC) of samples from four of the same outcrops, representative of each rock type. Erosion rates range from 1.16 ± 0.67 to 32.3 ± 7.8 m/m.y. We find strong correlations—across the four rock...
Journal Article
Published: 01 May 2012
Journal of the Geological Society (2012) 169 (3): 297-310.
... modulus 2.3–17.0 GPa, most values <6.9 GPa) and moderate to high subcritical crack index (45–78), resulting from compacted soft lithic grains and clay-mineral cements. Low abundance contradicts models that postulate persistent incipient failure by subsurface fracture. The fracture sequence resembles...
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Series: Geological Society, London, Special Publications
Published: 01 January 2004
DOI: 10.1144/GSL.SP.2004.231.01.05
EISBN: 9781862394797
...; and (2) the use of a subcritical crack-propagation rule, where propagation velocity during stable growth scales with the crack-tip stress intensity factor. Three regimes of fracture spacing are identified according to the magnitude of the subcritical index of the fracturing material. For low subcritical...
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Fracture patterns derived from geomechanical modeling, showing effects of d...
Published: 01 July 2000
Figure 4. Fracture patterns derived from geomechanical modeling, showing effects of differing subcritical crack index (n values) on resultant fracture spacing and clustering. Models show fracture traces (red lines) in map view and have identical boundary and initial conditions.
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Mechanical properties of Applecross sandstone samples at laboratory conditi...
Published: 01 May 2012
Fig. 6. Mechanical properties of Applecross sandstone samples at laboratory conditions ( T = 25 °C, P c = 1 atm). ( a ) Young’s modulus, E , for two specimens cut into 14 samples, each sample tested twice. ( b ) Subcritical crack index results for same two samples. Subcritical index
Series: Geological Society, London, Special Publications
Published: 01 January 2004
DOI: 10.1144/GSL.SP.2004.235.01.08
EISBN: 9781862394834
... of fractures in Permian Clear Fork dolostone (from Philip et al. 2002 ). Subcritical crack index and bed thickness are the only input parameters varied for the four realizations. Fig. 5. Irregular fracture pathways around dolomite rhombs (E) in Ellenburger dolostone and along internal zones (I...
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Journal Article
Journal: The Leading Edge
Published: 01 July 2000
The Leading Edge (2000) 19 (7): 704-711.
...Figure 4. Fracture patterns derived from geomechanical modeling, showing effects of differing subcritical crack index (n values) on resultant fracture spacing and clustering. Models show fracture traces (red lines) in map view and have identical boundary and initial conditions. ...
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Journal Article
Published: 01 May 2012
Petroleum Geoscience (2012) 18 (2): 191-199.
... Symbols Definition Value (unit) Rock matrix E Young’s modulus 2.0 GPa ν Poison’s ratio 0.4 ρ s Average sediment density 2350 kg m −1 A Subcritical crack growth constant 10 7 m s −1 (MPa-m 1/2 ) −10 n Subcritical crack growth index 10 a 0 Initial microcrack...
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Series: Geological Society, London, Special Publications
Published: 01 January 2007
DOI: 10.1144/SP289.8
EISBN: 9781862395374
... fracture propagation is initiated (the stress at the crack tip scales with the square root of fracture length). The increased delay before fracture propagation began for the higher subcritical index material affected fracture spacing in a couple of ways. First, at any given point in the strain history...
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Journal Article
Journal: GSA Bulletin
Published: 01 March 2005
GSA Bulletin (2005) 117 (3-4): 436-449.
... of the transition from region II to region III behavior. Region III crack growth has been evaluated (e.g., Yoshida et al., 1999 ; Ciccotti et al., 2000 ) and appears to extend up to at least v tl ≈10 −1 m/sec with a subcritical index n >100. If region III follows a Charles law to critical behavior...
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Series: Geological Society, London, Special Publications
Published: 01 January 2006
DOI: 10.1144/GSL.SP.2006.261.01.02
EISBN: 9781862395091
... the fracture mechanism of each phase, a damage model was tested by employing the constitutive laws of subcritical crack growth of crack populations with a fractal size distribution. Fig. 7. For two granitic samples WG and IG, the maximum likelihood b values during the secondary and nucleation...
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Series: GCSSEPM
Published: 01 December 2009
DOI: 10.5724/gcs.09.29.0483
EISBN: 978-0-9836096-1-2
... geomechanically generated fracture trace length and aperture patterns for a specified strain, mechanical layer thickness, and subcritical crack index. All segments having an aperture less than 0.6 mm (the given emergent threshold; emergent threshold defined in Laubach, 2003 ) in black to indicate...
Journal Article
Journal: Interpretation
Published: 11 August 2016
Interpretation (2016) 4 (4): T485-T496.
... for the generation of potential fracture patterns based on the specific formation rock properties. Subcritical crack index (SCI) describes the velocity of fracture propagation as a function of stress intensity factor ( Lawn, 1974 ). With a higher subcritical fracture growth index, fracture lengths...
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Journal Article
Published: 01 February 1991
Quarterly Journal of Engineering Geology and Hydrogeology (1991) 24 (1): 123-134.
... The Geological Society 1991 The Geological Society References Atkinson, B. K. 1979 . A fracture mechanics study of subcritical tensile cracking of quartz in wet environments. Pure and Applied Geophysics, 117 , 1011 – 1024 . Atkinson, B. K. 1984 . Subcritical crack growth...
Journal Article
Journal: The Leading Edge
Published: 01 March 2010
The Leading Edge (2010) 29 (3): 304-309.
... fluid pressure in such a reservoir causes pressure in the connected pore and fracture space of rocks to increase. Such an increase in the pore pressure consequently causes a decrease of the effective normal stress. This leads to sliding along pre-existing, favorably oriented, subcritical cracks. Figures...
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Journal Article
Published: 01 February 1998
Quarterly Journal of Engineering Geology and Hydrogeology (1998) 31 (1): 5-19.
... Geology, 19 , 364 – 371 . Anon 1990 . Methods of Test for Soils for Civil Engineering Purposes. Part 2. Classification Tests. British Standards Institution, London. Atkinson, B. K. 1984 . Subcritical crack growth in geological materials. Journal of Geophysical...
Journal Article
Journal: AAPG Bulletin
Published: 01 November 2009
AAPG Bulletin (2009) 93 (11): 1535-1549.
... of Geophysics and Space Physics , v.  15 , p.  77 – 104 . Asquith , G. , and D. Krygowski , 2004 , Basic well log analysis : AAPG Methods in Exploration Series 16 , 240  p. Atkinson , B. K. , 1984 , Subcritical crack growth in geological materials : Journal of Geophysical Research...
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Journal Article
Journal: The Leading Edge
Published: 01 December 2010
The Leading Edge (2010) 29 (12): 1494-1499.
... permeability are predominantly opening mode in origin, we employ a numerical model (boundary element method) based on a subcritical crack growth mechanism to generate realistic strata-bound fracture networks in finite thickness elastic layers. This numerical model predicts fracture network geometry, including...
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