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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: Geology
Published: 25 September 2018
Geology (2018) 46 (11): 951-954.
... (USA). We 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...
FIGURES
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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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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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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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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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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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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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: Geological Society, London, Special Publications
Published: 01 January 2007
DOI: 10.1144/GSL.SP.2007.270.01.08
EISBN: 9781862395183
..., single phase penneability results Table 1. Modelling parameters for fracture pattern generation Table 2. Steady-state, single phase penneability results Fig. 6. Fracture patterns generated using 200 starter cracks and a subcritical index of 50 for ( a ) isotropic initial...
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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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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: 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: Geophysics
Published: 26 February 2016
Geophysics (2016) 81 (2): M1-M6.
... rigorously prepared, and three scans were acquired from each aliquot. Subcritical nitrogen adsorption pore characterization was performed to determine the abundance of kerogen-hosted porosity. To fully characterize the pore system of samples from the oil window, toluene and then chloroform extraction were...
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Journal Article
Journal: GSA Bulletin
Published: 01 September 2014
GSA Bulletin (2014) 126 (9-10): 1340-1362.
... controlled fracture clustering may arise from the dynamic nature of fracture-set evolution. Fracture clusters are predicted by linear-elastic fracture mechanics under some conditions, including host rocks having extreme subcritical-crack-index values ( Olson, 1993 ; Olson et al., 2009 ). Such fractures may...
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Journal Article
Journal: Geosphere
Published: 04 September 2018
Geosphere (2018) 14 (5): 2157-2170.
... above, and bubbles and debris particles move in the bed crack network. The likelihood and completeness of plucking increases with average flow strength but relies on local flow properties for initiation of motion. Particle image velocimetry (PIV) analysis of flow during a plucking event suggests...
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Journal Article
Journal: Geophysics
Published: 16 February 2017
Geophysics (2017) 82 (2): D85-D106.
... represent each of the phases of organic-matter (OM) catagenesis under hydrous conditions: immature kerogen at low thermal stress (125°C for 72 h), low and peak bitumen generation with increasing thermal stress (300°C and 330°C for 72 h), cracking of bitumen to oil and gas at higher thermal stresses (330°C...
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Series: Geological Society, London, Special Publications
Published: 01 January 2017
DOI: 10.1144/SP454.16
EISBN: 978-1-78620-335-9
... to a clear and unambiguous conclusion regarding a preferred measure. Experimental determinations of fracture mechanics parameters (fracture toughness, subcritical crack growth index) are being carried out increasingly for shales (e.g. Chong et al. 1987 ; Thiercelin 1989 ; Warpinski & Smith 1990...
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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...
Image
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.