Strain rate effects in Kimmeridge bay shale

Swan, Gerry; Cook, J.M.; Bruce, Sue; Meehan, Rosa

doi:10.1016/0148-9062(89)90002-8

Cited by 67 publications

(30 citation statements)

References 18 publications

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“…For both shales, the failure mode of the high-pore-pressure samples changes from brittle at low strain rates (with a single, welldefined shear plane and sometimes a few cracks roughly parallel to the axis of the core) to ductile at high strain rates (with considerable barrelling of the sample, formation of shear microcracks and thick shear bands, and a general appearance of plasticity). 11 This behavior is opposite that expected from rocks and many other materials where high strain rates generally produce brittle behavior. 15 Influence of Total Pressure at High Strain Rate.…”

Section: Resultsmentioning

confidence: 91%

Effects of Strain Rate and Confining Pressure on the Deformation and Failure of Shale

Cook

Sheppard

Houwen³

1991

SPE Drilling Engineering

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Previous work on shale mechanical properties has focused on the slow deformation rates appropriate to wellbore deformation. Deformation of shale under a drill bit occurs at a very high rate, and the failure properties of the rock under these conditions are crucial in determining bit performance and in extracting lithology and pore-pressure information from drilling parameters. Triaxial tests were performed on two nonswelling shales under a wide range of strain rates and confining and pore pressures. At low strain rates, when fluid is relatively free to move within the shale, shale deformation and failure are governed by effective stress or pressure (Le., total confining pressure minus pore pressure), as is the case for ordinary rock. If the pore pressure in the shale is high, increasing the strain rate beyond about 0.1 %/sec causes large increases in the strength and ductility of the shale. Total pressure begins to influence the strength. At high strain rates, the influence of effective pressure decreases, except when it is very low (Le., when pore pressure is very high); ductility then rises rapidly. This behavior is opposite that expected in ordinary rocks. This paper briefly discusses the reasons for these phenomena and their impact on wellbore and drilling problems.

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Section: Resultsmentioning

confidence: 91%

Effects of Strain Rate and Confining Pressure on the Deformation and Failure of Shale

Cook

Sheppard

Houwen³

1991

SPE Drilling Engineering

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“…The normal n to the contacts between clay platelets is expected to vary from domain to domain, with a preferred orientation resulting from the depositional and stress history of the rock. Thus the clay particles vary in orientation but are aligned locally (Swan et al 1989; Hornby, Schwartz and Hudson 1994; Schoenberg, Muir and Sayers 1996).…”

Section: Effect Of Contact Regions Between Clay Particlesmentioning

confidence: 99%

Seismic anisotropy of shales

Sayers

2005

Geophysical Prospecting

223

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A B S T R A C TShales are a major component of sedimentary basins, and they play a decisive role in fluid flow and seismic-wave propagation because of their low permeability and anisotropic microstructure. Shale anisotropy needs to be quantified to obtain reliable information on reservoir fluid, lithology and pore pressure from seismic data, and to understand time-to-depth conversion errors and non-hyperbolic moveout. A single anisotropy parameter, Thomsen's δ parameter, is sufficient to explain the difference between the small-offset normal-moveout velocity and vertical velocity, and to interpret the small-offset AVO response.

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“…Although the Coulomb parameters are, like the rate and state dependent parameters, empirical, they have a significant data base which may help in understanding the underlying processes they describe (e.g. ; WHITMAN and HEALY, 1962;JEWELL, 1989;SWAN et al, 1989;WOOD, 1990;LAJTAI et al, 1991).…”

Section: Introductionmentioning

confidence: 99%

Coulomb constitutive laws for friction: Contrasts in frictional behavior for distributed and localized shear

Marone

Hobbs

Ord

1992

PAGEOPH

105

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Abstract--We describe slip-rate dependent friction laws based on the Coulomb failure criteria. Frictional rate dependence is attributed to a rate dependence of cohesion c and friction angle qS. We show that differences in the stress states developed during sliding result in different Coulomb friction taws for distributed shear within a thick gouge layer versus localized shear within a narrow shear band or between bare rock surfaces. For shear within gouge, shear strength is given by 9 = e cos ~b + an sin qS, whereas for shear between bare rock surfaces the shear strength is ~ = e + a n tan ~b, where z and a~ are shear and normal stress, respectively. In the context of rate-dependent Coulomb friction laws, these differences mean that for a given material and rate dependence of the Coulomb parameters, pervasive shear may exhibit velocity strengthening frictional behavior while localized shear exhibits velocity weakening behavior. We derive from experimental data the slip-rate dependence and evolution of c and q~ for distributed and localized shear. The data show a positive rate dependence for distributed shear and a negative rate dependence for localized shear, indicating that the rate dependence of c and ~b are not the same for distributed and localized shear, even after accounting for differences in stress state. Our analysis is consistent with the well-known association of instability with shear localization in simulated fault gouge and the observation that bare rock surfaces exhibit predominantly velocity weakening frictional behavior whereas simulated fault gouge exhibits velocity strengthening followed by a transition to velocity weakening with increasing displacement. Natural faults also exhibit displacement dependent frictional behavior and thus the results may prove useful in understanding the seismic evolution of faulting.

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Strain rate effects in Kimmeridge bay shale

Cited by 67 publications

References 18 publications

Effects of Strain Rate and Confining Pressure on the Deformation and Failure of Shale

Effects of Strain Rate and Confining Pressure on the Deformation and Failure of Shale

Seismic anisotropy of shales

Coulomb constitutive laws for friction: Contrasts in frictional behavior for distributed and localized shear

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