Compressional to shear velocity ratios in sedimentary rocks

Johnston, Joel E.; Christensen, Nikolas I.

doi:10.1016/0148-9062(93)90018-9

Cited by 28 publications

(13 citation statements)

References 9 publications

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“…An interesting geological fact about the Khorat Plateau is that the uppermost crust consists of 4-5 km thick sedimentary (sandstone and siltstone) layers formed during the Mesozoic (Kozar et al, 1992;Morley et al, 2011). Sandstone and siltstone yield a very low Poisson's ratio (below 0.2) (Johnston and Christensen, 1993). In order to increase the average crustal Poisson's ratio of the KP-ICT to around 0.25, we propose that the thicker lower crust of this region must contain higher mafic composition material than the lower crust of the other terranes.…”

Section: Discussionmentioning

confidence: 98%

Thailand's crustal properties from tele-seismic receiver function studies

Noisagool

Boonchaisuk

Pornsopin³

et al. 2014

Tectonophysics

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Section: Discussionmentioning

confidence: 98%

Thailand's crustal properties from tele-seismic receiver function studies

Noisagool

Boonchaisuk

Pornsopin³

et al. 2014

Tectonophysics

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“…As shear deformation cannot be sustained in liquid (μ=0) shear waves will not propagate in liquid material at all. Otherwise, equations (3)(4)(5) show that V ρ is greater than V s in given medium. Both radicals must be greater than one, the first because k and μ are always positive, the second because σ cannot be greater than 0.5 [7][8][9][10][11][12].…”

Section: Vp/vs Combinationmentioning

confidence: 98%

Identification of Pay Zones Using Compressional Wave Velocity and Shear Wave Velocity Data in Sandstone Reservoirs

Hamada

2007

All Days

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractSonic travel time of compressional wave is generally used as porosity tool for given lithology. Introducing shear wave travel time is very helpful in determining mechanical rock properties. It is found that compressional wave is sensitive to the saturating fluid type. The use of the ratio of compressional wave velocity to shear wave velocity" Vp/Vs" is a good tool in identifying fluid type. The fact that compressional wave velocity decreases and shear wave velocity increases with the increase of light hydrocarbon saturation, makes the ratio of Vp/Vs more sensitive to change of fluid type than the use of Vp or Vs separately. Field examples are given to identify fluids type (water, oil and gas) using the Vp/Vs ratio. Field examples have shown that shear travel time decreases while compressional travel time increases when the water saturated points become gas or light oil saturated points in the studied sections. The decrease of shear travel time (increase of shear wave velocity) is due to the decrease of density and the absorption of deformation by free gas in pores. The increase of compressional travel time (decrease of compressional wave velocity) is due to the decrease of bulk modulus of reservoir rocks which compensates the decrease of rock density.

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Section: Introductionmentioning

confidence: 99%

“…The observed anisotropy of shales is thought to result from a complex superposition of various sources. For example, a variety of secondary factors, including compliant porosity, fluid content, kerogen content and silt content, are known to enhance or contribute to shale anisotropy (Kaarsberg ; Jones and Wang ; Tosaya ; Johnston and Christensen ; Vernik ; Hornby et al . ; Sayers , ).…”

Section: Introductionmentioning

confidence: 99%

“…Owing to their highly laminar platelike structure, clay minerals exhibit strong elastic anisotropy, due to strong covalent atomic bonding within silicate layers compared to the much weaker electrostatic bonding between layers (Bailey 1966;Weaver and Pollard 1973). The presence of partially aligned anisotropic clay minerals thus causes shales to also exhibit strong elastic anisotropy (Kaarsberg 1959;Jones and Wang 1981;Tosaya 1982;Johnston and Christensen 1993; are known to enhance or contribute to shale anisotropy (Kaarsberg 1959;Jones and Wang 1981;Tosaya 1982;Johnston and Christensen 1993;Vernik 1993;Hornby et al 1994;Sayers 1994Sayers , 2013. Notwithstanding these other factors, the primary source of shale anisotropy is thought to be the strongly anisotropic nature of clay matrix in shales and, in particular, the anisotropy arising from deposition-induced alignment of its constituent clay platelets (Ulm and Abousleiman 2006;Ortega, Ulm, and Abousleiman 2007;Sayers 1994Sayers , 2013.…”

Section: Introductionmentioning

confidence: 99%

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The impact of different clay minerals on the anisotropy of clay matrix in shale

Sayers

Boer

2019

Geophysical Prospecting

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Although clay is composed of disconnected anisotropic clay platelets, many rock physics models treat the clay platelets in shale as interconnected. However, the clay matrix in shales can be modelled as anisotropic clay platelets embedded within a soft isotropic interplatelet region, allowing the influence of disconnected clay platelets on the elastic properties of the clay matrix to be analysed. In this model, properties of the interplatelet region are governed by its effective bulk and shear moduli, whereas the effective properties of the clay platelets are governed by their volume fraction, aspect ratio and elastic stiffness tensor. Together, these parameters implicitly account for variations in clay and fluid properties, as well as fluid saturation. Elastic stiffnesses of clay platelets are obtained from the literature, including both experimental measurements and first‐principles calculations of the full anisotropic (monoclinic or triclinic) elastic stiffness tensors of layered silicates. These published elastic stiffness tensors are used to compile a database of equivalent transverse isotropic elastic stiffness tensors, and other physical properties, for eight common varieties of layered silicates. Clay matrix anisotropy is then investigated by examining the influence of these different elastic stiffnesses, and of varying model parameters, upon the effective transverse isotropic elastic stiffness tensor of the clay matrix. The relationship between the different clay minerals and their associated anisotropy parameters is studied, and their impact on the resulting anisotropy of the clay matrix is analysed.

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Compressional to shear velocity ratios in sedimentary rocks

Cited by 28 publications

References 9 publications

Thailand's crustal properties from tele-seismic receiver function studies

Thailand's crustal properties from tele-seismic receiver function studies

Identification of Pay Zones Using Compressional Wave Velocity and Shear Wave Velocity Data in Sandstone Reservoirs

The impact of different clay minerals on the anisotropy of clay matrix in shale

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