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Castagna coefficients

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Series: GCSSEPM, GCSSEPM
Published: 01 December 1996
DOI: 10.5724/gcs.96.17.0059
EISBN: 978-0-9836097-6-6
... In conventional utilization of the seismic reflection method, it has traditionally been assumed that seismic signals can be viewed as a band-limited normal incidence reflection coefficient series with appropriate traveltime and amplitude variation due to propagation through an overburden...
Journal Article
Journal: Geophysics
Published: 01 January 2001
Geophysics (2001) 66 (5): 1359–1363.
...He Chen; John P. Castagna; Raymon L. Brown; Antonio C. B. Ramos Abstract Amplitude versus offset (AVO) interpretation can be facilitated by crossplotting AVO intercept ( A ), gradient ( B ), and curvature ( C ) terms. However, anisotropy, which exists in the real world, usually complicates AVO...
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Journal Article
Journal: Geophysics
Published: 01 January 2000
Geophysics (2000) 65 (4): 1028–1031.
...He Chen; John P. Castagna Abstract Nonhyperbolic moveout resulting from localized variations in anisotropy can create many misleading artifacts such as apparent faults, folds, channels, flat spots, dim spots, bright spots, and AVO anomalies on fully and partially stacked seismic sections...
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Journal Article
Journal: Geophysics
Published: 01 January 2001
Geophysics (2001) 66 (4): 1284–1293.
...D. Sarkar, Jr.; J. P. Castagna, Jr.; W. J. Lamb, Jr. Abstract Velocity analysis using semblance estimates velocities based on a constant amplitude model for seismograms and does not take amplitude variation with offset (AVO) into account. In the presence of AVO, the constant amplitude model becomes...
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Journal Article
Journal: Geophysics
Published: 01 January 2001
Geophysics (2001) 66 (6): 1721–1734.
...Antonio C. B. Ramos; John P. Castagna Abstract Converted-wave amplitude versus offset (AVO) behavior may be fit with a cubic relationship between reflection coefficient and ray parameter. Attributes extracted using this form can be directly related to elastic parameters with low-contrast or high...
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Journal Article
Journal: Geophysics
Published: 01 June 1998
Geophysics (1998) 63 (3): 948–956.
...John P. Castagna; Herbert W. Swan; Douglas J. Foster Abstract Amplitude variation with offset (AVO) interpretation may be facilitated by crossplotting the AVO intercept ( A ) and gradient ( B ). Under a variety of reasonable petrophysical assumptions, brine-saturated sandstones and shales follow...
Series: Investigations in Geophysics
Published: 01 January 1993
DOI: 10.1190/1.9781560802624.ch1
EISBN: 9781560802624
... lithology will have a well defined V P - V 5 relationship. Given V P and lithology, Greenberg and Castagna (1992) showed that S -wave velocity prediction can be quite robust, however, the prediction error (about 5 percent) may be inadequate when viewed in terms of reflection coefficients...
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Journal Article
Journal: Geophysics
Published: 01 January 2003
Geophysics (2003) 68 (3): 849–862.
...: Ph.D. diss., Univ. of Oklahoma. Nsoga Mah ob Z. P. Castagna J. P. , 2002 , AVO hodograms and polarization attributes : The Leading Edge , 21 , 18 – 27 . Ostrander W. J. , 1984 , Plane-wave reflection coefficients for gas sands at nonnormal angles of incidence...
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Series: Geophysical Developments Series
Published: 31 December 2020
DOI: 10.1190/1.9781560803799.appa
EISBN: 9781560803799
... When seismic waves hit an interface between two layers in the subsurface, some of the energy may be reflected. The amplitude of the reflection depends on the reflection coefficient. The reflection coefficient is the ratio of the reflected amplitude to the incident amplitude. When seismic...
FIGURES
Journal Article
Journal: Geophysics
Published: 01 January 2001
Geophysics (2001) 66 (1): 42–46.
... coefficients ( Chen and Castagna, 1999 ). Azimuthal anisotropy may confound AVO analysis or be used as a fracture characterization tool (e.g., Ramos and Davis, 1997 ; Lynn et al., 1999 , MacBeth and Li, 1999 ). A common pitfall in interpretation of amplitudes at far offsets is mistaking large...
Journal Article
Journal: Geophysics
Published: 01 January 2002
Geophysics (2002) 67 (6): 1835–1843.
...Luther White; John Castagna Abstract A probabilistic inversion approach is used with Gassmann's equation to determine pore fluid modulus using elastic wave velocity without reference information from a rock saturated with a second fluid of known modulus. Numerical examples show that even when...
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Journal Article
Journal: Geophysics
Published: 01 January 2004
Geophysics (2004) 69 (1): 45–55.
...Azzeldeen A. Saleh; John P. Castagna Abstract We suggest a generalized form of the Wyllie equation to better describe acoustic velocity variation with porosity in rocks with a mixture of intercrystalline and near-spherical pores. Introducing a pore shape factor in the Wyllie equation allows...
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Journal Article
Journal: Geophysics
Published: 15 April 2014
Geophysics (2014) 79 (3): T143–T155.
... in diffusive-viscous media. Our study demonstrated that the magnitude of the reflection coefficients in such a media is not only related to the incident angle and the parameters of the medium but also strongly depends on the frequency. We first demonstrated the validity of diffusive-viscous wave equation...
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Journal Article
Journal: Geophysics
Published: 27 July 2016
Geophysics (2016) 81 (5): N31–N39.
... reflection coefficients and complex characteristic parameters, such as peak instantaneous frequency or the amplitude spectrum. These parameters can be used in estimation of thin-bed thicknesses ( Liu and Marfurt, 2006 ; Puryear and Castagna, 2008 ). Under the assumption that the middle layer is thin...
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Journal Article
Journal: Interpretation
Published: 26 May 2015
Interpretation (2015) 3 (3): ST9–ST27.
... be obtained just by examining the AVAz. The AVAz can be described as a sum of sinusoids of different periodicities, each characterized by its magnitude and phase. This sum is mathematically equivalent to a Fourier series, and hence the coefficients describing the AVAz response are azimuthal Fourier...
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Journal Article
Journal: Geophysics
Published: 07 May 2014
Geophysics (2014) 79 (3): T169–T188.
... coefficients for second-order central finite-difference operators that minimize the numerical dispersion for up to five grid points per wavelength were found using a damped least-squares (LS) criterion as well as a global optimization scheme based on l 1 - and l 2 -norm criteria. The three sets produced very...
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Journal Article
Journal: Geophysics
Published: 13 November 2017
Geophysics (2018) 83 (1): C1–C11.
...Qi Hao; Alexey Stovas ABSTRACT We have developed an approximate method to derive simple expressions for the reflection coefficients of P- and SV-waves for a thin transversely isotropic layer with a vertical symmetry axis (VTI) embedded in a homogeneous VTI background. The layer thickness is assumed...
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Journal Article
Journal: Geophysics
Published: 01 January 2003
Geophysics (2003) 68 (6): 2063–2072.
...Luděk Klimeš Abstract Explicit equations for approximate linearized reflection–transmission coefficients at a generally oriented weak-contrast interface separating two generally and independently anisotropic media are presented. The equations are derived also for all singular directions...
FIGURES
Journal Article
Journal: The Leading Edge
Published: 01 February 2012
The Leading Edge (2012) 31 (2): 152–158.
... can significantly influence the velocities of elastic waves (Eshelby, 1957; Kuster and Toksöz, 1974; Xu and White, 1995; Yan et al., 2002; Sun et al., 2004). Empirical V P - V S relationships such as Castagna's (1985) mudrock line, Han's relations (1986), and Greenberg-Castagna's (1992) relationship...
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