Anisotropy Estimation Using Walkaway VSP Data

Zhou, Rui; Patval, Z.; McAdow, David; Singh, Shailesh Kumar; Doherty, Fran; Dushman, David; Barberan, Celine

doi:10.3997/2214-4609-pdb.6.f43

Cited by 4 publications

(1 citation statement)

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“…For depth imaging, we need subsurface anisotropy information down to the target zone, including the interval anisotropic parameters above the receiver array. Usually, a single effective VTI layer above the receiver array is considered (Leaney 2000; Zhou and Kaderali 2006). The effective anisotropic parameters δ and ɛ in this layer can be determined from walkaway VSP first breaks.…”

Section: Introductionmentioning

confidence: 99%

Interval anisotropic parameter estimation from walkaway vertical seismic profiling data

Blias¹

2012

Geophysical Prospecting

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This paper presents a new explicit method for the estimation of layered vertical transverse isotropic (VTI) anisotropic parameters from walkaway VSP data. This method is based on Dix‐type normal moveout (NMO) inversion. To estimate interval anisotropic parameters above a receiver array, the method uses time arrivals of surface‐related double‐reflected downgoing waves. A three‐term NMO approximation function is used to estimate NMO velocity and a non‐hyperbolic parameter. Assuming the vertical velocity is known from zero‐offset VSP data, Dix‐type inversion is applied to estimate the layered Thomsen anisotropic parameters ɛ, δ above the receivers array. Model results show reasonable accuracy for estimates through Dix‐type inversion. Results also show that in many cases we can neglect the influence of the velocity gradient on anisotropy estimates. First breaks are used to estimate anisotropic parameters within the walkaway receiver interval. Analytical uncertainty analysis is performed to NMO parameter estimates. Its conclusions are confirmed by modelling.

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Section: Introductionmentioning

confidence: 99%

Interval anisotropic parameter estimation from walkaway vertical seismic profiling data

Blias¹

2012

Geophysical Prospecting

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Estimation of anisotropy parameters in vertical transverse isotropy media using the ray‐based tomography

Böhm,

Farina

2024

Geophysical Prospecting

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In seismic exploration, it is very important to consider the presence of anisotropy in order to image the subsurface correctly. The knowledge of anisotropic parameters leads to more precise characterization of reservoir, fracture density and flow paths. However, conventional geophysical methods do not directly measure these parameters, and it is useful to have a method to estimate them from seismic data. In the weak transverse isotropy approximation, the fields to be considered are the vertical and horizontal velocity components and the Thomsen parameters and . We present a method for estimating the anisotropic Thomsen parameters in the presence of weak vertical transverse isotropy using P‐wave traveltime tomography based on anisotropic ray tracing. Depending on the available information, we propose different approaches to retrieve the unknowns. A conventional three‐dimensional traveltime tomography algorithm has been extended to include anisotropic ray tracing and using the algebraic reconstruction technique or modified simultaneous iterative reconstruction technique to retrieve the unknowns. We test the method on synthetic examples for the inversion of transmitted and reflected traveltimes, and we evaluate the sensitivity of the tomographic results to the available information. Furthermore, we also consider the case of tilted transverse isotropy in a seismic reflection example.

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First-break vertical seismic profiling tomography for Vinton Salt Dome

Zhou

2006

GEOPHYSICS

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Building laterally depth-varying velocity models for vertical seismic profiling (VSP) imaging is challenging because of the narrow ray-angle coverage of VSP data, especially if only first arrivals are used. This study explores the potential of a new deformable-layer tomography (DLT) for building velocity models with a VSP data set acquired over the Vinton salt dome in southwestern Louisiana. The DLT method uses first breaks to constrain the geometry of velocity interfaces from an initial model of flat, constant-velocity layers parameterized using a priori geologic and geophysical information. A progressive multiscale inversion loop gradually updates the interface geometry. The final solution model, containing 3D geometry, is well supported by resolution and reliability tests and closely matches the long-wavelength trends of area sonic logs. The presence of velocity anisotropy is also indicated.

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Anisotropy Estimation Using Walkaway VSP Data

Cited by 4 publications

References 0 publications

Interval anisotropic parameter estimation from walkaway vertical seismic profiling data

Interval anisotropic parameter estimation from walkaway vertical seismic profiling data

Estimation of anisotropy parameters in vertical transverse isotropy media using the ray‐based tomography

First-break vertical seismic profiling tomography for Vinton Salt Dome

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