scholarly journals Radiation pattern analyses for seismic multi-parameter inversion of HTI anisotropic media

2019 ◽  
Author(s):  
Fengxia Gao ◽  
Yanghua Wang
Keyword(s):  
Waveform Inversion ◽  
Anisotropic Media ◽  
The Third ◽  
Seismic Waveform ◽  
Parameter Inversion ◽  
Stage Scheme ◽  
Hti Media ◽  
Transverse Isotropic ◽  
Anisotropy Parameters ◽  
Elastic Coefficients

Abstract In seismic waveform inversion, selecting an optimal multi-parameter group is a key step to derive an accurate subsurface model for characterising hydrocarbon reservoirs. There are three parameterizations for the horizontal transverse isotropic (HTI) media, and each parameterization consists of five parameters. The first parameterization (P-I) consists of two velocities and three anisotropy parameters, the second (P-II) consists of five elastic coefficients and the third (P-III) consists of five velocity parameters. The radiation patterns of these three parameterizations indicate a strong interference among five parameters. An effective inversion strategy is a two-stage scheme that first inverts for the velocities or velocity-related parameters and then inverts for all five parameters simultaneously. The inversion results clearly demonstrate that P-I is the best parameterization for seismic waveform inversion in HTI anisotropic media.

scholarly journals Study of the influence of anisotropy parameters on reflection coefficients from a boundary between two azimuthally anisotropic media

2020 ◽  
pp. 18-29
Author(s):  
G. A. Dugarov ◽  
R. K. Bekrenev ◽  
T. V. Nefedkina
Keyword(s):  
Significant Influence ◽  
Anisotropic Media ◽  
Elastic Parameter ◽  
Media Analysis ◽  
Reflection Coefficients ◽  
Reflection Data ◽  
Hti Media ◽  
Target Layer ◽  
Anisotropy Parameters ◽  
Hti Medium

The paper considers an algorithm for calculating reflection coefficients from boundary between two HTI media. Analysis of the presence of anisotropy above and below the target boundary, as well as variations in the parameters of HTI media, was done. Interpretation of reflection data from the boundary between two HTI media with neglect of anisotropy above or below potentially leads to significant errors in estimation of symmetry axes directions, and hence fracturing orientation. Overestimation/underestimation of an elastic parameter in the overlying HTI medium could lead to a corresponding overestimation/underestimation of similar parameter in the underlying target layer in the result of AVAZ inversion. Furthermore, among the anisotropy parameters Thomsen parameter γ has most significant influence on the reflection coefficients dependences. Thus, the parameter γ could be used foremost as a result of the AVAZ inversion.

Anisotropy parameter inversion from sonic and density logs in horizontally transverse isotropic media

2017 ◽  
Vol 57 (2) ◽  
pp. 772
Author(s):  
Joseph Kremor ◽  
Khalid Amrouch
Keyword(s):  
Wave Velocity ◽  
Symmetry Plane ◽  
Anisotropy Parameter ◽  
Compressional Wave ◽  
Fracture Plane ◽  
Compressional Wave Velocity ◽  
Transverse Waves ◽  
Hti Media ◽  
Transverse Isotropic ◽  
Anisotropy Parameters

A methodology of calculating anisotropy parameters in horizontally transverse isotropic (HTI) media using a Backus average-like algorithm is presented herein. Anisotropy parameters in HTI media are calculated by mapping the stiffness parameters that exist in HTI media and vertically transverse isotropic (VTI) media by tilting the Christoffel equations. Fast and slow transverse waves, compressional wave and density logs are used as inputs into the averaging algorithm and, from these, anisotropy parameters are calculated over a predefined averaging window. From the results, the horizontal compressional wave velocity in the direction of the symmetry plane of isotropy can be determined, as can the compressional wave velocity that is perpendicular to the symmetry plane. When the anisotropy is caused by a single set of vertical fractures, these correspond to the directions perpendicular to and parallel to the fracture plane respectively. In cases where the thickness of the bed of interest is thin, a workflow is presented to choose an averaging length that will allow for the calculation of anisotropy parameters and velocities in thin beds. This technique was applied to a coal seam gas well situated in the Surat Basin and anisotropy parameters were calculated over two horizons.

scholarly journals Polynomial amplitude versus azimuth inversion in horizontally transverse isotropic media, as tested on fractured coal seams in the Surat Basin

2017 ◽  
Vol 57 (2) ◽  
pp. 776 ◽  
Author(s):  
Joseph Kremor ◽  
Randall Taylor ◽  
Khalid Amrouch
Keyword(s):  
Fourier Method ◽  
Compressional Wave ◽  
Seismic Inversion ◽  
Seismic Survey ◽  
Weak Anisotropy ◽  
Anisotropic Component ◽  
Hti Media ◽  
Transverse Isotropic ◽  
Anisotropy Parameters ◽  
Amplitude Versus

A new technique of amplitude versus azimuth (AVAZ) seismic inversion in horizontally transverse isotropic (HTI) media is presented. AVAZ is an effective method of characterising anisotropic variation within individual reflectors as well as characterising fractures. The compressional wave reflectivity equation in HTI media has been reformulated into a parabolic form that allows for fast and efficient inversion. The isotropic component of the azimuthal reflectivity has been separated precisely from the anisotropic component and the anisotropic component has been decoupled exactly into its constituent elliptic and anelliptic components. The exact isotropic, elliptic and anelliptic amplitude versus offset (AVO) gradient equations in HTI media are presented herein and the amount of error associated with previous approximations is also defined under the assumption of weak anisotropy. A method of calculating Thomsen’s weak anisotropy parameters using these AVO gradient terms is then outlined. Compared with the elliptic method, there is reduced error incorporated in the new AVAZ method and the error relationships of this method are compared with the Fourier method. Data from an open file 3D wide azimuth seismic survey in the Surat Basin were inverted to demonstrate the effectiveness of the techniques which are presented herein. Seismic amplitudes from six azimuthal stacks were extracted over two horizons and inverted around a well where full-wave sonic and density logs were acquired. For both horizons, the error between the inverted anisotropy parameters from seismic and the inverted anisotropy parameters from wire line logs were found to be less than 5% for both horizons.

scholarly journals Estimation of elastic constants for HTI media using Gauss-Newton and full-Newton multiparameter full-waveform inversion

Geophysics ◽  
2016 ◽  
Vol 81 (5) ◽  
pp. R275-R291 ◽  
Author(s):  
Wenyong Pan ◽  
Kristopher A. Innanen ◽  
Gary F. Margrave ◽  
Michael C. Fehler ◽  
Xinding Fang ◽  
...  
Keyword(s):  
Elastic Constants ◽  
Order Term ◽  
Fractured Reservoirs ◽  
Waveform Inversion ◽  
Anisotropic Media ◽  
Second Order ◽  
Full Waveform Inversion ◽  
Full Waveform ◽  
Fractured Medium ◽  
Hti Media

In seismic full-waveform inversion (FWI), subsurface parameters are estimated by iteratively minimizing the difference between the modeled and the observed data. We have considered the problem of estimating the elastic constants of a fractured medium using multiparameter FWI and modeling naturally fractured reservoirs as equivalent anisotropic media. Multiparameter FWI, although promising, remains exposed to a range of challenges, one being the parameter crosstalk problem resulting from the overlap of Fréchet derivative wavefields. Parameter crosstalk is strongly influenced by the form of the scattering pattern for each parameter. We have derived 3D radiation patterns associated with scattering from a range of elastic constants in general anisotropic media. Then, we developed scattering patterns specific to a horizontal transverse isotropic (HTI) medium to draw conclusions about parameter crosstalk in FWI. Bare gradients exhibit crosstalk, as well as artifacts caused by doubly scattered energy in the data residuals. The role of the multiparameter Gauss-Newton (GN) Hessian in suppressing parameter crosstalk is revealed. We have found that the second-order term in the multiparameter Hessian, which is associated with multiparameter second-order scattering effects, can be constructed with the adjoint-state technique. We have examined the analytic scattering patterns for HTI media with a 2D numerical example. We have examined the roles played by the first- and second-order terms in multiparameter Hessian to suppress parameter crosstalk and second-order scattering artifacts numerically. We have also compared the multiparameter GN and full-Newton methods as methods for determining the elastic constants in HTI media with a two-block-layer model.

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