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Title: Inversion of normal moveout for monoclinic media

Abstract

Multiple vertical fracture sets, possibly combined with horizontal fine layering, produce an equivalent medium of monoclinic symmetry with a horizontal symmetry plane. Although monoclinic models may be rather common for fractured formations, they have hardly been used in seismic methods of fracture detection due to the large number of independent elements in the stiffness tensor. Here, the authors show that multicomponent wide-azimuth walkaway VSP surveys provide enough information to invert for all but one anisotropic parameters of monoclinic media. In order to facilitate the inversion procedure, the authors introduce a Thomsen-style parametrization for monoclinic media that includes the vertical velocities of the P-wave and one of the split S-waves and a set of dimensionless anisotropic coefficients. The parameter-estimation algorithm, based on NMO equations valid for any strength of the anisotropy, is designed to obtain anisotropic parameters of monoclinic media by inverting the vertical velocities and NMO ellipses of the P-, S{sub 1}- and S{sub 2}-waves. A Dix-type representation of the NMO velocity of mode-converted waves makes it possible to replace the pure shear modes in reflection surveys with the PS{sub 1}- and PS{sub 2}-waves. Numerical tests show that this method yields stable estimates of all relevant parameters for both amore » single layer and a horizontally stratified monoclinic medium.« less

Authors:
; ;
Publication Date:
Research Org.:
Colorado School of Mines, Golden, CO (US)
Sponsoring Org.:
USDOE; Shell Faculty Career Initiation Grant
OSTI Identifier:
20076110
DOE Contract Number:  
FG03-98ER14908
Resource Type:
Journal Article
Journal Name:
Geophysical Prospecting
Additional Journal Information:
Journal Volume: 48; Journal Issue: 3; Other Information: PBD: May 2000; Journal ID: ISSN 0016-8025
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; GEOLOGIC FRACTURES; FRACTURED RESERVOIRS; SEISMIC SURVEYS; DATA ANALYSIS; SEISMIC DETECTION; SEISMIC P WAVES; SEISMIC S WAVES; ANISOTROPY

Citation Formats

Grechka, V., Contreras, P., and Tsvankin, I. Inversion of normal moveout for monoclinic media. United States: N. p., 2000. Web. doi:10.1046/j.1365-2478.2000.00200.x.
Grechka, V., Contreras, P., & Tsvankin, I. Inversion of normal moveout for monoclinic media. United States. doi:10.1046/j.1365-2478.2000.00200.x.
Grechka, V., Contreras, P., and Tsvankin, I. Mon . "Inversion of normal moveout for monoclinic media". United States. doi:10.1046/j.1365-2478.2000.00200.x.
@article{osti_20076110,
title = {Inversion of normal moveout for monoclinic media},
author = {Grechka, V. and Contreras, P. and Tsvankin, I.},
abstractNote = {Multiple vertical fracture sets, possibly combined with horizontal fine layering, produce an equivalent medium of monoclinic symmetry with a horizontal symmetry plane. Although monoclinic models may be rather common for fractured formations, they have hardly been used in seismic methods of fracture detection due to the large number of independent elements in the stiffness tensor. Here, the authors show that multicomponent wide-azimuth walkaway VSP surveys provide enough information to invert for all but one anisotropic parameters of monoclinic media. In order to facilitate the inversion procedure, the authors introduce a Thomsen-style parametrization for monoclinic media that includes the vertical velocities of the P-wave and one of the split S-waves and a set of dimensionless anisotropic coefficients. The parameter-estimation algorithm, based on NMO equations valid for any strength of the anisotropy, is designed to obtain anisotropic parameters of monoclinic media by inverting the vertical velocities and NMO ellipses of the P-, S{sub 1}- and S{sub 2}-waves. A Dix-type representation of the NMO velocity of mode-converted waves makes it possible to replace the pure shear modes in reflection surveys with the PS{sub 1}- and PS{sub 2}-waves. Numerical tests show that this method yields stable estimates of all relevant parameters for both a single layer and a horizontally stratified monoclinic medium.},
doi = {10.1046/j.1365-2478.2000.00200.x},
journal = {Geophysical Prospecting},
issn = {0016-8025},
number = 3,
volume = 48,
place = {United States},
year = {2000},
month = {5}
}