ARTICLE

Transmission amplitude variation with offset (TAVO)

AFEEZ K. POPOOLA* ABDULLATIF A. AL-SHUHAIL OLUSEUN A. SANUADE
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Geosciences Department, King Fahd University of Petroleum & Minerals, P.O. Box 5070, Dhahran 31261, Saudi Arabia,
* Earth Sciences Department, University of Toronto, Toronto, Canada,
JSE 2019, 28(5), 413–424;
Submitted: 12 July 2018 | Accepted: 18 August 2019 | Published: 1 October 2019
© 2019 by the Authors. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution -Noncommercial 4.0 International License (CC-by the license) ( https://creativecommons.org/licenses/by-nc/4.0/ )
Abstract

Popoola, A.K., Al-Shuhail, A.A. and Sanuade, O.A., 2019. Transmission amplitude variation with offset (TAVO). Journal of Seismic Exploration, 28: 413-424. Amplitude Variation with Offset (AVO) has been applied successfully in reservoir geophysics for various applications including fluid detection and lithology typing. Existing AVO methods utilize seismic waves reflected off elastic interfaces. Amplitudes of transmitted waves, usually recorded in vertical seismic profiling (VSP) surveys, also show angle dependence and can be used for AVO-like analysis. In this study, we derive new approximations of the exact Zoeppritz transmission PP (Tpp) and PS (Tps) coefficients that are convenient for conventional AVO analysis. Testing on a published reservoir model showed that the new approximations deviated from their corresponding exact coefficients by less than 7% at an incidence angle equal to 90% of the critical angle. Furthermore, a quantitative approach is described to invert the new Tpp and Tps approximations for the P-wave velocity contrast (Aa/a), density contrast (Ap/p), S-wave velocity contrast (AB/B) and S-wave/P-wave velocity ratio (6/a) across a subsurface interface. Testing this approach using the same reservoir model resulted in error amounts of 0%, 0%, 6% and 6.5% for Aa/a, Ap/p, AB/B and B/a, respectively. These small errors show that the new approximations and inversion approach are relatively accurate.

Keywords
AVO analysis
transmitted seismic wave
Zoeppritz equation
reservoir parameter estimate
VSP survey
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Journal of Seismic Exploration, Electronic ISSN: 0963-0651 Print ISSN: 0963-0651, Published by AccScience Publishing