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Least-squares reverse-time migration toward “true” reflectivity

Hao Zhang1 ,  Qiancheng Liu1 ,  Jun Hao2
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1 Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China, P.R. China,
2 Research Institute of Petroleum Exploration & Development, PetroChina, Qinghai, P.R. China,
JSE 2017, 26(2), 183–198;
Submitted: 16 February 2016 | Accepted: 10 January 2017 | Published: 1 April 2017
© 2017 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/ )
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Abstract

Zhang, H., Liu, Q. and Hao, J., 2017. Least-squares reverse-time migration toward 'true' reflectivity. Journal of Seismic Exploration, 26: 183-198. Conventional least-squares reverse time migration (LSRTM) usually aims to improve the quality of seismic image, by removing the acquisition footprint, suppressing migration artifacts, and enhancing resolution. We find that the conventional reflectivity defined in the LSRTM is related to the normal-incidence reflection coefficient and the background velocity . Compared with the defined reflectivity, our inverted result is approximate. With reflected data, LSRTM is mainly sensitive to impedance perturbations. According to an approximate relationship between them, we reformulate the perturbation-related system into a pseudo reflection-coefficient related one. Then, we seek the inverted image through linearized iteration. With the assumption that the density varies gradually compared to the migration velocity, only the knowledge of the velocity is required, although the reflected waves are produced at impedance discontinuities. We validate our scheme using the 2D Marmousi synthetic dataset.

Keywords
LSRTM
linear inversion
normal-incidence reflection coefficient
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Journal of Seismic Exploration, Print ISSN: 0963-0651, Published by AccScience Publishing
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