Elastic Gaussian beam migration in anisotropic media
DU Xiangdong1, HAN Wenming2, CAO Xiangyang2, ZHANG Yingde2, ZHANG Shixin2, LIU Qiang3
1. CNOOC Research Institute Co., Ltd., Beijing 100027, China; 2. CNOOC International Co., Ltd., Beijing 100027, China; 3. China University of Petroleum(East China), Qing-dao, Shandong 266580, China
Abstract:Elastic wave Gaussian beam migration is a multi-component seismic imaging method with higher imaging accuracy and computational efficiency. By now more researches have focused on acoustic and elastic imaging of isotropic media and acoustic imaging of anisotropic media,but less on elastic wave migration of anisotropic media. This paper proposes the ray tracing equation of elastic wave in anisotropic media,derives the forward and backward continuation formulas of the elastic wave field in anisotropic media based on the Kirchhoff-Helmholtz integration of 2D anisotropic elastic wave and using the Green tensor characterized by elastic dynamics,and establishes an elastic Gaussian beam migration method for multicomponent seismic data of anisotropic media. In addition,the weight function is introduced into the imaging formula to suppress the crosstalk caused by different waveforms; and the sign function is introduced to facilitate the polarity inversion during converted wave imaging. Applications on a TTI sag model and a TTI multilayer model show that the imaging results of anisotropic elastic Gaussian beam migration have higher SNR,more continuous seismic events,and more accurate structural position than the similar isotropic migration. With multicomponent seismic data,and information of P-wave and S-wave fields,the method provides the imaging result with higher resolution. Moreover,it has better adaptability than the conventional imaging method based on scalar wave field.
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