Acoustic anisotropic reverse time migration with dynamically focused beams
XIAO Jian'en1, LI Bo1, WAN Chengcheng2, CAI Jiexiong1, BAI Yingzhe1, LI Zhenchun3
1. SINOPEC Geophysical Research Institute, Nanjing, Jiangsu 211103, China; 2. Exploration & Development Research Institute of Henan Oilfield Company, SINOPEC, Zhengzhou, Henan 450000, China; 3. School of Geosciences, China University of Petroleum(East China), Qingdao, Shandong 266580, China
Abstract：Reverse time migration with Gaussian beams is a reverse time migration algorithm that uses Gaussian beam weighted integral to construct Green function. It integrates the flexibility and high efficiency of Gaussian beam migration and the accuracy of reverse time migration, which is capable of target imaging. The imaging quality of reverse time migration with Gaussian beams is highly dependent on initial parameters. When the initial beam width is small, the imaging accuracy of shallow structures is high. However, the beam width diverges rapidly as the distance increases, affecting the imaging effect of the middle and deep parts. When the initial beam width is large, the beam width changes slowly along the ray path but can reduce the calculation accuracy amplitude and travel time at the central ray, which thereby affects the imaging quality. In view of this, the idea of dynamically focused beams and the reverse time migration with Gaussian beams are combined. The Green function is constructed by the selection of an appropriate beam operator, with which the conti-nuation of forward and backward wave fields is rea-lized. Finally, the imaging results are obtained through the cross-correlation of forward and backward wave fields, and the anisotropic reverse time migration with dynamically focused beams is rea-lized. The correctness and effectiveness of the method are verified by numerical tests.
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