Multi-azimuth 3D converted wave prestack time migration in orthotropic medium

Most of the migration algorithms for converted wave prestack time migration (PSTM) only consider the VTI anisotropic medium effect. HTI anisotropic medium induced by vertical fractures has stronger azimuth velocity anisotropy, so velocity fields with different propagation directions will vary in the ellipse rule. Imaging quality of PSTM for multi-azimuth 3D converted wave data will reduce by using VTI anisotropy parameters without considering HTI anisotropy parameters in orthotropic medium. According to the above problem, we proposed a multi-azimuth 3D converted wave PSTM based on orthogonal anisotropic medium. The traveltime formula of the proposed PSTM algorithm simultaneously considers the VTI and HTI anisotropic parameters. This equation makes multi-azimuth 3D converted wave data processing closer to the actual formation medium. However, converted wave is also influenced by fast and slow shear waves mapping to R- and T-component unlike compression wave, therefore shear wave separation needs to be done for R- and T-component before converted wave PSTM in orthotropic medium. It is necessary to separate PS-wave into PS1-wave and PS2-wave from R- and T-component in orthotropic medium for multi-azimuth 3D converted wave data. The multi-azimuth 3D converted-wave PSTM based on orthotropic medium is applied on the seismic data in Southwest China, the structure interpretation is more reasonable and characteristics of events are clearer on the results of PSTM for multi-azimuth 3D converted wave after PS1 and PS2 wave separation, which demonstrates the rationality and practicability of our algorithm. ©, 2015, Science Press. All right reserved.