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Three dimensional angle domain double square root migration in VTI media for the large scale wide azimuth seismic data

Wu Chengliang, Feng Bo, Wang Huazhong, Wang Tianzhen

Acta Geophysica

2020

Vol. 68, no. 4

1021--1037

With the development of oil and gas exploration, the conventional seismic migration imaging technology based on the isotropic assumption no longer meets our current requirements for high-resolution images. Migration in anisotropic media has become an essential requirement for oil and gas exploration. Marine seismic exploration has gradually entered the wide azimuth and high-density seismic data acquisition stage. However, even for current large high-performance computer clusters, it is still very difcult to implement pre-stack depth migration based on shot gathers. Thus, we present a double-square-root (DSR) equation based on three-dimensional (3D) pre-stack depth migration in midpoint-ofset domain for a wide-azimuth dataset in transversely isotropic media with a vertical symmetry axis (VTI media). Considering VTI media, the DSR migra tion requires extensive memory and computation; we adopted the phase-shift plus interpolation approach to improve the computational efciency. Then, we extract the angle-domain common-image gathers (ADCIGs) during DSR migration. For real large-scale seismic data, we designed an efective parallel implementation of 3D DSR migration with ADCIGs outputs. Finally, we applied the proposed angle-domain VTI DSR migration on wide-azimuth SEG/EAGE salt dome-based data and real data from the China South Sea. Numerical and practical data illustrate the efectiveness of the proposed method.

Preliminary study on wave feld and dispersion characteristics of channel waves in VTI coal seam media

Ji Guangzhong, Li Hui, Wei Jiuchuan, Yang Sitong

Acta Geophysica

2019

Vol. 67, no. 5

1379--1390

Coal seam is a sedimentary rock with bedding, which can be regarded as VTI medium. VTI medium model is more suitable for real coal seam. However, existing channel wave theories generally assume that coal seams are isotropic for mathematical simplicity, and there is no study on the properties of channel waves in VTI media. In this paper, we deduce the theoretical dispersion equation of Love channel waves in the three-layer VTI model and analyze the parameter efects on the dispersion curve for the frst time. The channel wave feld in VTI media is simulated by three-dimensional staggered-grid finite diference method. The results indicate that polarization of both qP- and qSV-waves is not parallel or perpendicular to the orientation of the wave traveling in VTI media, while the polarization of SH wave is normal to wave propagation direction at horizontal plane. Therefore, it is wise to use Love channel waves to conduct feld exploration because of the uniqueness of dispersion curves in the VTI media for the Love channel waves comparing with that in isotropic media. The velocities of the Love channel wave in VTI media are higher than that in isotropic media. The coal seam thickness primarily infuences the Airy frequency phase, while the Airy phase velocity remains stable. Both the S-wave velocity and γ parameter of coal seam significantly afect Airy phase velocity. Severe errors may occur during in the coal thickness inversion when using the dispersion curve of Love channel wave in isotropic media, and dispersion curve in VTI media should be adopted. In terms of the amplitude distribution, Love channel waves appear to have similar patterns in both the VTI media and the isotropic media.