The Application of Multi-azimuth Grid Tomography Technology in River Channel and Fracture Imaging

In the study area of Block A, the Tertiary river channel sand bodies and Cretaceous carbonate rock fractures are extensively developed, both of which are important oil and gas reservoirs in the region. The key to improving the success rate of oil and gas exploration is accurate seismic imaging, and the high-precision velocity model is crucial for high-precision imaging. Grid tomography technology is an effective method to improve the accuracy of the velocity model. However, conventional single-azimuth grid tomography does not account for the variation of the velocity model with azimuth angle, resulting in lower accuracy in the updated velocity model and being less effective in dealing with azimuthally anisotropic media and media containing velocity anomalies. This paper uses a higher-precision multi-azimuth grid tomography technique, which divides the seismic data into several parts based on azimuth angles. Residual time shifts are picked from the offset traces at different azimuth angles, and then a system of equations is established by jointly using the residual time shifts to solve and update the velocity model. By considering the variation of the velocity model with azimuth during the tomography process, the accuracy of the updated velocity model is significantly improved. This technique is applied to the Block A, effectively enhancing the imaging accuracy of the Tertiary river channel sand bodies and Cretaceous carbonate rock fractures, laying a foundation for improving the success rate of oil and gas exploration in this block.