3D Amplitude-preserved Full-azimuth Anisotropic Imaging - Offering More Reliable Azimuthal AVO for Fracture Detection

Abstract

For fractured reservoirs, the routinely used imaging methods are usually isotropic or azimuth-sectored migration, which will result in distorted migration events and amplitude because they fail to handle azimuthal anisotropy problem. In order to obtain focused subsurface imaging and accurate azimuthal AVO, full-azimuth anisotropic imaging which incorporates azimuthal anisotropy into migration algorithm is a better choice. Even so, most azimuthal anisotropic imaging only concerns source-receiver azimuth and offset on the surface, which may not properly represent the wavefield propagating in complex structures area. In this case, anisotropic imaging in subsurface scattering-azimuth and incident-angle domain is more superior. In this paper, firstly full-azimuth isotropic imaging is conducted to analyze azimuthal velocity variation and calculate anisotropic parameters. Then they are used to perform full-azimuth anisotropic imaging. Through the application to data of fractured physical model, it proves that, compared with isotropic and azimuth-sectored migration, full-azimuth anisotropic imaging generates higher-quality CRP gathers, which results in accurate fracture inversion. What’s more, compared with anisotropic imaging in source-receiver azimuth and offset domain, anisotropic imaging in subsurface scattering-azimuth and incident-angle domain is more suitable for amplitude-preserved CRP gathering in complex structures area.