3D amplitude-preserved full-azimuth anisotropic imaging and CRP gathering: An appealing method for integrated fracture detection

Abstract

Summary Revealing azimuthal velocity or amplitude variation (VVAZ or AVAZ) is of great significance for fracture prediction. Traditionally, azimuth-sectored migration is used to analyze velocity and output azimuthal CRP gathers. However, this method does not get the exact azimuthal velocity and amplitude anisotropy. Using azimuthal velocities to fit an ellipse may be quite unstable due to insufficient sector numbers. Without the knowledge of azimuthal velocity variation, azimuth-sectored migration may result in distorted events and destroy true azimuthal amplitude on CRP gathers. Therefore, in this paper, a 3D amplitude-preserved fullazimuth anisotropic imaging method is introduced. Velocity anisotropy is derived through anisotropic imaging, which can be used to detect fractures based on VVAZ inversion. With the help of accurate velocity information, more amplitudepreserved azimuthal CRP gathers are generated, which allows fracture prediction using AVAZ inversion. Then, precise and reliable fracture information can be detected by integrating these two results. Through the application to physical model data and field seismic data, it is proven that full-azimuth anisotropic imaging and gathering is regarded as more superior strategy for fracture prediction.