A Rapid Time-domain Full-azimuth Anisotropic Migration for Fracture Analysis – A Case Study of Leijia Area, Songliao Basin

Fracture is the one of important reservoir spaces in Leijia area, Songliao Basin. Traditionally, azimuth-sectored migration is used to analyze velocity and output azimuthal CRP gathers. However, this method can hardly get exact azimuthal velocity and amplitude variations. Moreover, due to repeated and tedious labor on velocity analysis, azimuth-sectored migration has higher computational cost. Different from this conventional method, we employ an amplitude-preserved rapid time-domain full-azimuth anisotropic migration algorithm in this paper for better fracture characterization. In implementation, kinematic variations on CRP gathers obtained from isotropic migration are used to estimate anisotropic parameters for subsequent anisotropic migration. With the help of accurate velocity information, more amplitude-preserved azimuthal CRP gathers are generated, which allows fracture prediction using AVAz inversion. Then, precise and reliable fracture information can be detected by fracture prediction method based on the incorporation of NMOz and AVAz inversion. Resultantly, fracture detection results with our method well agree with the FMI data and well production. All of these results suggest the new method is a more accurate and reliable fracture detection method in comparison with traditional method based on azimuth-sectored migration.