Imaging method of table-driven Kirchhoff pre-stack time migration within the angle-domain

For dealing with ray-bending effect in vertically varied velocity media and directly providing the common imaging point gathers within angle-domain for AVO analysis and inversion, the table-driven Kirchhoff pre-stack time migration based on ray tracing algorithm was proposed. The basic principles are that, according to the reflection time-distance equation in laterally homogeneous media, numerical tables of travel-time and reflecting angle are established through improved two points ray tracing algorithm, and then, during the course of migration, the information of two-way travel-time and incidence angle of each reflection path in imaging aperture can be obtained from these tables, finally, the angle-domain common-image gathers and migration sections are obtained by using the impulse responses stacking method. For partially considering the ray-bending effect into the weighting function, the imaging amplitudes should be more accurate. Moreover, the time invariant feature of waveform stretching in angle domain is beneficial to the sequent waveform correction. Test results of synthetic data and actual seismic data have verified the feasibility of this method.