Kirchhoff Integral Prestack Time Migration with Full Azimuth Angle Gathers Generation Method and its Implementation

The azimuth angle domain common image gathers can objectively reflect the velocity, anisotropy parameter anomaly and amplitude versus angle (AVA) and fracture information of the subsurface medium. The traditional Kirchhoff PSTM usually outputs offset domain common image gathers, which have many inconveniences for velocity analysis, anisotropy analysis, AVA analysis, and fracture identification. This paper proposes a Kirchhoff pre-stack time migration with full azimuth angle gathers output method based on travel timegradient and proposes an industrially feasible implementation. The wave field propagation direction vector is calculated by the travel time field gradient to form full azimuth angle gathers, which can reflect seismic acquisition parameters and wave fields propagation effect. In order to process large-scale seismic data, this paper gives a practical strategy, which bases on input-imaging point. Imaging subsurface inline-by-inline, which greatly reduces the total the pressure of the azimuth angle gather output on the computer memory, and greatly improves the feasibility of the Kirchhoff integral time migration with full azimuth angle gathers output. The three-dimensional SEG salt model data and real data test in a certain offshore dataset proves the correctness of the method.