Abstract:Natural gas hydrate lateral velocity distribution is not uniform, and has a close relationship with the faults,carbonate rock,seepage and salt diapir structure;therefore,geological imaging obtained by the time offset is not accurate.It is hence necessary to obtain geological imaging in the depth domain by depth migration.The velocity model in the depth domain is optimized by tomography,which is widely used at present because of its high accuracy and reliability.In this paper,a high precision grid tomography method is used to optimize the pre-stack depth migration velocity model.The residual curvature analysis (RCA) principle is described.The steps and methods of using high precision grid tomography velocity inversion method to optimize interval velocity model in the depth domain are introduced in detail.The application effect of the actual acquisition of quasi three-dimensional Xisha hydrate seismic velocity model shows that this method has high operation efficiency,significantly improves imaging accuracy within the fault zone,shows fracture structure more clearly,and obviously changes wave group characteristics for the better,as can be seen in the migration profile.