Abstract: Seismic velocity model accuracy significantly influences the quality of depth-migrated images.However,a quantitative analysis and clear understanding of this relationship remain lacking.Based on the seismic images of ultradeep fault-controlled fractured-vuggy reservoirs in the Tarim Basin,this study constructed a depth-domain numerical velocity model that approximates the conditions of subsurface media.The 3D seismic forward modeling was performed using a seismic acquisition and observation system for practical production.Different interval velocities within the numerical model were smoothed and used to quantitatively analyze their effects on reverse time migration(RTM) images based on identical parameters.Using seismic simulation data as input,the isotropic and anisotropic depth-domain velocity models were constructed following a standard industrial workflow.A quantitative analysis was subsequently conducted to analyze the differences of the constructed models and corresponding migration images from the numerical velocity model and its RTM image across different intervals and for various geological features.Overall,this study quantitatively analyzes the velocity accuracy of different velocity types in various intervals and its influence on migration imaging, obtaining several clear insights.