Near Surface Velocity Analysis in the Common Image Cube (CIC) Domain

摘要

Low relief structures are increasingly important onshore exploration targets.Accurate resolution of these structures and reservoir characterization can be difficult because seismic reflections of these targets are contaminated with distortions due to complicated near surface geology. Downward continuation wave equation datuming techniques offer a solution to the near surface problem but they require a detailed knowledge of the near surface velocity. Near surface Migration VelocityAnalysis (MVA) can be quite challenging due to the low fold of the data involved. In this paper, we integrate different MVAmethods into the common image cube (CIC) approach. These methods include residual curvature analysis (RCA), depth focusing analysis, and common focus point (CFP). We use the CIC as a domain for near surface velocity analysis to address the low fold problem. For 2D data at a lateral position, instead of invoking the zero-lag imaging condition, we store other lags at each depth level. The result is a cube of data that offers more information than other methods. We illustrate two uses of this cube by applying wave equation datuming to a synthetic dataset, simulated from topography, using correct and incorrect velocity models, respectively.