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3D地震数据处理中的关键是偏移步骤,因为既要考虑它的3D特性,又要顾及到计算的费用。3D偏移的效率和准确性是由所用到的波场外推技术决定的。以变长度的二阶微分算子为基础的波场外推同时具有很高的效率和准确度。与基于McClellan变换和算子分裂的偏移方法相比,变长度二阶微分算子的使用展示出了明显的优势。这种3D偏移算子具有近乎完美的圆对称性,在纵测线与横测线间的45°方位角上没有明显的定位误差。理论算例的试算结果表明,这种方法只受到空间假频的限制,不需要昂贵的数据内插来消除数值假象。这样就大大地减少了3D一步法深度偏移的计算费用。
The key to 3D seismic data processing is the offset step, since it takes into account both its 3D characteristics and its computational cost. The efficiency and accuracy of the 3D offset is determined by the wave field extrapolation technique used. The wave field extrapolation based on the second-order differential operator with variable length has high efficiency and accuracy at the same time. The use of variable-length second-order differential operators shows distinct advantages over the offset method based on McClellan transforms and operator splitting. This 3D-shift operator has near-perfect circular symmetry with no apparent positioning error at 45 ° azimuth between the in-line and the in-line. The trial calculation of the theoretical example shows that this method is only limited by space aliasing and does not require expensive data interpolation to eliminate the numerical artifacts. This greatly reduces the computational cost of 3D one-step depth migration.