三维波场延拓复杂表层模型校正方法及应用

The Method and application of 3D wave field continuation correction based on complicated surface layer model

如何正确地消除复杂地表对地震波场的影响,提高地下构造成像的质量一直是中国西部复杂地区地震勘探中存在的难题.本文在三维复杂表层速度模型层析反演[1]的基础上,研究了关于复杂地表的静校正问题,提出用三维波动方程在炮集上对地震波场进行正、反向延拓,消除复杂地表对波场的影响,实现三维复杂表层模型校正.理论和实际应用证明,该方法已超越常规静校正的含义,属时变校正方法.用本方法处理复杂地表问题,不但能消除表层对不同深度反射波产生的不同时差影响,提高叠加剖面质量,而且能使校正后的地震波场保持波动特征不发生畸变,可为建立正确的深层速度模型和波动方程叠前深度偏移奠定良好的基础.

It is a difficult problem how to eliminate the complex surface layer effect on seismic wave filed and improve the image quality of geologic conformation in the complicated seismic prospecting area of the western China. On the basis of the velocity model tomographic inversion of 3D complicated surface layer, this paper has studied the static correction problem on complicated surface layer and puts forward a method by continuing the seismic wave-field down- ward and upward on the shot gathers with 3D wave equation based on the 3D surface layer model. We can eliminate the complex surface layer effect on seismic wave filed, and realizes 3D complicated surface layer model correction. The theory and practice prove that this method has overstepped the signification of normal static correction and it pertains to the variable-time static correction. Using this method to process the complex surface layer data, we can not only remove the different time difference effect of surface layer on the reflection wave coming from the different depth and enhance the quality of stack section, but also keep the wave characteristic of seismic wave field in no change and establish the foundation for creating correct velocity model of deep layers and wave equation pre-stack depth migration.