基于角道集剩余曲率分析的层析速度建模

Tomography velocity model building based on ADCIG's residual curvature

中深层地下构造由于地震波场复杂、覆盖次数不足、信噪比低及有效反射较弱等原因造成速度建模精度低,进而影响了深度偏移质量。为此,本文提出一种中深层层析方法:利用角道集作为速度分析道集,推导了基于剩余曲率的层析建模方程,并将角道集的剩余曲率沿射线路径反投影进行速度更新。该方法既避免了常规反射层析在低信噪比叠前数据上同相轴拾取困难的问题,又无须在射线追踪中进行试射以拟合炮检点坐标,具有较高的反演精度。模型试算和实际数据处理结果均验证了方法的有效性。

In middle and deep subsurface layers,complex wavefield,low fold,low S/N,and weak reflection may cause poor accuracy of velocity model building,thereby affecting depth migration quality.We propose in this paper a new tomography velocity model building method for middle and deep structure.Using angle domain common imaging gathers(ADCIGs)in velocity analysis,we deduce tomography model building equations based on residual curvature,and back project the residual curvature of ADCIGs along ray paths to get velocity update.This method avoids both difficult event picking from low S/N prestack data in conventional reflection tomography and ray tracing to fit source and receiver coordinates.So it can obtain high inversion accuracy.Model and real dataset test results verify the correctness and validity of the proposed tomography method.