基于一步法层析速度建模方法建立

像域层析速度建模方法利用偏移道集剩余曲率构建目标函数并迭代更新速度场.迭代更新速度场需反复进行叠前深度偏移,对于三维地震数据,偏移成像计算时间长,迭代更新过程成倍增加层析成像计算时间.本文由剩余时差拾取机理出发,提出隐式剩余时差概念,并建立隐式剩余时差与剩余速度之间的函数关系,利用该关系通过一次计算就可以对剩余速度进行精确求取并对速度模型进行精确更新,该方法避免了常规层析方法需要多次迭代的流程.由模型数据测试及实际数据应用证明,本文提出方法是有效可行的,该方法与常规层析方法进行比较,在保证提高层速度场建模精度的同时有效提高计算效率,为后续偏移成像节省大量时间.

Establishment of an one-step method for modeling tomographic velocity

The modeling of tomographic velocity requires the use of migration results to update and iterate the layer velocity field.When the velocity is not accurate,the phase axis will bend;this kind of bending in the geophysics field is called residual curvature.In this paper,the residual curvature is analyzed in common domain image gathers,and a concept of the true residual curvature is proposed,which includes zero offset residual curvature and non-zero offset residual curvature.These two kinds of residual curvature have great influence on velocity update.According to this concept,a new method of true residual curvature tomography is proposed in this paper.This method can make the layer velocity model updating convergence more fully.Proved by the model data and actual data,the proposed method is effective and feasible.Compared with the conventional method,our method has faster convergence speed and higher accuracy.It can ensure the precision of the modeling layer velocity field and enhance the calculation efficiency.It saves a lot of time for subsequent migration imaging and other processes.