最短路径树法井间地震层析成像及应用

Cross-borehole seismic tomography using shortest path tree method and its application

本文将T．J．Moser的最短路径树法网络理论引入井间地震数据的层析成像处理，以其作为正演的基础。此法的基本思路是先将井间剖分成网格，在网格边界上布设节点，连接相邻非跨网格边界的节点构成网络。然后利用网络理论最短路径树法计算出源点至网络各节点的最小走时和路径，形成自源点的最小走时树。任一节点的最小走时和路径即为源点至该节点的初至走时和射线路径。反演采用共轭梯度法的变形LSQR法。理论模型和实际资料证实，此法是一种有效的方法。

Shortest path tree method, which is the network theory advanced by T. J.Moser and functions as the basis of forward computation,is introduced into crossborehole seismic tomography. The technique includes the following essential points:. Divide the cross--borehole area into grids,with nodes at grid cell boundary.. Connect the nodes at adjacent grid--cell boundaries to form a network.. Shortest path tree method is then used to estimate both the minimum traveltime and the shortest path from source point to each node in the network, thus forming the shortest travel--time tree that originates in source point.. The minimum travel time and the shortest path of any node are respectively the first break time and ray path from source point to the node.. The inversion is achieved by using LSQR algorithm,the improved conjugate gradient algorithm.Theoretical modeling and real data processing prove the technique effective.