四面体单元剖分下三维各向异性TI介质中多次波射线追踪  

Multiples raytracing in 3D anisotropic TI media with a tetrahedron cell model

作　　者：李兴旺[1] 白超英[1,2] 李晓玲 

机构地区：[1]长安大学地质工程与测绘学院地球物理系,陕西西安710054 [2]长安大学计算地球物理研究所,陕西西安710054 [3]国家知识产权专利局专利审查协作河南中心,河南郑州450000

出　　处：《石油地球物理勘探》2017年第1期48-55,共8页Oil Geophysical Prospecting

基　　金：国家重大科技专项子课题"海上斜井井间地震资料成像处理技术及应用研究"(2011ZX05024-001-03);长安大学中央高校基本科研业务费课题(310826150006)资助

摘　　要：采用不规则四面体单元做模型剖分,实现了三维复杂层状各向异性TI介质中多次(透射、反射及转换)波的追踪计算,弥补了现行算法主要采用规则网格计算多次波的不足。根据介质的5个弹性参数及其对称轴倾角和走向,计算主节点上qP、qSV和qSH波群速度,由此线性插值得到次级节点的群速度值;然后采用不规则最短路径算法,并结合分区多步计算技术实现多次波追踪计算。均匀各向异性介质中计算出的数值解与解析解吻合,验证了算法的有效性。复杂层状模型数值模拟结果表明:采用不规则四面体单元可有效拟合起伏地表及地下不规则速度间断面,同时该算法适用于任意倾角的TI介质,且不受各向异性强度限制。The current algorithms can only trace first arrivals and primary reflections (or conversions),but cannot well trace multiples.To overcome this problem,with a tetrahedron cell model we extend the function of multistage irregular shortest-path method into 3D anisotropic TTI media for tracking multiple arrivals composed of any kind of combinations of transmissions,conversions and reflections.The basic principle is that the 7 parameters (5 elastic parameters and 2 titled angles of symmetry axis) of TTI media sampled at the primary nodes are used to calculate the group velocity of three-mode (qP,qSV,and qSH) waves.The group velocity values at the secondary nodes are obtained by a linear interpolation function via the defined values at the primary nodes of the cell.Finally we conduct grid (or cell) wavefront expansion to trace multiple arrivals from one layer to the next.The calculation in the uniform anisotropic media indicates that the numerical result is coincided with the analytic solution,which verifies the accuracy of the methodology.Several simulation results show that the proposed method is able to efficiently approximate the undulated topography and velocity discontinuity,and suitable for any combination of multiple arrivals tracking in TTI media with any titled angle of symmetry axis and not subject to the strength (no weak anisotropic assumption) of anisotropic media. © 2017, Editorial Department OIL GEOPHYSICAL PROSPECTING. All right reserved.

关 键 词：三维各向异性TI介质 改进型最短路径算法 多次波射线追踪 四面体单元 分区多步计算技术 

分 类 号：P631[天文地球—地质矿产勘探]