摘要
叠前时间偏移是转换波数据处理流程中的重要技术环节.由于下行P波和上行S波对应着不同类型的传播速度和传播机理,使得转换波偏移的诸多实施环节和实现技巧均有别于常规的纵波偏移.本文就VTI介质转换波Kirchhoff叠前时间偏移实现过程中的几个关键技术环节进行研究分析,并给出了相应的实施方案.首先,依据常速假设推导了简化的转换波时间偏移振幅加权函数,在保证偏移的高效计算的同时,兼顾了成像振幅的准确性;其次,依据直射线近似假设,推导了转换波偏移的最大无假频频率计算公式,确保了算子假频的有效滤除;接下来,设计使用了依据共转换点对称的偏移孔径,保证了偏移孔径的优化选取.此外,本文还提出利用三次卷积插值进行成像网格上参数值的插值运算,以避免传统线性插值算法的非平滑性对偏移剖面中高频信息的不良影响.多个算例的应用效果证明,本文所给出的关键技术环节的实施方案可以有效的提升转换波叠前时间偏移的成像效果.
PS-wave Kirchhoff time migration is a crucial step in the processing flow of converted wave data. However, because of the different propagation velocities and mechanisms of downing- going P-waves and up-going S-waves, its implementation is quite different from that of PP-wave Kirchhoff migration. In this paper, we discuss several important technical issues of PS wave Kirchhoff time migration in a VTI medium. First, we derive a simplified PS-wave migration amplitude weight based on constant velocities, which can both ensure computation efficiency and amplitude accuracy. Secondly, we derive the maximum aliasing-free frequency formula based on straight ray assumption to filter operator aliasing. Then, we choose an optimized migration aperture which is symmetrical with common conversion points so as to save computational expense and reduce migration noise. In addition, in order to eliminate the influence of non- smoothness caused by the traditional linear interpolation method, we propose to use the cubic convolution interpolation method to calculate the parameters at fine image grids. Tests on real datasets demonstrate the validity of our methods.
作者
岳玉波
李振春
钱忠平
孙鹏远
杨雪霖
薛贵仁
YUE YuBo1, LI ZhenChun2 ,QIAN ZhongPing1 , SUN PengYuan1 , YANG XueLin1, XUE GuiRen1(1 R＆Dcenter, BGP, CNPC, Hebei Zhuozhou 072751, China 2 School of Geosciences, China University of Petroleum, Shandong Qingdao 266555, Chin)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2018年第3期1188-1195,共8页
Chinese Journal of Geophysics
基金
国家科技重大专项(2017ZX05018005-002)
中国石油天然气集团公司科学研究与技术开发项目(2016E-1005)
中国科协青年人才托举工程(2016QNRC001)联合资助
关键词
转换波
加权函数
算子反假频
偏移孔径
三次卷积插值
PS-wave
Amplitude weight
Operator anti-aliasing
Migration aperture
Cubic convolutioninterpolation
