摘要
时频分析方法是沉积旋回判别中常用方法．不同时频分析方法时频谱对沉积旋回的刻画能力、模式判别精度和稳定性大为不同，因而有必要加以分析和甄别，优选出一种能准确反映沉积旋回频率变化趋势的时频分析方法．采用波动方程正演模拟方法对正旋回、反旋回、正反旋回、反正旋回共四种旋回地层进行正演模拟；选取广义s变换、小波变换、Wigner—Ville时频分布、仿射类时频分布（尺度图）计算地震记录的时频谱．考察不同时频分析方法对沉积旋回单元的判别极限，及其对噪声、突变层、反射系数突变、旋回单元组合方式变化的适应性．研究发现，时域波形特征与旋回模式有一一对应关系，但其判别稳定性差．在多种时频分析方法中，仿射类时频分布（尺度图）不仅能有效压制Wigner—Ville时频分布的交叉项干扰，同时对随机噪声的随机频率能量也有很好的压制作用．仿射类时频分布方法通过对频谱进行平滑，模糊瞬时频谱变化细节，突出主要频率变化趋势，使得主频受小层厚度突变、反射系数突变、旋回单元组合方式变化的影响小，具有很好的稳定性，在四种方法中具有最好的沉积旋回判别能力．
Time-frequency analysis method is a common method for identifying sedimen- tary cycle. There may have great differences between stability, pattern recognition precision and the ability to depict the sedimentary cycle for diferent time-frequency analysis methods. Therefore, it is necessary to analyze the characteristics of different methods and select the optimum which can reflect the frequency tendency of sedimentary cycle. In this paper, the forward modelling method based on wave equation is applied to simulate four types of sedimen- tary cycle, namely normal cycle, inverse cycle, normal-inverse cycle and inverse-normal cycle. The time-frequency spectrum of seismic record is obtained by generalized S transform, wavelet transform, Wigner-Ville distribution and affine class time-frequency distribution separately. The identification threshold of sedimentary cycle units and the adaptability to noise, layer of discontinuity, reflection coefficient mutation as well as combination mode change Of sedimen- tary cycle unit of different time-frequency analysis methods are investigated. The study finds that the time domain features has a one-to-one correspondence with the cyclic pattern, but its discriminant stability is poor In all of these methods, affine class time-frequency distribution can not only suppress the cross-term interference of Wigner-Ville distribution effectly, but also has a good effect for random noise suppression, having the strongest ability to identify sedimentary cycle. It can reduce the impact of reflection coefficient mutation, layer of discon- tinuity and combination mode change of sedimentary cycle unit on the dominant frequency by spectral smoothing which can smear out the details of instantaneous spectrum and underline the tendency of the dominant frequency, having good stability.
出处
《数学的实践与认识》
北大核心
2018年第4期206-214,共9页
Mathematics in Practice and Theory
基金
东北石油大学研究生创新科研项目(YJSCX2017-005NEPU)
东北石油大学科研培育基金(NEPUPY-1-101)
关键词
沉积旋回
正演模拟
时频分析
尺度图
波动方程
sedimentary cycle
forward modelling
time-frequency analysis
scalogram
wave equation
