地震波穿过油气储层时会发生高频能量的异常衰减,通过计算频率衰减梯度能够反应地下储层的分布情况.为了有效提高计算频率衰减梯度的精度,提出一种基于局部最大同步挤压变换(Local Maximum Synchrosqueezing Transform,LMSST)的频率衰减梯度计算方法.该方法首先利用LMSST时频变换对地震信号进行时频分析,然后采用基于最小二乘法的Nelder-Mead拟合方法对高频段进行拟合,获得衰减梯度值.理论调频-调幅信号、单道合成地震信号和单道实测地震信号表明LMSST具有更高时频聚集性和抗噪能力,进而能够提升地震信号的时频分辨率.在实际的地震资料应用中,本文提出的方法相比STFT、FSST、FSST2和FSST4具有更高的计算精度,与实际油气测试井更吻合,为计算地震信号的频率衰减梯度提供了 一种新技术.
Research on frequency attenuation gradient method based on LMSST time frequency analysis
High-frequency energy suffers remarkable attenuation when seismic waves travel through reservoirs.It is possible to reflect the distribution of subsurface reservoirs by computing the frequency attenuation gradient.A frequency attenuation gradient calculation method based on the Local Maximum Synchronous Squeezing Transform(LMSST)is proposed in order to significantly improve the accuracy of the calculation.This method first performs time-frequency analysis on seismic signals using the LMSST time-frequency transform,and then uses the Nelder-Mead fitting method based on the least squares method to fit the high-frequency band and obtain the attenuation gradient value.Theoretical frequency-modulated amplitude modulation signals,single channel synthetic seismic signals,and single channel observed seismic signals all show that LMSST has better time-frequency clustering and noise resistance,which improved time-frequency resolution of seismic signal.The method proposed in this paper offers more computational accuracy in practical seismic data applications than STFT,FSST,FSST2,and FSST4,and is more consistent with actual oil and gas testing wells.It provides a novel method for calculating the frequency attenuation gradient of seismic waves.
Local maximum synchronous squeezing transformFrequency attenuation gradientPrediction of oil bearing reservoirsTime-frequency analysis
NETL
NSTL
万方数据
