Reservoir information extraction using a fractional Fourier transform and a smooth pseudo Wigner-Ville distribution

基于分数阶Fourier变换及SPWD分布的储集层信息提取(英文)

Currently, it is difficult for people to express signal information simultaneously in the time and frequency domains when analyzing acoustic logging signals using a simple-time or frequency-domain method. It is difficult to use a single type of time-frequency analysis method, which affects the feasibility of acoustic logging signal analysis. In order to solve these problems, in this paper, a fractional Fourier transform and smooth pseudo Wigner Ville distribution （SPWD） were combined and used to analyze array acoustic logging signals. The time-frequency distribution of signals with the variation of orders of fractional Fourier transform was obtained, and the characteristics of the time-frequency distribution of different reservoirs under different orders were summarized. Because of the rotational characteristics of the fractional Fourier transform, the rotation speed of the cross terms was faster than those of primary waves, shear waves, Stoneley waves, and pseudo Rayleigh waves. By choosing different orders for different reservoirs according to the actual circumstances, the cross terms were separated from the four kinds of waves. In this manner, we could extract reservoir information by studying the characteristics of partial waves. Actual logging data showed that the method outlined in this paper greatly weakened cross-term interference and enhanced the ability to identify partial wave signals.

在分析声波测井信号时,单纯的时间域与频率域方法不能同时了解信号在时间和频率这两方面的信息,而采用单一的一种时频分析方法时又会遇到一些困难,因此,也就会影响声波测井信号分析的可行性。为了解决这些问题,本文将分数阶Fourier变换及平滑伪Wigner-Ville(SPWD)分布的方法相结合,并运用于阵列声波测井信号的分析之中,得到信号的时频分布随分数阶Fourier变换阶数变化的规律,从而总结出不同性质储集层在不同阶数下的时频分布特点。由于分数阶Fourier变换具有旋转特性,而交叉项旋转速度较纵波、横波、斯通利波、伪瑞利波要快,因此,对于不同性质的储集层,根据实际情况选择不同的阶数,交叉项同4种分波会相互分离。通过研究各组分波的性质,就能达到提取储集层信息的目的。结合实际测井数据,表明,此方法极大地削弱了交叉项的干扰,增强了对信号中各组分波的识别能力。