Morlet小波在测井层序地层划分中的应用

Application of Morlet wavelet in sequence stratigraphic division on well-logging data.

测井曲线包含了丰富的地质信息,对研究地层多级别旋回性及识别地层信息多分辨突变具有优势。测井信号的时频分析将一维测井信号拓展到二维时频域,从而使地层内部的旋回性结构得以清晰展示。对测井曲线进行Morlet连续小波变换,将测井信号与深度的关系转换为与深度和尺度域的变化关系,通过研究最佳尺度因子下小波系数曲线表现出的周期性振荡特征,可与各级层序地层单元界面建立一定的对应关系。以胜坨油田某井为例,运用小波变换的多尺度特性,探测到地层序列中不同尺度的层序地层单元界面,与传统方法所划分的界面基本一致。这些探索为地层层序的划分提供了一种新的思路和有效途径。

Logging curve contains a great amount of geologic information and it has advantage in studying multilevel cycle of strata and in recognizing multi-resolution abrupt change of strata. Time-frequency analysis of well logs transforms the one-dimension well logs into time-frequency domain, which makes the cycle structure of strata clearly revealed. Morlet continuous wavelet transformation was applied to logging curve, which transfers the relation between logs and depth into depth-scale space. Through studying the periodic vibratory characteristics of wavelet coefficients under optimal scales, the relations between the coefficients and sequence boundaries were established. The method was demonstrated by the logging data from a well in Shengtuo Oilfield. The results are in good agreement with those obtained from traditional methods.