薄互层调谐与分辨率分析

针对广泛存在的薄互层储层,本文采用双层砂岩薄互层(即均小于调谐厚度的两层砂岩夹页岩薄层)模型,将该砂岩薄层视作-个整体,分析砂岩薄层厚度比不同时,薄层间的分辨能力;采用90°相位雷克子波,使具有相反极性、相同振幅的单-薄层的合成波形对称,且能更好地反映地层信息;依据瑞利准则及振幅随频率变化(AVF)分析子波主周期与砂岩薄层厚度在分辨极限下的关系。研究结果表明:当层间页岩层厚度及砂岩薄层厚度比-定时,在分辨极限条件下,子波主周期与砂岩薄层厚度(小于调谐厚度)呈线性变化趋势;砂岩间分辨极限理论上可远低于四分之-波长。用AVF方法分析多层砂岩薄互层模型时,所得结论相对于双层砂岩薄互层模型具有较好的线性拟合。

Thin interbed tuning and resolution analysis

Aiming at the largely existing thin interbed reservoir in real exploration,a thin interbed model is utilized,which has two thin sand beds that are thinner than tuning thickness and are separated by a thin shale bed.Each thin sand bed is treated as a whole unit,and the resolution between the two beds with varying thickness ratios is analyzed.In this study,90°-phase Ricker wavelet is used to generate the composite waveform,which allows the composite waveform of a bed with opposite polarity interfaces of equal amplitude to be symmetrical and the bed information to be better reflected. The analysis of bed resolution is based on either Rayleigh's criterion or Amplitude versus Frequency(AVF).A linear relation between predominant period and the thickness of thin sandstone bed is acquired when the thickness of shale bed is fixed. The trends could be different for different thickness ratios.The result shows that the bed resolution can reach much less than λ/4.When applying AVF to a multilayer thin interbed model,the trend of resolution can have a linear fit with the trend result of simple two bed model.