基于反射系数谱理论的薄层多波AVO

摘要

Seismic AVO analysis now is one of the major criteria for recognizing potential hydrocarbon reservoirs. Volume scattering information that carries information of stratigraphic structure, lithology, and pore fluid is more useful for seismic exploration.However, traditional AVO analysis is based on the Zoeppritz equation, which only contains single-interface information. Quantitative interpretation of the thin bed thickness is essential to thin bed structure interpretation, reservoir description, and lateral reservoir prediction. The reflectance spectrum equation based on the elastic wave propagation matrix in the frequency domain derived in this paper shows that both interfaces and intervals have an effect on amplitude. The equation includes information about both single interfaces and volume scattering. Since the reflectance spectrum equation is a continuous function of thin bed thickness and frequency, it is convenient to analyze the effects of a single frequency and bed thickness on the reflectance spectrum. Bed thickness is analyzable until the bed thickness is vanishingly small. These characteristics can't be achieved by Fourier transform.The propagation of seismic waves is complex and various wave modes exist simultaneously.The reflectance spectrum includes various propagating wave modes and multiples and is better for simulating multi-component thin bed AVO responses than the ray tracing method.%AVO分析是目前地震勘探潜在油气储层的一个重要方法.体散射信息包含了层结构、岩性和孔隙流体信息,对地震勘探非常有用.但是基于Zoeppritz方程的传统AVO分析之只包含了单层信息.薄层厚度定量解释对构造解释、储层描述和储层横向预测都非常重要.本文阐述的基于频率域弹性传播矩阵反射系数谱方法既考虑了层界面引起的振幅变化(Zoeppritz方程),也考虑了层内传播引起的振幅变化.因此该反射系数谱既包括单一层界面信息,也包括层内体散射信息.该反射系数谱是层厚和频率的连续函数,便于分析频率和层厚对反射系数谱的影响.可分析的薄层厚度可以无限小,直至消失.可分析的频率是任意的和连续的.这是对时间域反射系数做傅里叶变换无法实现的.地震波的传播是复杂的,各种波型是同时存在而且相互转换的,该反射系数谱考虑了各种波型在传播过程中的相互转换以及多次波.与比射线方法比更便于正演薄层多波多分量AVO响应.