线性过渡层复合体的地震反射特征研究

Seismic reflection feature of complex linear transient layers

石油大学(华东)地球资源与信息学院,山东东营 257061

College of Geo-resources and Information, China University of Petroleum, Dongying 257061,China

速度在某一方向上呈线性连续变化的地层称为线性过渡层。2个或2个以上速度梯度不同的线性过渡层的组合。即为线性过渡层复合体。从弹性动力学理论出发,讨论了由2层过渡层构成的复合体的反射滤波特点, 推导了2层不同速度梯度的过渡层夹在2个均匀层中所构成的复合界面的反射滤波特性公式。通过一系列组合形式的数值试验,给出了它们的滤波特征。研究表明,不同的速度梯度及组合方式分别表现出低通、高通和带通的性质,它们对应着不同的沉积环境。据此可以从滤波特性来判断沉积类型,还可以结合振幅谱中零点的间隔和第一个零点的位置推断该地层的厚度。

Layer with velocity changing linearly is called linear transient layer, combination of many layers makes complex linear transient layers. Based on the theory of elastody-namics, a detailed discussion of the wave propagation and reflection from complex linear transient layers is carried out, and an analytical reflection coefficient from complex interfaces of linear transient layers with different velocity gradient is derived. Series digital models are designed and their seismic reflection properties are listed. As a result, different models show low-pass, high-pass and band-pass filtering properties respectively, and they correspond to different sediment environments in geological mean. In conclusion, filtering properties can be used to deduce sediment styles. Thickness of layers can also be estimated from the interval of zero points and the position of fist one in frequency axis. This is useful to sedimentary studies, struc-tural-formational interpretation and hydrocarbon prediction.