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反射层的几何形态及其岩性对地震振幅都有影响。观测到的“亮点”不仅与孔隙流体饱和度有关,而且也与地层厚度和围岩类型有关。为了评价波分析在明确孔隙流体类型中的应用,文中所提出的数值模型采用了反射波和转换波的有限求和。单纯地用振幅分析对确切地表达孔隙流体类型是不够的,但振幅分析与相位以及波型转换横波的特征相结合,就有可能区分孔隙流体类型。文中对各种各样可产生亮点的反射层形态作了评价,包括煤层和灰岩层。文中根据数值模型的例子提出了一种算法,它可把气层亮点与其它亮点资料区分开。因反射波各分量的干涉,故水平层的厚度便成了确定总反射率的重要因素。地层的气饱和度并不是产生亮点的充分条件,但对厚度范围适当的地层(相对入射波长)它可能产生”暗点”。当厚度与波长变化时,边界岩层的岩性可决定振幅变化的极值。若先前对构造的岩性与厚度有所了解的话,则可应用振幅-相位-转换波的算法,而不用亮点资料来表征构造。这表明振幅-相位-转换波算法对油田开发和亮点分析具有极其重要的应用价值。
The geometry of the reflector and its lithology have an impact on the seismic amplitude. The observed “bright spots” are not only related to the pore fluid saturation but also to the formation thickness and the type of surrounding rock. In order to evaluate the application of wave analysis in the determination of pore fluid types, the numerical model proposed in this paper uses the finite summation of reflected waves and converted waves. Simply using amplitude analysis is not sufficient to express the exact pore fluid type, but the combination of amplitude analysis with phase and shear-wave transformed shear waves makes it possible to distinguish pore fluid types. The article evaluates various reflector patterns that produce bright spots, including coal and limestone formations. In this paper, an algorithm is proposed according to the numerical model, which distinguishes the bright spots of gas from those of other bright spots. Due to the interference of the components of the reflected wave, the thickness of the horizontal layer becomes an important factor for determining the total reflectance. The gas saturation of the formation is not a sufficient condition to produce a bright spot, but it may produce a “dark spot” for the appropriate thickness of the formation (relative to the incident wavelength). As the thickness and wavelength change, the lithology of the boundary strata determines the extremum of the amplitude change. If the lithology and thickness of the structure were previously known, then the amplitude-phase-converted wave algorithm can be applied instead of the highlight data to characterize the structure. This shows that the amplitude-phase-converted wave algorithm has extremely important application value for oilfield development and bright spot analysis.