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前言我们已经认识到与偏移距有关的地震振幅变化包含着岩性情况和孔隙——流体情况。但是,根据几种地质模型预测的结果却很难说明计算平面波反射系数的精确公式。一种岩石地层单位中的流体相互接触时(在地震资料上可能显示为“平点”),简化的近似计算公式能用于预测纵波(P)和横波(S)的反射系数。本文所推导的公式(假设孔隙——流体的变化不影响岩石基质的弹性性质)表明,气——盐水、气——油或油——盐水接触时 P 波和 S 波的反射系数随着偏移距的增加而单调增加;而且表明当气——盐水接触时,这两种波的反射系数之比对含气饱和度反应敏感。
Preface We have come to recognize that changes in seismic amplitude associated with offset involve lithology and pore-fluid conditions. However, based on the results predicted by several geological models, it is difficult to explain the exact formula for calculating the reflection coefficient of a plane wave. When fluids in a lithostratigraphic unit are in contact with each other (“flat points” may appear on seismic data), a simplified approximation formula can be used to predict the reflection coefficients for longitudinal (P) and transverse (S) waves. The formulas deduced in this paper (assuming that the pore-fluid changes do not affect the elastic properties of the rock matrix) show that the reflection coefficients of P-wave and S-wave as gas-brine, gas-oil or oil- Increasing the distance increases monotonically; and shows that the ratio of the reflectance of these two waves is sensitive to the gas saturation when the gas-brine contact occurs.