溶洞体宽度对偏移剖面反射振幅影响的定量研究

Quantitative study of the effect of cavern width on reflection amplitude of migration section

针对在碳酸盐岩溶洞储层地震响应研究中出现的"偏移剖面反射振幅随溶洞体宽度增大而增强"的现象,以空间子波概念为基础,定量分析了地质体宽度与偏移剖面反射振幅之间的关系,并通过地震正演实验加以验证。研究表明:当地质体宽度较小时,偏移剖面反射振幅随地质体宽度的增加而显著增加,当地质体宽度大于振幅临界宽度时,反射振幅受地质体宽度影响较小;振幅临界宽度与地震波长成正比,与最大出射角正弦值成反比,其值可通过地震正演实验获得,这有助于对小尺度岩性体地震振幅的定量研究。

In recent years, a phenomenon that reflection amplitude of migration section increases with the cavern width was proposed in researches about the seismic response of carbonate cavern reservoir. Based on the concept of spatial wavelet, the relationship between reflection amplitude of migration section and the width of geological body was discussed by analyzing the horizontal trace amplitude function of horizontal geologic body derived from the focal beam theory,and the results from the theoretical study were verified through numerical and physical seismic forward modeling experiments. The result shows that when the geologic body width is less than the critical width of amplitude, the reflection amplitude of migration section increases with the width of geologic body, and when the geologic body width is larger than the critical width of amplitude, the influence of geologic body width on reflection amplitude of migration section is weakly. The critical width of amplitude is proportional to the seismic wavelength, and is inversely proportional to the sine of the maximum emergence angle. In practical, the critical width of amplitude can be obtained by seismic forward modeling. This research is favorable for the quantitative study of seismic amplitude of small geologic bodies.