碳酸盐岩溶洞成像宽度的地震物理模型分析

Seismic physical model analysis on the imaging width of carbonate caves

对不同尺度和不同填充物的2个溶洞物理模型进行了正演模拟和叠前偏移成像,分析了溶洞的成像宽度。研究表明,溶洞偏移响应水平道振幅曲线不同幅值下的成像宽度对溶洞真实宽度都比较敏感,且不同幅值成像宽度之间仅相差一个线性量。分析半幅值成像宽度与溶洞真实宽度之间的关系发现溶洞半幅值成像宽度对溶洞的真实宽度具有放大效应,其放大倍数随溶洞真实宽度增大迅速衰减直至趋于1;溶洞半幅值成像宽度不受溶洞反射系数的影响。为溶洞真实宽度估算提供了可靠的实验依据。

Forward modeling was carried out on two cavern physical models with different scale and different fillings.After prestack migration, the imaging width of caves was analyzed.On the prestack migration section,the imaging width of caves is obtained by extracting horizontal trace amplitude of the string.The result indicates that different-amplitude imaging width is sensitive to the actual cave width.The analysis on the relationship between half-amplitude imaging width and actual width reveals that the half-amplitude imaging width has amplification effect on the actual width,and along with the increasing of the actual cave width,the magnification coefficient attenuates rapidly till verges to one.Moreover,the half-amplitude imaging width is not influenced by the reflection coefficient of caves.The achievements provide reliable experimental basis for the estimation of actual cave width.