煤层顶底板反射波的干涉效应

Coal Roof and Floor Reflection Wave Interference Effects

理论分析与实际资料证实,煤层顶、底板反射波的干涉,在煤层厚度所产生的时差小于半个周期时,导致反射波的振幅随着煤层厚度的减小而减弱,且在煤层厚度较小(趋于0m)的情况下,仍然是可以连续对比追踪的;大于半个周期时,反射波的振幅与干涉效应无关。通过实际资料的分析计算发现,在煤层厚度趋于0m时,其顶、底板反射波的干涉所形成的振幅极限值仍然是砂、泥岩界面反射波振幅的3倍,依据这个特征可有效识别煤系地层中的薄、无煤带。

The theoretical analysis and actual data have confirmed that the reflection wave interference from coal roof and floor caused coal thickness moveout less than a half of cycle time and the amplitude of reflection weakening along with coal thickness decreasing, when the coal thickness is small （level off to 0m）, still can correlate and trace continuously. When larger than a half of cycle time, the reflection amplitude has no relation with interference effect. The analytic computation of actual data has found that when coal thickness is level off to 0m, the amplitude limiting value from coal roof and floor interference is still 3 times of reflection amplitude from boundaries between sandstone and mudstone. Based on this character can identify coal thin and barren belts in coal measures strata effectively.