煤层陷落柱散射波数值模拟与成像

煤层陷落柱是煤田勘探开发中常见的一种典型的非均匀地质体.由于来自陷落柱的反射信号少、反射能量弱,使得基于反射波原理的常规地震成像方法难以有效识别陷落柱.本文以散射波理论为基础,采用数值模拟方法,研究了陷落柱的散射波场特征,研究表明地面接收的波场中含有来自陷落柱陡倾角界面的散射波场.通过共散射点道集波场的模拟,可以清晰地识别散射波,获得地下散射点和非均匀地质体的信息,判断散射点的位置,从而勾画出不均匀地质体的形态.采用等效偏移距假设抽取共散射点道集,在此基础上进行叠前偏移,对陷落柱成像;模拟与实际数据成像结果对比表明此方法能够合理地提取散射点的散射波场信息,对陷落柱形态及内部结构准确成像,是一种有效的煤田陷落柱成像方法.

Numerical simulation and imaging of scattered wave of sunk pillar in coal seam

The scattered wave theory has built the basis of scattered wave imaging of the sunken pillar in coal field seismic exploration.When seismic waves meet with the scatter point underground,the waves propagate around and generate scattered waves.And then reflection is formed by enhancing energy interference of scattered waves.Through the numerical modeling,we can receive the scattered waves from the steep dip interface of the sunken pillar in coal seam.After researching wave characteristic on common scatter point(CSP) gathers,we can recognize the scattered waves,and obtain the information of geologic structure underground,including the structure position and the outline of heterogeneous geologic body.Tested with field seismic data,the result of scattered wave imaging indicates that the equivalent offset method(EOM) can reasonably and accurately use the information of scattered waves,and the pre-stack time migration based on EOM is an effective method for the imaging of sunken pillars and inhomogeneous geologic bodies.