【摘要】 针对鄂尔多斯盆地二叠系山2段煤层直接上覆或下伏于砂岩的地层结构特征,设计了六个地质模型(包括3个层状砂岩模型及3个楔状砂岩模型),利用褶积模型,将相应的反射系数模型与主频为5~120Hz、步长为5Hz的0°和90°相位的雷克子波进行褶积(采样间隔为1ms),从而得到了不同子波主频的合成地震记录。通过提取合成地震记录的砂岩顶、底界面或砂岩中心振幅,首次模拟了0°和90°相位子波情况下煤层对砂岩地震反射特征的影响。结果表明:煤层的厚度、位置及与砂岩的距离对砂岩地震反射的调谐频率、振幅及极性都会产生影响,煤层可以使砂岩地震反射同相轴极性反转,以致于难以预测薄层砂岩厚度,特别是当煤层厚度不稳定或煤层与砂岩的距离发生变化时,砂岩顶、底界面或中心的振幅不能反映薄层砂岩的厚度;在存在不同厚度、位置煤层的情况下,应考虑采用其他方式预测薄层砂岩的厚度,如利用不同位置的振幅地层切片等。更多还原

【Abstract】 According to the fact that sand is directly overlain or underlain by coal seam of Permian Shan2 member in Ordos Basin,six geologic models were designed,which include three layered sand models and there wedge-shaped sand models.The corresponding reflection coefficient of the models and Ricker wavelets with 0°and 90°phases and dominant frequencies from 5to 120Hz(step 5Hz&sample interval 1ms)are calculated by convolution model,and then synthesis seismic datasets with different frequencies were obtained. Coal seam influence on seismic reflection characteristics of sand under wavelets with 0°and 90°phases were firstly simulated by extracting synthetic seismogram of upper,lower,and medium sand amplitude.The results show that coal seam thickness,position and the distance between coal and sand have influence on tuning frequency,tuning amplitude,reflection strength and polarity of seismic reflection.Coal seam can reverse polarity of sand seismic reflection,so sandstone thickness prediction is very difficult.When both coal seam thickness and the distance between coal and sand vary,the upper,lower,and medium sandstone amplitude cannot indicate its thickness.When thickness and position of coal seam vary,other methods should be used,such as amplitude slice at different positions.更多还原