黄土塬区延安组煤层地震响应特征物理模拟研究

针对黄土塬区延安组煤层地震响应复杂问题进行地震物理模拟研究。首先，研发适用于黄土塬地表干黄土层和煤层的模型材料，经过多次试验，最终选用在硅橡胶中添加硅气凝胶粉末的混合材料模拟疏松黄土塬地表层，选用在硅橡胶中添加超细碳粉的混合材料模拟低速低密度煤层；通过模具控制层位、逐层浇筑、三维雕刻起伏地层等方法，制作黄土塬区典型地质结构的三维地震物理模型，并开展地震物理模拟及地震成像分析。结果表明，延安组煤层与围岩较大的波阻抗差异形成较强的反射振幅，对下部地层的成像有较强的屏蔽作用；较厚的多组煤层之间会形成层间多次波，影响下伏地层的成像。用地震振幅属性对煤层进行刻画时，计算时窗大于40 ms更有利于煤层识别，但由于煤层存在调谐效应，用地震属性预测煤层厚度存在一定陷阱。 

Physical modeling of seismic response for the coal seams of Yan'an Formation in loess tableland of North China

A seismic physical simulation is carried out for the complex seismic response of the coal seam of Yan'an Formation in the loess tableland. First, the physical model materials for the dry layer near the surface of the loess tableland and the coal seam are developed. After several tests, a mixture of silicone rubber with silicon aerogel powder is selected to simulate the surface of the loess tableland, and the mixture with ultra-fine carbon powder added to silicone rubber is used to simulate the low-speed and low-density coal seam. Through the methods of molds control layer, layer by layer pouring, three-dimensional carving of undulating strata, a three-dimensional seismic physical model of the typical geological structure in the loess tableland is constructed, and seismic physical simulation and seismic imaging analysis are carried out. The results show that there is a strong reflection amplitude because of the great difference in impedance between the coal seam and surrounding rock of Yan'an Formation. Therefore, it has a strong shielding effect on the imaging of the lower strata. There are internal multiple waves in the multiple sets of coal seams, affecting the imaging of the underlying layer. The calculation time window greater than 40 ms is more favorable to coal seam identification when the coal seam is described by the seismic amplitude attribute. But there are some traps in predicting coal seam thickness by seismic attributes because of the coal seams tuning effect.