Li Mengqi, Lu Jun, Xiong Shu
School of Energy Resources, China University of Geosciences, Beijing, 100083, China.
Sci Rep. 2019 Apr 24;9(1):6488. doi: 10.1038/s41598-019-42956-7.
Fractures that develop in coal seams threaten safety in many ways, but they can be predicted using fracture parameters derived from seismic data. However, the post-stack split shear waves are difficult to thoroughly separate by Alford rotation due to wavefield mixing. We propose a method of predicting fractures in a coal seam using multi-component seismic data, which was applied to coal seam 13-1 of the Huainan coalfield, China. We employed the Alford rotation to separate the split PS-waves (P-to-S converted waves) and perform interlayer travel-time inversion of the fast shear waves using geophysical logs, rock-physics parameters, and tunnel-excavation information as constraints. However, post-stack wavefield mixing of the coal seam interfered with the Alford rotation of the real post-stack seismic data. Therefore, we only performed the Alford rotation on radial and transverse component post-stack sections to derive fracture azimuths, which were then applied to the pre-stack separation of the split PS-waves. Using joint PP- and PS-wave inversion, anisotropy parameters were derived for use in fracture prediction. Finally, we predicted unsafe mining areas with a high probability of coal and gas outbursts. The application results were verified by excavation data from the mine tunnels. Our method contributes to fracture prediction on coal mine safety.
煤层中发育的裂缝在许多方面威胁着安全，但可以利用从地震数据中得出的裂缝参数进行预测。然而，由于波场混合，叠后分离剪切波很难通过阿尔福德旋转彻底分离。我们提出了一种利用多分量地震数据预测煤层裂缝的方法，并将其应用于中国淮南煤田的13-1煤层。我们利用阿尔福德旋转来分离分离的PS波（P波至S波转换波），并以地球物理测井、岩石物理参数和巷道开挖信息为约束条件，对快剪切波进行层间走时反演。然而，煤层的叠后波场混合干扰了实际叠后地震数据的阿尔福德旋转。因此，我们仅对径向和横向分量叠后剖面进行阿尔福德旋转以得出裂缝方位，然后将其应用于分离PS波的叠前分离。利用PP波和PS波联合反演，得出各向异性参数用于裂缝预测。最后，我们预测了煤炭与瓦斯突出可能性高的不安全开采区域。应用结果通过矿井巷道的开挖数据得到了验证。我们的方法有助于煤矿安全方面的裂缝预测。
