反射槽波探测法在煤层褶曲与断层识别中的研究与应用

Research and application of the seismic exploration technique using reflected in-seam waves in identifying folds and faults in coal seams

【背景】煤矿智能化转型中,精准识别地下异常体对地质透明化体系构建至关重要,褶曲异常体的精确探测是井下物探技术的难点,其准确辨识对减少掘进成本、回采难度及安全风险有重要意义。【目的和方法】基于以往的槽波勘探实践,发现褶曲对槽波的传播特性具有显著影响,但传统槽波反演技术难以区分褶曲与断层。为此,构建了几何形态类似、勘探距离相等的断层与褶曲数值模型,首先运用三维波场模拟技术挖掘波场信息,明确了二者波场响应差异;其次采用绕射偏移成像方法反演处理,获取了成像结果。【结果和结论】研究结果表明:(1)褶曲异常相较于断层,其反射槽波波形更为分散且模糊,不同反射点能量分布不均。(2)褶曲异常在远偏移距处的直达槽波信噪比高于断层构造,且能减缓直达槽波的衰减速度,使得直达槽波在褶曲异常中的传播距离约为断层构造中的1.5倍。(3)断层的反射槽波与直达槽波能量差异较小,而褶曲异常则表现出较大的能量差异。(4)褶曲异常的反射槽波主频低于断层构造,并导致直达槽波与反射槽波的频带变宽;褶曲异常反射槽波频率和速度均略高于直达槽波,断层构造此特征不明显。(5)断层构造的反射面通常位于断层面中上端,而褶曲异常的反射面则倾向于褶曲面中部,且褶曲异常的绕射偏移成像反射面在连续性上较断层构造差。基于上述波场特征与频散特性的深入分析,以山西阳泉某矿15号煤层为例,通过反射槽波绕射偏移成像技术,成功实现了巷道侧帮煤层中断层与褶曲的定性识别,并清晰描绘了褶曲的发育形态。研究成果不仅为采区工作面的合理布局提供了更为精确的地质依据,也为煤矿的安全生产、高效开采提供了有力的技术支撑。

Background Accurately identifying subsurface anomalies is crucial to building a geological transparency system in the transformation to intelligent coal mines.The precise exploration of fold anomalies is a challenge of underground geophysical exploration technology,holding great significance for reducing excavation costs,mining difficulties,and safety risks.Objective and Methods Previous in-seam seismic explorations reveal that folds pose significant impacts on the propagation characteristics of in-seam waves.However,conventional inversion techniques of in-seam waves are difficult to distinguish folds from faults.This study constructed numerical models for faults and folds with similar geometric shapes and equal exploration distances.Specifically,the differences in wave field responses between faults and folds were determined by mining information on wave fields using the 3D wave field simulation technology.Subsequently,images were obtained through inversion using diffraction migration imaging.Results and Conclusions The results of this study are as follows:(1)Compared to fault anomalies,fold anomalies exhibit more dispersed and fuzzier waveforms of reflected in-seam waves,with energy unevenly distributed across different reflection points.(2)The direct in-seam waves corresponding to fold anomalies display higher signal-to-noise ratios at far offsets than those associated with faults.Moreover,fold anomalies can reduce the attenuation speed of direct in-seam waves.As a result,the distances that direct in-seam waves propagate in folds are about 1.5 times those in faults.(3)The energy difference between the reflected and the direct in-seam waves in faults is slight but that in folds is significant.(4)Fold anomalies manifest a lower dominant frequency of reflected in-seam waves than faults.This results in broadened frequency bands of direct and reflected in-seam waves.The reflected in-seam waves of fold anomalies exhibit slightly higher frequencies and velocity than their direct in-seam waves,while this feature is subtle for faults.(5)The reflecting surfaces of faults are typically located in the middle-upper part of fault planes,whereas the reflecting surfaces of fold anomalies tend to be in the middle part of the fold planes.Besides,fold anomalies display less continuous reflecting surfaces for diffraction migration imaging than faults.Based on the thorough analysis of wave fields and dispersion characteristics mentioned above,this study investigated the No.15 coal seam in a coal mine in Yangquan,Shanxi,as an example.Using the seismic exploration technique through diffraction migration imaging of reflected in-seam waves,this study qualitatively identified faults and folds in the coal seam on the side walls of the roadway in the coal mine and clearly described the morphologies of folds.The findings of this study provide both a more accurate geological basis for the rational layout of the mining face in mining areas and strong technical support for the safe production and efficient mining of coal mines.