煤巷前方煤层断点绕射波特征及其在极小偏移孔径下的成像方法研究

The fault is one of the important subtle disaster-causing factors in important accident of coal roadway driving. Seismic technology has been used into the deep mine, under the influence of complex terrain, upper multiple coal seams gob and surface subsidence. At present, limited to the detection conditions of coal roadway, picking of breakpoint diffraction and imaging of coal seam under small migration aperture are difficult, so the accurate construction of fault model is difficult. Aimed to solve this problem, various fall numerical models with different dips, throws and trends will be established. Under conditions of the cavity and surrounding rock loose circle effect in coal roadway, breakpoint diffraction characteristics of different shot and receiver parameters will be analyzed. The breakpoint diffraction of broken wing coal seam will be extracted. Combined with seismic physical model test, the principal polarization direction of breakpoint diffraction will be determined by S-transform multi-component analysis method. The imaging study on prestack migration restrained by principal polarization direction of diffraction will be carried out to realize breakpoint convergence under small migration aperture. Coal seam breakpoint, fault plane and coal seam dislocated location information will be merged to build fault model by point center method which based on weights-making. The accurate forecast of fault parameters, such as dip, throw and trend, will eventually be achieved. Above research results will be perfected by using a field experiment. The formation of an advanced and detailed fault detection method of coal roadway will provide theoretical guidance and technical support for the detailed detection of fault in coal mine.

断层是煤巷掘进重大灾害事故的重要隐蔽致灾因素。受地面复杂地形、上组多煤层采空及地表沉陷等影响，地震技术进入了深部矿井。目前，受煤巷探测条件的限制，煤层断点绕射波拾取及其在极小偏移孔径条件下成像困难，进而难以准确构建断层模型。针对该问题，建立中厚煤层掘进工作面前方不同落差、倾角、倾向的断层数值模型，分析全空间条件下煤巷空腔及围岩松动圈效应耦合影响下不同激发、接收点参数的煤层断点绕射波特征，提取断点绕射波；结合地震物理模型试验，采用基于S变换的多分量极化分析法确定断点绕射波主极化方向，开展绕射波主极化方向约束的叠前偏移成像研究，以实现极小偏移孔径下煤层断点归位；融合煤层断点、断层面及煤层错断位置信息，构建断层几何模型，并计算断层落差、倾角、倾向参数；采用现场实证方法对上述研究成果进行验证和完善，以期形成一种煤巷断层超前精细定量探测方法，为井下断层精细探测提供理论指导和技术支持。

断层是煤巷掘进重大灾害事故的重要隐蔽致灾因素，对其精细超前探测是研究热点。以中厚煤层巷道前方断层为研究对象，通过理论分析、数值模拟、物理模拟及现场试验方法，项目系统揭示了小偏移距条件下煤层断点绕射波的特征，以煤层断点信息为关键参量构建了二维断层几何模型，预报了断失翼煤层位置及断层参数，形成了一种煤巷断层超前二维精细定量探测方法。项目取得了如下创新性结论：1）揭示了迎头前方正、逆断层有效波的运动学、动力学差异特征。当正断层超前探测时，上盘断失翼煤层断点绕射波与下盘煤层断点绕射波、反射槽波混叠，断点绕射波无法识别；当逆断层超前探测时，上、下盘煤层断点绕射波到时差异显著，易于分离提取，且下盘断点绕射波极化倾角指向性强；2）揭示了煤巷空腔及围岩松动圈效应耦合影响下的前方断层地震波极化特征。由于煤巷空腔、围岩松动圈耦合作用，巷道面波发育，断点绕射波极化方位角与理论值存在较大偏差，而极化倾角与理论值偏差较小；当断点绕射波直接到达检波器时，极化参数准确，可以通过极化参数对断点进行精确成像；3）在水槽界面模型超前探测实验中，四种不同倾角异常界面的极化成像结果表明二维极化成像可有效判定异常体位置；岩体模型测线前方异常体空间轮廓收敛效果证实了极化偏移可显著提高成像空间分辨率；4）提出了一种对迎头前方断失翼煤层进行高精度定位的希尔伯特极化成像新方法，通过希尔伯特极化分析计算断点绕射波极化参数，利用检波器组合计算可能存在的绕射点并以其空间密度分布为衡量标准，对断失翼煤层实现了收敛成像；5）开发了矿井巷道多波多分量地震数据处理系统，在典型矿区开展了现场试验，构建了超前断层探测模型，为煤巷安全掘进提供必要的技术参数。本项目大幅度超额完成了论文、专利、奖励、人才培养等目标。项目成果保障了构造复杂矿区煤巷安全掘进，相关事迹被《科技日报》、《新华日报》、《学习强国》等主流媒体正面报道，社会效益显著。