基于钻孔多参数测井的煤层顶底板岩性及厚度识别

Identifying the lithologies and thicknesses of coal seam roofs and floors based on multiparameter logging of boreholes

  • 摘要:背景】在煤层开采过程中,有效的地层特征探测方法对于井下工作开展至关重要,精确掌握煤层及其顶底板围岩的地层特征信息,有助于煤层瓦斯治理,保障矿井安全高效生产。【方法过程】采用底抽巷穿层钻孔进行多参数测井,重点分析了低位上行钻孔轨迹信息与自然伽马、自然电位和电阻率等参数的变化特性;通过综合对比多个钻孔的轨迹数据钻孔视频成像和测井结果,详细描述了工作面煤层及周围岩层的分布特征,并准确界定了各岩石类型及其真厚度;基于钻孔测井曲线特征和对应区域成孔视频,识别煤层中煤体结构异常区域和煤层含水区域。【结果和结论】研究结果表明:研究区域煤层顶底板岩性主要包括砂质泥岩、泥岩、细砂岩、煤岩四种岩石,不同岩性具有显著的测井响应特征,结合岩性划分结果和对应的钻孔轨迹信息,能有效划分煤层及其顶底板围岩层位。对单个钻孔开展重复性测井,提高了岩石岩性和厚度的识别精度,孔内厚度测量误差控制在0.2 m内,验证了测井结果的可靠性。煤层自然电位和电阻率曲线交会图表明,底抽巷第三、四组钻孔之间存在长8.4 m,厚1.1 m的煤体结构异常区域;自然伽马、电阻率曲线交会图曲线和钻孔视频表明,第6组钻孔间存在长3.4 m,厚0.9 m的含水区域,研究结果与工作面瞬变电磁法勘测结果相一致,区域表现为弱富水性。多参数测井为快速判别井下钻孔的目标层位提供了高效手段,在推进矿井地质信息的透明化建设上有着良好的应用前景。

     

    Abstract: Background In the process of coal mining, effective exploration methods for stratigraphic characteristics are crucial to underground operations. The reason is that the accurate stratigraphic characteristics of coal seams, along with the surrounding rocks of coal seam roofs and floors, facilitate the treatment of gas in coal seams, thereby ensuring safe and efficient coal mining. Method Based on the multiparameter logging of boreholes crossing strata in a bottom drainage roadway, this study highlighted the lowstand, upgoing borehole trajectories, as well as the variations in parameters including natural gamma rays, spontaneous potential, and resistivity. By comprehensive comparison of the trajectories, video-derived images, and log results of multiple boreholes, this study detailed the distributions of the coal seams and surrounding rocks of the mining face and determined the accurate types and true thicknesses of various rocks. Besides, using the log curves of boreholes and corresponding video-derived. images, this study identified zones with anomalous coal structures and the water-bearing zones within coal seams. Results and conclusions The results indicate that the coal seam roofs and floors in the study area consist primarily of sandy mudstones, mudstones, fine-grained sandstones, and coals, which exhibit significantly different log responses. The combination of the lithologic classification results and corresponding borehole trajectories allows for the effective definition of coal seams, as well as the horizons of the surrounding rocks of coal seam roofs and floors. Repeated logging of a single borehole can improve the accuracy of identified lithologies and thicknesses of rocks. With errors of thickness measurements within boreholes controlled at below 0.2 m, the log results proved valid. The cross plot of spontaneous potential and resistivity curves reveals a zone with anomalous coal structures measuring 8.4 m in length and 1.1 m in thickness between the third and fourth groups of boreholes in the bottom drainage roadway. Additionally, the cross plot of natural gamma ray and resistivity curves and borehole videos suggest the presence of a water-bearing zone with a length of 3.4 m and a thickness of 0.9 m between the boreholes of the sixth group. These results align with the results obtained using the transient electromagnetic method (TEM), suggesting regionally weak water-yield properties. Overall, multiparameter logging serves as an efficient method for rapidly determining target horizons in underground drilling, demonstrating promising prospects for advancing the geological transparency of coal mines.

     

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