Development of sealed pressure maintaining sampling device for deep holes in coal mines
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摘要: 采用敞口式岩心管取样来测定深孔煤层瓦斯含量时煤样暴露时间长、煤样易被污染、瓦斯损失量难以计量导致测量误差大,而现有密闭保压取样大多需要二次扩孔、结构复杂、取样成功率低造成难以大规模推广应用。针对上述问题,研制了一种煤矿井下深孔密闭保压取样装置。该装置采用“两级活塞+双层套管+煤样筒”的整体结构设计,通过控制井下高压水泵注入装置内的注水流量及注水时间,实现球阀由取样前密闭到取样时开启,再到取样后密闭的动作转换,达到煤样被密闭在煤样筒内的目的,防止煤样被污染及取样过程中瓦斯逸散。采用敞口式岩心管常规取样方法和深孔密闭保压取样装置分别采集了4组同钻孔同深度处煤样,进行瓦斯含量测定对比分析,现场试验结果表明:深孔密闭保压取样装置的取样深度接近350 m;相较于常规取样方法,深孔密闭保压取样测得的瓦斯含量偏大5.4%~37%,且随着取样钻孔深度增加,偏大的程度增加,表明密闭保压取样装置能够提高深孔煤层瓦斯含量测试的准确性。Abstract: When using open core tube sampling to measure the gas content in deep hole coal seams, the coal sample has a long exposure time. It is prone to pollution, and the gas loss is difficult to measure, resulting in large measurement errors. However, most of the existing sealed pressure maintaining sampling requires secondary expansion and complex structure. The sampling success rate is low, making it difficult to promote and apply on a large scale. In order to solve the above problems, a sealed pressure maintaining sampling device for deep holes in coal mines has been developed. The device adopts an overall structural design of "two-stage piston+double-layer casing+coal sample cylinder". By controlling the injection flow rate and injection time of the underground high-pressure water pump into the device, the ball valve switches from being sealed before sampling to being opened during sampling, and then to being sealed after sampling. The goal of sealing the coal sample in the coal sample cylinder is achieved, preventing contamination of the coal sample and gas escape during the sampling process. Four sets of coal samples from the same borehole and depth are collected using the conventional sampling method of an open core tube and a deep hole sealed pressure maintaining sampling device for comparative analysis of gas content. The on-site test results show that the sampling depth of the deep hole sealed pressure maintaining sampling device is close to 350 meters. Compared to conventional sampling methods, the gas content measured by deep hole sealed pressure maintaining sampling is 5.4% to 37%. The degree of deviation increases with the increase of sampling drilling depth. It indicates that the sealed pressure maintaining sampling device can improve the accuracy of deep hole coal seam gas content testing.
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表 1 深孔密闭保压取样装置关键部件参数
Table 1. Parameters of key components of deep borehole sealed pressure maintaining sampling device
部件 尺寸 取样装置长度/mm 1 200 外套管/mm ϕ73×1 106 推进套管/mm ϕ60×438 推进齿条管/mm ϕ60×581 煤样筒/mm ϕ50×830 第二流通孔/mm ϕ2×24 球阀通孔直径/mm 26 表 2 密闭保压取样与常规取样下煤层瓦斯含量测试结果对比
Table 2. Comparison of test results of gas content in coal seam under sealed pressure maintaining sampling and conventional sampling
孔号 取样方式 取样深度/m 煤样质量/g 瓦斯含量/(m3·t−1) 1号 常规取样 126 1 128 5.3 密闭保压取样 126 856 5.6 2号 常规取样 196 753 2.6 密闭保压取样 196 553 3.1 3号 常规取样 273 1 038 4.2 密闭保压取样 273 637 4.9 4号 常规取样 342 815 2.9 密闭保压取样 342 694 4.6 -
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