综放工作面难放顶煤架间定向水力压裂技术研究

发布时间：2018-12-19 16:25

【摘要】：本论文针对厚度大且坚硬的煤层实施综合机械化放顶煤开采时,存在顶煤难以断裂、即使断裂但垮落块度过大,也不易放出,直接影响顶煤回收率的实际问题,通过广泛实际调研和现场观测,提出采用架间定向水力压裂技术弱化难放顶煤,从而达到提高综放工作面顶煤回收率的目的。通过在芦子沟煤矿、铁北煤矿采用深孔非接触位移检测方法、智能钻孔电视成像技术观测手段,发现硬厚难放顶煤存在"短悬臂梁"结构,这类短悬臂梁结构具有一定的自稳性,滞后工作面冒落,是影响顶煤放出的关键因素。在此基础之上,建立了难放顶煤的力学模型,并从理论上推导出拉断和剪切条件下的短梁极限厚度,为确定水力压裂分段切槽位置间距奠定理论基础。论文依据弹性力学最大拉应力准则,在理论上分别得到了非开槽钻孔和开槽钻孔水压裂缝起裂力学模型的起裂压力和起裂位置。同时采用ABAQUS数值模拟手段,对比分析了不同角度的未切槽钻孔和切槽钻孔周围应力分布情况。在开槽钻孔切槽尖端处,裂缝扩展分为三个阶段,即起裂阶段、近场裂缝扩展阶段和远场裂缝扩展阶段,推导出了各个阶段用流量表示的裂纹扩展判据,并得到了Ⅰ型裂缝扩展终止半径。在实际中,通过利用电磁波CT层析成像技术探测了定向水力压裂水压裂缝的扩展区域分布,为钻孔间距的确定提供参考。最后,根据铁北煤矿煤层具体赋存条件,依据理论分析和数值模拟得到的参数,采用架间定向水力压裂技术弱化难放顶煤。工业性实践结果表明,铁北煤矿的顶煤能随采随落,且破碎块度适中,放煤顺利,工作面顶煤回收率得到大幅提高。架间定向水力压裂是弱化难放顶煤的有效技术途径,具有广泛的实用推广价值。
[Abstract]:In this paper, when mechanized caving coal mining is carried out in thick and hard coal seam, it is difficult to break the top coal, even though it is broken but the falling block is too big, it is difficult to release, which directly affects the practical problem of the recovery rate of top coal. Through extensive practical investigation and field observation, it is put forward to use the technology of directional hydraulic fracturing between shelves to weaken the difficult caving coal, so as to increase the recovery rate of top coal in fully mechanized caving face. In Luzigou coal mine and Tiebei coal mine, the "short cantilever beam" structure is found to exist in hard and hard caving coal by using the non-contact displacement detection method of deep hole and the observation means of intelligent borehole television imaging technology. This kind of short cantilever beam structure has certain self-stability and the falling of lag working face is the key factor that affects the top coal caving. On this basis, the mechanical model of difficult top coal caving is established, and the limit thickness of short beam under the condition of pulling and shearing is deduced theoretically, which lays a theoretical foundation for determining the spacing of section cut slot in hydraulic fracturing. According to the maximum tensile stress criterion of elastic mechanics, the starting pressure and location of hydraulic crack initiation mechanical model of non-slotted and slotted boreholes are obtained theoretically in this paper. At the same time, ABAQUS numerical simulation method is used to compare and analyze the stress distribution around the uncut boreholes and grooved boreholes at different angles. At the cutting tip of slotted boreholes, the crack propagation is divided into three stages, I. e., initiation stage, near-field crack propagation stage and far-field crack propagation stage. The crack propagation criterion expressed by flow rate in each stage is derived. The termination radius of type I crack propagation is obtained. In practice, the spread area distribution of hydraulic fractures in directional hydraulic fracturing is detected by using electromagnetic wave CT tomography technique, which provides a reference for the determination of borehole spacing. Finally, according to the specific occurrence conditions of coal seam in Tiebei coal mine and the parameters obtained by theoretical analysis and numerical simulation, the interframe directional hydraulic fracturing technique is used to weaken the difficult top caving coal. The industrial practice results show that the top coal energy of Tiebei coal mine follows with the mining, and the crushing degree is moderate, the coal drawing is smooth, and the recovery rate of top coal in the working face is greatly improved. Interframe directional hydraulic fracturing is an effective technical way to weaken hard top coal caving, and has extensive practical value.
【学位授予单位】：煤炭科学研究总院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD823.49

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