煤矿重复扰动“采动-采空”地面井抽采技术及应用

Research and application of“mining-gob”surface well extraction under repeated disturbance in coal mines

为攻克煤矿开采重复扰动地层导致地面井变形破坏的技术难题,深入分析了重复扰动下地层的移动规律、地面井的变形破坏力学机理、失效方式与特征,发现地面井破坏的直接原因是发生了过量的位移变形,据此总结分析出地面井破坏失效的判识条件:①套管剪切位移量超过其管内直径;②套管的最小拉伸安全系数小于阈值“1”。在此认识基础上提出了“避、抗、让、疏、护”五大地面井防护技术理念,能够从井位选择、井身结构、钻完井工艺、安全防护装置等方面有效减少重复扰动地面井的破坏性位移量。应用技术成果在岳城煤矿设计5口地面井,实现了“采动-采空”地面井持续抽采,累计抽采标况纯瓦斯量约5240万m^(3),保障煤矿安全生产的同时提高了瓦斯抽采利用量。进一步分析地面井抽采数据发现,采动区地面井经过5 a持续运行后的抽采影响半径超过800 m。

In order to overcome the technical problem that the repeated disturbance of the ground in coal mining leads to more easily de⁃formed and damaged surface wells,the paper analyzed the movement law of strata,the deformation mechanism of surface well,as well as the failure mode and characteristics,and found that the direct cause was excessive deformation of surface well.As a result,the identification conditions for failure of surface well were summarized as follows:①the casing shear displacement exceeds the inner diameter of the pipe;②The minimum tensile safety factor of the casing is less than the threshold value“1”.On the basis of this understanding,the five major surface well protection technology concepts such as“avoiding,resisting,yielding,dredging and protecting”were put forward,which can ef⁃fectively reduce the repeated disturbance of the ground in terms of well location selection,well structure,drilling and completion technology and safety protection device.The research team used the results in designing five surface wells in Yuecheng Mine,all of which achieved“mining-gob”long-term continuous extraction,bringing about 52.4 million m^(3) pure gas volume in standard condition,which not only en⁃sured the safe production of coal mine,but also improved the utilization of gas.Further analysis of the drainage data showed that the influ⁃ence radius of surface well in the mining area after five years of continuous operation exceeded 800 m.