摘要:
钻孔预抽是目前抽采煤层瓦斯的主要方式,钻孔深度是影响煤层瓦斯抽采效果的重要因素。普通钻进过程中钻具前方会形成高围压区,限制了钻孔的深度。提出了一种新的射流辅助钻进理念,通过射流超前切割来消除钻具前方的围压,降低钻进难度,提高钻进深度。在上述基础上,研究了围压对煤体力学性质的影响,分析了射流辅助钻进过程中的破围压理论,并开发了新式射流钻头,同时进行了现场工业性应用。研究表明,高围压会显著提高煤体的极限破坏强度,增加钻进难度;利用射流能够有效的破除围压区,降低钻进阻力;射流钻孔深度明显高于普通钻孔,平均深度提高了25%,有利于瓦斯抽采。
关键词:
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围压
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射流
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破岩
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辅助钻进
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钻孔深度
Abstract:
Drilling forepumping is the main form of gas drainage,and the drilling depth is the key factor to affect the effect of gas drainage.Common drilling can form high confining pressure area,which can limit the drilling depth.In view of this,a new jet assisted drilling concept was developed,the drilling depth can be increased through eliminating confining pressure by jet cutting.On this basis,the effect on mechanic character of coal under confining pressure area was studied,and the theory of eliminating confining pressure in jet assisted drilling process was analyzed;The new jet drilling was designed,and the industrial application in the scene was put on.Studies show that confining pressure can increase the ultimate breaking strength of coal significantly,which enhance the difficulty of drilling;jet drilling can eliminate confining pressure area effectively and reduce the drilling resistance;The jet drilling depth is deeper than the normal one,the average depth increased by 25%,which do benefit to gas drainage.
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