摘要
针对我国低渗透煤层瓦斯抽采困难的问题,提出了液氮冷冲击致裂增透方法。该方法将高压液氮注入煤层钻孔,结合低温液氮的冷冲击作用、水冰相变的冻胀作用和液氮气化的膨胀作用,在煤体内部构造发育的孔裂隙网络,从而提高瓦斯的抽采效率。本文分别从热应力、冻胀力和气化膨胀力角度阐释了液氮冷冲击多重效应致裂煤体的机理。关于液氮致裂煤体的基础机理与技术应用方面的研究,需考虑含瓦斯煤体及原位地层条件,同时脉动液氮压裂值得引起进一步关注。当前存在液氮高效致裂增透的技术环节有待优化完善和液氮多重致裂作用下裂隙扩展机制认识不清的问题。未来可将液氮压裂与水力射流等技术相结合,降低煤层起裂压力,实现裂隙的定向、大范围扩展。
The liquid nitrogen fracture technique has been proposed to solve the issue in gas extraction from a single low-permeability coal seam in China.Liquid nitrogen is injected into coal seams through the drilled boreholes.Combining the cold-shock effect of liquid nitrogen,the water-ice phase change,and liquid nitrogen gasification,a complex pore-fracture network can be constructed inside coal.Therefore,the coal permeability is largely improved which promotes the gas extraction efficiency.In this paper,the mechanism of liquid nitrogen cold-shock fracturing is presented from the perspectives of thermal stress,frost-heaving stress,and gasification expansion stress,respectively.However,the current research on the basic mechanism and application of liquid nitrogen fracturing has not considered the gas-bearing coal and in-situ stress conditions.Additionally,pulsating liquid nitrogen fracturing technology deserves further investigation.Up to now,two key problems exist in this field that includes the optimization of the technical workflow and pore-fracture propagation mechanism.In the future,liquid nitrogen fracturing can be combined with hydraulic jet to reduce the coal seam initiation pressure and create the directional and large-scale extension of fractures.
作者
翟成
孙勇
武建国
Zhai Cheng;Sun Yong;Wu Jianguo(School of Safety Engineering,China University of Mining and Technology,Xuzhou 221116;National Engineering Research Center for Coal Gas Control,Xuzhou 221116;Kailuan(Group)Co.,Ltd.,Tangshan 063018)
出处
《中国科学基金》
CSSCI
CSCD
北大核心
2021年第6期904-910,共7页
Bulletin of National Natural Science Foundation of China
基金
国家自然科学基金项目(51774278,51925404)的资助。
关键词
低渗透煤层
致裂增透
液氮冷冲击
瓦斯抽采
low-permeability coal seam
fracturing and permeability enhancement
liquid nitrogen cold shock
gas extraction
作者简介
通信作者:翟成,中国矿业大学安全工程学院教授,博士生导师。主要从事低透气性煤层致裂增透、瓦斯高效抽采、矿井瓦斯灾害防治以及页岩储层压裂开发等方面的研究,Email:gretazc@cumt.edu.cn。
