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煤矿瓦斯抽采增产机制及关键技术

Increasing production mechanism and key technology of gas extraction in coal mines

  • 摘要: 瓦斯抽采是煤矿瓦斯灾害治理的主要途径。长期以来,广大科技与工程技术人员研制了多种瓦斯抽采技术,为我国煤矿安全生产提供了有力保障。但是对于一些突出严重的低渗煤层仍存在抽采效率低、成本高的问题,迫切需要形成一套系统的、能够实现瓦斯抽采由“抽得出向抽得快、抽得省、抽得纯、抽得净”转化的技术体系。为此,首先系统介绍了煤岩体结构的定量表征、瓦斯运移产出机制和基于煤岩体结构的瓦斯运移产出过程,并以此瓦斯抽采增产理论为基础,从物理、生化和表面改性等方面厘清了瓦斯抽采增产机制,最后结合团队近20年从事瓦斯治理工作的研究成果,系统分析了水力压裂、钻冲压一体化、老孔修复、三堵两注固液两相封孔、下向瓦斯抽采孔自动排水排渣气驱、地面以孔代巷等六项瓦斯抽采技术的增产原理,简要介绍了研制的相关装备、装置和器材以及现场应用效果。指出煤体结构决定了煤层的可改造性,决定了瓦斯的运移产出流态,进而决定了瓦斯抽采增产技术的选择,是瓦斯治理技术体系建立的基础。揭示了瓦斯抽采的多重增产机制:造缝增透、增容增透、气驱增产、气胀致裂增透、微生物降解增产、强氧化剂氧化增产和表面改性增产等,指出水力压裂、钻冲压一体化、地面以孔代巷三项技术是以增透增产为主要途径的水力强化措施;三堵两注固液两相封孔、老孔修复增透、下向孔自动排水排渣三项技术则是以多重增产机制为基础,以延长抽采钻孔使用寿命、提高抽采瓦斯的质和量为途径的增产技术;气驱技术的本质是增加瓦斯压力梯度、实现抽采后期低压煤层瓦斯抽采增产。已经完成的工程试验和推广应用充分显示出这一技术体系的潜在优势,随着这一技术体系进一步的标准化和程序化,将成为煤矿瓦斯高效抽采的一种普适性技术,其推广应用将大幅度降低瓦斯治理成本。

     

    Abstract: Gas extraction is the main way to control gas disasters in coal mines. For a long time, a variety of gas extraction technologies have been developed, which provide a powerful guarantee for the safe production of coal mines in China. However, for some serious outburst low-permeability coal seams, there are still problems of low extraction efficiency and high cost. There is an urgent need to form a system that can realize the transformation of gas extraction from " regular extraction to the quick, economical, pure and clean extraction" . Therefore, the quantitative characterization of coal and rock mass structure, gas migration and production mechanism, and gas migration and production process based on the structure of coal and rock mass were introduced firstly in this paper. The mechanism of gas extraction and production-increasing mechanism was clarified from the aspects of physical, biochemistry and surface modification. The research results of the team engaged in gas control work in the past 20 years are combined, a systematic analysis of six gas extraction technologies including hydraulic fracturing, integrated drilling and stamping, old hole repair, solid-liquid two phase hole sealing device and technology for three blocks and two injections, downhole automatic drainage, slag discharge and gas flooding, ground hole replacement for roadway were systematically analyzed, and self-developed equipment, devices and field application results were briefly introduced. It is pointed out that the coal body structure determines the transformability of the coal seam, determines the migration and production flow pattern of gas, and then puts forward the choice of gas extraction and production-increasing technology, which is the basis for the establishment of gas treatment technology system. The multiple production increase mechanisms of gas extraction were revealed, including permeability improvement from fracture generation, compacity enhancement, gas flooding, gas dilation, fracturing, microbial degradation, strong oxidant oxidation and surface modification, etc. It is indicated that the three technologies of hydraulic fracturing, drilling and stamping integration and the ground hole replacement for roadway are the hydraulic strengthening measures with permeability improvement and production increase as the main approaches. The three technologies of solid-liquid two phase hole sealing device and technology for three blocks and two injections, old holes repairing, downhole automatic drainage, slag discharge and gas flooding are based on multiple production-increasing mechanisms to extend the service life of the extraction boreholes and improve the quality and quantity of the extracted gas. The essence of gas flooding technology is to increase gas pressure gradient and realize gas extraction and increase production in low-pressure coal seam at the later stage of gas extraction. The completed engineering tests and application have fully demonstrated that the potential advantages of this technical system. With the further standardization and proceduralization of this technical system, it will become a universal technology for high-efficiency gas extraction in coal mines, and its popularization and application will greatly reduce cost of gas control.

     

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