煤储层造缝及卸压增透实验研究

Experimental study of permeability enhancement in coal layers by fracture making or unloading

煤矿井下瓦斯抽采难易程度取决于煤体渗透性,煤体增透是瓦斯抽采研究的关键之一。以煤岩体加载作用下的渗透率测试实验为前提,揭示了不同结构煤体水力强化的造缝和卸压两种增透机理;提出了硬煤(原生结构煤和碎裂煤)可通过水力压裂造缝提升渗透率,软煤(碎粒煤和糜棱煤)可通过冲孔出煤卸压增透或顶底板围岩水力压裂抽采的两种工艺,从而形成了基于煤体结构的水力强化增透瓦斯抽采技术。现场应用结果充分说明了实验室研究结论的正确性。

The difficulty of gas extraction in underground coal layers depends on the coal permeability,coal permeability enhancement is a key for gas extraction. In this paper,based on the measurements of penetration rates in coal-rocks with loading,two different mechanisms were proposed for the hydraulic-induced permeability enhancements in different coal structures. Consequently,the experimental results show that the permeability of hard coal( original structural and cracked coal) can be improved by hydraulic fracturing,and that of soft coal( crashed and mylonitic coal) may be enhanced by unloading through taking coal out with hole-drilling or by mining with hydraulic fracturing of roof,floor and surrounding rock. Thus,a gas mining technique has been developed,which is suitable for different coal structures based on hydraulic strength. The experimental results were also verified by the site applications.