摘要
针对我国单一低透气性煤层常规钻孔瓦斯抽采困难的问题,提出了低温循环致裂增透方法。该方法将液氮等低温介质注入煤体,实现煤体的降温冻结;之后冻结煤体从周围煤岩吸热融化,循环地注入低温流体可使煤体产生交变的冻结-融化现象,从而改变煤体的孔隙结构和渗透性。采用冻融机对饱水煤样进行了共20次循环的冻融试验,并利用核磁共振测试方法,分析了低温循环冻融作用下煤体孔隙结构特征的演化规律。研究结果表明:随着冻融次数的增加,煤样的中、大孔占比、总孔隙度、有效孔隙度和渗透率显著增加,表明多次冻融能使煤体孔隙数量增加,尺寸变大,连通增强,从而形成交织贯通的孔裂隙网络,使煤体透气性大幅增强。
For the ineffective gas drainage in single low-permeability coal seam in China, the method of cyclic cryogenic fracturing coal is proposed. In the process of cyclic cryogenicfluld injection,the coal freezes.Then the trnzen coal thaws by absorbing heal from surrounding cnals.So the freezing and thawing cycles emerge in coal mass and the pore structure and permeability of coal will also be changed.The ex- periment which coal samples were treated by Keezing and thawing in a total of 20 cycles was carried ouhThe nuclear magnetic resonance test was used to the coal samples.The evolution of pore stmcfure characterislics at different freeze-thaw cycles was researched.The results show that the inacropores and fraetures＇ proportion,the total porosity,the effective porosity,the permeability is rising with increasing freeze -thaw cycles.This proves that the pores of coal samples have bigger quantities,larger size and t）e more connecled after multiple freeze- thaw cycles, so the pore-fracture network forms.Finally, the gas permeability of coal seam increases significantly.
出处
《煤炭科学技术》
CAS
北大核心
2017年第6期24-29,共6页
Coal Science and Technology
基金
国家自然科学基金资助项目(U1361106
51274195)
国家重大科学仪器设备开发专项资助项目(2013YQ17046309)
关键词
瓦斯抽采
冻融
核磁共振
孔隙结构
渗透率
gas drainage
freeze-thaw
nuclear magnetic resonanee
pore structure
permeahility
