This paper takes Zhaozhuang mine in Shanxi province as an example to study the technology of hydraulic reaming drill hole for improving the gas extraction.The influence of the physical properties of coal seam on the h...This paper takes Zhaozhuang mine in Shanxi province as an example to study the technology of hydraulic reaming drill hole for improving the gas extraction.The influence of the physical properties of coal seam on the hydraulic reaming drill holes and the draining of coal mine gas were analyzed and discussed for different coal structure areas,and the following conclusions were made.Hydraulic drill hole reaming has had a positive impact in Zhaozhuang Mine,and can improve the efficiency of gas extraction to different degrees.The water jet pressure used in hydraulic drill hole reaming mainly depends on the structure of the coal.When the coal seam basically becomes integrated,the critical water jet pressure increases,the discharge becomes relatively easy to achieve,the blocking effect on the gas extraction decreases,and the gas extraction significantly increases after the reaming process.When the coal seam is broken,the critical water jet pressure decreases,the discharge becomes difficult to achieve,the blocking effect on the gas extraction becomes obvious,and the gas extraction changes slightly after reaming.展开更多
A method of hydraulic grid slotting and hydraulic fracturing was proposed to enhance the permeability of low permeability coal seam in China. Micro-structural development and strength characteristics of coal were anal...A method of hydraulic grid slotting and hydraulic fracturing was proposed to enhance the permeability of low permeability coal seam in China. Micro-structural development and strength characteristics of coal were analysed to set up the failure criterion of coal containing water and gas, which could describe the destruction rule of coal containing gas under the hydraulic measures more accurately. Based on the theory of transient flow and fluid grid, the numerical calculation model of turbulence formed by high pressure oscillating water jet was used. With the high speed photography test, dynamic evolution and pulsation characteristics of water jet water analysed which laid a foundation for mechanism analysis of rock damage under water jet. Wave equation of oscillating water jet slotting was established and the mechanism of coal damage by the impact stress wave under oscillation jet was revealed. These provide a new method to study the mechanism of porosity and crack damage under high pressure jet.Fracture criterion by jet slotting was established and mechanism of crack development controlled by crack zone between slots was found. The fractures were induced to extend along pre-set direction,instead of being controlled by original stress field. The model of gas migration through coal seams after the hydraulic measures for grid slotting and fracking was established. The key technology and equipment for grid slotting and fracking with high-pressure oscillating jet were developed and applied to coal mines in Chongqing and Henan in China. The results show that the gas permeability of coal seam is enhanced by three orders of magnitude, efficiency of roadway excavation and mining is improved by more than 57%and the cost of gas control is reduced by 50%.展开更多
基金the National Natural Science Foundation of China (No. 51404094)Postdoctoral Science Foundation of China (No. 2014M561988)Doctor Funds of Henan Polytechnic University of China (No. B2012-026) for their support with this project
文摘This paper takes Zhaozhuang mine in Shanxi province as an example to study the technology of hydraulic reaming drill hole for improving the gas extraction.The influence of the physical properties of coal seam on the hydraulic reaming drill holes and the draining of coal mine gas were analyzed and discussed for different coal structure areas,and the following conclusions were made.Hydraulic drill hole reaming has had a positive impact in Zhaozhuang Mine,and can improve the efficiency of gas extraction to different degrees.The water jet pressure used in hydraulic drill hole reaming mainly depends on the structure of the coal.When the coal seam basically becomes integrated,the critical water jet pressure increases,the discharge becomes relatively easy to achieve,the blocking effect on the gas extraction decreases,and the gas extraction significantly increases after the reaming process.When the coal seam is broken,the critical water jet pressure decreases,the discharge becomes difficult to achieve,the blocking effect on the gas extraction becomes obvious,and the gas extraction changes slightly after reaming.
基金supported by the National Natural Science Foundation of China(Nos.51374258,51504046,51404045)Program for Changjiang Scholars and Innovative Research Team in University of China(No.IRT13043)the National Basic Research Program of China(No.2014CB239206)
文摘A method of hydraulic grid slotting and hydraulic fracturing was proposed to enhance the permeability of low permeability coal seam in China. Micro-structural development and strength characteristics of coal were analysed to set up the failure criterion of coal containing water and gas, which could describe the destruction rule of coal containing gas under the hydraulic measures more accurately. Based on the theory of transient flow and fluid grid, the numerical calculation model of turbulence formed by high pressure oscillating water jet was used. With the high speed photography test, dynamic evolution and pulsation characteristics of water jet water analysed which laid a foundation for mechanism analysis of rock damage under water jet. Wave equation of oscillating water jet slotting was established and the mechanism of coal damage by the impact stress wave under oscillation jet was revealed. These provide a new method to study the mechanism of porosity and crack damage under high pressure jet.Fracture criterion by jet slotting was established and mechanism of crack development controlled by crack zone between slots was found. The fractures were induced to extend along pre-set direction,instead of being controlled by original stress field. The model of gas migration through coal seams after the hydraulic measures for grid slotting and fracking was established. The key technology and equipment for grid slotting and fracking with high-pressure oscillating jet were developed and applied to coal mines in Chongqing and Henan in China. The results show that the gas permeability of coal seam is enhanced by three orders of magnitude, efficiency of roadway excavation and mining is improved by more than 57%and the cost of gas control is reduced by 50%.
文摘煤的层理面倾角(bedding plane angle,BPA)对射流破岩的效果影响显著。为探讨真三轴应力下不同BPA煤的射流破坏机制,开展了不同BPA煤在真三轴应力下的纯水射流冲蚀试验。结果表明,当煤的BPA较低或较高时,射流冲击分别容易形成锥形破碎坑和裂缝坑,破碎坑开口随着BPA的增大由圆形逐步向椭圆形过渡,煤的破坏模式由剪切破坏主导转变为拉伸-水楔效应主导。随着BPA增至60°,破岩体积增加了154.35%。当施加三轴应力时,煤层理面对射流破煤性能的影响被抑制,不同BPA煤的破坏模式仅呈现圆孔破碎坑,水锤压力引起的剪切破坏是煤在三轴应力下破坏的主要原因,60°BPA煤样的破坏体积减少了95.60%,相比其他倾角降低幅度达到最大。BPA对煤的轴向损伤演化具有驱动作用,随着倾角增大,轴向损伤发生波动。当施加三轴应力时,三轴应力抑制了射流破煤的损伤演化,煤的轴向损伤出现收缩。煤的破碎坑壁面的扫描电子显微镜(scanning electron microscope,SEM)结果表明:当施加三轴应力时,0°BPA煤样的破碎孔壁不再出现微裂隙与脆性剪切破坏的痕迹,并且孔隙的数量与尺寸大幅减小;60°BPA煤样的破碎孔壁不再出现水楔作用导致的大量锯齿状痕迹,三轴应力下不同BPA煤的破碎孔壁面均出现明显的延性剪切破坏特征。
