成都平原浅层天然气高瓦斯隧道抽排性能评价

Evaluation of Drainage Performance of High-gas Tunnel in Chengdu Plain Shallow Natural Gas Area

摘要:

针对浅层天然气工区高瓦斯隧道盾构施工难的问题，借助工程实例，采用理论分析、数值模拟和现场试验的方法，分析了成都平原浅层天然气抽排性能的影响因素，确定了研究区的有效抽排半径和抽排时间。结果表明，当裂隙渗透率为39 mD、瓦斯压力为0.31 MPa时，研究区浅层天然气高瓦斯工区的有效抽排半径为5 m、抽排时间为60 min，与煤层瓦斯的抽排参数差异巨大；抽排负压对抽排流量影响较大，对有效抽排半径影响较小；抽排流量和有效抽排半径与地层初始渗透率的变化呈现正相关关系。

Abstract:

Aiming at the difficulty of shield construction of high-gas tunnel in the shallow natural gas work area， with the help of engineering examples， the influencing factors of drainage performance of shallow natural gas in Chengdu Plain were analyzed by using theoretical analysis， numerical simulation and field test， and the effective radius and drainage time in the study area were determined. The results show that when the fracture permeability is 39 mD and the gas pressure is 0.31 MPa， the effective pumping radius of high-gas area of shallow natural gas in the study area is 5 m， and the pumping time is 60 min， which is greatly different from the coal seam gas. The negative pressure of pumping has a great effect on the discharge， but a little effect on the effective pumping radius. The discharge and effective pumping radius are positively correlated with the change of initial permeability of formation.