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压裂层双重介质中煤层水渗流规律仿真试验研究

Simulation of dual-porosity medium seepage flow in fractured zone

  • 摘要: 为了探究发生井间干扰前煤层水的渗流规律及双重介质的渗透性规律,利用COMSOL Multiphysics多物理场仿真软件,对煤层气开采压裂煤储层后形成双重介质中煤层水渗流特性进行了仿真试验研究。试验结果表明:排水一段时间后,裂缝区域裂隙水压力明显低于周围煤岩孔隙水压力;在任意一条垂直于裂缝的压力切面上,裂缝处压力最低,向两边压力逐渐升高;沿裂缝方向,裂缝末端压力最高,靠近井筒,压力降低,井筒处压力最低;排水时,裂缝中的煤层水最先进入井筒,并且水头降低很快,同时,在压差作用下,煤岩中的水不断渗流进入裂缝,再经裂缝流入井筒;将测得的该速水头数据拟合后,得到双重介质x方向上渗透系数为0.013 5 m/s,y方向渗透系数为8×10-8m/s。研究结果可为分析煤层气开采对地下水水动力条件和储存条件的影响提供参考。

     

    Abstract: This paper focuses on studying the coalbed water flow and dual-porosity medium permeability before the inter-well interference.Coalbed water flow in dual-porosity medium formed by fracturing coal seams is simulated using COMSOL multi-physics software.The results show that the fissure water pressure in fissure zone is significantly lower than the pore water pressure in the coal after a period of draining.The pressure at the fracture is the lowest and increases gradually toward both sides on any tangential plane. Along the direction of fracture, the pressure at the end of the fracture is the highest while the pressure is the lowest at the wellbore.When draining,coalbed water of fracture firstly enters the wellbore with rapid decrease of head. Due to differential pressure,the coalbed water flows into the fracture continuously, then flows into the wellbore.According to the measuring datas of flow velocity head, the permeability of the dual-porosity medium is 0.013 5 m/s in the x-direction and 8×10-8 m/s in the y-direction.The researeach results can provide the reference for the analysis of the influence of CBM exploitation on the hydrodynamic and storage conditions of ground water.

     

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