煤岩气储层滑脱效应实验研究

Experimental study on slippage effect of coal-rock-gas reservois

岩石的孔隙度与岩石的渗透率成正相关。岩石的气透测渗率高于液测渗透率,且具有压力依赖性,该现象被称作滑脱效应或Klinkenberg效应。气测渗透率的压力依赖性是由于在计算渗透率时气体黏度取值不当所致,气体黏度在低压下随压力变化很大,但计算渗透率时却选用了定值。滑脱效应将使气体的黏度无法测量,从而出现测试悖论。气体分子每时每刻都在做不规则的热运动,会不停地与孔隙壁面发生碰撞,致使气体无法出现滑脱。岩石渗透率的气测值高于液测值,是测试介质的分子尺度与孔隙尺度对比的结果。

The porosity of rock is positively correlated with the permeability of rock. The permeability of rock measured by gas permeability is higher than that by liquid permeability, and it is pressure-dependent. This phenomenon is called slippage effect or Klinkenberg effect. The pressure dependence of gas permeability measurement is due to the improper value of gas viscosity in the calculation of permeability.The gas viscosity varies greatly with pressure at low pressure, but a fixed value is selected to calculate permeability. The slippage effect will make the viscosity of the gas unmeasurable, resulting in a test paradox. Gas molecules are doing irregular thermal movement all the time, will constantly collide with the pore wall, resulting in the gas can not appear slippage. The gas permeability of rock is higher than that of liquid, which is the result of the comparison of molecular scale and pore scale of the tested medium.