关键词: 渗透率, 周期振荡法, 低渗透测量, 周期波, 数值模拟, 孔隙率

Abstract: Periodic oscillation method is a new method for permeability measurement of porous media. It exhibits advantages of short testing period, good stability and high precision. However, it has not been widely used for low permeability measurement in laboratory due to lack of systematic research. In this paper, the effects of different porosities and medium permeabilities on the permeability measurement results of the periodic oscillation method are numerically analyzed. In addition, the applicability of different forms of periodic waves in the permeability measurement is discussed. Conclusions from the study results can be drawn as follows. First, both the porosity and permeability can affect the process of gas pressure transfer. Second, the initial pressure equilibrium process in medium may not be needed for the periodic oscillation method as the measurement results are almost unaffected by the initial pressure distribution after a certain period of time. Third, compared with sinusoidal wave, square wave exhibits a more notable influence on the pressure response of the downstream gas. Moreover, it is observed that square wave, triangular wave and sawtooth wave are easier to be loaded in practice. Finally, based on the numerical analysis, it is suggested to use the square wave instead of sinusoidal wave in the periodic oscillation method. This study will be helpful to guide the application of the periodic oscillation method test in low permeability measurement.

Key words: permeability, periodic oscillation method, low permeability measurement, periodic wave, numerical simulation, porosity