周期振荡法在低渗透测量中的应用研究

周期振荡法是一种新兴的多孔介质渗透率测量方法,具有测量周期短、稳定性好、精度高等优点。然而,由于缺乏对周期振荡法的系统研究,该方法未能在低渗透测量领域得到推广应用。采用数值模拟方法,分别研究了不同孔隙率、渗透率对周期振荡法气压测量结果的影响,以及不同形式周期波在周期振荡法渗透率测量中的适用性。结果表明:无论是孔隙率,还是渗透率都会影响气体压力传递过程;周期振荡法渗透率测量时可以不需要初始气压平衡过程,一定时间后测量结果几乎不受初始气压状态影响;与正弦波相比,方波对下游气体压力响应的影响更明显,而且方波、三角波和锯齿波具有容易加载的特点,建议采用方波取代正弦波进行周期振荡法试验。研究成果对指导周期振荡法试验和解决低渗透测量难题有一定帮助。

Application of periodic oscillation method in low permeability measurement

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.