Jannot Yves, Lasseux Didier
LEMTA, Nancy-Université, CNRS, Vandoeuvre, France.
Rev Sci Instrum. 2012 Jan;83(1):015113. doi: 10.1063/1.3677846.
A new quasi-steady method for the determination of the apparent gas permeability of porous materials is presented in this paper along with the corresponding interpretative physical model derived from the unsteady flow equations. This method is mainly dedicated to the measurement of very low permeability of thin porous media, although thicker but more permeable samples may also be analyzed. The method relies on quasi-steady flow resulting from a (quasi) constant pressure maintained at the inlet face of the sample. Gas flow-rate, as low as 3 × 10(-10) m(3)/s, is determined from the record of pressure increase in a reservoir connected to the outlet face of the sample. An estimate of the characteristic time, t(c), to reach quasi-steady flow after imposing a constant pressure at the inlet is derived. It is validated by direct numerical simulations of the complete unsteady flow, clearly defining the required experimental duration for the method to apply. Experimental results obtained on rather permeable and thick rock samples are reported showing an excellent agreement of the measured permeability with that determined independently on the same sample whereas the experimental value of t(c) is also in very good agreement with the predicted one. The method is further employed on a composite material sheet allowing the identification of an apparent gas permeability of about 10(-23) m(2).
本文提出了一种测定多孔材料表观气体渗透率的新准稳态方法，并给出了从不稳定流动方程导出的相应解释性物理模型。该方法主要用于测量薄多孔介质的极低渗透率，不过也可分析较厚但渗透率较高的样品。该方法基于在样品入口面维持（准）恒定压力所产生的准稳态流动。通过记录连接到样品出口面的储液器中的压力升高来测定低至3×10^(-10)立方米/秒的气体流速。推导出在入口施加恒定压力后达到准稳态流动的特征时间t(c)的估计值。通过对完整不稳定流动的直接数值模拟对其进行了验证，明确界定了该方法适用所需的实验持续时间。报告了在相当渗透且较厚的岩石样品上获得的实验结果，结果表明测量的渗透率与在同一样品上独立测定的渗透率非常吻合，而t(c)的实验值与预测值也非常吻合。该方法进一步应用于一种复合材料片材，测定出其表观气体渗透率约为10^(-23)平方米。
