Gas Flow Property in Microtube and Its Effect on Gaseous Seepage

Abstract

The flow characteristics of nitrogen in microtubes with the diameters of 2.05, 5.03, and 10.1 μm are investigated experimentally. The results indicate that all the flow characteristics of nitrogen in microtubes depart from the classical Poiseuille's theory, and microscale effect appears apparently in gaseous flow. The experimental flow values are higher than the theoretical values calculated by Poiseuille's equation, and the deviations between experimental flow values and calculated values increase with the decrease of the inner diameter of microtube. However, the first-order slip boundary theory considered, the experimental flow values are in accordance with the theoretical predictions. Microscale effect can be characterized by the size of kn, and the larger kn, the stronger microscale effect. When Knudsen number is smaller than 0.002, the experimental microscale effect becomes negligible. Based on capillary bundle model, the influence of microscale effect on the gas seepage law in low-permeability porous media is researched. The results show that gas percolation has an obvious characteristic of non-Darcy flow, which is in accordance with the Klinkenberg effect.

Keywords:

• capillary bundle model
• flow characteristic
• Knudsen number
• microscale effect
• microtube
• non-Darcy flow