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Experimental Study of the Real Gas Flow in Microtubes

The flow characteristics of nitrogen in microtubes with diameters of 14.9, 10.1, 5.03 and 2.05μm are investigated experimentally under high pressure conditions. The results show that the high pressure flow characteristics of nitrogen in microtube with the diameter of 14.9μm are in accordance with the classical fluid mechanics theory. However, with the decrease of the inner diameter of microtube, gas flow shows an apparent microscale effect and the results depart from the theoretical predictions of the conventional theory, moreover the smaller the diameter, the stronger the microscale effect. Besides, the high pressure microscale effect can not be characterized by the Knudsen number, which is proposed for studying rarefaction effect at low-pressure. Because of the existence of high-pressure microscale effect, it is inappropriate to study the real gas seepage characteristic in reservoir through the flow experiment at low pressure.