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The Effect of the Absorbed Fluid Layer on Flow in a Capillary Tube

There exists an absorbed fluid layer (AFL) on solid surface for the interaction between fluid molecules and the solid surface. A simple capillary model considering absorbed fluid layer is developed to investigate the influence of AFL on the dynamic behavior of flow in micron scale capillary tubes. An empirical formula for calculating the thickness of AFL is presented. The correlation between the effective permeability, the driving pressure gradient and the thickness of AFL is studied. On this basis, the flow mechanism in low-permeability reservoirs is researched preliminarily. The results reveal that the thickness of AFL is not fixed, but a function of driving pressure gradient, which causes a modification of effective permeability of single tube in accordance with driving pressure gradient and the formation of threshold pressure gradient.