Inertial property of oscillatory flow for pulse injection in porous media

Abstract

The low-frequency pulse wave makes the velocity of the fluid in the reservoir fluctuate dramatically, which results in a remarkable inertia force. The Darcy’s law was inapplicable to the pulse flow with strong effect of inertial force. In this paper, the non-Darcy flow equation and the calculation method of capillary number of pressure pulse displacement are established. The pressure pulse experiments of single-phase and two- phase flow are carried out. The results show that the periodic change of velocity can decrease the seepage resistance and enhance apparent permeability by generating the inertial force. The higher the pulse frequency improves the apparent permeability by enhancing influence of inertial force. The increase of apparent permeability of high permeability core is larger than that of low permeability core, which indicates that inertial force is more prominent in high permeability reservoir. For the water-oil two-phase flow, inertia force makes the relative permeability curve move towards right, and the equal permeability point becomes higher. In other words, with the increase of capillary number, part of residual oil is activated, and the displacement efficiency is improved.