Effect of SDS Solutions on the Jamin Effect in a Capillary Tube with a Contracted Throat.

With the continuous exploitation of petroleum resources, the distribution and displacement of residual oils have become key issues in enhancing oil recovery. In a reservoir, there are various forms of residual oils caused by the capillary force, viscous force, and some other hydrodynamic effects, which lead to the Jamin effect, and they restrict the oil displacement process. In this study, the morphologies of oil droplets in a capillary tube laden with water and sodium dodecyl sulfate (SDS) solutions are experimentally investigated. The pinning behavior of the oil droplet is observed in the waterflood with a lower velocity, while depinning and rupturing behaviors occur at a higher velocity. Hereto, we build a mechanics model to analyze the evolution of the Jamin effect in a capillary tube with varying cross sections. Using this theoretical model, we obtain the two critical velocities for the depinning and rupture of the oil droplet, which agree with the experimental results. Moreover, we find that oil droplets can more easily pass through the entire capillary tube in SDS solutions compared with water. The time required for oil droplets to pass through the pore throat becomes shorter with the increase of SDS concentration. Therefore, a theoretical model is established to determine the total pressure difference and the minimum applied pressure difference. These findings are beneficial to obtain a deep insight into the detailed oil displacement and achieve a higher oil recovery rate.