Critical parameters of the Jamin effect on the oil droplet passing through an abruptly constricted capillary tube laden with sodium dodecyl sulfate solutions

The Jamin effect, as a resistance arising from the morphological changes of droplets during two-phases flow in the capillary tube, plays a crucial role in enhancing the oil recovery efficiency (EOR) in petroleum engineering. In the present study, we investigate the critical parameters of the Jamin effect in a sloped capillary tube laden with water and sodium dodecyl sulfate (SDS) solutions, including the critical water velocity and pressure difference. The pinning behavior of the oil droplet is observed in the waterflood with a lower velocity, while depinning and rupturing behavior occur at the higher velocity. Hereto, we build a mechanics model to analyze the underlying mechanism of the Jamin effect in the sloped capillary tube with varying cross sections. Using this theoretical model, we determine the critical velocity required for the depinning of the oil droplet. The results reveal that the critical velocity decreases with the decrease in sloped angles, consistent with the experimental results. Moreover, we find that oil droplets can pass through the entire sloped capillary tube more easily in SDS solutions than in water, and the required time becomes shorter with the decrease in sloped angles and increase in SDS concentrations. To address this, a theoretical model is established to determine the minimum applied pressure difference. These findings provide a deep insight into the mechanisms of oil displacement and contribute to achieving the higher EOR.