Oil–wall interaction induced droplet deformation dynamics in a capillary tube

Displacement of residual oil droplet in high water-cut oilfields can be optimized through the understanding of droplet deformation dynamics. The current studies demonstrated that the changing of capillary number or the radius ratio of droplet and tube can control the droplet deformation, but neglects the intricate interaction between the wall and droplet. Due to the complex physicochemical properties of the reservoir wall and crude oil, the interaction forces between them are very rich and unoverlooked. The current contact angle and atomic force microscope measurement are insufficient in accurately describing the oil–wall interaction forces system, resulting in discrepancies of droplet deformation dynamics with the actual reservoir conditions. We used the extended Derjaguin–Landau–Verwey–Overbeek (EDLVO) theory to establish a system of oil–wall interaction forces. The deformation dynamics of high-viscosity droplets (plug and slug droplets) and low-viscosity droplets (tail-concaved droplets) in a capillary tube were studied under various EDLVO forces values. The results showed that: (1) for high-viscosity droplets, the influence of the EDLVO forces differs significantly between plug and slug droplets, with a greater tendency to suppress the deformation of slug droplets. (2) For low-viscosity droplets, the EDLVO forces cause an increased degree of droplet concavity and hinder the reconnection of the droplet tail. These findings significantly contribute to our understanding of droplet deformation dynamics within reservoir pores and hold great importance for optimizing droplet control strategies in enhance oil recovery processes.