The Oil Droplet Passing through Parallel Dual-Throat Capillary Tubes Laden with Sodium Dodecyl Sulfate Solution: Overcoming the Jamin Effect

Understanding the distribution and mobilization of residual oil is critical for enhancing oil recovery efficiency (EOR). Yet effectively mitigating the Jamin effect remains a challenge in complex pore structures. Previous studies have not fully addressed the behavior of oil droplets within parallel constricted throats, particularly under dynamic interfacial conditions. In this study, a complex capillary model featuring two parallel pore throats is proposed, and the model is more suitable for complex scenarios where fluids encounter multiple migration paths in actual reservoirs. We present a comprehensive investigation of oil droplet dynamics in a capillary tube with two parallel constricted throats containing the sodium dodecyl sulfate (SDS) solution. Through experimental observations, we characterize the oil droplet's morphology evolution as oil droplets encounter pore throats and subsequently bifurcate into the middle tube and the small tube. To elucidate these phenomena, we develop a theoretical model to analyze the Jamin effect in parallel constricted throats, and then we present a numerical model to validate the observed oil droplet's morphological transformations, which shows excellent agreement with the experimental data. Our findings reveal that oil droplets enter the smaller throat only when the oil droplet's volume, viscosity, and oil-SDS interfacial tension are below their corresponding thresholds. This study experimentally identified and quantified a series of critical conditions governing whether an oil droplet can enter a smaller throat. We identify a critical applied pressure difference essential for optimizing the EOR, and a pressure difference criterion for regulating and controlling the migratory behavior of the oil droplets is proposed. Moreover, a dimensionless parameter η is defined to characterize the EOR. The combined experimental and modeling approach for overcoming the Jamin effect lays a robust foundation for developing more effective EOR strategies in complex pore networks.