Abstract
In this study, the impacts of solutal Marangoni phenomenon on multiphase flow in static and micromodel geometries have experimentally been studied and the interactions between oil droplet and two different alkaline solutions (i.e. MgSO4 and Na2CO3) were investigated. The static tests revealed that the Marangoni convection exists in the presence of the alkaline and oil which should carefully be considered in porous media. In the micromodel experiments, observations showed that in the MgSO4 flooding, the fluids stayed almost stationary, while in the Na2CO3 flooding, a spontaneous movement was detected. The changes in the distribution of fluids showed that the circular movement of fluids due to the Marangoni effects can be effective in draining of the unswept regions. The dimensional analysis for possible mechanisms showed that the viscous, gravity and diffusion forces were negligible and the other mechanisms such as capillary and Marangoni effects should be considered in the investigated experiments. The value of the new defined Marangoni/capillary dimensionless number for the Na2CO3 solution was orders of magnitude larger than the MgSO4 flooding scenario which explains the differences between the two cases and also between different micromodel regions. In conclusion, the Marangoni convection is activated by creating an ultra-low IFT condition in multiphase flow problems that can be profoundly effective in increasing the phase mixing and microscopic efficiency.
Highlights
Chemical flooding for the purpose of enhanced oil recovery (EOR) methods is gaining increased attention in recent years
As a chemical EOR method, alkaline flooding where different chemical species such as sodium hydroxide (NaOH) and sodium carbonate (Na2CO3) are dissolved in aqueous solution are known for their potential for improving oil recovery factor (Liu et al 2008)
Similar to the surfactant flooding method, the main mechanisms enrolling in alkaline flooding process are interfacial tension (IFT) reduction, wettability alteration, and emulsification (Sheng 2010)
Summary
Chemical flooding for the purpose of enhanced oil recovery (EOR) methods is gaining increased attention in recent years. Khosravi et al (2015) evaluated the impacts of Marangoni convection on oil recovery in a near-miscible CO2 injection process They introduced an interfacial tension gradient in the investigated system and found that the maximum influence of Marangoni flow during CO2 flooding processes was visible at near-critical (pressure/temperature) conditions. Masoudi et al (2019) in a gas flooding micromodel study showed that the thermal-induced Marangoni effect may help the injection stream to enter the unswept oil-saturated zone (e.g. dead-end pores and matrix/fracture systems) and increase the oil production They concluded that the main reason behind this enhancement was the ability of the Marangoni effect in improving the mixing of phases by applying swirling flow velocities. The experimental and theoretical results are discussed for both static and dynamic tests, separately
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