Numerical Study of the Effects of Viscosity Ratio and Capillary Number on The Displacement Efficiency in Homogeneous and
Heterogeneous porous media by Newtonian, viscous-thinning and viscous-thickening fluids
Nome: AYRTON CAVALLINI ZOTELLE
Data de publicação: 24/03/2023
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Resumo: The increase of the fraction of extracted oil in petroleum reservoirs is one of the greatest challenges of the petroleum industries, since the oil corresponds to one of the most important energy resources. One of the most useful methods to increase the oil recovery is the injection of a fluid on the reservoir to displace the oil. Immiscible liquid-liquid displacement is a fundamental problem in fluid mechanics and has many applications, like the enhanced oil recovery (EOR). With the adventure of the computational science, the numerical methods become capable of predicting complex phenomena. The primary motivation of this work is to evaluate the liquid-liquid displacement in homogeneous and heterogeneous porous media using the Computational Fluid Dynamics (CFD) by Direct Numerical Simulations (DNS). The injected fluid has Newtonian, shear-thinning and shear-thickening characteristics. The viscous and interfacial tension effects were evaluated for the Newtonian case. It is observed that while the viscosity of the injected fluid increases, the residual oil that remains trapped in the porous media reduce due to the increase of the shear-stress imposed by the injected fluid and the tip of the interface becomes sharp. The interfacial tension effects are more complex, but quite interesting. When the displacement is dominated by the viscous forces of the recovery fluid (viscosity of the injected fluid is lower than the viscosity of the recovered fluid), the increase in the interfacial tension makes the interface flat, assisting the displacement. Specially on the porous medium in which the grains have random size and position distribution, the effects of the increment of the interfacial tension differs from the homogeneous porous medium. On the homogeneous porous medium, the fluid passes through all the pores, and the fingering formation is symmetric, but on the heterogeneous disordered porous medium, the high interfacial tension reduces the sweep on minor pores due to the high capillary pressure, so, more of the recovered fluid is left behind. The Pseudoplasticity was evaluated at low interfacial tension (the viscous forces dominate the flow). It is observed that the shear-thinning fluid recovers more fluid than the Newtonian or shearthickening fluids, specially at the heterogeneous porous media. Due to the tendency of the injected fluid to pass through the largest pores, the velocity and consequently the shear-rate on minor pores is low, contributing to the increase in the viscosity of the shear-thinning fluid on those regions and also increasing the capability to displace the oil due the high shearstress and, therefore, the sweep of minor pores increase. The opposite occurs for the shearthickening fluids. The viscosity reduces at low shear-rates, so that shear-rate also is low and the fluid is inefficient to displace the recovered fluid.
