Tese: Pore-scale mechanisms of oil displacement by emulsion injection
Aluno(a) : Clarice de AmorimOrientador(a): Marcio Carvalho e Ranena Veronica Flores
Área de Concentração: Petróleo e Energia
Data: 29/07/2024
Link para tese/dissertação: https://doi.org/10.17771/PUCRio.acad.68648
Resumo: Water injection is the most commonly used method for extending the productive life of oil reservoirs; however, its efficiency is limited by an unfavorable mobility ratio between the injected aqueous phase and the displaced oil phase. Reservoir heterogeneity exacerbates this issue, driving water through preferential flow paths with lower capillary resistance, leaving trapped oil behind. Recent studies propose oil-in-water emulsions as a pore-blocking agent to reduce aqueous phase mobility, leading to a more uniform displacement front and enhancing oil recovery. Despite recent developments in emulsion injection for enhanced oil recovery (EOR), fundamental aspects of the pore-scale dynamics of oil-in-water emulsion flow and its correlation with observed macroscopic mobility reduction remain not completely understood. This study explores key factors influencing the design of an effective emulsion injection process, including emulsion drop size, pore throat distribution, and injection flow rate, and their impact on the mobility reduction of the aqueous phase. Two-dimensional porous media micromodels were employed to visualize drop dynamics, examining how pore-scale phenomena affect aqueous phase mobility reduction. Two distinct geometries were designed for this purpose. The linear micromodel ensures a constant pressure gradient and flow velocity along its length, while the radial configuration assesses emulsion flooding performance under varying capillary numbers. In the latter configuration, the flow area increases with the radius, reducing the flow velocity as the fluid moves away from the injection point. Results show that mobility reduction can be finely controlled by the capillary number and the drop size distribution. At sufficiently high capillary numbers, the pressure difference in most pores is strong enough to overcome the capillary pressure needed to push a drop through the constriction; the number of trapped drops is relatively small, and mobility reduction is weak. Conversely, at low capillary numbers, the number of trapped drops is large; the mobility reduction is strong and dependent on the drop size distribution. Additionally, in radial flow, stronger pore-blocking occurs below a critical capillary number, where capillary resistance surpasses viscous pressure. Flow visualization demonstrates that emulsion flooding improves pore-level displacement efficiency, reducing residual oil saturation. These findings offer valuable insights into tailoring oil-in-water emulsions for injection into reservoirs with known pore throat distributions, aiming to achieve the necessary aqueous phase mobility reduction and consequently increase oil recovery factors.