Tese e Dissertação

Tese: Pore-scale visualization and relative permeability curves of two-phase flow in fractured porous media microfluidics models

Multiphase flow in highly heterogeneous systems, such as naturally fractured reservoirs, plays a crucial role in oil production. In the petroleum industry, hydrocarbons extracted from these reservoirs account for a significant portion of the global oil and gas production each year. The presence of fractures, vugs, and interconnected channels in such systems introduces complexity to fluid flow either by enhancing permeability through preferential flow paths or by acting as structural barriers that restrict flow. This behavior contrasts with that of homogeneous formations and requires a deeper understanding of fluid displacement mechanisms, especially at the pore scale. Thus, the goal of this research is to investigate two-phase flow behavior in fractured porous media, focusing on the determination and analysis of relative permeability curves as a function of pore-scale phenomena. To achieve this, an experimental approach was employed, using micromodels fabricated from PDMS. These devices replicate some geometric aspects of a porous matrix composed of a random arrangement of microchannels, into which different fracture geometries were incorporated. The experimental setup enabled real-time visualization of flow dynamics and the acquisition of the data and images needed for analysis. Steady-state water–oil injection experiments were performed on both fractured and non-fractured micromodels, aiming to direct comparison the resulting relative permeability curves. The results indicate that incorporating fractures into a porous matrix alters the relative mobility of the fluid phases, and anticipates water breakthrough. These effects reduce oil displacement within the matrix and eventually lower the oil recovery. Hysteresis effects were observed during the drainage and imbibition processes, highlighting the influence of fluid saturation history on phase distribution. Moreover, distinct flow regimes were identified within the fractures as a function of the fractional flow rate of water, which affected phase interactions and, consequently, influenced the relative permeability behavior. These findings emphasize the importance of pore-scale characterization in understanding multiphase flow in fractured porous media and reinforce the potential of microfluidic as a powerful tool for analyzing transport properties in complex porous systems.

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