Samaneh Vahid Dastjerdi, a doctoral researcher at the Institute of Applied Mechanics and SFB 1313 member (Central Project Z), will defend her dissertation:
Title: "Image-based Characterization of Multiphase Flow in Porous Media"
Date: 15 July 2024
Time: 2:30 pm CET
Venue: Pfaffenwaldring 9, room 3.141 (IAM’s seminar room).
Abstract
Multiphase flow in porous media encompasses a wide range of applications, including groundwater management, energy resources extraction, and carbon dioxide sequestration by intersecting various fields such as geophysics, hydrology, and environmental science. The dynamics of fluid displacement processes in porous media and the relevant underlying physics, as well as developing effective models to describe them, are among the main focuses of research in multiphase porous media flow.
This work primarily revolves around continuum theories, which try to model multiphase porous media flow and attempt to accommodate its intrinsic features such as hysteresis. To follow this aim, experimental observations are examined by integrating two continuum theories for multiphase flow in porous media. One theory extends the understanding of multiphase flow by incorporating essential elements in thermodynamic equations, namely phases, and their interfaces, formulating capillary pressure as a function of saturation and fluids' specific interfacial area. The fact that interfaces are the locus of the force exchange between all the present phases supports the necessity of considering them in describing a multiphase flow system. The other theory addresses limitations in conventional approaches by differentiating between percolating and non-percolating fluid clusters. This theory employs the fact that the distribution of forces is different in the percolating and non-percolating fluid elements. The current research merges these theories to enhance the available comprehension of two-phase flow. In order to collect pore-scale information necessary as the input parameters in the mentioned continuum theories, microfluidic experiments are carried out and visualized by a customized open-air microscope with a high temporal and spatial resolution. Subsequently, the recorded snapshots are processed via an in-house-developed MATLAB code. The REV-scale parameters gathered from the experiments, among others, include saturation and specific interfacial area.
The results from the experiments show that an approach that considers saturation and specific interfacial area as state variables when differentiating between percolating and non-percolating fluid elements includes the experimental data better. Thus, it is closer to a universal modeling approach for two-phase porous media flow, than the conventional models. Moreover, a linear correlation of saturation and specific interfacial area of percolating fluid phases is observed, alongside a domain where all the experimental data are included. The properties of this linear relationship provide insights into the underlying phenomena such as the formation of preferential flow paths. These preferential flow paths, referred to as effective porous medium, remain unaltered after some cyclic fluid displacements when enough fluid clusters are stranded. The stranded fluid clusters and the solid matrix form the effective porous medium, which constrains the flow to the preferential flow pathways for both fluids, regardless of the wetting properties of the flow system. This observation highlights the need to differentiate between primary and scanning events. These results can contribute to advancing a two-phase flow theory capable of capturing dynamic conditions and hysteresis phenomena, emphasizing the importance of considering interfacial area and phase connectivity in continuum theories.