InterPore2021

Image-based morphological characterization of multiphase porous media flow

2 Jun 2021, 09:00

1h

Poster (+) Presentation (MS6-A) Physics of multi-phase flow in diverse porous media Poster +

Speaker

Samaneh Vahid Dastjerdi

Description

Understanding the physics of immiscible two-phase flow in porous media is not a straightforward process due to the large number of influencing factors. Such factors are, among others, the inherent fluid properties, the solid-fluid interactions, the properties of the solid structure, and the boundary as well as the initial conditions. Since two-phase flow has a significant impact on many applications, such as geological carbon sequestration (GCS), enhanced oil recovery (EOR), and non-aqueous phase liquid (NAPL) contamination of groundwater and consequent soil remediation, it is of great interest to elaborate further on these aspects and to understand the underlying pore-scale physics.
Given the pronounced effects of the pore-scale geometry and the pore-fluid configuration on two-phase flow, various attempts have been made to embed these parameters on the continuum scale, i.e., mean-field, models. However, even in the best-case scenario, these models fail to incorporate the effect of small-scale topological features of the fluid phases, e.g. phenomena related to trapping mechanisms (like wetting cones, single ganglia or films, which are typical for disconnected phases) in the evolution of flow.
One of the existing approaches used in the prediction of the configuration of fluids in a porous medium, was proposed by Lenormand et al. [1]. The Lenormand phase diagram relates the capillary number (Ca: = μn q/σwn) and the mobility (or: viscosity) ratio (M: = μn/μw) with the three characteristic displacement regimes in a porous medium. However, this approach does not account for the structure of the flow domain at all.
In order to put Lenormand’s phase diagram to test with regards to the pore structure and identify the effect of the geometrical characteristics (e.g. the pore and throat size distribution, or the porosity and connectivity) of each domain on the evolution of flow, two-phase flow experiments are performed for various pore structures as well as several capillary number/viscosity ratio combinations. Micromodels, employed in the experiments are either made of PDMS (Poly-Di-Methyl-Siloxane) [2] or glass (commercially available). The transparency of the micromodels facilitates the experiments with real-time pore scale visualization of two-phase displacement and the processes involved.
An image-processing tool has been developed and applied, in order to segment and analyze the microscopic images which are acquired. From the segmented images, the local and REV-scale capillary pressure is calculated and the Euler characteristics (obtained from the Minkowski functionals, i.e., M0 ~ M3 [3],[4]) as a measure of topological assessment of the flow process is determined. Furthermore, the discontinuities occurring during the flow process can be classified into cones, films and pendular disconnections and used as another characterization criterion.