REAL PORE FLOWS

Towards the deterministic modelling of immiscible flows in porous media: Mesoscale simulations and Experimental verification

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 Obiettivo del progetto (Objective)

'Immiscible two-phase flow in macroporous materials is a subject of significant applied and scientific interest. It is encountered in a series of environmental and energy-related processes such as soil remediation, enhanced oil recovery from fractured petroleum reservoirs, geothermal processes, CO2 sequestration etc. The study and optimization of such processes requires the development of rigorous modelling tools that successfully capture the physics of the flow process at the pore scale, and the careful setup of experimental studies to verify the precision of these tools. The proposed research aims at advancing the state-of-the-art in this direction through an integrated approach combining numerical and experimental techniques. The modelling of such processes will be based on a mesoscale description of the flow field within porous materials using a thermodynamically consistent Lattice-Boltzmann model that accounts for the interfacial physics and wetting properties from first principles. The complicated structure of the porous materials will be represented by digital domains constructed using a stochastic reconstruction method that reproduces the statistical properties of real porous media. This numerical approach will be validated through a series of experiments in mechanically engineered 2D porous domains, produced according to predefined specifications using a computer controlled etching machine. An experimental apparatus for controlling and monitoring the immiscible flow process through the domains will be used for the study of the population dynamics of Non Aqueous Phase Liquid blobs (NAPL’s) in oil/water systems and the construction of relative permeability curves. The proposed approach is expected to offer significantly improved quantitative results compared to other methods commonly used in these processes that lack this amount of detail in the description of both the flow problem and the representation of the medium.'

Introduzione (Teaser)

Scientists developed accurate models of complex flow phenomena relevant to a number of environmental and energy fields.

Descrizione progetto (Article)

Water flowing through an aqueduct is a relatively simple transport phenomenon well described by mathematical equations and physical laws. Deriving accurate system models for complex flow phenomena of substances in more than one phase travelling through porous materials is a highly complicated task. However, it is a critically important one in applications as varied as soil remediation, oil recovery and carbon dioxide (CO2) sequestration.

Scientists initiated the EU-funded project REAL PORE FLOWS to develop models of pore-scale transport phenomena for two cases. Researchers studied isothermal evaporation of volatile hydrocarbons (volatile organic compounds (VOCs)) from porous media as well as the dynamics of immiscible flows of non-aqueous phase liquids (NAPLs). VOCs are found in natural gas and crude oil whereas NAPLs are common liquid contaminants of water.

An accurate description of isothermal evaporation of VOCs during drying has to account for several factors. These include bulk liquid and gas phase distribution patterns as well as the liquid films that form on the pore walls as the bulk gas phase passes. Observations and experimental measurements enabled scientists to delineate three distinct regions of drying space. This resulted in a pore network model accounting for all major transport mechanisms within the porous medium, including diffusion across the outer surface.

In the case of NAPLs, scientists developed a model of immiscible displacement (simultaneous movement of the other liquid and water) through a porous medium. The NAPL is modelled as blobs flowing under the combined action of capillary, viscous and gravity forces. Under different conditions, the process is governed by the coalescing and breaking up of blobs. Scientists identified three flow regimes and the corresponding model demonstrated good agreement with recent experimental and theoretical work.

REAL PORE FLOWS has contributed complex and accurate medium-scale models of the flow of immiscible fluids in porous media. This has direct relevance to a number of environmental and energy applications. Detailed descriptions should help resolve important problems and challenges in many fields.