Percolation without trapping: how Ostwald ripening during two-phase displacement in porous media alters capillary pressure and relative permeability

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Hauptverfasser: Adebimpe, Ademola Isaac, Foroughi, Sajjad, Bijeljic, Branko, Blunt, Martin J.
Format: Preprint
Veröffentlicht: 2024
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author Adebimpe, Ademola Isaac
Foroughi, Sajjad
Bijeljic, Branko
Blunt, Martin J.
author_facet Adebimpe, Ademola Isaac
Foroughi, Sajjad
Bijeljic, Branko
Blunt, Martin J.
contents Conventional measurements of two-phase flow in porous media often use completely immiscible fluids, or are performed over time-scales of days to weeks. If applied to the study of gas storage and recovery, these measurements do not properly account for Ostwald ripening, significantly over-estimating the amount of trapping and hysteresis. When there is transport of dissolved species in the aqueous phase, local capillary equilibrium is achieved: this may take weeks to months on the centimetre-sized samples on which measurements are performed. However, in most subsurface applications where the two phases reside for many years, equilibrium can be achieved. We demonstrate that in this case, two-phase displacement in porous media needs to be modelled as percolation without trapping. A pore network model is used to quantify how to convert measurements made ignoring Ostwald ripening to correct trapped saturation, capillary pressure and relative permeability to account for this effect. We show that conventional measurements over-estimate the amount of capillary trapping by 20-25\%.
format Preprint
id arxiv_https___arxiv_org_abs_2404_01313
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Percolation without trapping: how Ostwald ripening during two-phase displacement in porous media alters capillary pressure and relative permeability
Adebimpe, Ademola Isaac
Foroughi, Sajjad
Bijeljic, Branko
Blunt, Martin J.
Fluid Dynamics
Conventional measurements of two-phase flow in porous media often use completely immiscible fluids, or are performed over time-scales of days to weeks. If applied to the study of gas storage and recovery, these measurements do not properly account for Ostwald ripening, significantly over-estimating the amount of trapping and hysteresis. When there is transport of dissolved species in the aqueous phase, local capillary equilibrium is achieved: this may take weeks to months on the centimetre-sized samples on which measurements are performed. However, in most subsurface applications where the two phases reside for many years, equilibrium can be achieved. We demonstrate that in this case, two-phase displacement in porous media needs to be modelled as percolation without trapping. A pore network model is used to quantify how to convert measurements made ignoring Ostwald ripening to correct trapped saturation, capillary pressure and relative permeability to account for this effect. We show that conventional measurements over-estimate the amount of capillary trapping by 20-25\%.
title Percolation without trapping: how Ostwald ripening during two-phase displacement in porous media alters capillary pressure and relative permeability
topic Fluid Dynamics
url https://arxiv.org/abs/2404.01313