Keywords: Carbon capture and storage, porous media, two-phase flow, microfluidics, pore-doublet

1.Introduction
Carbon Capture and Storage, or CCS, is one of the solution proposed by the Paris
agreement to keep the global warming under the 2°C threshold. This technique
relies on 4 main mechanisms to trap the CO 2 underground : the structural
trapping, the solubility trapping, the mineralization and last but not least the
capillary or residual trapping, where the CO 2 is trapped by the capillary forces in
the rock matrix of a reservoir. But before implementing this technology at the
industrial scale, we need to correctly asses the amount of CO 2 that can be
trapped in the targeted geological formations. In this work, we study the residual
trapping, which relies on complex interractions between the two fluids (brine and
supercritical CO 2 ) and the porous media. To tackle this task, we need to study the
phenomenon at the pore-scale (order of micrometers). This is done by
reproducing the two-phase flows at the pore scale, using both microfluidics
devices and numerical models. This allows us to study the wetting layers forming
in porous media during drainage and the impact they may have on the flow.

2.Method
Microfluidics devices, also called micromodels or aquifer-on-chips, are designed
to mimic the porous media and to allow for the direct observation of the fluid flow
and interfacial dynamics thanks to their transparent nature. In this work,
particular interest is given to pore-doublets, whose geometry is composed of two
parallel channels linked together at the inlet and the outlet. These pore-doublet
are widely used to study two-phase flow in porous media [1] . Their particular
structure allow us to experimentally reproduce the complex phenomenons
occuring during flow (snap-off, Haine's jump) [2] , while keeping a geometry simple
enough to describe the flow using analytical equations. We couple the
experimental approach with numerical models derived from the Stoke‘s
equations.

3.Results
The methodology developed allows us to experimentally demonstrate theoretical
results describing an instability occuring during the drainge of a symmetrical
pore doublet [3] . We also present a new way to take into account the wetting
layers forming in porous media during a drainage, and their impact on the
interfacial dynamics during two phase flows. Our study shows that negelecting
these effects, as most studies do, can lead to significant errors in the models.
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JEMP 2023 – IFPEN, Rueil-Malmaison, France –17-19 October 2023References
[1]Mahdi Mansouri-Boroujeni, Cyprien Soulaine, Mohamed Azaroula, Sophie Roman, How
interfacial dynamics controls draingae pore-invasion patterns in porous media, Advances in Water
Ressources, 171, (2023).
[2]Sophie Roman, Moataz O. Abu-al-Saud, Tetsu Tokunaga, Jiamin Wan, Anthony R. Kovscek, Hamdi
A. Tchelepi, Measurements and simulation of liquid films during drainage displacements and snap-
off in constricted capillary tubes, Journal of Colloid and Interface Science, 507, (2017)
[3]Talal T. Al-Housseiny, Jesus Hernandez, and Howard A. Stone , Preferential flow penetration in a
network of identical channels, Physics of Fluids, 26, (2014).