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[SCG39-P18] Pattern of injected fluid into a cell filled with swelling gel particles—effect of pressure
Keywords:analog experiments, fluid flow, fluid pressure
In the silica-rich subduction zone, silica dissolution induces enhanced permeability and pore-fluid pressure reduction, which leads to a higher frequency of slow slip events [1]. For a comprehensive understanding of slow earthquakes, the spatio-temporal pattern induced by variation of permeability due to chemical reaction is worthy of inspection. For this purpose, we explore the fluid dynamics in varying permeability by an analog injection experiment.
In this study, we injected an aqueous sodium chloride solution into gel particles packed in a thin 2-dimensional cell made of two acrylic plates. While fluid flows, gel particles swell and interrupt fluid flow. We imitated the fluid dynamics in varying permeability by conducting the experiment.
The gel particle is a so-called ionic gel particle. The typical radius is 350 µm in dry condition and can increase to be ten times by immersing in pure water. This increase is 1000 times in its volume corresponds to the one for gas-liquid transition. We should note that one can control the swelling rate of ionic gel particles by changing water’s salinity [2]. We packed the particles into the cell whose gap between plates is 1 mm. The cell was tapped ten times to have particles packed well [3]. Then, we injected the aqueous phase from the bottom of the cell and measured fluid pressure in the injection-tube. As a control parameter, we changed the concentration of sodium chloride C and injection rate Q. The schematic illustration of the experimental setup is shown in Fig. 1.
We obtained a phase diagram of the flow pattern (shown in Fig.2). In the diagram, particles are displaced by fluid flow at the boundary of white areas, and fluid penetrates the pore of particles in deep black areas. At high C and Q, particles didn’t swell significantly, and fluid percolated isotropically without interruption. On the contrary, at low C and Q, due to the swelling of gel particles, fluid flow was blocked, and the injection front branched. We explored the relationship between these patterns and fluid pressure.
[1] P. Audet and R. Burgmann, Nature 510, 389-392(2014).
[2] T. Tanaka, From gels to life, University of Tokyo Press (2002).
[3] M. Suzuki, J. Soc. Powder Technol., Japan, 40, 348-354(2003)
In this study, we injected an aqueous sodium chloride solution into gel particles packed in a thin 2-dimensional cell made of two acrylic plates. While fluid flows, gel particles swell and interrupt fluid flow. We imitated the fluid dynamics in varying permeability by conducting the experiment.
The gel particle is a so-called ionic gel particle. The typical radius is 350 µm in dry condition and can increase to be ten times by immersing in pure water. This increase is 1000 times in its volume corresponds to the one for gas-liquid transition. We should note that one can control the swelling rate of ionic gel particles by changing water’s salinity [2]. We packed the particles into the cell whose gap between plates is 1 mm. The cell was tapped ten times to have particles packed well [3]. Then, we injected the aqueous phase from the bottom of the cell and measured fluid pressure in the injection-tube. As a control parameter, we changed the concentration of sodium chloride C and injection rate Q. The schematic illustration of the experimental setup is shown in Fig. 1.
We obtained a phase diagram of the flow pattern (shown in Fig.2). In the diagram, particles are displaced by fluid flow at the boundary of white areas, and fluid penetrates the pore of particles in deep black areas. At high C and Q, particles didn’t swell significantly, and fluid percolated isotropically without interruption. On the contrary, at low C and Q, due to the swelling of gel particles, fluid flow was blocked, and the injection front branched. We explored the relationship between these patterns and fluid pressure.
[1] P. Audet and R. Burgmann, Nature 510, 389-392(2014).
[2] T. Tanaka, From gels to life, University of Tokyo Press (2002).
[3] M. Suzuki, J. Soc. Powder Technol., Japan, 40, 348-354(2003)