InterPore2023

Solute transport in partially saturated porous media with spatially correlated disorder

24 May 2023, 10:30

1h 30m

Poster Presentation (MS08) Mixing, dispersion and reaction processes across scales in heterogeneous and fractured media Poster

Speaker

Mr Ali Saeibehrouzi (University of Warwick & Coventry University)

Description

Solute transport in porous materials is important in many natural and industrial applications, such as soil contamination and subsurface CO2 storage. While in many cases there is more than one fluid phase ("partially unsaturated" conditions), most studies focus on the simpler case of the single-fluid phase ("saturated"). This study investigates the effect of spatial correlations in pore sizes on fast two-phase displacement under an unfavorable viscosity ratio (viscous fingering regime), using Direct Numerical Simulation (DNS). We consider immiscible fluids and simulate transport in the invading (lower viscosity) fluid phase. Considering the short timescale of invasion compared to that of solute transport, for computational efficiency and avoiding the transient velocity streamlines affecting transport, the latter is simulated only once the fluid phase distribution reaches steady-state. Analysis of the developed DNS model shows that spatial correlation affects solute transport via the distribution of mobile and trapped regions. The Probability Density Function (PDF) of pore-scale Peclet number shows a bimodal variation with (1) highly advective and (2) highly diffusive regions. While for the saturated case transport is mainly controlled by advection, the creation of stagnant zones in the partially-saturated case focuses the solute into narrow regions. The numerical results show that the inclusion of a second fluid phase increases dispersivity, and reduces breakthrough time with a sharp gradient of solute concentration between stagnant and flowing regions.