Pore scale analysis of the impact of mixing-induced reaction dependent viscosity variations

Expanding interest in enhanced subsurface natural resource recovery and carbon sequestration motivates study of reacting flows in porous media. In this work, we examine the case of reaction products that increase or decrease the viscosity of the fluid. Parallel reactant streams flow through porous media and react transversely along the centerline. We utilize a pore scale, finite element numerical method that couples the reaction with fluid flow through two arrangements of porous media at three Damkohler (Da) numbers and two viscosity conditions. When the product increases the fluid viscosity, the flow velocity is reduced and higher amounts of product are formed due to increased diffusion time. Conversely, reduced fluid viscosity leads to greater fluid velocity and lower amount of product formation. An exception is the viscous thinning case of high Peclet (Pe) number and high Da where an instability develops (in low Reynolds (Re) number flow) that enhances mixing between the reactants, resulting in increasing product formation.

► Pore scale reactive transport model for reaction dependent fluid viscosity.
► Viscosity variations impact chemical mixing at pore scale and product formation.
► Viscous thinning at high Pe and Da produces instability and increased product.