How Viscoelastic Effects Impact Polymer Fluid Flow in Porous Media

Polymer fluids are widely used in subsurface and geotechnical engineering applications. While the shear rheology of polymer fluids is known to be Carreau-like shear thinning, there is no comprehensive understanding of how their elastic rheological features impact their flow behavior in porous media. This study numerically investigates these effects using direct, pore-scale numerical simulations. By comparing data from simulations using the FENE-P model, which incorporates viscoelastic effects, with data from corresponding simulations using the Carreau model, which captures only shear thinning, we confirm that fluid elasticity can induce recirculation upstream of restrictions, leading to a reduction in polymer fluid conductance in porous media. As this recirculation is controlled by the geometric conditions, we conducted detailed comparisons between a two-dimensional model, a three-dimensional model mimicking microfluidics experiments, and an axisymmetric model, analagous to a constricted capillary tube. We also simulate flow in an ordered packing of uniform spheres to develop an understanding for the implications for flow in a 3D porous material. We find that these flows are regulated by the interplay between shear-thinning and elasticity effects. When the shear-thinning effect is sufficiently strong, the effects of elasticity are suppressed. In subsurface applications, viscoelastic effects are significant due to pore-scale confinement and fluid rheology itself, requiring explicit consideration in modeling, pilot design, and performance forecasting. PACS: 0000, 1111 2000 MSC: 0000, 1111