Immiscible displacement of a shear-thinning fluid in heterogeneous porous media

The subsurface fluids could show shear-thinning property at certain pressure and temperature. The shear-thinning property affects the viscosity field of the fluid, thus altering the displacement behaviors during immiscible displacement. In this work, a lattice Boltzmann two-phase model implemented with a power law rheological model is adopted to simulate the displacement process of a Newtonian fluid displacing a shear-thinning fluid in heterogeneous porous media. After validating the model with non-Newtonian Poiseuille flow, the effect of the shear-thinning property of the displaced fluid on the displacement process is investigated from various aspects such as interface evolution, displacement efficiency, velocity field and viscosity field. The simulation results show that with stronger shear-thinning property in the displaced fluid, the interface evolves more rapidly and the displacement efficiency is increased, the invading fluid could better displace the residual displaced fluid. The mechanism for this phenomenon is that with stronger shear-thinning property, there are lower viscosities in the fingering paths and higher viscosities in the regions without fingering. The displacement process is dominated by the viscosity in the high mobility regions at the fingering paths. Increasing the shear-thinning property has similar effects to decreasing the viscosity of the displaced fluid, thus increasing the displacement efficiency. This research reveals the influence of the shear-thinning property on immiscible displacement in heterogeneous porous media, and is of guidance for industries concerning displacements of non-Newtonian fluids. © 2019, Science Press. All right reserved.