Flow and displacement of Bingham plastics in porous media. Topical report

Bingham plastics, which exhibit a finite yield stress at zero shear rate, have been used to model the flow behavior of certain heavy oils at reservoir conditions. In such fluids, the onset of flow and displacement occurs only after the applied pressure gradient exceeds a minimum value. Understanding the flow behavior of such fluids has been limited to phenomenological approaches. In this paper, we present numerical simulations and experimental visualization of flow and immiscible displacement of Bingham plastics in porous media using micromodels. First, we describe a novel pore network simulation approach to determine the onset of flow. The dependence of the critical yield stress on the pore-size distribution is discussed. Visualization experiments of the constant-rate immiscible displacement of Bingham plastics in glass micromodels and Hele-Shaw cells are next presented. The process is subsequently simulated in a pore network. Experiments are successfully simulated with the pore network model. We discuss the effect of the yield stress and injection rate on the displacement patterns. We also propose a classification of the displacement patterns, similar to that for Newtonian displacement