Pore-scale modeling of preformed particle gel (PPG) extrusion in porous media

Preformed particle gel (PPG) is a promising profile control agent for enhanced oil recovery in heterogeneous reservoirs. For an improved sweep, the remigration behavior of PPG once blocked by pore throats is of crucial importance. In this paper, the process of a hyper-elastic particle passing through a pore throat is simulated, allowing investigation of the extrusion mechanism of PPG with deformation under a certain hydraulic pressure. The results reveal that PPG is subjected to a varying resistance during the process of entering, penetrating and leaving the throat. The maximal radial resistance occurs when the particle center arrives at the narrowest throat, whereas the maximal axial resistance occurs before that. In the meantime, it is shown that the particle gel bears over 80% body strain during the extrusion process through frictional pore throat. The hydraulic pressure needed for the PPG extrusion through the pore throat depends on the mechanical behaviors (hyper-elasticity of PPG, and friction coefficient of the PPG-throat interface) and geometrical properties (the particle size, and the shape of throat wall) of the PPG-throat system. Based on the simulation results, an empirical model is finally established to predict the required driving pressure. Eventually, the pore-scale model is upscaled and employed to attain effective pressure windows for profile-control in a reservoir scale formation with 10 times permeability heterogeneity.