Bridging adsorption of flexible polymers in low-permeability porous media

Polymers used in water control are believed to always invade low-permeability layers to a sizable extent, impairing oil production. For this reason, water-shutoff treatments are usually combined with zone isolation; however, zone isolation is impractical in most wells, and the polymer must be injected through the whole open interval. Small invasion of low-permeability layers must then be ensured by some intrinsic property of the polymer. This idea was proved in a recent study, where polymer penetration in low-to-medium permeability cores was shown to be much smaller than usually predicted. This effect was explained by the bridging adsorption of stretched chains across the smallest pores. This paper develops a mathematical model for this phenomenon, and checks its true effect on placement by use of a prototype reservoir. The simulations confirm that polymer penetration in low-permeability layers decreases greatly when bridging adsorption is present.