Mechanistic Study of Disproportionate Permeability Reduction

Abstract

Abstract It is a common observation that gels in a porous media reduce the permeability to water more than that of oil. Core floods on sand packs using well defined model media has been carried Out to elucidate the matter. Three different packing materials have been used, acid cleaned quartz sand, Teflon powder and a mixture of quartz and Teflon. Quartz is strongly water-wet and Teflon is oil- wetting. The use of model media gives a good control of wettability effects. The systems used are:HPAM based polymer with an added crosslinker orbiopolymer. The brine is synthetic sea water and the oil is a white oil. The results show that the disproportionate permeability reduction (DPR) effect can be interpreted by a mechanism with segregated pathways for oil and water. In a porous media preferred pathways for oil and water are governed by the wettability and to some extent the pore size. A water based gelant will flow in the water preferred pathways and block these channels. The largest DPR effect is observed in mixed wetting media where the difference between oil preferred and water preferred pathways is enhanced compared to homogeneous wetting media. The oil saturation at which the gelant is placed has also been shown to be of importance. Decreasing the oil saturation at which the gelant is placed gives a stronger permeability reduction towards both phases. P. 335