Novel Method for Characterizing Single-Phase Polymer Flooding

Abstract

Summary Polymer flooding has been used to enhance oil production and reduce water cut for a long time. However, there are still many fundamental challenges in characterizing the multiphase-fluid flow, even the single-phase-fluid flow, associated with polymer flooding. For example, it is difficult to measure and calculate two-phase polymer solution/oil relative permeability. One of the difficulties comes from the non-Newtonian and time-dependent properties of polymer solutions; another comes from the change in absolute permeability caused by the adsorption of polymer on rock surfaces. Almost all the methods for computing relative permeability are based on the assumption that the absolute permeability is constant. It may be helpful to further understand the mechanisms and develop more-reliable methods for calculating two-phase polymer solution/oil relative permeability by investigating single-phase polymer flooding more profoundly. In this study, a new method has been developed to calculate the pseudopermeability during single-phase polymer flooding. The non-Newtonian property of the polymer solutions was considered in the new method. Polymer-flooding experiments with different concentrations of polymers were designed and conducted to study the single-phase flow of polymer solution in rocks with different permeabilities. The values of the pseudopermeability of single-phase polymer flooding were then calculated with the method. It has been found that the relationships between the pseudopermeability and the reciprocal of shear rate were linear. The polymer-flooding pseudopermeability extrapolated at the infinite shear rate was close to the brine-flooding permeability after polymer injections in many cases.