Surface Complexation Modeling of HPAM Polymer–Brine–Sandstone Interfaces for Application in Low-Salinity Polymer Flooding

Understanding the synergetic effects of wettability alteration by low salinity waterflooding and mobility control by polymer flooding are important to assess the outcome of a low salinity polymer flooding in sandstone reservoirs. Moreover, investigating the interfacial chemical interactions within a polymer-brine-sandstone rock system allows for further understanding of the mechanistic mechanisms that dictate HPAM polymer’s viscosity and polymer adsorption on sandstone surface. In this work, we utilise triple-layer surface complexation modelling in combination with the Derjaguin-Landau-Vervey-Overbeek (DLVO) theory to investigate the HPAM polymer-brine and sandstone-brine interactions that govern the polymer rheological properties. The zeta potential predicted from the proposed triple-layer model was used to investigate how salinity, polymer concentration and temperature affect the HPAM polymer’s viscosity. We also propose the application of the novel concept of maximum energy barrier, calculated from the DLVO theory’s interaction potential curve, as an indicator of polymer’s adsorption to rock surface.

Analysis revealed that polymer solution viscosity and zeta potential are potentially inherently correlated. Moreover, results analysis showed that the maximum energy barrier can indeed be used to predict the polymer’s adsorption on the rock surface. Analysis of the factors controlling the polymer’s adsorption using the maximum energy barrier concept led to the conclusion that higher brine salinity and lower temperature results in higher polymer adsorption. This is explained by the reduction in the energy barrier when higher brine salinity and lower temperature are encountered, which results in lower system stability leading to the higher attraction between the polymer chains and rock surface.