The along-flow-path dynamic adsorption behavior of polymers on mineral surfaces with different roughness

During enhanced oil recovery, polymer adsorption onto reservoir surfaces reduces displacement efficiency and can cause formation damage. To address this, we combined core flooding experiments on natural clay-rich cores from the Daqing P Block with molecular dynamics simulations to investigate the adsorption behavior of four polyacrylamide-based polymers: polyacrylamide (PAM), neutralized polyacrylamide (NPAM), hydrolyzed polyacrylamide (HPAM), and sulfonated polyacrylamide (SPAM). Experiments showed that HPAM and SPAM exhibit weak adsorption, whereas PAM and NPAM are strongly retained. Simulations reveal that this contrast arises from differences in polymer charge and surface interactions. HPAM adsorption decreases with increasing surface roughness due to enhanced electrostatic repulsion from negatively charged clay surfaces. In contrast, PAM and NPAM adsorb more readily on rougher surfaces, where cavities and hydroxyl groups promote anchoring via van der Waals forces and hydrogen bonding—NPAM shows the strongest response owing to its higher polarity. SPAM displays only a marginal increase in adsorption at high roughness, likely due to limited mechanical trapping in deep pores. Overall, polymer adsorption is governed by electrostatics, chain polarity, surface chemistry, and surface topography.