Experimental and Molecular Dynamics Simulation Study on Influencing Factors of Barium Sulfate Scaling in Low-Permeability Sandstone Reservoirs

Abstract

This study aims to investigate the influencing factors and mechanisms of barium sulfate (BaSO4) scaling under low-permeability reservoir conditions, providing a scientific basis for water quality selection during water injection. The effects of key scaling ions and flow conditions on scaling behavior were examined through integrated experimental core flooding tests and molecular dynamics (MD) simulations. Experiments were conducted using synthetic cores simulating the ultra-low permeability Chang-8 Reservoir of the Jiyuan Oilfield, analyzing the impact of ion concentrations (Ba2+, SO42−, Na+, Ca2+, HCO3−), flow velocity, and injection pressure. MD simulations were performed based on an interfacial SiO2(010)–BaSO4 solution model constructed in Materials Studio to elucidate the micro-mechanisms. Results indicate that increasing concentrations of Ba2+ and SO42− significantly promote scaling. High Ca2+ concentration (>8000 mg/L) inhibits BaSO4 deposition via competitive adsorption. High Na+ concentration (>70,000 mg/L) reduces Ba2+ activity due to ionic strength effects. When HCO3− concentration exceeds 600 mg/L, CaCO3 coprecipitation occurs, reducing effective SO42− concentration and thus inhibiting BaSO4 scaling. Increased flow velocity enhances scaling, whereas elevated injection pressure suppresses deposition. MD simulations reveal that increased ion concentrations decrease the mean square displacement (MSD) of Ba2+ and SO42−, weakening diffusion and enhancing scaling tendency. Elevated temperature promotes ion diffusion and inhibits scaling, while pressure shows negligible effect on ion diffusion at the molecular scale. This study provides theoretical insights for scaling prevention in low-permeability sandstone reservoirs.