Evaluation of the inhibitory efficacy of ionic liquids on asphaltene precipitation in crude oil

CO2 flooding technology demonstrates advantages such as injectability and miscibility in low-permeability reservoir development; however, asphaltene deposition during the displacement process leads to pore-throat blockage and permeability reduction. To address this issue, this study systematically investigated the inhibitory effects of three ionic liquids and one commercial inhibitor on asphaltene deposition in crude oil, with the underlying mechanisms elucidated through molecular dynamics simulations based on interaction energy. Additionally, CO2 flooding coupled with nuclear magnetic resonance was employed to quantitatively characterize the damage extent of asphaltenes to reservoir physical properties and pore structures during CO2 displacement. Experimental results demonstrated that after inhibitor addition, the asphaltene precipitation onset point of oil samples significantly increased from 34% to 52%, asphaltene aggregate particle size decreased from 1,082 nm to 410 nm, and turbidity values declined by 10–30%. This improvement is attributed to the ionic liquids’ ability to disrupt asphaltene molecular association via electrostatic interactions, steric hindrance, and hydrogen bonding, while simultaneously modifying the system’s polarity, thereby effectively inhibiting asphaltene deposition. Molecular dynamics simulation results exhibited strong consistency with experimental findings. The inhibitors mitigated the adverse impacts of asphaltene deposition on core porosity, permeability, and blockage rates. This study reveals that ionic liquids hold significant potential for inhibiting asphaltene deposition during CO2 flooding in low-permeability reservoirs.