Abstract
<jats:title>Abstract</jats:title> <jats:p>Surfactant huff-n-puff has shown significant promise for enhancing oil recovery (EOR) from tight shale reservoirs; however, the fundamental pore-scale mechanisms governing its performance in organic-rich nanopores remain insufficiently understood. In this study, molecular dynamics (MD) simulations are employed to systematically investigate the effects of surfactant type, temperature, and pore size on hydrocarbon recovery from kerogen nanopores. A realistic Type-II kerogen molecular model and a multicomponent hydrocarbon mixture representative of Eagle Ford shale oil are used to simulate surfactant-assisted huff-n-puff processes under reservoir-relevant conditions. Two surfactants, nonionic C12E6 and cationic C16TAB, are evaluated over a temperature range of 293–393 K in nanopores of 5 and 10 nm width.</jats:p> <jats:p>The results show that surfactant injectivity decreases with increasing temperature due to enhanced thermal motion and reduced effective compressibility under nanoconfinement. Despite this, hydrocarbon recovery increases with temperature for both surfactants, driven by enhanced molecular mobility and weakened hydrocarbon–kerogen interactions. The nonionic surfactant C12E6 consistently outperforms C16TAB, yielding significantly higher recovery across all temperatures and pore sizes. This improved performance is attributed to pronounced micelle deformation and strong competitive adsorption of C12E6 on kerogen surfaces, which effectively displace pre-adsorbed hydrocarbons and promote their mobilization. In contrast, C16TAB largely preserves its micellar structure, limiting surface interactions and resulting in recovery enhancement primarily through volumetric displacement and thermal effects. These findings provide critical molecular-scale insights into surfactant selection and temperature optimization for shale EOR applications, with direct implications for the design of more effective chemical treatment strategies.</jats:p>