Unveiling the potential of helium enrichment in shale reservoirs: A molecular and experimental perspective

Abstract Helium-bearing shale reservoirs are gaining attention as unconventional strategic resources, yet the fundamental mechanisms governing helium occurrence and migration remain poorly resolved. In this study, we integrate high-pressure adsorption–diffusion experiments (308 K, 1300 psi) with molecular simulations under reservoir-relevant conditions (70 MPa, 403–423 K) to investigate helium behavior in organic-rich shale. Results show that during CH 4 –He co-adsorption, methane preferentially occupies adsorption sites, thereby reducing the adsorption capacity of helium. Meanwhile, molecular simulations indicate that methane enhances helium’s near-wall residence (adsorption-layer fraction) through confinement and steric hindrance within nanopores. In this stage, varying helium concentration from 0.05% to 5% yields a limited impact on the overall diffusion coefficient. However, during desorption, helium shows a sharp mobility enhancement, and the diffusion coefficient increases from 0.3 × 10 to 17 × 10 − 12 m 2 /s. This increase is attributed to methane evacuation and weak helium binding. Interaction energy analysis reveals that clay minerals dominate helium retention, and increasing methane content strongly non-linear enhances He–shale interactions as helium concentration decreases from 100% to 5%. These findings clarify helium’s occurrence state and its competitive dynamics with methane, offering molecular-level insights into the potential for helium preservation and co-production in CH 4 -rich shale systems.