Microscopic coupling mechanisms between helium and carrier gas molecules and their influence on accumulation and retention behavior

Helium (He) is an indispensable strategic resource for global high-technology industries, and its migration and preservation during accumulation are strongly governed by synergistic interactions with fluid carrier gases such as methane (CH 4 ), carbon dioxide (CO 2 ), and nitrogen (N 2 ). To elucidate the microscopic coupling mechanisms between He and carrier gas molecules, as well as their environmental dependence, this study employs quantum chemical calculations combined with molecular configuration screening to systematically evaluate coupling energies and the stability of He-carrier coupled structures under anhydrous and hydrous conditions. The results show that, under anhydrous environments, the coupling affinity between He and carrier molecules follows the order CO 2 >CH 4 >N 2 >He. In contrast, under hydrous conditions, the interactions of He with CO 2 and CH 4 are weakened, whereas the coupling stability with N 2 is significantly enhanced, accompanied by a spatial reorganization of coupling sites. Solvation effects induced by water molecules strengthen He–N 2 interactions, indicating that pore water within mineral matrices facilitates the co-existence of He and N 2 . In multi-molecular systems, He–H 2 O complexes exhibit the highest stability, followed by He–CO 2 , He–CH 4 , and He–N 2 . Moreover, owing to their relatively large molecular sizes and their propensity to form molecular clusters, carrier gas molecules can physically block caprock pore throats, thereby enhancing sealing efficiency and reducing He leakage. Based on these findings, three key microscopic contributions of carrier gases to He accumulation are identified, namely aggregation in water, cooperative transport through fractures, and effective retention by caprocks. From a molecular-scale perspective, this study reveals the cooperative role of the He-carrier system in helium accumulation and provides a theoretical basis for elucidating accumulation mechanisms and predicting He-rich sweet spots.