A Review of Drilling-Induced Risks in Gas Hydrate-Bearing Formations: Mechanisms, Control Strategies, and Numerical Models

Gas hydrate-bearing formations are characterized by low temperature and high pressure, weak cementation, strong phase sensitivity, and pronounced heterogeneity. During drilling in such formations, the drilling fluid is required to maintain wellbore stability, transport cuttings, and control bottom-hole pressure; however, it may also alter near-wellbore hydrate stability through heat transfer, pressure-driven invasion, and component migration. Previous studies have shown that drilling-induced disturbances may trigger or intensify the dissociation of hydrates, sediment strength degradation, pore-pressure redistribution, seepage-channel development, and secondary hydrate formation in the wellbore. Under certain conditions, these processes may manifest as wellbore instability, gas invasion, changes in drilling-fluid properties, and wellbore blockage. This review summarizes recent progress in four aspects: risk manifestations, formation-response mechanisms, control strategies, and numerical modeling. The reviewed studies indicate that thermal disturbance, pressure disturbance, and component migration jointly control the phase, mechanical, and seepage responses of hydrate-bearing formations; temperature–pressure window management, inhibitors, plugging particles, functional materials, and dynamic load control act at different stages of risk evolution; and numerical models mainly include thermal–chemical, thermal–hydraulic–chemical, thermal–hydraulic–mechanical–chemical, wellbore multiphase flow and phase transition models and wellbore–formation coupled models. Current research still faces challenges in representing realistic formation heterogeneity, characterizing dynamic mud-cake evolution, integrating multiscale experiments with field data, and reducing the computational cost and improving the numerical robustness of fully coupled models. Future work should strengthen field-constrained multiscale experiments, dynamic parameter calibration, and integrated wellbore–formation control models, thereby providing a more reliable theoretical and technical basis for safe drilling in hydrate-bearing formations.