Natural gas hydrates and geothermal energy are potential sources of low-carbon geo-energy that are crucial in achieving a sustainable energy future for human society. The exploitation and utilization of these sources inherently involve thermal-hydraulic-mechanical-chemical coupling processes, and these complex coupling processes need to be numerically simulated for exploitation and utilization technology developments. This paper provides a brief overview of the current status and future challenges of numerical simulations for these coupling processes in the context of exploiting and utilizing natural gas hydrates, shallow and deep geothermal energy. It also presents perspectives on how to address these challenges, aiming to advance the development of numerical coupling technology within the geo-energy exploitation and utilization communities.

As a promising substitute for conventional fossil fuels with huge reserves, clayey-silt natural gas hydrate has been proved to be widely distributed in the continental margins of the marine environment. Characterization and development of this kind of natural gas hydrate reservoirs face unique challenges, compared with that of natural gas hydrate in marine sandy sediments. This review summarizes the basic methods for natural gas hydrate reservoir characterization and development, and discusses the applicability of these methods in marine clayey-silt natural gas hydrate reservoirs. Feasibilities of classical oil and gas reservoir characterization methods and models applied to hydrate-bearing strata remain elusive, let alone clayey-silt hydrate deposits. Current natural gas hydrate development methods are restricted by low gas productivity, potential geomechanical instability, and extremely high costs. Economically feasible technologies considering the influences of geotechnical issues are needed for the commercialization of natural gas hydrate contained in clayey-silt sediment.