Natural gas hydrate exploitation: A comprehensive review of structural properties, technical progress and environmental challenges

Natural gas hydrates (NGH), represent a promising and environmentally friendly energy resource due to their high energy density and global abundance in permafrost and deep marine sediments. However, their commercial exploitation remains constrained by significant technical, geological, and environmental challenges. Although various extraction technologies, such as depressurization, thermal stimulation, CO₂ replacement, and chemical additives have demonstrated potential in laboratory settings, there is limited synthesis of how technical advancements align with environmental risk management strategies. This review provides a comprehensive assessment of NGH extraction technologies, beginning with an overview of hydrate structures and classifications. The effectiveness and limitations of major extraction methods were critically evaluated, with further discussion on the role of hybrid techniques and reservoir transformation strategies in enhancing recovery efficiency. Particular attention was given to the environmental risks and scalability barriers associated with offshore development. In addition, the review highlights the growing importance of numerical modeling for simulating coupled thermal, hydraulic, and kinetic processes, emphasizing the need for multiscale approaches calibrated with field data to improve predictive accuracy. Future research should focus on optimizing hybrid recovery methods, enhancing model fidelity, and facilitating real-world implementation. These efforts are essential for enabling safe, efficient, and climate-aligned NGH exploitation in support of clean energy development and the global energy transition.