In-situ temperature- and pressure-preserved sampler for marine natural gas hydrates: Principles, techniques, and field application

• Developed an in-situ temperature- and pressure-preserved sampler for marine gas hydrates, addressing limitations of conventional samplers. • The magnetically controlled pressure-preserved controller achieves autonomous triggering and self-sealing with an initial sealing force of 83 N and can maintain pressures up to 40 MPa. • The temperature-preserved system maintains temperature rise within 0.3 °C over 2 hours, ensuring thermal stability. • Field application at Haima Cold Seep successfully recovered hydrate samples under in-situ conditions of 13.8 MPa and 6.5 °C.