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

Marine gas hydrates are highly sensitive to temperature and pressure fluctuations, and deviations from in-situ conditions may cause irreversible changes in phase state, microstructure, and mechanical properties. However, conventional samplers often fail to maintain sealing and thermal stability, resulting in low sampling success rates. To address these challenges, an in-situ temperature- and pressure-preserved sampler for marine applications has been developed. The experimental results indicate that the self-developed magnetically controlled pressure-preserved controller reliably achieves autonomous triggering and self-sealing, provides an initial sealing force of 83 N, and is capable of maintaining pressures up to 40 MPa. Additionally, a custom-designed intelligent temperature control chip and high-precision sensors were integrated into the sampler. Through the design of an optimized heat transfer structure, a temperature-preserved system was developed, achieving no more than a 0.3 °C rise in temperature within 2 h. The performance evaluation and sampling operations of the sampler were conducted at the Haima Cold Seep in the South China Sea, resulting in the successful recovery of hydrate maintained under in-situ pressure of 13.8 MPa and a temperature of 6.5 °C. This advancement enables the acquisition of high-fidelity hydrate samples, providing critical support for the safe exploitation and scientific analysis of marine gas hydrate resources.