In-situ separation of natural gas hydrates and sediment backfilling

Natural Gas Hydrates (NGH) offer a promising solution to the global energy shortage. Nevertheless, the extraction of NGH encounters complexities and challenges in marine environments, necessitating the systematic separation of seawater, NGH particles, and sand, as well as the backfilling of sand to prevent damage to the seabed geological structure. Leveraging computational fluid dynamics (CFD) studies on operational and structural parameters, we have developed an optimized Axial Annulus In-situ Hydrocyclone Desander (AAIHD-2). By enhancing the radial forces exerted and extending the suspension time of particles within the flow field, the separation efficiencies of sand and NGH reached 84.7 % and 76.1 %, respectively. Increasing the length of the separation zone proves advantageous in boosting the separation efficiency of both sand and NGH. Notably, while the sand separation efficiency increases with higher flow rate, the NGH separation efficiency decreases. AAIHD-2 exhibits a maximum pressure drop of 320.7 kPa, constituting a mere 2.1 % of the environmental pressure (15.2 MPa), thereby ensuring the preservation of NGH equilibrium throughout the extraction process. This study is poised to facilitate the efficient separation of NGH and the backfilling of sand in order to enable the safe extraction of seabed NGH.