Numerical Assessment of Ocean Temperature and Steady Current Effects on Methane Hydrate Airlift Recovery

Ocean conditions influence the throughput and product composition of methane hydrate airlift recovery. A stationary gas–liquid–solid model couples hydrate dissociation, particle shrinkage, liquid cooling, and separate air and methane balances with static riser deformation. World Ocean Atlas 2023 profiles define Japan Sea and western North Pacific conditions. The hydraulic component is assessed against 33 air–water measurements at three injection depths, and spatial refinement and conservation balances are checked independently. Across 34 stationary cases, intake temperature and depth dominate the environmental effects on recovery. At 1000 m, the colder Japan Sea intake reduces the gaseous share of recovered methane by 10.29 percentage points relative to the Pacific case. Holding the Pacific intake temperature fixed, replacing the stratified exterior with a uniform temperature changes liquid delivery by only 0.06%. Increasing Pacific intake depth from 500 to 5000 m reduces total methane-equivalent delivery by 31.0%. Increasing prescribed surface current speed from 0.5 to 1.5 m s−1 increases maximum pipe displacement from 2.08 to 10.37 m, while liquid delivery changes by less than 0.1%. Particle size strongly affects methane partitioning. Additional paired calculations quantify the effects of liquid heat capacity, saline freezing temperature, and alternative transport correlations on the regional comparison. These results support separate assessment of recovery throughput, surface product composition and structural clearance under the investigated operating conditions.