Numerical simulation and optimization of gas-liquid separation process in gas hydrate lifting pipe

In order to improve the gas-liquid separation efficiency of natural gas hydrates and accelerate the recovery and utilization of natural gas hydrates, this research performed numerical simulation hydromechanics analysis of three types of gas-liquid separation devices, namely the axial guide vane, tubular and spiral separators. The numerical simulation was based on the working conditions of hydrate recovery in the South China Sea and the principles of gas hydrate recovery scheme design. The influences of liquid-phase content on the gas-liquid separation efficiency and the applicable working conditions of the three gas-liquid separators were clarified. The results showed that the axial guide vane and tubular gas-liquid separators are suitable for high liquid flow rates and liquid levels in the separation chamber, while the spiral gas-liquid separator is applicable to low liquid content and small flow rates. According to the water content of natural gas hydrates exploited in the South China Sea and the optimization conditions of liquid content of 10% and gas production of 30,000 m³/d, the optimization was performed with the separation efficiency and pressure drop as the objective parameters. The spiral separator was found more suitable for downhole gas-liquid separation in natural gas hydrates wells. The findings of this research provide guidance for the design and optimization of gas-liquid separation schemes of natural gas hydrates recovery.