In the process of solid⁃state mining of deep⁃sea natural gas hydrates, when the balance of temperature and pressure is broken, the hydrate slurry in the production pipeline changes from liquid⁃solid (hydrate, seawater) two⁃phase to gas⁃liquid⁃solid (natural gas, hydrate,seawater). The three⁃phase flow of particles and seawater is the main research object in gas⁃liquid⁃solid three⁃phase flow. The Fluent simulation of the hydrate slurry flow in the vertical production pipe is performed using the CFD⁃PBM model, and the model is verified. The simulation results are in good agreement with the experimental values. The results show that the distribution of flow patterns simulated by PBM model is relatively uniform, and the size of bubbles in the flow process is mainly from small to large， the initial velocity of bubbles has a great influence on the hydraulic lifting speed of the pipeline， the turbulent kinetic energy in the slurry is 0.5 m2/s3. When the content is 0.3, bubbles will appear to be secondarily broken and broken. The bubble size distribution in the hydrate slurry system can be predicted by CFD⁃PBM to better predict the flow characteristics of the hydrate slurry after it is decomposed by natural gas.

Hydrate formation process is a mass transfer process between gas and liquid, which lead to phase change. As the mass transfer efficiency between gas and liquid is low, the hydrate formation rate is slow, as the mass transfer efficacy is low, the amount of consumed gas is small. Therefore, improving the hydrate formation rate and storage capacity is actually improving the efficiency and efficacy of mass transfer between gas and liquid.The variation of hydrate formation rate and storage capacity is studied in static pure water, pure water with stirring, for kinds of surfactants solution and surfactants solution with stirring systems.The promoting mechanism is analyzed from mass transfer. The results showed that hydrate formation rate in system of pure water with stirring is effectively improved but the storage capacity improve not obviously compared with in systems of surfactants solution and surfactants solution with stirring. The reason that surafactants can promote hydrate formation is related to its amphipathicity and ability to adsorb at metal surface. As the surfactants HLB value increase, hydrate formation rate improved but storage capacity decreased slightly. Hydrate formation rate can be further improved in system of surfactants solution with stirring.

Natural gas hydrate has the advantages of abundant reserves, large calorific value and low emission, which can mitigate the environmental pollution problems caused by traditional fossil energy. The generation process of natural gas hydrate form is a system with multicomponents and multiphysical states. The nucleation process is complex, which needs to consider the effects of pressure, temperature, promoters, stirring speed and so on. It is difficult to accurately predict the hydrate formation, because the hydrate formation process not only involves thermodynamics problems but also dynamics problems. In our paper, the support vector machine theory combined with experimental data was used to establish support vector machine prediction model for predicting natural gas hydrate equilibrium pressure. The prediction accuracy was estimated by using the mean square error, the square correlation coefficient, the square absolute percentage error and the average absolute error. The results are 8.370 08×10-5，99.897 6%，0.542 4%，1.990 0%，respectively. The pretreatment origin data were normalized (［1，2］) and the nuclear parameter g(4)and punishment factor c(1.414 2) were optimized by using cross validation methods. Simulation results show that the equilibrium pressure obtained by support vector prediction model is good in agreement with the equilibrium obtained by experiments. The better ideal prediction effects prove that the model has advantages of accuracy and reliability. It can provide certain reference for research on natural gas hydrate in future.

In the exploitation of offshore oil and gas resources, the severe slugging will appear due to the special piping system, gravity, flow, and other factors. The severe slugging will cause secondary hazards and threaten the safety of production. Therefore, it is needed to adopt the method to eliminate the severe slugging. In this paper, OLGA software and PVTsim software were used to simulate the gaslift to eliminate the severe slugging. The results showed that the severe slugging could be eliminate by gaslift in a certain extent. Different gas injection position had different effect to eliminate severe slugging. When the position of gas injection was in the upstream at the bottom of the riser, severe slugging could be eliminated effectively.