The reserves of natural gas hydrate determine its potential commercial development value. Combining the composition of seabed sediments and the seabed environment, the experiments were conducted to study the effect of calcium carbonate as a porous medium and sodium dodecyl sulfate (SDS) on methane hydrate formation under the conditions of 2 ℃ and 6.08 MPa and its mechanism was analyzed. The results show that the gas storage effect and gas storage rate of the two synergistic systems are better than pure SDS solutions. Changes in the particle size of calcium carbonate could change the amount of hydrate formation and gas storage effect, of which 1 mm calcium carbonate has the best gas storage effect. The synergistic system greatly shortens the induction period of hydrates and accelerates the rate of hydrate nucleation. The promotion effect of the synergistic system is reflected in the promotion effect of SDS and the promotion effect of calcium carbonate surface characteristics and particle size changes and its adsorption characteristics. It breaks the micelle effect of SDS and the "solid sealing" effect of hydrates, increases the formation rate of hydrate in heterogeneous heterogeneous environment, and promotes hydrate formation. Therefore, the synergistic system of porous media and surfactant can significantly improve the hydrate generation rate and gas storage effect, and provide a theoretical basis and research direction for the rapid hydrate generation technology.

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.

The three dimensional flow and mass transfer mathematical model of oilwater flow in the soil around underground pipeline is built using the finite volume methodo. The ground temperature change in different locations is numerical simulated by the CFD software when oil pipeline leaks in winter and the range of oil distribution in the soil. The simulation results show that there is a stable temperature field around the pipe before leak, while the changed of temperature fields and the oil distributions are different under three conditions after leak.

Due to the oilgaswater three phase existing unstable mixing interface, it can produce a variety of flow patterns in different conditions. The oilgaswater three phase in horizontal pipeline flow by numerical simulation of VOF model of multiphase flow was studied, and it gets the phase distribution diagram of oilgaswater three phase in horizontal pipeline flow in different conditions of volume gas fraction, oil fraction, viscosity and velocity. The analysis shows that, during the high watercut period, with the increasing of the volume air fraction, flow patterns develop from the bubble flow to the laminar flow; with the increasing of the mixture velocity, flow patterns develop from the laminar flow to slug flow. Volume air fraction and mixture velocity have a major influence on flow pattern. And volume oil rate and viscosity of crude oil do not. Calculation results are fitted with the related theory, which has some guiding significance for actual engineering.