The change of external conditions effects on the phase equilibrium curve of gas hydrate and the thickness of hydrate stability zone

At present the study on the gas hydrate increases rapidly.The study about the phase equilibrium curve of gas hydrate and thickness of hydrate stability zone has become more important.This paper uses Sloan's CSMHYD program to study the effects of change of external conditions on phase equilibrium curve of gas hydrate and the thickness of hydrate stability zone.N_2 can decreases the area of gas hydrate stabilization,but other gases increase it.The methane content decreases,gas hydrate forms easier(exclude N_2).The effects of the propane and hydrogen sulfide are most.The area will decrease when the salinity increases.The geothermal gradient,depth,bottom water temperature,gas compositions and salinity affect on the thickness of hydrate stability zone, but their effects are different.The relation between the thickness of hydrate stability zone and the geothermal is index,the relation between the thickness of hydrate stability zone and the depth is logarithm,the relation between the thickness of hydrate stability zone and the bottom water temperature,methane content and salinity is linearity.The thickness of hydrate stability zone increases 400m when the depth changes from 1000m to 4000m. It decreases about 660m when the geothermal gradient changes from 0.02℃/m to 0.1℃/m.It decreases about 1000m when the bottom water temperature increases 17℃.It increases about 170m when gas composition changes from the methane to put 20% ethane to gas hydrate.It decreases about 130m when the salinity changes from 0wt% to 4.5wt%.The effects of the geothermal gradient and bottom water temperature are great.