Abstract:

There are a large number of natural gas hydrate resources in marine sediments. The hydrate stability zone (HSZ) is an important factor to reflect gas hydrates mineralization and distribution, and the thickness of HSZ is a decisive factor for the resource of gas hydrates, thus the study of HSZ and its influencing factors is of guiding significance to the mineralization rule, distribution pattern and resource assessment of gas hydrates. The previous studies show that there are a lot of factors which can affect the HSZ, but their influencing degrees are different. In this paper, the phase equilibrium of natural gas hydrate was firstly analyzed, and then the important factors affecting HSZs thickness were emphatically discussed, ie. gas component, geothermal gradient, seawater depth, temperature in seafloor and salinity of pore water. With program CSMGem, the influencing degree of these factors were simulated and calculated. Moreover, these calculated data were used to do curve fitting for a more accurate curve of phase equilibrium. According to this accurate curve, combined with the geothermal gradient the thickness of HSZ was obtained. With the regression analysis method, the relationship among the HSZs thickness and these influencing factors are semiquantitatively analyzed in detail.

Key words: natural gas hydrate, hydrate stability zone, influencing factor, thickness, phase equilibrium, semiquantitative analysis