外界条件变化对天然气水合物相平衡曲线及稳定带厚度的影响

目前，有关天然气水合物的相关研究越来越多，而天然气水合物相平衡曲线和稳定带厚度的研究也变得越来越重要.本文利用Sloan的CSMHYD程序研究了外界条件变化对天然气水合物相平衡曲线及稳定带厚度的影响.研究结果表明：当天然气水合物中含有其他气体时，除了氮气会使水合物稳定存在的区域变小外；其他气体都会使稳定区域变大，且甲烷含量越少，水合物越容易形成；对于本文中所提到的几种气体，丙烷和硫化氢对相平衡曲线的影响最大；另外，水合物稳定存在的区域会随着盐度增加而变小.地温梯度、水深、海底温度、气体组成和孔隙水盐度对稳定带厚度的影响不同，其中稳定带厚度与地温梯度呈指数相关关系，与水深呈对数相关关系，与海底温度、水合物中甲烷含量及气体组成呈线性相关关系.水深从1 000 m增加到4 000 m时，稳定带厚度增加了大约400 m；水深2 000 m情况下，地温梯度从0.02℃/m到0.1℃/m变化时，稳定带厚度减薄了大约660 m；底水温度从0~17℃的变化过程中，稳定带厚度减薄了大约1000m；在水合物中气体组成从纯甲烷到含20%乙烷时，稳定带厚度增加了大约170m；盐度在0~4.5 wt％的变化中，稳定带厚度减薄了大约130 m.由此可见，在这几种因素中，地温梯度和底水温度对稳定带厚度的影响较大.

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 temperatureare great.