Measurement and the influencing factors of hydrate phase equilibrium
水合物相平衡测试及其影响因素研究
A set of experimental device was built up to investigate formation and dissociation of hydrates. Effects of pore size and salinity on methane and carbon dioxide
hydrate equilibrium have been systematically investigated. Equilibrium properties of mixture gas hydrate were also studied.The phase equilibrium conditions of methane
hydrate in porous media under different components and concentrations of cations and anions were determined at 56 bar using orthogonal test method.The permeability
character of sediments containing methane hydrates were also investigated experimentally and theoretically.
设计开发了天然气水合物相平衡特性一维实验装置，系统的进行了甲烷水合物和二氧化碳水合物在不同沉积层孔隙尺寸、盐分浓度下的相平衡特性实验，此外对甲烷、乙烷和丙烷的混合气水
合物进行了相平衡特性实验研究，获得了不同气体组分下混合气水合物的相平衡特性的实验数据。系统的分析了不同浓度阴、阳离子存在条件下对甲烷水合物相平衡的影响特性。对含甲烷水
合物沉积层渗透率特性进行了实验与理论研究.
1 Experimental device, material and procedure
1实验装置、实验材料及实验方法
The experimental devicemainly included high pressure vessel, thermostatbath, high pressure pump, vacuum pump and data acquisition unit. The core of the test rig is a
high-pressure hydrate vessel, whose volume is about 476 ml and material is 316-stainle steel. The estimated errors of temperature and pressure measurements are
±0.1K and ±0.1MPa, respectively.
本实验系统主要由反应釜、冷库和浴槽温控系统、高压计量泵、真空泵和计算机数据采集系统组成。本系统的核心部件是高压反应釜，容积是476ml，由316不锈钢制作而成。实验系统中温度
和压力的测试精度分别是±0.1K和±0.1MPa。
2 Influencing factors of methane hydrate phase equilibrium
2甲烷水合物相平衡影响因素研究
The decrease in the pore size leads to the enhancement in the equilibrium pressure as the salinity and the temperature are kept the same. While the increase of
salinity makes the equilibrium pressure increase too as the pore size and the temperature are kept the same. It can be concluded that the equilibrium at the condition
of decreased methane concentration needs a lower pressure and a higher temperature.
实验结果显示在其它条件一致情况下，随着孔隙尺寸的增加，甲烷水合物相平衡曲线向高温、低压方向移动；随着盐分浓度的增加，甲烷水合物相平衡曲线向低温、高压方向移动；混合气体
中随着甲烷浓度的减少，相平衡曲线向低压、高温方向移动。
Figure 2 Equilibrium curves of methane hydrate in Different glass Beads
图2 不同玻璃砂中甲烷水合物相平衡曲线
Figure 3 Equilibrium curves of methane hydrate with different salinity
图3 不同盐度条件下玻璃砂中甲烷水合物相平衡曲线
Figure 4 Effects of different gas components on hydrate equilibrium curves
图4 不同气体组分相平衡曲线
The influences of cations on methane hydrate equilibrium are compared each other as follow order: Mg2+, Ca2+, Na+, K+. The
influences of all halogen ions on methane hydrate phase equilibrium are similar. The variance analysis demonstrates that the concentrations of Mg2+and
Cl-, CO32-, SO42-have a significant effect on the phase equilibrium condition.
四种阳离子对甲烷水合物相平衡的影响效果次序为Mg2+, Ca2+, Na+, K+.。所有卤素离子对甲烷水合物相平衡的影响一致。方差分析显示
Mg2+、Cl-、CO32-、SO42-对甲烷水合物相平衡影响显著。
Figure 5 Influence of cations on methane hydrate equilibrium temperature
图5 阳离子对甲烷水合物相平衡温度影响趋势图
Figure 6 Influence of halogen ions on methane hydrate equilibrium temperature
图6 卤素离子对甲烷水合物相平衡温度影响趋势
Figure 7 Influence of anions on methane hydrate equilibrium temperature
图7 阴离子对甲烷水合物相平衡温度影响趋势
3 Characters of carbon dioxide hydrate equilibrium
3二氧化碳水合物相平衡特性
Figure 8 Equilibrium conditions of CO2 hydrate in NaCl solutions
图8 不同氯化钠浓度条件下二氧化碳水合物相平衡
The CO2 hydrate equilibrium curves with different salinities in BZ-01 were shown in Figure 9. It could be concluded that the presence of NaCl in the solution caused
the equilibrium curve to move to the left, while the increase of concentrations led to the increase in the extent of equilibrium curve movement. When temperature was
lower than ice point, the experimental data indicated that the CO2 hydrate equilibrium points were nearly at the same line.
二氧化碳水合物在BZ-01玻璃砂中的相平衡条件进行了测试。氯化钠溶液会引起水合物相平衡曲线向左移动，随着浓度的增加移动程度增加。当温度降低到低于冰点时，不同氯化钠溶液中二
氧化碳水合物相平衡曲线重合。
4 Effects of hydrate saturation on permeability
4水合物饱和度对渗透率的影响
The experimental data were compared with parallel capillary model, Kozeny grain model and Masuda model. Results showed that the simulated sediments can be considered
to be packs of constant diameter spheres and the relationship between permeability and porosity agrees with Kozeny-Carman equation. Formation of methane hydrates in
sediments induces distinguished decline of permeability and the parallel capillary model with hydrate formed in pore center is well fitted with experimental data.
Methane hydrate mainly formed in pores of sediments but not enveloped the glass beads in our experiment. Permeability of sediments reduced exponentially with
saturation of methane hydrates under a low saturation not great than 25%.
将实验结果与平行毛细管模型、Kozeny颗粒模型以及Masuda模型进行了比较。结果表明，实验采用玻璃砂模拟的沉积层可以近似认为是等径球体颗粒堆积物，其渗透率与孔隙度基本符合修正
的Kozeny-Carman公式关系；沉积层中甲烷水合物的存在使其渗透率急剧下降；与多个模型比较后发现平行毛细管中心生成水合物模型与实验结果吻合的较好，说明实验中的甲烷水合物主要是
在沉积层的孔隙中生成而不是对玻璃砂颗粒形成包络；甲烷水合物饱和度低于25%的沉积层渗透率与饱和度的关系成指数递减关系。
Figure 9 Comparison of experimental result and permeability models
图9 实验结果与渗透率模型计算数据对比
