基于温度震荡的天然气水合物增量合成实验

Experimental study on incremental synthesis of gas hydrate based on temperature oscillation

在多孔介质中生成较均一的高饱和度天然气水合物,是进行水合物开采模拟实验的基础。“爬壁效应”和“铠甲效应”是制约水合物生成质量低于理论值的重要影响因素,温度震荡方法是提高水合物生成饱和度的重要手段。目前基于温度震荡的方法虽然增加了天然气水合物的生成饱和度,但其温度震荡区间下限选择在冰点以下,没能很好地解决水合物生成的均一性问题。从增大诱导阶段气-水过渡区域角度出发,提出了在冰点以上进行温度震荡,在1~17℃震荡区间内,可有效克服水合物合成的不均一性。共进行了3轮次的温度震荡水合物增量合成实验,结果表明:冰点以上的多轮次温度震荡,能够实现天然气水合物的增量合成,但随着震荡次数的增加,水合物合成增量不断减小,具有明显的次效性,温度震荡次数不宜超过3次。

The formation of homogeneous gas hydrates with high saturation in porous media is the basis of hydrate exploitation simulation experiments.“ Wall-climbing effect” and“ armor effect” are important factors that restrict the formation quality of hydrate to be lower than the theoretical value, the method of temperature oscillation is a necessary means to improve the formation saturation of hydrate. The current method which based on temperature oscillation had increased the formation saturation of natural gas hydrate, however, the limitation of its temperature oscillation interval under the freezing point caused the uniformity of hydrate formation cannot be resolved better. In this paper, starting from increasing the gas-water transition region in the induction stage, it is proposed that temperature oscillation above freezing point which can effectively overcome the heterogeneity of hydrate synthesis in the oscillation range of 1 ℃~17 ℃. A total of three times of incremental hydrate synthesis experiments were carried out, the results show that the incremental hydrate synthesis can be achieved by multiple times of temperature oscillation above freezing point, however,with the increase of the number of oscillation continuously, which has obvious secondary effect, the number of temperature oscillations should not exceed three.