近冰点多孔介质中甲烷水合物生成的温度敏感性

Temperature sensitivity of methane hydrate formation in porous media near freezing point

水合物技术是实现天然气储存、气体分离、海水淡化和二氧化碳捕集等的潜在可行途径之一,水合物技术为了降低生产成本同时又保持系统流动性,通常选择冰粉或冰浆等形式使生成反应在冰点附近进行;自然界的天然气水合物多数赋存于天然的多孔介质内,随着全球气温升高,甲烷水合物在临界条件附近的敏感性会导致储层的稳定性下降及潜在的甲烷大量释放,尤其是受气候变化影响较大的冻土带天然气水合物,其储层温度一般也处于冰点附近。本工作研究了硅砂(0.1~0.5 mm)中甲烷水合物在近冰点的形成过程与动力学特征,分别在273.75,273.85和273.95 K小温差下研究了压力、温度、反应速率和甲烷吸收量变化,分析并计算了硅砂孔隙中水合物、水相和气相的最终体积饱和度。温度与反应速率的变化表明,水合物生成过程呈现出明显的三个阶段,在不同的阶段,温度和反应速率表现出独特的变化特征如峰值、持续时间等,同时对环境温度的敏感性非常强,温度升高后甲烷水合物生长速率及其在孔隙中的饱和度均有所降低,低温下水合物生长点晚及对应诱导期持续更长。

Hydrate based technology is a potential approach for gas storage,separation,desalination,and carbon dioxide capture.At the same time,natural gas hydrate is also one of the potential important energy because of its huge resources.Most natural gas hydrates exist in natural porous media while it has unique properties in porous media.At the same time,with the increase of global temperature,the sensitivity of methane hydrate sediment has uncertainty on reservoir stability and potential environmental impact at low temperature.In this study,the formation process and kinetics of gas hydrates in silicon sand(0.1~0.5 mm)were investigated.The pressure and temperature profile,reaction rate,and gas uptake were studied at 273.75,273.85,and 273.95 K.According to the change of temperature and reaction rate,the hydrate formation process presented three obvious stages.In different stages,the temperature and reaction rate showed unique characteristics,such as peak value,duration,and so on.At the same time,they were very sensitive to the reaction temperature.In the first stage,the peak value of temperature was the highest,but the duration time was the shortest.In the second and third stages,the temperature peak was gentle and the duration time was relatively long.The change of reaction rate was like that of temperature,the peak and average value of reaction rate decreased with the increase of temperature.The final gas content and hydrate saturation also slightly decreased with the increase of reaction temperature.The final saturation of hydrate,aqueous phase,and gas-phase was calculated in the pore of silicon sand.The analysis of the results showed that the commencement of hydrate growth was sensitively related to temperature,and the scatter of the onset of hydrate growth was greater at low temperatures.