盐含量对天然气水合物防聚剂性能的影响

传统的天然气水合物(以下简称水合物)防聚剂评价实验一般在纯水中进行,而现场的水相中通常会混入一定的海水或含有矿化度的地下水,因而前者的评价结果与现场的实际情况存在着较大的差距。为了在更加接近现场实际情况的条件下评价水合物防聚剂的性能,首先使用高压透明蓝宝石釜从宏观角度对水合物浆液的形态进行观察,然后应用粒度仪从微米级进行水合物浆液中液滴—水合物粒径分布的观察测试,最后结合油水界面张力的变化规律对含盐体系水合物防聚剂的防聚行能进行了分析。研究结果表明:①在含3%NaCl条件下,水合物防聚剂CJ(以下简称CJ)对水合物的防聚效果较好;②水合物形成以前,在机械力的搅拌作用下,含CJ的水合物乳液粒径随着含盐量的增加而减小,含盐有利于液滴在油相中的分布;③水合物形成以后,在含3%NaCl的条件下,水合物颗粒分布更小,适量的盐有利于水合物形态的控制;④在2℃条件下,含盐量为3%时,油水界面张力值为最大,达到4.453 mN/m。结论认为,随着盐含量的增加,CJ对水合物的抑制效果增强,但在水合物形成以后抑制效果则不明显,相反盐含量的增加还容易破坏油水乳液的稳定性甚至破坏水合物防聚剂的使用效果。

Effect of salt contents on the gas hydrate anti-agglomerant performance

Traditional evaluation experiments on the anti-agglomerant of natural gas hydrate are usually carried out in pure water, but the water phase on site is often mixed with a certain degree of seawater or groundwater containing salinity, so the evaluation results of traditional evaluation experiments cannot reflect the actual situations on site accurately. In order to evaluate the performance of gas hydrate anti-agglomerant under the condition which is closer to the actual situation on site, this paper adopted the high-pressure transparent sapphire cell to observe the morphology of gas hydrate slurry from the macroscopic perspective. Then, a particle size analyzer was applied to observe and test the particle size distribution of liquid droplet-hydrate in the gas hydrate slurry in the scale of micrometer. Finally, based on the change laws of oil/water interfacial tension, the anti-agglomeration performance of gas hydrate anti-agglomerant in a salt-containing system was analyzed. And the following research results were obtained. First, the gas hydrate anti-agglomerant CJ (hereinafter "CJ" for short) has a better anti-agglomeration effect on gas hydrates under the condition of 3% NaCl. Second, before the formation of gas hydrate, the particle size of CJ containing hydrate emulsion decreases with the increase of the salt content under mechanical stirring, which indicates that salt is beneficial to the distribution of liquid droplets in oil phase. Third, after the formation of gas hydrate, hydrate particle distribution is smaller under the condition of 3% NaCl, which proves that an appropriate amount of salt is conducive to the control of hydrate morphology. Fourth, at 2 ℃, the oil/water interfacial tension reach the maximum value (4.453 mN/m) when the salt content is 3%. In conclusion, with the increase of salt content, the inhibition effect of CJ on gas hydrate is enhanced. After the formation of gas hydrate, however, such effect is not remarkable. On the contrary, the stability of oil-water emulsion will be damaged easily and even the application effect of gas hydrate anti-agglomerant is deteriorated with the increase of salt content.