Liu Yang, Wu Chengxuan, Lv Xiaofang, Xu Xinyi, Ma Qianli, Meng Jiawei, Zhou Shidong, Shi Bohui, Song Shangfei, Gong Jing
Jiangsu Key Laboratory of Oil and Gas Storage and Transportation Technology, Changzhou University Changzhou Jiangsu 213164 China
Institute of Petroleum Engineering Technology, Sinopec Northwest Oil Field Company Urumqi Xinjiang 830011 China.
RSC Adv. 2022 May 12;12(23):14456-14466. doi: 10.1039/d2ra02266d.
In the exploitation of deep-sea oil and gas resources, the multiphase production and transportation process is frequently plagued by pipeline blockage issues. Especially when hydrates and wax coexist simultaneously, the viscosity and plugging tendency of multiphase flow systems will synergistically increase. Understanding the evolution of morphology of hydrate particles and the agglomeration characteristics of hydrate particles in the presence or absence of wax crystals is crucial to flow assurance industry. With the assistance of a visualized reactor equipped with a three axis moving platform, microscopic images of cyclopentane hydrate during hydrate growth were obtained, and the cohesive force between hydrate particles was measured. It was found that during the hydrate growth on wax-free water droplets, the untransformed water inside the particles gradually wetted the surface of the particle. With the increase in temperature and contact time, the shell of hydrate particles changed from solid and rough to smooth and moist. The cohesive force measured in this work ranges from 3.14 ± 0.52 to 11.77 ± 0.68 mN m with different contact times and temperature. When the contact time was 0 s and 10 s, the cohesive force between particles increased first and then stabilized with temperature. When the contact time was 20 s, the cohesive force was greater than the first two cases and showed an overall stable trend. An interesting phenomenon was also discerned: a large water bridge between particles formed during their separation process. For the wax-containing system, it required a longer time for water droplets to be converted into hydrate particles than that for wax-free systems. After wax participated in hydrate growth, hydrate particles showed the properties of elasticity and stickiness, which resulted in a larger liquid bridge between hydrate particles after their contact. It was suggested that wax crystal would alter the shell structure of hydrate particles, and change the surface properties of hydrate particles and the formation process of the liquid bridge, leading to significant and rapid increase in the cohesive force.
在深海油气资源开发中，多相生产和输送过程经常受到管道堵塞问题的困扰。特别是当水合物和蜡同时存在时，多相流系统的粘度和堵塞倾向会协同增加。了解水合物颗粒形态的演变以及在有或没有蜡晶存在的情况下水合物颗粒的团聚特性对于流动保障行业至关重要。借助配备三轴移动平台的可视化反应器，获得了水合物生长过程中环戊烷水合物的微观图像，并测量了水合物颗粒之间的内聚力。研究发现，在无蜡水滴上生长水合物的过程中，颗粒内部未转化的水逐渐润湿颗粒表面。随着温度和接触时间的增加，水合物颗粒的外壳从固体且粗糙变为光滑且湿润。在这项工作中测量的内聚力在不同的接触时间和温度下范围为3.14±0.52至11.77±0.68 mN/m。当接触时间为0 s和10 s时，颗粒之间的内聚力随温度先增加后稳定。当接触时间为20 s时，内聚力大于前两种情况并呈现总体稳定趋势。还发现了一个有趣的现象：在颗粒分离过程中形成了颗粒之间的大水桥。对于含蜡体系，水滴转化为水合物颗粒所需的时间比无蜡体系更长。蜡参与水合物生长后，水合物颗粒表现出弹性和粘性，导致接触后水合物颗粒之间形成更大的液桥。研究表明，蜡晶会改变水合物颗粒的外壳结构，改变水合物颗粒的表面性质和液桥的形成过程，导致内聚力显著快速增加。
