流动体系下油基天然气水合物颗粒管壁粘附机制
Pipe wall adhesion mechanism of natural gas hydrate particles in oil-dominated flowlines
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摘要: 天然气水合物在管壁上沉积可导致管道堵塞, 对沉积机制进行研究有助于解决水合物管堵问题。通过分析管壁上水合物颗粒的微观受力及移除机制, 建立油基天然气水合物颗粒管壁粘附动力学模型, 并以临界移除粒径和粘附率为标准, 定量探究了油包水乳状液中水合物颗粒在不同壁面环境下的粘附情况。结果表明: 当管壁表面无水时, 范德华力为水合物颗粒-管壁间的主要粘附力, 水合物颗粒的粘附率低于30%, 粒径大于20 μm的水合物均不会附着在管壁上; 当管壁表面润湿或存在水膜时, 毛细液桥力为主要粘附力, 此时水合物颗粒粘附率接近100%, 仅靠管流自身流动力很难将管壁上的水合物颗粒移除掉。研究证明了水合物颗粒在壁面上直接粘附是水合物管壁沉积机制之一。Abstract: Natural gas hydrate deposition on the pipe wall may lead to pipe plugging. A better understanding of deposition mechanism will enable such plugging to be effectively managed. By analyzing the microscopic forces applied on hydrate particles and the particle removal mechanism, a dynamic model for adhesion of hydrate particles in oil-dominated flowlines was established. Moreover, removal critical size and adhesion rate were defined and used to predict the pipe wall adhesion of hydrate particles in W/O emulsion. The results show that, in absence of water on pipe wall, Van der Waals attractive force is the dominated adhesion force between hydrate particles and pipe wall, the adhesion rate is lower than 30%, and hydrate particles with diameter bigger than 20 μm would not adhered to pipe wall. When the pipe wall is water-wet or waterfilmed, capillary force becomes the dominated adhesion force and the adhesion rate approaches 100%, in which case hydrate particles on the pipe wall are difficult to be removed only by pipe flow. This study clarifies that direct adhesion of hydrate particles to pipe wall serves as one of the hydrate deposition mechanisms.