Pipe wall adhesion mechanism of natural gas hydrate particles in oil-dominated flowlines

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.