Effect of SDS on the Formation and Blockage Characteristics of the CH₄ Hydrate in a Flow Loop

Abstract

Hydrate is easily formed in deep-sea pipelines and brings serious flow assurance problems, so it is necessary to look for appropriate hydrate control strategies. In this work, the effects of the anionic surfactant sodium dodecyl sulfate (SDS) on hydrate growth and flow characteristics in the methane−water system were investigated under horizontal and tilted conditions using a highpressure flow loop, and the growth and plugging rules of hydrates in the SDS solution and the effects of different flow rates and tilt angles on hydrate induction time and plugging time were obtained. The experimental results show that hydrates can be easily deposited on the tube wall in the freshwater system. After the addition of SDS, the hydrate can hardly deposit on the wall, allowing the hydrate slurry to flow stably for a long time and a higher volume fraction. The volume fraction of hydrates in the freshwater system is plugged at less than 15%, while in the SDS solution, hydrate slurry can flow steadily for a longer time at more than 30% volume fraction. Although increasing the flow rate reduces the hydrate induction time, the plugging time is significantly prolonged. With the increase in the inclination angle of the loop, hydrate particles with larger particle sizes are more likely to appear, and the time until blockage is decreased. The flow rate in the loop decreases with increasing hydrate particle size. The sensitivity analysis of different influence factors was carried out by the linear regression coefficient method, and the initial flow rate has the most influence on the hydrate induction time, followed by the initial pressure, and the inclination angle has the least influence. This work provides insights into the flow characteristics of the hydrate in the SDS solution, which facilitates the flow assurance studies of hydrates in the gas−water system.