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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.

To ensure the safe flow of the hydrate slurry in the pipeline, a high-pressure flow loop with visual capability was designed, and flow characteristics and growth kinetics of methane (CH 4 ) hydrates from the pure water system were investigated. Experiment results showed that with an increase in the flow rate, the induction time first increased and subsequently decreased. When the flow rate was higher than 360 L/h, the loop was not blocked. The effect of NaCl on polyvinylpyrrolidone (PVP) as the kinetic inhibitor on the nucleation and growth of methane hydrates was studied by measuring the hydrate induction time and gas consumption. The results show that the addition of PVP was found to significantly prolong the hydrate induction time and decrease the amount of gas consumption; the presence of NaCl enhanced the inhibition strength of PVP. Through the focused beam reflectance measurement (FBRM), the results indicated that the hydrate particle size in the loop decreases with an increase of flow rate, and the added PVP to the system led to smaller average particle size. Based on the analysis of pressure difference and flow rate, the mechanism of pipe clogging in the pure water system was put forward. We believe that this research can provide theoretical support for the industrial application of CH 4 hydrate slurry flow to some extent.

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