Formation and Flow Characteristics of Methane Hydrates in High-Pressure Pipelines

Abstract

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.