关键词: Hydrate, Micron-sized sand, Phase equilibria, Hydrate formation, Rheological behavior, Viscosity

Abstract: During the production of natural gas hydrates, micron-sized sand particles coexist with hydrate within the transportation pipeline, posing a significant threat to the safety of pipeline flow. However, the influence of sand particles on hydrate formation mechanisms and rheological properties remains poorly understood. Consequently, using a high-pressure reactor system, the phase equilibrium conditions, hydrate formation characteristics, hydrate concentration, and the slurry viscosity in micron-sized sand system are investigated in this work. Furthermore, the effects of sand particle size, sand concentration, and initial pressure on these properties are analyzed. The results indicate that a high concentration of micron-sized sand particles enhances the formation of methane hydrates. When the volume fraction of sand particles exceeds or equals 3%, the phase equilibrium conditions of the methane hydrate shift to the left relative to that of the pure water system(lower temperature, higher pressure). This shift becomes more pronounced with smaller particle sizes. Besides, under these sand concentration conditions, methane hydrates exhibit secondary or even multiple formation events, though the formation rate decreases. Additionally, the torque increases significantly and fluctuates considerably. The RoscoeBrinkman model yields the most accurate slurry viscosity calculations, and as sand concentration increases, both hydrate concentration and slurry viscosity also increase.

Key words: Hydrate, Micron-sized sand, Phase equilibria, Hydrate formation, Rheological behavior, Viscosity