Study on crystal growth and aggregated microstructure of natural gas hydrate under flow conditions

The microstructure of hydrate particles plays an important role in the safety of pipeline flow assurance. The growth and aggregation of hydrate particles in natural gas + pure water systems were experimentally evaluated by using an autoclave and a high-speed camera, and the microstructural evolution was monitored. Initially, the tiny agglomerated structures were successively transformed into a snowflake and dendritic structure. Then, through the mutual combination and self-growth, polyhedral solid particles dominated in the stability stage. The maximum dominant size of the dendritic granules was selected as the size-critical value to judge the leading roles in the microstructure evolution, which was 165–413 μm and in the early stage growth was the main effect. Moreover, shearing within a certain range can cause the formation of chain particles and promote particle aggregation. The actual aggregation process and the micro generation mechanism closely correspond. Based on the evolution of the microstructure of the hydrate under flow condition, a microscopic model for the growth and aggregation of natural gas hydrate particles was established. This model better explains the mechanism of microstructural evolution of the hydrate particle, which can facilitate understanding of the effects of hydrates on flow assurance.