Visual experimental study on hydrate occurrence patterns and growth habits in porous media

[Display omitted] •Initial gas and water saturation play a major role in hydrate occurrence patterns.•The hydrate occurrence pattern is determined by growth habits.•The growth habit of hydrate is related to mass transfer.•The hydrate memory effect accelerates the growth of hydrate in pores. The distribution and morphology of natural gas hydrates in pores have significant impacts on the macroscale physical properties of hydrate-bearing sediments. This paper investigated hydrate morphology characteristics using a micromodel, and the memory effect was used to accelerate the hydrate formation process. It is found that the initial gas and water saturation play a significant role in hydrate occurrence patterns and growth habits. When water is the initial main continuous phase, the hydrate prefers to grow towards the center of pores during hydrate formation. When gas is the initial main continuous phase, hydrates grow towards the center of pores and along the wall, and the mass transfer happens between the water and gas phases. It can be realized that the hydrate occurrence pattern is determined by the growth habit, which is related to mass transfer. These findings provide a theoretical foundation for future natural gas hydrate development.