Behaviors of methane hydrate formation and growth with halo

Gas production efficiency is closely linked to the formation and growth of pore-scale methane hydrates (MH). This study presents a novel high-pressure micromodel equipped with a high-resolution CCD camera to observe MH morphology in situ, revealing the dynamic mechanisms during MH formation via diffusion. We describe the growth evolution of hydrate halos under static conditions and the influence of temperature. Halos grow from the interface to the gas phase, increasing the contact area between hydrate and grains. The halo's complexity, characterized by the fractal dimension, increased from 1.489 to 1.753 as it developed. Small droplets supplied water for halo growth through vapor pressure gradients. A dimensionless parameter H* was introduced to indicate the potential contact between hydrate halos and liquid droplets, with a critical value of 1. The halo profile became more complex over time and with decreasing temperature. Halos slow hydrate decomposition and pose challenges for exploitation. Numerous small hydrate shell fragments formed under gas-water flow, enhancing gas-to-hydrate conversion rates. This study elucidates the kinetic growth mechanisms of hydrate halos under water vapor diffusion, offering valuable insights into MH storage in subsurface environments and providing crucial reference for their exploitation.