Effects of crystal facets of quartz on the formation and dissociation of natural gas hydrates

Natural gas hydrates are non-stoichiometric crystalline compounds composed of natural gas and water, typically found in the pore spaces constructed by minerals. Mineral crystals exhibit significant variations in surface properties among different crystal facets. Despite the importance of these mineral crystal facets, previous studies have not reported their influence on natural gas hydrates. To address this gap, we focused on quartz, a vital component of hydrate reservoirs, and studied the process of natural gas hydrates formation and dissociation on its distinct crystal facets. In our investigation, we simplified pores as narrow gap spaces between two parallel quartz substrates, and captured the entire process with a microscope. The results indicate that the formation and dissociation of natural gas hydrates are notably influenced by the distinct crystal facets of quartz. The influences of quartz crystal facet on the hydrate formation are primarily attributed to two factors, wettability and hydroxyl concentration of quartz crystal facet. We have also revealed the mechanism of how quartz crystal facet influences the hydrate dissociation. This research provides a fundamental understanding of how mineral crystal facets influence the hydrate formation and dissociation, offering a novel perspective for the design of processes for extracting hydrate.