Crystal Growth of CO₂–CH₄ Hydrate on a Solid Surface with Varying Wettability in the Presence of PVCap

Abstract

Pipeline transportation has become the main way of long-distance and large-scale energy transportation because of its high efficiency, safety, economy, and environmental friendliness. During the exploitation of offshore gas fields containing CO 2 , the pipelines easily form hydrates under appropriate environmental conditions, which can cause great harm to the flow assurance. Therefore, adding inhibitors and surface coatings in the pipeline is used to prevent hydrate formation. To better fit the actual blockage problem of the deep-sea oil and gas pipeline transportation process, it is necessary to study the hydrate growth kinetics of mixed gases on different wettability surfaces with or without inhibitors. The crystal morphology and growth process of CH 4 and CO 2 mixed hydrate crystals forming from a droplet were investigated by a CCD camera and microscope. The results showed that the droplets will not form hydrates completely in a high CO 2 content system, but all converted into hydrates in a low CO 2 system. The villous dendrites on the surface of droplets are more abundant, and the growth rate is slower with the increase in PVCap concentration. On the superhydrophobic surface, the hydrate nucleation rate and hydrate growth rate are the lowest, which means inhibition to hydrate nucleation and growth. These research results are hoped to provide a solid theoretical basis for solving the actual flow safety problems of deep-sea oil and gas pipelines.