An Investigation on the Impact of Submicron-Sized Bubbles on the Fragmentation of Methane Clathrates Using Molecular Dynamics Simulation

Abstract

Summary The formation of submicron-sized bubbles is frequently associated with the fragmentation of methane clathrate. A bubble refers to a pocket or a round particle of one substance trapped inside another. In most cases, these spherical pockets are made of gas trapped inside of a liquid. Usually, bubbles can lie underneath the surface of the liquid until the surface tension breaks and the gas escapes back into the atmosphere. Therefore, understanding the fluid dynamics behavior of the clathrate phase shift and enhancing the production efficiency of natural gas requires knowledge of the impact of submicron-sized bubbles on the clathrate fragmentation. In this scenario, molecular dynamics simulation (MDS) models were carried out to investigate the methane clathrate fragmentation rate with and without preexisting submicron-sized bubbles. The findings demonstrate layer-by-layer fragmentation of the methane clathrate cluster in the liquid phase. Furthermore, this mechanism shows temperature and submicron-sized bubble existence independent of simulation settings or conditions. However, because of the stability of the supersaturated methane solution for a long period, methane clathrate fragmentation does not always result in the formation of submicron-sized bubbles. It was observed that between the bubble (submicron-size) of methane and the cluster surface of methane clathrate, there is a steep slope of methane concentration. This results in the liquid phase efficiently decreasing the methane concentration and improving the migration of natural gas in different directions, hence the driving force increases for methane clathrate fragmentation. Our discoveries in this research show that the existence of submicron-sized bubbles near the surface of the methane clathrate can speed up the rate of intrinsic decomposition while decreasing the activation energy of methane clathrate fragmentation. The mass flow rate toward submicron-sized bubbles linearly correlates with the methane clathrate fragmentation rate. The mass flow rate is governed by the size of the submicron-sized bubbles and the spacing between the methane clathrate submicron-sized bubbles. Our results contribute to the in-depth knowledge of the fragmentation technique in the liquid phase for methane clathrates, which is critical in optimizing and designing effective gas clathrate development methods.