Natural gas hydrate in marine sediments is a promising energy resource, while the atomistic level understanding of its formation on the organomineral complex remains limited. Microsecond molecular dynamics simulations were performed to investigate the methane hydrate growth in the sodium montmorillonite interlayer in the presence of natural sediment organic matter [leonardite humic acid (LHA)] at mass concentrations of 2 and 11%. The hydrate growth was characterized by the global and local four-body order parameter, surface distribution function, snapshots of molecular configurations, and face-saturated incomplete cage analysis. It clearly demonstrated the kinetic inhibition effects of LHA on hydrate formation on clay minerals, especially when the self-aggregation of LHA took place at a high concentration. Overall results highlighted the role of methane adsorption on LHA aggregates on the observed inhibition phenomenon, which changed the pathway of gas molecules by complex dynamic processes, such as aggregate deformation, cage break, and cage reformation.
Oil asphaltene and gas hydrate are two major challenges for the flow assurance in the oil−gas industry, but it remains unclear about their interactions because they were often investigated separately. Molecular dynamic (MD) simulations were performed to gain insights into the role of asphaltenes on the hydrate formation in bulk water and at the water−gas interface, respectively. The promotion and inhibition effects were elaborated by quantifying the partitioning of water and methane, the distribution of different types of hydrate cages, and the linkage and crystallization of hydrate cages. The influence of asphaltenes on the hydrate decomposition was also investigated, which suggested the theoretical feasibility to employ temperature-programmed heating to initially destroy the hydrate cages at low temperatures and then disassociate the asphaltene aggregates at high temperatures. To our knowledge, this was the first study on the atomic interactions between asphaltenes and gas hydrate, which added knowledge for a realistic understanding of the oil−gas flow assurance issues when they coexisted in the multiphase system.
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