Study Of Methane Hydrate Heterogeneous Nucleation

Liquid-solid interface plays an important role in the research of gas hydrate,such as the formation of gas hydrate in pores and the distribution of gas hydrate in reservoirs;During the mining process,the content of solid particles increases due to sand production in the wellbore,which promotes the re-formation of gas hydrate and aggravates the wellbore blockage;Gas hydrate blockage caused by the change of solid particle content in oil and gas pipeline transportation.Therefore,the study on the micro-promotion mechanism of liquid-solid interface on gas hydrate formation has become particularly important.The generation of liquid-solid interface gas hydrate belongs to the process of heterogeneous nucleation,but the mechanism of heterogeneous nucleation is still unveiled.However,the full description on the mechanism of heterogeneous nucleation is an important issue to research.Especially,it is not clear that accurate mechanism of how and when hydrate nuclei will be tremendously beneficial for the development of sustainable hydrate management strategies in oil and gas flow lines,as well as for their applications in energy storage and recovery,gas separation carbon sequestration,seawater desalination,and refrigeration.First,we studied the effect of hydrophobicity and thermal conductivity coefficient of particles on the nucleation of hydrate,and found out which has a greater effect.Then we designed the atomic force microscopy experiment to explain this mechanism from nanometer scale and proposed the nucleation mechanism.Last,the theoretical model was used to describe the methane gas nucleation of mixture system.The results from this paper were list as follow:(1)The effect of surface hydrophilicity of particles is greater than thermal conductivity coefficient,and it was found that the hydrophobic graphite and silica particles would promote the nucleation of hydrate but the hydrophilic silica particles inhibited the nucleation.(2)The results showed that the methane nanobubbles were formed on the hydrophobic highly ordered pyrolytic graphite(HOPG)surface but they were hard to form on the hydrophilic mica surface.(3)The methane nanobubbles on the hydrophobic surface could provide the gas hydrate nucleation sites and may induce a rapid nucleation of methane hydrate.(4)New theoretical model was proposed to describe the heterogeneous nucleation of methane hydrate,which couples the local structuring hypotheses and High dense gas bubble hypotheses.(5)The surface of glass bead showed the hydrophobic because of the adsorption of SDS molecular,then the methane nanobubbles formed and provide the site of nucleation of methane hydrate.There are many deficiencies in this paper,Due to the limitations of time and instruments,there is no quantitative description of the microscopic mechanism model of the heterogeneous nucleation of methane hydrate.The specific physical and chemical properties of methane nanobubbles need to be quantitatively tested and characterized.These questions are very important for the study of heterogeneous nucleation of methane hydrate.In the future work,we should not only rely on the progress of experimental techniques,but also strengthen the combination and verification of experimental methods and computer simulation methods.