Probing the nucleation and growth mechanism of hydrates in emulsion system under the influence of asphaltenes: A molecular dynamics simulation study

Asphaltenes are important components in crude oil, and hydrates are key elements impairing deep-sea flow assurance. So far, the study on the interaction mechanism between the two in water-in-oil emulsion systems is still limited. In this article, the effects of the molecule number of asphaltenes on the nucleation and growth of hydrates was investigated through 2500 ns molecular dynamics simulation. Moreover, hydrate growth experiments were conducted synchronously to verify the relationship between the effect of an increase in asphaltene concentration on hydrate growth at the macro level and the effect of an increase in asphaltene molecule number on hydrate growth at the micro level. The simulation results indicate that the addition of 5 and 10 asphaltene molecules can inhibit the nucleation of hydrates while 15 asphaltene molecules will shorten the induction period. Besides, hydrate growth is promoted in the presence of 5 asphaltene molecules but inhibited with further increase of asphaltene molecules. Experimentally, all concentrations of asphaltenes show inhibitory effects on the growth of hydrates. Based on the comprehensive analysis of structural parameters, potential energy and molecular transport properties, and by combining the measurement results of dynamic interfacial tension and interfacial dilational modulus, it is concluded that affecting the mass transfer process is the major way of asphaltenes affecting the growth of hydrates.