Aggregation Behavior of Asphalt on the Natural Gas Hydrate Surface with Different Surfactant Coverages

Abstract

The aggregation behaviors of asphalt on the hydrate surface with different surfactant coverages were studied by molecular simulations. The molecular polarity index of asphalt (10.47 kcal/mol) is higher than that of Span 80 (8.19 kcal/mol). Asphalt is easier to occupy the binding sites between Span 80 and hydrate. Asphalt mainly depends on the π–π interaction to form aggregates. The dispersion interaction up to −114.17 kcal/mol is the main factor to maintain the asphalt aggregate stability. With the increase of surfactant coverage, the polar groups of asphalt are easier to associate with each other, promoting the formation of larger asphalt self-aggregates. The self-aggregation increases the complexity of asphalt stacking, and the proportion of edge-to-face stacking types increases from 40 to 60%. When the Span 80 molecule number reaches 12, the diffusion coefficient of asphalt is only (2.31 ± 0.5) × 10–8 cm2/s. Asphalt with low diffusivity can provide new sites for hydrate nucleation. The results are helpful to understand the aggregation mechanism of asphalt on the hydrate surface. Increasing the concentration of surfactant only is not a good solution to solve blocking-pipeline problems. We need to use surfactant reasonably and give full play to the anti-agglomerant effect of asphalt itself.

Mechanically Strong, Hydrostable, and Biodegradable Starch–Cellulose Composite Materials for Tableware

“…To calculate and visualize the noncovalent interaction (hydrogen bonding, van der Waals (vdW) interaction) between starch and cellulose from bagasse pulp fiber, reduced density gradient (RDG) analysis was used to demonstrate intermolecular noncovalent interaction between starch ( Figure b) and cellulose molecules (Figure 4c) through visualized isosurface map. [ 57 ] The blue region on the RDG isosurface (Figure 4a) represented strong attraction between starch and cellulose molecules, corresponding to hydrogen bonding interaction (O−H···O bonds); the green region displayed vdW interaction. RDG scatter diagram (Figure 4d) was used to illustrate the strength of intermolecular interaction.…”

Experimental Study on the Gas Permeability of Marine Sediments with Various Hydrate Saturations and Effective Stresses

“…Methane hydrate hosts more than 90% of the total hydrate reservoirs . NGH is widespread in oceans and permafrost zones limited by the formation conditions of low temperature and high pressure. , The gross proven reserves are considered to be twice as much as known conventional fossil fuels . Up to now, the United States, China, Canada, Japan, and other major energy demand countries have successively made considerable investments in natural gas hydrate exploration and exploitation. , Several hydrate trial production projects in the northern slopes of Alaska, the South China Sea, the Mackenzie Delta of Canada, and the Nankai Trough of Japan have been carried out, respectively, in recent years.…”

“…5 NGH is widespread in oceans and permafrost zones limited by the formation conditions of low temperature and high pressure. 6,7 The gross proven reserves are considered to be twice as much as known conventional fossil fuels. 8 Up to now, the United States, China, Canada, Japan, and other major energy demand countries have successively made considerable investments in natural gas hydrate exploration and exploitation.…”

Study of the Physical Characteristics of a Pore-Filling Hydrate Reservoir: Particle Shape Effect

“…Methane gas hydrate (MGH) is regarded as a clean energy source because it is high in energy density, 1,2 tremendous reserves, etc. 3 Naturally, MGH reservoirs mainly exist in the excess-gas environment (typically in the permafrost and Arctic regions, where the hydrate occurrence is usually cementingtype) and excess-water environment (typically in submarine continental margins, where the hydrate occurrence is usually pore-filling-type).…”