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As a compound multi-phase dispersion system, nanofluids can enhance the energy transfer performance of solutions and are considered to be effective in promoting the formation of hydrates. Hence, in this study, a compound system of SiO2 nanofluid and sodium dodecyl sulfate (SDS) solution at 6 MPa and 275.15 K was used to study the effects of Cu and SiO2 nanofluids on CH4 hydrate formation at different concentrations, and the results were compared. The results showed that the Cu nanofluids promoted the formation of natural gas hydrates. At lower Cu nanofluid concentrations, the gas storage capacity of the hydrates increased with increasing Cu nanofluid concentration. At a concentration of 2200 ppm, the gas storage capacity reached 111.57 Vg/Vw. However, the SiO2 nanofluid only promoted the formation of hydrates at lower concentrations. The gas storage capacity reached 108.26 Vg/Vw at a concentration of 800 ppm. As the concentration of the SiO2 nanofluid increased, the gas storage capacity of the hydrates gradually decreased, and hydrate formation was eventually inhibited. Therefore, reasonable selection of the type and concentration of nanofluids is required to improve the gas storage capacity of hydrates. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of different nonionic surfactants on hydrate formation in oil-water emulsion systems, the hydrate formation experiments were carried out in a diesel water-in-oil emulsion system with a water cut of 40% using nonionic surfactants such as Span80, Tween80, Span20 and Tween20, respectively. The results show that under the experimental conditions of 275 K and 7 MPa, a certain concentration of nonionic surfactant can promote the growth of hydrates in diesel emulsion systems, shorten the hydration reaction time, and have a significant effect on the improvement of gas storage density. The combination of Span80 and Tween80 in a mass ratio of 1:1 was the most effective in promoting the formation of hydrate in the emulsion system. When the mass fraction was 0.5%, the hydration reaction time was the shortest and the hydrate gas storage density was the highest. Due to the addition of the nonionic surfactant, a stable interfacial film and interfacial charge are formed around the water droplets of the emulsion system, making it difficult for the droplets to approach and polymerize, which maintains the stability of the water-in-oil emulsion system and has great reference value for the study of hydrate storage and transportation. [ABSTRACT FROM AUTHOR]