Effect of porous media and its distribution on methane hydrate formation in the presence of surfactant

Abstract

Hydrates are mainly stored within sediment pores in nature. Therefore, understanding their formation characteristics within the porous space is essential to the transportation of natural gas based on the hydrate-based technology. In this paper, solutions of sodium lauryl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), and alcohol ethoxylate (AEO) were used with different-sized porous media to investigate the characteristics (gas storage capacity, formation rate, and formation distribution) of the hydrate formation. The experimental results show that the gas storage capacity was higher in the complex system composed of a small-size porous media. The improvement of hydrate formation in the complex system composed of SDS or SDBS solution was more significant than that in the AEO system which could enhance the hydrate formation. In the three complex systems, the surface of alumina particles was positively charged by hydrolysis, which resulted in a double electron layer consisting of the counter ion in the adjacent liquid phase. The anionic active groups ionized by surfactants (i.e., SDS and SDBS) were aggregated to the surface of particles under Coulomb force. This increased the content of the methane molecules by non-polar adsorption and micellar solubilization. Finally, in the complex system of SDS solution and porous media, the capillary force caused by the pores of porous media could enhance the liquid phase migration in the pores which change the distribution of hydrate formation. This work presents useful insights on the hydrate formation characteristics which are beneficial to the rapid formation of hydrate and its industrial application of both storage and transportation of natural gas in complex porous systems.