Effect of fulvic acid on methane hydrate formation and dissociation in mixed porous media

Abstract

In this work, the effect of fulvic acid (FA) concentration and memory effect on methane hydrate formation and dissociation in mixed sand-clay porous media were studied at 15 MPa and 8.0 ºC. The mixed sand-clay porous media were prepared based on the marine sediments composition of the South China Sea. The results demonstrated that the hydrate formation in porous media includes rapid formation stage and slow formation stage, and there is no obvious difference in fresh and memory solution systems. The low mass concentration of FA (2.0 wt.% FA) has a slightly acceleration effect for the hydrate formation and the hydrate formation time is shorter than that in pure water system. The high mass concentration of FA evidently inhibit the hydrate formation, especially for the 10.0 wt.% FA, the amounts of hydrate formation is significantly less than that in pure water system. The FA solutions can significantly accelerate the hydrate dissociation, and the gas released rate from hydrate increases with the increase of FA concentration. In addition, the gas recovery rate can be improved effectively by high concentrated FA.