The Synergistic Effect of Saturated Na ₂ SO ₄ and SDS on Methane Hydrate Formation

The methane hydrate formation rate and storage capacity seriously restrict hydrate storage and transportation technology development. In this study, the methane hydrate formation process in a 0.30 wt % sodium dodecyl sulfate (SDS) and mixed systems of 0.30 wt % SDS with saturated sodium sulfate (Na2SO4) was investigated. The effects of SDS concentration and initial pressure in the mixed systems on the methane hydrate formation rate and amount were studied. It was found that the methane hydrate formation process can be divided into four stages: the first rapid formation stage, the nucleation aggregation stage, the second rapid formation stage, and the hydrate stable stage. The precipitated Na2SO4 crystals provided seeds for methane hydrate formation, which can improve the hydrate formation rate and storage capacity. The Na2SO4 crystals mainly affect the first rapid formation stage and the nucleation aggregation stage. The methane hydrate formation rate in the first stage under the synergistic effect of 0.30 wt % SDS+Na2SO4 is 1.2 times higher than that of SDS alone. When increasing the formation pressure from 6 to 10 MPa, the hydrate formation rate under the synergistic effect of 0.30 wt % SDS+Na2SO4 in the first stage increased by 8 times. In the SDS+saturated Na2SO4 system, the methane hydrate formation rate and storage capacity increase with the increase of SDS concentration. SDS concentration mainly affects the first rapid formation stage. This paper is helpful to propose a new method for the methane hydrate rapid formation and is crucial for the development of hydrate storage and transportation technology.