A covering liquid method to intensify self-preservation effect for safety of methane hydrate storage and transportation

Abstract

In this work, experiments and comprehensive insights into the proposed covering liquid method to intensify self-preservation effect for methane (CH 4 ) storage are presented. The CH 4 hydrate decomposition percentage was 17.6% with the pressure of 0.61 MPa after 12 h at 266.0 K without a covering liquid, which can be reduced to 12.4%, 13.8%, 13.0%, and 8.3% with the pressure of 0.26 MPa, 0.33 MPa, 0.51 MPa, and 0.37 MPa by covering with tetrahydrofuran (THF), cyclopentane (CP), cyclohexane, and n-tetradecane, respectively. When the temperature for CH 4 hydrate decomposition was 274.2 K, covering with THF, CP, cyclohexane, and n-tetradecane failed to inhibit CH 4 hydrate decomposition. The results suggested that the covering liquid may form a new solid layer (a hydrate layer or other solidified layer) around the CH 4 hydrate, which inhibit CH 4 transfer below the freezing point of water. However, the new solid layer cannot resist the fast transfer of CH 4 from decomposed CH 4 hydrate above the freezing point of water. The same phenomenon was also observed in a sodium dodecyl sulfonate (SDS)-dry solution CH 4 hydrate formation system. Therefore, the covering method can only intensify the self-preservation effect below the freezing point of water, but cannot generate a self-preservation effect.