Large Scale Experimental Evaluation to Methane Hydrate Dissociation below Quadruple Point by Depressurization Assisted with Heat Stimulation

The Pilot-Scale Hydrate Simulator (PHS), a three-dimensional 117.8 L pressure vessel, is applied to study the methane hydrate dissociation below the quadruple point in the sandy sediment in this work. The hydrate dissociation behaviors below and above the quadruple point by depressurization method and depressurization assisted with heat stimulation method are compared. The results indicate that methane hydrate dissociation below the quadruple point causes ice formation, which can strongly enhance the dissociation rate of the hydrate. The water generated from hydrate dissociation below the quadruple point may immediately form ice. Meanwhile, the hydrate dissociation below the quadruple point consumes the latent heat released by ice formation. In addition, it is found by depressurization assisted with heat stimulation that the heat injection has little influence on hydrate dissociation, because the injected heat is used for ice melting rather than hydrate dissociation. (C) 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the 9th International Conference on Applied Energy.