Influence of reservoir permeability on methane hydrate dissociation by depressurization

Hydrate dissociation incorporates heat transfer and fluid flow with hydrate dissociation kinetics. We previously developed and validated a two-dimensional axisymmetric model to investigate the effect of heat transfer on gas production from methane hydrate dissociation by depressurization, thermal stimulation, and a combination of the two methods. We herein extend our focus to the influence of reservoir permeability on methane hydrate dissociation by depressurization. Initially, pressure reduction propagated slowly from the outlet valve into a low permeability sediment. However, propagation of this pressure reduction was rapidly promoted deep into the sediment core boundary in a high-permeability case. Dissociation behavior was affected by reservoir permeability, with high permeability exhibiting spatial hydrate dissociation, followed by an inward moving dissociation front from the surrounding wall of the sediment core. The hydrate exhibited a sharp dissociation front with pressure reduction regime from the outlet valve to the right end of the sediment in a low-permeability case. The sediment permeability in the presence of hydrate ranged between 0.01 mD and 0.5 mD for the transition from a sharp front dissociation to a spatial dissociation. Furthermore, in the case of a high permeability, a spatial temperature decrement followed by temperature bounce back resulted from heat transfer from the surrounding wall. In the case of a low permeability, ambient heat transfer transmitted from the water bath to the dissociation region with the moving dissociation front. Moreover, gas production from the low-permeability sediment relied significantly on the surrounding ambient heat transfer. Finally, a higher reservoir permeability resulted in an earlier peak gas generation time and a higher peak gas generation rate. (C) 2016 Elsevier Ltd. All rights reserved.