Development and application of gas hydrate reservoir simulator based on depressurizing mechanism

Natural gas hydrates are known to occur in vast quantities at the ocean flo or or in permafrost regions. In-situ hydrate contains great volumes of meth ane gas, which indicates a potential future energy resource. In this study we have developed a three-dimensional, multi-phase (gas, water, and hydrate ) flow finite-difference model by using implicit pressure explicit saturati on technique in order to investigate simultaneous flow through ice-liked hy drate reservoir. The developed model is based on the depressurizing method as producing mechanism. The model evaluates local gas generation dissociate d from the hydrate with the aid of kinetic dissociation theory proposed by Kim-Bishnoi. The computation of kinetic dissociation uses the empirical dis sociation rate as a function of specific surface area between phases and pr essure difference. With the developed model, a one-dimensional system has b een simulated for analyzing the production performance of a hydrate reservo ir and for investigating the effect of hydrate saturation on absolute perme ability and relative permeability characteristics. Also, for the three-dime nsional field-scaled reservoir system, a number of numerical exercises have been conducted to understand the effect of mass transfer and to characteri ze the flowing mechanism under the conditions of increased permeability res ulting from the dissociation hydrate.