Depressurizing dissociation of natural gas hydrate with different saturation
Natural gas hydrate(NGH),a high quality,clean and efficient new energy,has received worldwide attention.Among the NGH dissociation methods,depressurization has been considered as an effective way.However,the result of depressurization dissociation is different for NGH with different saturations.A home-made one-dimensional experimental system is used for studying formation and dissociation behavior of NGH.At simulation marine geological conditions,NGH with different saturations is formed in the simulated porous media.Then they are dissociated by depressurizing slowly.Dissociation performance and saturation influence of NGH are analyzed.The results show that:the NGH dissociation by depressurization can be divided into three stages:free gas production in the early stage,gas release from hydrate dissociation in the second stage and surplus free gas release in the third stage.In the second stage,with NGH saturation increasing from 16% to 48%,the average rate of gas production increases first and then decreases.It shows that the effect of NGH saturation on gas production rate by NGH dissociation is of non-linear relation.Higher NGH saturation results in a large range of temperature decrease.Within the range of our experimental conditions,the dissociation rate of NGH with medium saturation(32%) is relatively larger,so depressurization is a appropriate method for NGH reservoirs with medium saturation.