Experimental Study On Dissociation Of Natural Gas Hydrate By Heat Injection And Depressurization

Natural gas hydrate is a new type of high efficient fossil energy with the characteristics of shallow and wide distribution.Therefore,with the increasingly energy-hungry,the Study of hydrate production mechanism is of great significance.In this thesis,it uses the NGH formation and exploitation 2D experimental simulation system to stimulate depressurization and hot water injection method for gas hydrate production under the marine conditions,and the related experimental results were analyzed to optimally select the mining method under corresponding different geologic conditions,the mining parameters of corresponding different mining methods,and corresponding well pattern in different mining methods.The results about the experiments of optimally selecting the mining method under different geologic characters corresponding show that:(1)During the heat injecting experiments,with the initial temperature 1.0?,while the hydrate saturation are 16%,32%,and 48%,the hot water flooding method will be feasible,and if the hydrate saturation was over 64%,this kind of method will not be possible;during the depressurization experiments,with the initial temperature 1.0?,while the hydrate saturation are 12%,24%,and 36%,the depressurization method will be feasible,and with the hydrate saturation increasing,the adaptability of this kind of method will be worse;(2)During the heat injecting experiments,with the hydrate saturation 32%,while the initial temperature are-1?,1?,3? and 5?,the hot water flooding method will be feasible;during the depressurization experiments,the hydrate saturation is about 12%,related to the initial temperature 1.0?,3.0? and 5.0?,in these cases,the depressurization method will keep the decomposition stable,and with the decrease of initial temperature,the adaptability of this kind of method will be worse.The results about the experiments of optimally selecting the mining parameters of corresponding different mining methods show that:(1)In heat injection experiments,while the initial temperature is 1.0?,the hydrate saturation is 32%,and the initial pressure is 3.0MPa,the best heat injection condition is about water injection rate on 15~20m L/min,water injection temperature on 120?,water injection time on 255min;(2)In pressure reduction experiments,while the initial temperature is 1.0?,the hydrate saturation is 36%,and the initial pressure is 3.0MPa,relating to 0.14 MPa/h,higher depressurization speed on 0.8MPa/h can ensure gas production and hydrate decomposition stable with short producing time,so it is the best depressurization condition.The results about the experiments of optimally selecting corresponding well pattern in different mining methods show that:(1)In pressure reduction experiments,while the initial temperature is 1.0?,the hydrate saturation is 14%,and the initial pressure is 3.0MPa,relating to single well and four well,the double well pattern is adapted to the depressurization method;(2)In heat injection experiments,while the initial temperature is 1.0?,the hydrate saturation is 14%,and the initial pressure is 3.0MPa,relating to central injection side corner mining and five point pattern,the diagonal injection production pattern is more adapted to the hot injection method.