Numerical Simulation Of Natural Gas Hydrate Production By Thermal Stimulation

Natural gas hydrate is recognized as an important energy resource,because its large reserve, clean and high energy efficiency. At the present time, great progress has been gained ground in the fundamental research of hydrates. But there hasn't a perfect software about numerical simulation of hydrates at home.Based on the study of mathematical models both here and abroad, we build a three- phase (gas, liquid, hydrates), five-components (free methane, dissociated methane, water, salt, hydrate) mathematical model for NGH development by thermal stimulation. The model includes mass balance and energy balance functions,in addition,it has the kinetic model.The seepage of gas and water are considered and the conductive-convective heat transfer equations are used.The over-and under-burdens are takeing into consideration.The software of numerical simulation of hydrates production by thermal stimulation. is developed on the basic of the mathematical model. By matching the numerical simulation results with those physical experimental datas and real NGH reservoir (Mallik),we find they are consistent.Then we use this model to simulation three kinds of NGH reservoirs:the first is the totally hydrate interval;the second is the hydrate layer with an underlying gas free zone, the third is the hydrate layer with an underlying water free zone.Comparing the results producted by depressurization and thermal stimulation.We find that the second kind is better than the first if they development just by depressurization . Injection temperature ,injection pressure and production pressure play an important role. Gas pruduction rate increase with injection temperature. If the production pressure is high and the injection temperature is also high enough then warm water flooding is more favorable than just depressurization and gas pruduction rate increases with injection rate. If the production well has a low pressure or the injection temperature is not high then just depressurization is the best method for production and gas pruduction rate decreases with injection rate.