Numerical Simulation And Exergy Analysis On Gas Production From Hydrate Reservoir By Warm Brine Stimulation Combined Depressurization

Depressurization is the most widely used hydrate exploitation method in the world which has the characteristics of low cost,low gas production and low gas production speed.However,combined with warm brine stimulation,it can further improve the gas production and speed of gas production.Therefore,based on the geological parameters of Dongsha Area in the South China Sea derived from literatures,thermal simulation combined depressurization and exergy analysis are adopted in the hydrate exploitation which is carried out in the South China Sea.Exergy analysis is also employed to evaluate the process of hydrate exploitation to determine the optimal injecting brine temperature,injecting brine rate and well spacing and provides reference guidance for the exploitation of natural gas hydrate in Dongsha Area of South China Sea.The main contents of this subject are as follows:(1)According to the geological parameters of Dongsha Area in the South China Sea provided by literatures,the parameters of the four-phase,four-component and two dimensional dynamic model involved in TOUGH hydrate numerical simulation software were determined.(2)It is necessary to consider the influence of injecting brine temperature,injecting brine rate and well spacing according to the results of the TOUGH numerical stimulation software used to study the depressurization and warm brine simulation in the target area.In the period of hydrate exploitation(4 years),the spatial distribution law of cumulative water production,cumulative gas production,gas-water ratio,gas saturation and temperature was obtained under the working conditions with different injecting brine temperate,injecting brine rate and well spacing.(3)Exergy analysis is composed of exergy consumption and exergy production under the working conditions with different injection brine temperature,injection brine rate and well spacing.Exergy production includes methane chemistry exergy and concentrated brine sequestration exergy.Exergy consumption includes exergy consumed by hot brine production and exergy consumed by depressurization.According to the total net exergy,day net exergy and production cycle under the working conditions with different injecting brine temperature,injecting brine rate and well spacing,the optimal injecting brine temperature,injecting brine rate and well spacing are determined.