Design And Simulation Study Of A Visualized Experimental Device For Natural Gas Hydrate Drainage And Production

The world is facing increasingly serious problems such as energy shortage and environmental pollution.It is imperative to promote energy transformation.China is rich in natural gas hydrate resources,as a kind of clean and efficient energy,the development potential is huge,but the current mining technology is still immature,and a large amount of water production,serious sand out of the formation and other problems appeared in the trial mining process.In order to study technically and economically reasonable natural gas hydrate extraction methods,it is necessary to carry out indoor physical simulation experiments.The indoor simulation experimental device is the key to carry out simulation studies.In order to realize the monitoring of the physical-chemical change process of natural gas hydrate during its generation,discharging and extraction under high-pressure environment,the modular design idea is adopted.And each module is relatively independent,which is convenient for disassembling and transportation,and the experiments can be carried out after connection.The system mainly consists of preheating and pressure stabilizing gas supply module,high-pressure visualization reactor module,gas-liquid processing,data acquisition module,temperature control system module and related pipelines.In order to observe the physical-chemical change process of natural gas hydrate inside the reactor,a column with a high-strength transparent material wrapped with a camera is set up inside the reactor during the design of the high-pressure visualization reactor module.Based on the principle of force and thin plate theory,the material parameter indexes and dimensions of each part were optimized through force calculation and strength checking.Based on the design scheme,a perfect experimental device was processed;relevant experiments were carried out;certain results were achieved.Natural gas hydrate synthesis,buckling decomposition experiments and numerical simulation studies are carried out by using the designed natural gas hydrate experimental device with visualization function.Firstly,the experiments of natural gas hydrate synthesis and decompression decomposition process under different temperature and pressure conditions were carried out,and the pressure and temperature fields as well as the physical-chemical change processes at different stages of natural gas hydrate generation and decomposition were completely monitored.Then the numerical simulation software FLUENT was used to establish a three-dimensional hydrate decomposition mathematical model for the self-designed reactor,and numerical simulations of the spatial distribution characteristics of the temperature and pressure fields as well as the rule of change in the decomposition process of methane hydrate buckling under three different gas extraction port pressures were carried out respectively.Three results were obtained: 1.In the process of methane hydrate generation,the higher the pressure under the same temperature is,the faster the methane hydrate generation rate is.The lower the temperature under the same pressure is,the faster the methane hydrate generation rate is;2.Natural gas hydrate decompression decomposition experimental results show that,under the same temperature,the lower the pressure in the methane hydrate decomposition process is,the faster the methane hydrate decomposition rate per unit of time is;3.Numerical simulation results show that,throughout the hydrate decompression decomposition process,the pressure inside the kettle in the spatial distribution of the reactor is uniform,and the temperature shows a stepwise decrease in temperature from the outer boundary to the inner boundary.The temperature decreases from the outer boundary to the inner boundary in a stepwise manner.Through the development and experiment of natural gas hydrate visualization device,the simulation of natural gas hydrate generation and decomposition process was realized,and the physical-chemical change process and the change rule of temperature and pressure fields were monitored.