Experimental Study On The Characteristics Of Carbon Dioxide Hydrate Displacement/static Formation

As the most important greenhouse gas affecting the ecological environment,carbon dioxide is increasing with the use of primary energy such as oil and coal.The use of hydrate technology to deposit carbon dioxide on the seabed is an effective way to reduce the carbon dioxide content in the atmosphere.At present,the research on hydrates by domestic and foreign scholars mainly focuses on static experiments.The experimental research on displacement synthesis of hydrates in actual seabed environment is relatively rare,but the hydration of CO2 is buried in porous media sediments in seabed and permafrost regions.Things are a dynamic process.Therefore,experimental research on the formation characteristics of hydrate displacement in porous media sediments is needed to provide important theoretical reference data for seabed storage of CO2.In this paper,a set of hydrate displacement experimental device was developed to simulate the environment of porous media sediments in the seabed.CO2 hydrate was used as the research object to carry out experimental research on hydrate displacement/static formation characteristics,and the initial pressure and reaction temperature were analyzed.The effects of the displacement/static reaction process and the relationship between CO2 hydrate saturation and natural seawater permeability.Through a large number of experimental studies,this paper mainly draws the following conclusions.(1)In the process of CO2 hydrate displacement formation,the pressure difference between the upstream and downstream of the reactor is increasing,and the induction time during the formation of hydrate in the reactor is random.Compared with the static formation process,the flow system used in the displacement process inhibits the nucleation of hydrates,while the natural sea sand promotes the rapid nucleation of hydrates.Under the same reaction conditions,the peak temperature of the displacement formation process is lower than static.This is because the displacement formation process is a dynamic cycle process,and the heat generated by the hydration reaction is taken away in time along with the circulating flow of the fluid in the kettle.After the formation reaction of hydrate displacement,the second generation of C02 hydrate during decomposition by temperature rise.(2)When the initial pressure is high,the hydrate displacement reaction slows down.This may be because the initial pressure is higher,resulting in an increase in the amount of dissolved CO2 gas in the water,thus forming a larger number of hydrate nucleuses,but the nucleus first forms a hydrate at the gas-liquid junction,blocking the CO2 gas and The contact of water reduces the contact area and forms a "armor effect" which slows down the reaction.In addition,under the same conditions,the induction time required in the process of CO2 hydrate displacement and static formation experiment was shortened with the increase of initial pressure and increased with the increase of reaction temperature,but the induction time in the process of displacement formation was significantly shorter than that in the static synthesis.(3)The increase of CO2 hydrate saturation will reduce the permeability of natural sea sand,and in the range of CO2 hydrate saturation(0～30%)obtained in this paper,the two have a polynomial distribution law.In addition,the experimental data obtained in this paper are close to the permeability of hydrate porous media Masuda model N=7 and Dai model M=2.