Analyzing Permeability Of The Heterogeneous Porous Media Containing Gas Hydrate

The search for clean energy has become a major subject in many countries because of the environment is damaged.Natural gas hydrates a large number of exist in deep of the earth through a long time evolution.It is a kind of clean energy.The scientists focus on when it was found which about the exploration of the reserves of the earth and the presence of location.They study efficient and safe exploitation.There are many factors affecting gas hydrate mining,among which permeability plays a key role.The permeability controls the flow characteristics of gas and water in the reservoir,the transfer of matter and the transfer of heat.It is very important to study the seepage characteristics of gas hydrate-bearing in the process of gas production.We developed a high vessel which can control temperature and pressure in CT scanning based on CT imaging technology.Using the X-ray CT visualization system,the hydrate sediments skeleton structure characteristics was obtained;based on the change of pore structure characteristics in porous media and mutual restriction characteristics,we study the gas and water flow in pores.The pore network model is widely applied in the oil field was used to study the percolation properties in the hydrate sediments.We analyzed the gas flow in porous media which containing gas hydrate during hydrate decomposing by the pore network model.Because the hydrate sediments in the nature have inhomogeneous pore structure,we systematic analyzed the changes in pore structure affected by the hydrate formation and decomposition in different shape of sands.We also researched the gas hydrate influence on local permeability.It is found that the heterogeneity of porous media has different influence on the flow of gas and water,and the hydrate can change of the pore throat radius,thus affecting the flow of gas and water.The hydrate in pore made more small pores which lead to increase capillary pressure as well as tortuosity.Moreover,the connectivity of the porous media is decrease.The result leads to reduce absolute permeability.At the same time,the relative permeability of the gas and water were different with the change in the direction of the fluid flow,which is the inspiration for the import direction of the actual extraction.The two-phase seepage characteristics of porous media in the process of hydrate decomposition were discussed.The study shows that with the decomposition of hydrate,small pores are produced,and gas is trapped in pores,and the residual gas saturation increases.The effect of particle size on permeability and capillary pressure in hydrate decomposition was found.