| Abstract:With the rapid development of social economy and the improvement of people's material level,people pay more and more attention to the quality of life and social development.The key problem of development is to solve the problem of energy and energy,and to rely on the development of energy technology and natural resources.Uranium is an important nuclear energy resource.The expansion of nuclear power production and the acceleration of national defense construction,and the urgent need for a large number of nuclear fuel uranium,will promote the further exploitation of uranium resources.In order to solve practical problems of in-situ leaching process of low permeability sandstone and to improve the leaching rate of uranium,this paper studies the seepage characteristics of low permeability sandstone type uranium deposits to improve the process of in situ leaching sandstone uranium permeability.In this paper,the fractal theory and dynamics theory are used to study the particle size distribution experiment in the low permeability sandstone.The influence of pore structure and particle size distribution on the seepage law of sandstone porous media is analyzed,and the relationship between porosity and permeability is established.In this paper,the percolation characteristics of the fluid in the porous medium of low permeability uranium bearing sandstone are studied.Major work and results:?1?By analyzing the experimental data of fluid characteristics,the viscosity of the solution increases with the increase of the concentration of uranium in the solution and the reaction time.At the beginning,the slope of the relationship between the concentration of uranium and the viscosity is bigger,that is,with the increase of uranium concentration,the viscosity of the solution increases rapidly.In the middle stage,with the increase of uranium concentration,the viscosity of the solution fluctuates.In the later stage,with the increase of uranium concentration,the viscosity of the solution increases slowly,and it is in the stable phase.The reason may be due to the presence of uranium ions change the original molecular balance of the dissolved solution,there has been a rapid increase in viscosity.With the combination of ions in the solution,the viscosity of the solution changes,and the viscosity of the solution is stable until the new molecular equilibrium is reached.?2?Based on the data of particle size distribution test,the influence of particle size distribution on the seepage characteristics of sandstone porous media is analyzed.Based on the existing data,the relationship between porosity and permeability is analyzed,and the relationship between permeability and porosity is established.It is found that the variation of permeability with the porosity of ore and rock is not linear,but the exponential increasing function.?3?Through the transformation and upgrading of the existing uranium leaching test device,the seepage experiment device is added to carry out the seepage test of the fluid in the high carbonate sandstone uranium ore medium.By changing the pressure,the seepage characteristics of low permeability rock under pressure are studied.The samples of the horizontal permeability coefficient is about 2.2-5.0 cm/d,the sandstone uranium ore belongs to low permeability rock.?4?The coefficient of permeability is about 2-5 cm/d,while the vertical permeability coefficient is about 0.5-7 cm/d.When the pressure gradient is in the range of 0.2-0.8 MP.m-1,the permeability coefficient in the vertical direction changes rapidly,while the horizontal permeability coefficient changes very slowly.The horizontal permeability coefficient changes rapidly after the pressure gradient of 1.4 MP.m-1,and the vertical permeability coefficient may reach its maximum value before 1.4 MP.m-1.Because of the gravity effect,the pore water pressure and the existence of vertical joints make the fluid flow in the vertical direction is larger than that in the horizontal direction. |
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