Study On Flow Characteristics And Thermal Diffusion Law Of Supercritical Steam

At present,the main technology of exploiting heavy oil reservoirs is steam injection for shallow heavy oil reservoirs,while steam thermal recovery for deep heavy oil reservoirs is still a difficult problem.China is rich in heavy oil resources,but its burial depth is generally deep,so there is a higher requirement for steam injection and oil recovery.Steam needs high temperature and high pressure characteristics to be more conducive to injection into deep reservoirs and maintain high heat.In view of the above problems,this paper will study the flow characteristics and thermal diffusion law of supercritical steam based on the basic knowledge of heavy oil thermal recovery,combined with heat transfer,simulation experiments,numerical analysis,software programming and other methods.Firstly,according to IAPWS-IF97 industrial standard for water and steam properties and its supplementary model,the physical and chemical properties of supercritical steam are described mathematically.Then,the physical and chemical properties,mass conservation,momentum conservation and energy conservation of supercritical steam as well as the heat conduction law of supercritical steam flow are considered comprehensively.The heat loss of supercritical steam flowing in vertical wellbore is established.Mathematical model of loss calculation.Subsequently,based on the direct interaction between supercritical steam and heavy oil reservoir,the seepage experiment of supercritical steam was carried out to analyze the change of rock permeability.The oil displacement mechanism of supercritical steam in heavy oil reservoir was studied by combining the dissolution contrast experiment of supercritical steam to crude oil and the corrosive contrast experiment of rock.Finally,the thermal diffusion law of supercritical steam in porous media is studied.Combined with the exploitation mechanism of supercritical steam,the analytical formula of thermal diffusion zoning of supercritical steam around wellbore in formation is deduced by Laplace transformation,and the heating radius of different thermal zones under formation is calculated.Through research,this paper introduces the data volume of Pv T,Pn T and Ph T of supercritical steam,and analyses the factors of injection pressure,temperature,steam flow rate and steam injection days in the calculation model of supercritical steam wellbore heat transfer.A set of supercritical steam thermodynamic zoning is introduced to solve the heating radius of W supercritical steam area,superheated steam area,steam area and hot water area.Based on the experiment,the physical property change law of reservoir after supercritical steam acting on rock is quantified.The experiment shows that the pore permeability of reservoir increases obviously after dissolution,and the maximum increase rate of permeability reaches 21.74%.