Reaction Heat Calculation And Temperature Prediction Of Crude Oil During In-situ Combustion Process

In-situ combustion(ISC)process is considered as a potential EOR(Enhanced oil recovery)method for heavy oil and extreme heavy oil reservoir.Toe-to-heel air injection(THAI)process has been widely concerned due to the combination of traditional ISC method with horizontal well technology to improve oil recovery.One of the main oil displacement mechanisms during ISC is the thermal viscosity reduction process of heavy oil.The exothermic reactions during oil combustion process,which occur at the fire front,are the main sources of heat sustaining ISC,and the heat and mass transfer of upgrading oil or air causes the temperature of other regions rising.Therefore,the research of temperature prediction in fire front and the heat contribution of each pseudo-component to ISC is greatly vital for ISC process.In this study,the standard combustion curves of n-alkanes are applied to quantitatively analysis the heat contribution of each oil pseudo-component and to calculate the total reaction heat of heavy oil in underground combustion process via matching the average carbon number and average molecular formula of the pseudo-components with those parameters of n-alkanes.Then,the total heat is converted to the combustion temperature at fire front by the equation of specific heat capacity.The effects of heating rate and pressure on the exothermic process of pseudo-components are studied by changing experiment conditions,and the temperature prediction in different conditions is achieved by using this method.Compared with the measured temperature values in combustion tube experiments,the calculated values with the application of standard combustion curves are only 0-50? higher and the relative error can be controlled within 13%,and the values in three dimensional experiment are 0-100 ? and 20%,which shows the feasibility of the calculation method in this study.The temperature field distribution with the application of elliptic equations is closely similar with that in three-dimensional THAI experiment,which also shows the practicality of this study in actual THAI process.The heat contribution and the mass of burned oil by this method are consistent with the conclusions in the previous papers,which also shows the potential of this method to be applied in actual mining process.