Dimensionless analysis of self-ignition of hydrocarbons during the high-pressure air injection process based on numerical simulation
Air injection into the reservoir accompanied by in-situ combustion is a complex process in which heat and mass transfer phenomena, heat conduction, heat transfer, phase transformations and chemical reactions take place. Interaction between these processes is characterized by a set of dimensionless parameters. In this work we consider a one-dimensional mathematical model of the self-ignition and propagation of combustion zone in conditions of a non-isothermal three-phase filtration with phase transitions and chemical reactions in the undeformable porous media. Mathematical model includes equations for mass balance of phases and components, and equations for energy balance, supplemented by the corresponding closing relations. The following assumptions are used: liquid phases are considered to be in-compressible; the gas phase is compressible and defined by the ideal gas law; the gas consists of water vapor, oxygen and inert gas; gas components are insoluble in oil and water; heat exchange with the surrounding rocks is considered. The system of equations of mathematical model is solved numerically with the usage of finite volume method and IMPES-method. In the process of analysis of the mathematical model the original dimensionless complexes were selected. These complexes are composed by parameters of Frank-Kamenetskii, Peclet, Bio and oil saturation, which characterize interactions of the aforementioned processes during the in-situ combustion. The results of multi-parametric analysis of the in-situ combustion problem based on these dimensionless complexes are presented. On the basis of performed computations the diagnostic graph, that allows to determine the possibility of application of the in-situ combustion technique, is constructed.