Reaction schemes and characteristics in crude oil oxidation process using a TGA testing method

Stage characteristics of heavy oil oxidation is important for ignition and production control of fire flooding. A thermogravimetric (TG) experiment is carried out to study the oxidation process on a certain heavy oil sample mixing with quartz sand. Firstly, based on multicomponent theory of heavy oil, four stages corresponding to earlier low temperature oxidation (LTO), later LTO, fuel deposition and high temperature oxidation (HTO) are identified. The kinetic parameters of each oil oxidation stage are calculated by the Coats-Redfern integral method. It demonstrates that the orders of reaction have a great influence on the results of calculation. Then logical and reasonable reaction equations are derived out based on the mechanism of staged crude oil oxidation. The result shows that phase boundary reaction (also known as interfacial reaction, which is defined as a chemical reaction that occurs on a two phase contact interface.) is the main reaction at the stage of low temperature oxidation. And three dimensional diffusion reactions are primary at the stage of high temperature oxidation reaction. Finally thermogravimetric analysis of different viscosity crude oil verifies that the kinetic process of oxidation is determined by reaction mechanisms. And different mechanisms appears at different reaction stages.