Experimental study on dynamic characteristics of low temperature oxidation for Bohai offshore light oil under reservoir conditions

Abstract

Air flooding has shown to be a promising method for enhanced oil recovery (EOR). The air injection into reservoir causes complex oxidation reaction, resulting in the change of the properties and components of crude oil. Most studies on thermal behavior and kinetics of crude oil were not conducted under realistic reservoir conditions, bringing difficulties to understand the suitability of air flooding for a light oil reservoir. The objectives of this research were to investigate dynamic characteristics of low temperature oxidation (LTO) of Bohai offshore light oil under realistic reservoir conditions. Thermogravimetry experiments (TG), static and dynamic oxidation experiments were used to evaluate the oxidation reaction of Bohai light oil reservoir. Besides, the thermal behavior of the light oil and alteration of oil components during LTO were comprehensively measured. The results indicated that there were three stages for light oil in LTO stage, the first and second stages of LTO showed positive activation energy but the third stage showed negative activation energy, manifesting the LTO stage might include multiple mechanisms. The LTO of light oil was promoted by pressure, and the negative temperature coefficient (NTC) stage of LTO might be controlled by medium oil component (C7-C17). Additionally, oxygen consume rate of dynamic oxidation experiment was much higher than that of static oxidation experiment, which was closer to the realistic reservoir conditions. This study can provide insights to the LTO of light oil reservoir and explore the potential of air flooding based on EOR projects.