Investigation on effect of water on oxidation behaviors and kinetics of heavy crude oil using STA and ARC

In situ combustion has already been applied in reservoirs which were adopted steam recovery. It is essential to investigate the effect of water on oxidation behaviors, especially in high water content. Simultaneous thermal analysis (STA) and accelerating rate calorimeter (ARC) were used to study the impacts of water on heavy oil oxidation characteristics at atmosphere pressure (0.1 MPa) and reservoir pressure (7.2 MPa). It was found from STA data at atmosphere pressure that water in a vapor state could promote the process of heavy crude oil oxidation. Besides, the exothermicity of low-temperature oxidation (LTO) would decrease due to evaporative heat absorption of liquid water at high water saturation, resulting in lower peak temperatures, peak pressures, and self-heating rate. It is indicated that water in a liquid state would inhibit the LTO reaction. High-pressure ARC curves suggested that self-ignition technology is not advisable under the reservoir pressure (7.2 MPa) and temperature (100 °C) after steam recovery. Subsequently, the iso-conversational methods were used to calculate the kinetic parameters. Steam could increase the oxidation activity of heavy oil evident in the decreased activation energy with elevated steam fraction. This work can assist the development and application of air injection in reservoirs after steam recovery and co-injection of steam and air technology.