Experiment and reservoir simulation on air injection assisted in situ upgrading for ultra heavy oil recovery

Key words:  ultra heavy oil  in situ upgrading  air injection  thermal cracking  reservoir simulation

Abstract:

In situ upgrading (ISU) via underground heating and thermal cracking is regarded as an effective technique for exploiting ultra heavy oils, in which heavy oil components can be cracked into light oils and gases for production. This technique has some advantages over conventional thermal recovery technique, such as high oil recovery rate, high thermal efficiency and improved oil quality. However, slow heating rate via conduction from wellbore to oil formation is one of the main issues concerned in the conventional ISU process. Considering the exothermic characteristics of oxidation reaction of oil during the air injection process, an air injection assisted ISU technique (AAISU) was proposed, which can enhance the heat transfer through gas convection and utilize the thermal effect of low temperature oxidation (LTO) reaction. In this study, thermal cracking experiments of ultra-heavy oil in the presence of air were conducted at high pressure to study the thermal cracking reaction mechanism of heavy oil components, and reservoir simulation the AAISU process was carried out. The experimental and numerical simulation results show that ultra heavy oil can be effectively cracked into gases, light oils and coke-like substances in the presence of air at temperature over 350 ℃. The heat transfer rate can be effectively enhanced by air injection comparing with the conventional ISU without air, and the total oil recovery factor can be increased over 21% and the energy conversion efficiency can be improved by 53% via air injection.