High Pressure Air Injection (HPAI) is an Improved Oil Recovery (IOR) technique in which compressed air is injected into light oil, high-pressure reservoirs. The aim of this process is to react the oxygen from the injected air with a small fraction of the reservoir oil at an elevated temperature to produce a mixture of carbon dioxide and nitrogen. The produced gas flowing from the reaction region mobilizes the oil downstream of the thermal zone, sweeping oil towards the production wells. Knowledge of the oil's oxidation behavior is a key to the successful implementation of the process. However, information on oxidation behavior of oils based on their composition is limited, especially for light oils. An experimental study was designed to examine the oxidation behavior of oils by using the Pressurized Differential Scanning Calorimeter (PDSC) at pressures from 16 psi to 1000 psi. Selected paraffins, aromatic hydrocarbon samples, two light oils and Athabasca bitumen were tested in the research. The PDSC heat flow curves clearly demonstrate the effect of chemical structure of the samples on their oxidation behavior. The pressure impact is also significant on the exothermic behavior of selected samples. An increase of pressure results in an increase in the heat released from oxidation reactions. The peak temperatures of exothermic activity in as low well as high temperature oxidation region drop as pressure increases. The extent of oxidation of hydrocarbon samples is strongly dependent on the nature of the hydrocarbon. The two light oils compared with Athabasca bitumen display different thermo-oxidative behavior
Air injection continues to be an important oil recovery process, used to increase both the amount and the rate of oil recovered from a petroleum reservoir [1,2]. When air is injected into a light oil reservoir, exothermic chemical reactions occur between the reservoir oil and the oxygen contained in the injected air. The reactions are mainly oxidation reactions resulting in heat generation and the production of carbon dioxide, carbon monoxide and water with corresponding consumption of oxygen. The heat of reactions results in a temperature elevation leading to vaporization of some lighter components. Therefore, the driving gas, which can sweep the oil to production wells, is not the injected air but an in-situ generated flue gas, composed of CO, CO2, N2 and vaporized light hydrocarbon components.
Air injection is a complex process, involving simultaneous heat, and mass transfer in a multiphase environment coupled with oxidation chemical reactions. Oxidation reactions play an important role in this process. In order to improve the efficiency of the air injection process it is necessary to have additional knowledge of the factors influencing the process and how they affect the oxidation of oil. In recent years, the application of thermal analysis techniques, thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC) to study the combustion behavior of oil has obtained wide acceptance.
Attempts to use thermal analysis techniques to study crude oil combustion began with Tadema [3]. He reported the existence of two main reactions, one at a higher and one at a lower temperature. Yoshiki and Philips [4] used DTA and TG at high temperature and pressure.
