A series of Accelerating Rate Calorimeter (ARC) and Thermo Gravimetric Pressurized Differential Scanning Calorimeter (TG/PDSC) tests was conducted on oil-rock systems from three light-oil reservoirs (Oils A, B and C) to screen and evaluate the potential of the air injection process. ARC tests helped determine, a priori, whether the test oils would autoignite under reservoir conditions of pressure and temperature. Also, the limits of the low temperature range were established and Arrhenius oxidation kinetics parameters were estimated. The goals of the TG/PDSC tests were to identify temperature ranges over which the oil reacted with oxygen in the injected air, and to determine the fraction of the sample responsible for the reactivity. ARC and TG/PDSC tests demonstrate that Oils A and C offer favourable exothermic behaviour in the low temperature range with lower activation energies and low orders of reactions?the conditions typically favouring autoignition. The presence of rock material lowered the ignition temperature, confirming its impact on O2 uptake. Oil A had a lower energy generation (ignition) temperature, and a stronger and smoother transition to the higher temperature region. Both oils responded favourably during isothermal aging with air as manifested by a drop in the initial self-heating temperature (a 15 °C drop for Oil A and a 10 °C drop for Oil C). The third oil, Oil B, showed unusual characteristics, with almost no impact of the core material on the starting temperature of the exotherm; rather, the core material appeared to have acted as a heat sink. Overall, Oil B needed a much higher activation energy to ignite, and its order of reactions was very high. Furthermore, it showed no response to isothermal aging, and hence, it is less likely to autoignite in the reservoir. esults revealed that ARC and TG/PDSC tests could be an effective tool to rank and study the oxidation characteristics in the low temperature range of the candidate oils. Also, it was observed that the oil composition and rock mineralogy are important factors affecting the type and rate of the oxidation reactions occurring in the low temperature range. Introduction The air injection process is now a proven and viable process in improving oil recovery from several light-oil reservoirs. As a result, it has generated much interest in recent years(1–5). Cheap and abundant, air is also touted as a possible alternative to highcost hydrocarbon and CO2 gases in certain circumstances or locations where water is scarce(6–10). Moore et al(11) suggest that in an air injection process in lightoil reservoirs, both oxygen addition and bond scission reactions take place. Oxygen addition reactions are believed to occur at temperatures between 100 °C and 150 °C. These reactions are characterized by heavier oxygenated hydrocarbon products. Bond scission reactions for light oils typically occur at temperatures in the 150 to 300 °C and the 350 to 700 °C range. These reactions produce carbon oxides, water (steam) and heat, which contribute significantly towards mobilizing oil.

In nmr spectroscopy involving organic substrates, one often has a situation in which there is a dominant species in rapid equilibrium with one or more minor components. In general, one knows, a priori, neither the population of these minor components nor the rate constants involved in the equilibrium process. In fact, from the physical appearance of these spectra, one cannot normally even deduce that such an equilibrium exists. For example, in cases involving 13C nmr spectroscopy, this minor component may not be observable under slow exchange nmr conditions because of signal-to-noise ratio problems and hence is referred to as a 'hidden' exchange partner. In this paper, we have analyzed the extent of nmr line broadening to be expected from a two-component system of this type, varying the populations, chemical shift separations, and intrinsic line widths. Thus, the presence of a 'hidden' partner can sometimes be detected by a characteristic, but often very subtle, peak broadening–resharpening sequence involving first of all the 'averaged' peak and finally the peak of the dominant component, these peaks being virtually identical in area and very similar in chemical shift so that one is not easily alerted. Assuming there is some experimental line broadening, equations developed in this paper, together with chemical shift estimates for this 'hidden' partner, allow one to quickly estimate both the amount of the minor partner and the rate constant involved. Three 'real life' situations are subsequently analyzed.

Low temperature oxidation (LTO) of hydrocarbon liquids generally results in a more viscous end product; this has clearly been shown in the literature of the past 30 years. However, under the right conditions, LTO can be used to achieve viscosity reduction in heavy oils. The In Situ Combustion Group at the University of Calgary conceived of a two-stage LTO process whereby oil is contacted with air, first at low, then at elevated, temperatures. The first, low temperature, step incorporates oxygen into some of the hydrocarbons, yielding labile bonds that should break at lower-than-usual temperatures. Once these free radicals are formed, the second step promotes bond cleavage at higher temperatures, resulting in shorter chain hydrocarbons. In a field situation, this process would be analogous to first injecting air into a formation at low temperature, then starting a steam soak or steam flood. Experimental runs carried out on Athabasca bitumen examined the effects of oxygen partial pressure, temperature, reaction time, and the presence of rock and brine. On completion of each experiment, the gas composition was determined using gas chromatography, water acidity (pH) was measured, and the hydrocarbon products were analysed for coke and asphaltenes contents, viscosity, and density. Some instances of viscosity reduction have been observed; these are linked to lower oxygen partial pressures, higher second stage temperatures and longer run times. This paper discusses the experimental work, and estimates the optimum conditions for successful viscosity reduction of a given heavy oil. Introduction Heavy oil and oil sands are important hydrocarbon resources that total over 10 trillion barrels, nearly three times the conventional oil in place in the world. The oil sands of Alberta alone contain over two trillion barrels of oil. In Canada, approximately 20﹪ of oil production is from heavy oil and oil sand resources(1). The application of thermal energy to increase heavy oil recovery has become more popular as conventional reserves decline. Steam injection accounts for the majority of the thermal recovery projects currently in operation; however in situ combustion offers many theoretical advantages if the operational characteristics of the process are incorporated in the design and operation of the field project. A major difficulty encountered in operating in situ combustion processes is low temperature oxidation (LTO), which involves oxygen addition reactions that occur at temperatures lower than 300 °CDATA [C. Typically, the byproducts of these reactions are oxidized hydrocarbons that have an increased polarity. This makes them more viscous, and thus detrimental to the in situ combustion process. Because of the major impact that LTO can have on the performance of an in situ project, a significant number of investigations have been carried out on the nature and effect of LTO reactions(2-27). In some circumstances, however, it may be beneficial to subject oil to LTO. The experimental results of Cram and Redford showed that air/steam combinations can provide better recovery rates and better thermal efficiencies than steam alone, at comparable volumes of steam injected, when the process is carried out in the low temperature oxidation region((28). It is believed that energy generation by the exothermic oxidation reactions is a significant factor in the LTO process.

This research is aimed at providing a better understanding of the oxidation behaviour of fractions of crude oil, and to then develop an approach to improve ignition for air injection processes. In this research, Thermogravimetric and Differential Thermal Analysis (TG/DTA) techniques were used to investigate oxidation behaviour using thermal fingerprinting effects on pure paraffin samples and mixtures of pure components with crude oil. The results demonstrated that each paraffin sample shows different oxidation behaviours at low temperatures and high temperatures. The fractions lighter than C16 distill before they reach a temperature where oxidation reactions are significant. Only low temperature exothermic activities are apparent for the fractions between C16 and C26. The heavier fractions show both low and high temperature exothermic activities. The lower molecular weight samples show lower onset temperatures for oxidation reactions. With increasing molecular weight, the exothermic peak temperatures both in the low and high temperature regions shift to higher temperatures and increased energy release. When low activity Oil B and the more reactive Oil C were mixed with a small amount of paraffin sample heavier than C26, both crude oils showed intensified low temperature oxidation behaviour, with a greater magnitude of heat evolution. The addition of heavier paraffins offers the potential to accelerate reactions and improve ignition. Introduction High Pressure Air Injection (HPAI) has been proven as a potential and viable process for improving oil recovery from several light oil reservoirs. When air is injected into an oil reservoir, the oxygen contained in the air can potentially react with the oil in place by various oxidation reaction schemes. Success of such a process depends mainly on the crude oil properties and rock properties, as well as operating conditions. The oxidation behaviour and the conditions typically favouring auto-ignition of crude oils are of the utmost importance for light oil air injection. However, because of the low initial temperature of many of the formations, and the poor reactivity of some crude oils, the magnitude of timedelay is often so great that spontaneous ignition is not economically attractive. Chemical ignition is one of the options to improve ignition(1, 2). Unfortunately, little research has been documented. The potential for using thermal analysis techniques to investigate oxidation behaviour of crude oils during combustion has been realized. Thermal analysis techniques include Thermogravimetric (TG) and Differential Thermal Analysis techniques (DTA) or Differential Scanning Calorimetry (DSC). In TG, a small amount of a sample of crude oil, with or without sand, is heated in the presence of flowing air and the change in weight of the sample is recorded as a function of temperature. In DTA or DSC, the difference in temperature or energy input/output during hemical or physical transitions based on the differences between the sample and a reference material is recorded as a function oftemperature or time.

The undersigned certify that they have read, and recommend to the Faculty of Graduate Studies for acceptance, a thesis entitled "In-Situ Upgrading of Heavy Oils by Low-Temperature Oxidation in the Presence of Caustic Additives" submitted by Gordon C. Wichert in partial fulfilment of the requirements for the degree Master of Science.