The principal objective of this study was to provide low temperature oxidation (L.T.O.) reaction models which are suitable for use in numerical simulators of in situ combustion for bitumen and heavy oil reservoirs. A systematic study was carried out to investigate the L.T.O. reactions of the liquid phase components of bitumen and heavy oils. Athabasca bitumen, free of water and minerals, was oxidized using a laboratory stirred semiflow batch reactor. Kinetic studies were carried out in the 60C to 150C temperature range and at oxygen partial pressure of 50 kPa to 2233 kPa. The total pressures partial pressure of 50 kPa to 2233 kPa. The total pressures applied in the reactor ranged from 2190 kPa to 4415 kPa. Experimental data were collected in the kinetic subregime. Reactor product gas was analyzed using a gas chromatograph and the liquid product gas was analyzed using a gas chromatograph and the liquid phase oxidation product was separated into six main components phase oxidation product was separated into six main components (lumped components): saturates, aromatics, resins I, resins II, asphaltenes and coke. Kinetic models are established for the liquid phase reaction components involved in the L.T.O. reactions of a mixture of complex hydrocarbons. Based on the experimental kinetic data, two main types of reaction models are proposed. These are:A non-steady state kinetic model to represent the overall rate ofoxygen consumption.Four non-steady multiresponse kinetic models representing theoxidation reactions of the liquid phase components. Proposed models were found statistically adequate and are Proposed models were found statistically adequate and are suitable for use in numerical simulators. Introduction Several articles have been published describing in situ combustion processes and giving detailed results of laboratory and field experiments. The methods that have received extensive studies are dry forward combustion, wet forward combustion and reverse combustion. It is documented that the performance of these processes depends on the L.T.O. reactions accompanying the in situ processes depends on the L.T.O. reactions accompanying the in situ combustion operations. Furthermore, results of published laboratory and field studies indicate that more meaningful analysis of combustion data cannot be made until the L.T.O. reaction kinetics are studied and the reaction mechanism elucidated. Consequently, a reliable numerical simulator for performance prediction or for evaluation of the in situ combustion processes must model adequately the L.T.O. reactions. The simulator should include a L.T.O. reaction model able to do the following:represent the overall rates of oxygen consumption;represent the major reaction components and products in the liquidphase and their individual rates of transformations. Most studies reported in the literature have considered only the overall rates of oxygen consumption for the L.T.O. reactions of crude oils. Summaries of these studies have been published. The kinetics data presented in this study were measured on bitumen from the Athabasca oil sands formation. oil sands were obtained from the Suncor mine in Fort McMurray, Alberta. The bitumen was extracted from the sand using toluene as a solvent. Table 1 summarizes the properties and composition of the original bitumen sample. Efforts were directed, in this study, towards building mechanistic type models rather than empirical ones. The intricate chemical nature of the oil sands bitumen suggests immediately that the reaction mechanisms involved in L.T.O. reactions are many and complex.

The prime purpose of this work was to provide thermal cracking reaction models which can be incorporated into numerical simulators of thermal recovery processes for the Athabasca Oil Sands. processes for the Athabasca Oil Sands. Athabasca bitumen, free of water and minerals, was thermally cracked at constant temperatures in a closed system under an inert atmosphere. The products of cracking were separated into six pseudo products of cracking were separated into six pseudo components: coke, asphaltenes, heavy oils, middle oils, light oils, and gases. Experimental runs were made over the temperature range from 303 deg. C to 452 deg. C. Three series of runs were made at 360 deg. C, 397 deg. C, and 422 deg. C in which the reactions were terminated at various degrees of cracking. For these runs, reaction time versus product concentration curves were obtained for the above six pseudo components. Several pseudo reaction mechanisms are proposed to simulate the experimental results. The reaction rate constants were represented by an Arrehnius type expression, the activation energies and corresponding frequency factors were determined for each reaction mechanism proposed. Introduction Recently, the use of numerical simulators to predict the performance of steamfloods has become predict the performance of steamfloods has become a common practice. As far as the numerical simulation of in situ combustion is concerned, a number of simulators have been developed and many of them have been successful in predicting the fluid flow and the temperature profiles along with the production history. The model presented by Crookston et al. incorporates most of the physical and chemical phemonema including the fluid flow, the phase phemonema including the fluid flow, the phase behavior and oxidation and thermal cracking reactions. Although it is claimed that the model can be applied to any thermal recovery process, it has not yet been thoroughly tested. In the case of the in situ combustion process, the fuel which is a coke-like material is deposited on the reservoir rock by a combination of gas stripping, vaporization and thermal cracking. The major operational cost of the in situ combustion process is for compressing air. The quantity of process is for compressing air. The quantity of air required depends on the amount of fuel available underground, thus the quantitative prediction of the extent of thermal cracking is directly related to the economic evaluation of an in situ combustion project. Thermal cracking reactions also play an important role in fluid flow in the reservoir because the flowing oils do not have the same fluid properties as the original oil in place. Thermal cracking reactions are also important for the design of bitumen upgrading facilities. Although rather extensive studies have been made of thermal cracking reactions involving Athabasca bitumen, most studies reported so far are concerned with the chemical and physical properties of the cracked products. In this study emphasis was placed on the collection of experimental data and the development of a prediction model of the thermal cracking reactions. EXPERIMENTAL PROGRAM A. Equipment The experimental apparatus used in this study is schematically shown in Figure 1. The reaction vessel was placed in an electrically heated furnace which was equipped with a stirrer in order to obtain an even temperature distribution within the furnace. The temperature of the bitumen sample was measured with a 1.59 mm O.D. stainless steel sheathed C/A K type thermocouple. The pressure of the system was monitored by a pressure transducer. Vacuum and helium gas lines were provided as shown in Figure 1 to achieve an inert gas atmosphere in the reaction vessel at the beginning of each experimental run.

The objective of this work was to measure the effect of dissolved carbon dioxide, methane and nitrogen on the viscosity of Athabasca bitumen. To accomplish these measurements, an apparatus was designed and built. The experimental results of gas-saturated bitumen show that carbon dioxide dramatically reduces the viscosity of bitumen particularly at low temperatures. The viscosity reduces with increasing pressure and temperature. The effect of pressure on lowering the viscosity is less prominent beyond a temperature of about 100 °C. The effect of dissolved methane on the viscosity is less dramatic but still significant. Dissolved nitrogen produced a negligible change in Viscosity. Introduction The viscosity of bitumen is a physical property, the knowledge of which is essential to solving the problems associated with the development of in-situ recovery of oil from oil sands deposits. The movement of high-viscosity crude would require extremely high and impractical pressure gradients. A viscosity reduction step is thus essential in transporting the bitumen. It has been well established that at reservoir pressures. dissolved gases have a substantial effect on the viscosity of crude oil. The most complete body of data on the effect of dissolved gases on the viscosity of crude oils is contained in the work published by Simon and Graue(1). However, their work was limited to crude oils with specific gravities of less than 0.95. For Athabasca bitumen with specific gravity greater than 1.00. the only substantial volume of data that has been published is that of Ward and Clark(2). Recently. Dealy(3) reported additional data on the rheological properties of bitumen. However, no data have been reported on the effect of dissolved gases on the viscosity of oil sand bitumen. Hence, the objective of this work was to measure the effect of dissolved nitrogen, carbon dioxide and methane on the viscosity of Athabasca bitumen. To accomplish this objective, an apparatus was designed and built to saturate the bitumen with gas and measure the resultant viscosity. Experimental Apparatus A schematic flow diagram of the apparatus is shown in Figure 1. The pump draws the bitumen along with its dissolved gas from the base of the mixing cell. The liquid is then pumped through a recycle line and a circulation line. The recycle line is used to supply bitumen to the top of the mixing cell, where a large surface area is provided for gas-liquid contact. The circulation line passes through the densitometer and the viscometer before returning to the-mixing cell. The division of flow in the two lines is controlled by means of the valve in the circulation line. The entire apparatus is placed in an electrically heated air bath to achieve a uniform temperature. A Contraves Model DC 44 viscometer, consisting of a torque meter and a driving motor, which was magnetically coupled to the measuring bob inside the flow-through cup, was used for viscosity measurements. The measuring cup was modified to reduce the hold-up volume of the viscometer. The viscometer calibration curves were supplied by the manufacturer.

Multiresponse kinetic models are established for the low-temperature oxidation (LTO) reactions of Athabasca oil sands bitumen. The models provide adequate description of the overall rate of oxygen consumption and of the reactions of the liquid phase bitumen components.The LTO models are suitable for use in the in sifu combustion numerical simulators of the oil sands. SCOPESeveral articles have been published describing in sifu combustion techniques and giving detailed results of laboratory and field experiments. These papers include: Alexander et al. (1962), Bennion et al. (1977), Burger and Sahuquet (1973). Cram and Redford (1977), Dietz (1 970), Dietz and Weidjema (1 968), Morse (1 976), Nelson and McNiels (1956), Showalter (1963), Smith and Perkins (1973), Reed et al. (1960), andWalter (1977). The performance of in situ combustion processes depends on the accompanying low-temperature oxidation (LTO) reactions (Alexander et al., 1962;Dabbous and Fulton, 1974;Burger and Sahuquet, 1973). Furthermore, results of published laboratory and field studies indicate that more meaningful analysis of combustion data cannot be made until the LTO reaction kinetics are studied and the reaction mechanisms elucidated. Consequently, a reliable numerical simulator of the in situ combustion processes must model adequately the LTO reactions. The simulator should include an LTO reaction model able to do the followCorrespondence concerning this paper should be addressed to K. 0. Adegbcsan, who is now with Esso Rcsourca Canada Ltd.

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