Low-Temperature Oxidation Kinetic Parameters for In-Situ Combustion Numerical Simulation

Abstract

Abstract 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.