Numerical simulation of low temperature oxidation reactions of Athabasca bitumen using sara fractions
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2007
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Abstract
In this thesis, Low Temperature Oxidation (LTO) reactions of the Athabasca bitumen were studied through numerical simulation and history matching of In Situ Combustion experiments operated under LTO conditions. A new kinetic model in terms of SARA fractions (Saturates, Aromatics , Resins and Asphaltenes) was presented (Model LTO 1) which was based on the four reaction model proposed by Jia et al. (2003). It was necessary to interpret this model in terms of SARA fractions to make it applicable for numerical simulation. Isothermal semi batch experiments for temperatures ranging from 60°C to 150°C (Adegbesan , 1982) were simulated in STARS (the commercial reservoir simulator developed by CMG) using this new Model LTO 1. Multiple variable analyses on the kinetic parameters of each reaction were performed , to match the experimental concentration profiles. The delay in coke formation observed from previous investigators (Adegbesan , 1982; Millour et al. , 1987) was included in the numerical model. The SARA concentration profiles reported by Adegbesan (1982) for different temperatures were matched with Model LTO 1 tuning the kinetic parameters individually for each temperature. It was not possible to match the concentration profiles for all temperatures when using a single set of kinetic parameters, which reflects the change in the oxidation reaction mechanism during liquid phase oxidation as the temperature increases. Simulation and history matching of the experimental results from a Ramped Temperature Oxidation (RTO) experiment operated under LTO conditions were performed. The heats of reaction generated by the Low Temperature Oxidation reactions were incorporated to the simulation. It was found that the Saturates Burning reaction does not occur under the temperature range of the RTO experiment (T <325 °C) . Modifications of Model LTO 1, based on the chemical nature of LTO, were made to match the results of Athabasca Test No. 44 . This led to an improved kinetic model (Model L TO 2) . Temperature profiles, coke yield , oxygen consumption, carbon oxides production , residual hydrocarbon and front velocity were reproduced with an experimental deviation of less than 15%. These results are acceptable considering that the complex liquid phase oxidation reactions of Athabasca bitumen are represented with a relatively simple set of reactions. The improved Model LTO 2 captures the main changes occurring in the bitumen due to oxidation reactions at low temperature conditions . This model can be readily incorporated into numerical simulations of In Situ Combustion to obtain a more realistic representation of this complex process. This study greatly contributes to the understanding of the Low Temperature Oxidation reactions of heavy oils and bitumens .
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Bibliography: p. 126-133
Some pages are in colour.
Some pages are in colour.
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Sequera Marin, B. M. (2007). Numerical simulation of low temperature oxidation reactions of Athabasca bitumen using sara fractions (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/1040