580
Energy & Fuels 1998, 12, 580-588
Kinetic Analysis of Oxidation Behavior of Crude Oil SARA Constituents Mustafa Versan Ko¨k,* O ¨ zgen Karacan, and Reha Pamir Department of Petroleum and Natural Gas Engineering, Middle East Technical University, 06531 Ankara, Turkey Received September 22, 1997
In this research two Turkish crude oils (medium and heavy) were separated into their saturate, aromatic, resin, and asphaltene (SARA) fractions by column chromatographic techniques, and combustion experiments were carried out on whole crude oils and their fractions by thermogravimentric analysis (TD/DTG) under air atmosphere at a 10 °C/min heating rate. Investigation of SARA fractions allows quantitative determination of the temperature intervals at which evaporation, oxidation, and combustion effects operate for each fraction. In the course of this research, the kinetic parameters of SARA fractions were determined according to the Coats and Redfern technique. By using the data and findings of this research, one can take advantage of studying the kinetics of SARA fractions instead of those of the complex whole oil for modeling of the overall process to accurately predict combustion.
Introduction In situ combustion technology is considered to be an efficient process not only for heavy oil reserves but also for depleted light and medium oil bearing reservoirs. In situ combustion is a method of thermal oil recovery in which the energy is generated in the reservoir, creating a combustion front that is propagated through the reservoir by continuous air injection. The success of this process depends mainly on the crude oil and rock properties as well as operational conditions. While much work has been carried out to study the thermal and fluid dynamics aspects of the in situ combustion process, the chemical reaction kinetics remain the least investigated aspects of underground combustion. Limited kinetic data are available in the petroleum literature on the rates and nature of the partial oxidation reactions and the high-temperature combustion reactions of crude oils and their saturate, aromatic, resin, and asphaltene (SARA) fractions. Adequate and sufficient kinetic data are necessary for any reliable performance predictions by mathematical and numerical models because of the great deal of coupling between the heat transfer, mass transfer, and chemical reaction phenomena taking place in the in situ combustion process. Verkocy and Kamal1 performed thermogravimetric analysis (TG/DTG) experiments on heavy oils and cores. They have estimated kinetic and thermochemical data for low-temperature oxidation, cracking, coking, and combustion reaction in cores and oils. Yoshiki and Philips2 used DTA and TG/DTG at high temperatures and pressures and concluded that both low- and hightemperature oxidation rates increased with pressure as (1) Verkocy, J.; Kamal, N. J. J. Can. Pet. Technol. 1986, 47-57. (2) Yoshiki, K. S.; Phillips, C. R. Fuel 1985, 64, 1591-1596.
Table 1. Properties of Crude Oils property
Garzan crude oil
B.Raman crude oil
°API gravity viscosity (cP)
