Study of the Ignition Characteristics of Light Fractions of Crude Oil and Their Surrogate Fuels under a Range of Low-to-Medium Temperatures

Abstract

To improve the self-ignition capability of oil reservoirs and build a detailed reaction kinetics mechanism of in situ combustion (ISC), ignition and reaction characteristics of light fractions of crude oil (boiling point of <100 °C, 100–125 °C, 125–150 °C, 150–175 °C, 175–200 °C, and 200–225 °C) were investigated on a rapid compression machine at compressed pressures of 20 bar and a compressed temperature range of 660–900 K, with a stoichiometric ratio of 1.0. According to our analysis with a gas chromatography–mass spectrometry instrument (GC-MS), cyclohexane, methyl-cyclohexane, p-xylene, and mesitylene were selected as surrogate fuels and were tested under the same conditions on a rapid compression machine (RCM). The experimental results show that three groups of light fractions, <100 °C, 100–125 °C, and 175–200 °C, display strong reactions at low and high temperatures and negative temperature coefficient (NTC) behavior. These phenomena imply that these reactive components can be used as possible promoters to accelerate the development of an ISC project and to improve the reaction speed of the entire process. Two groups of 125–150 °C and 200–225 °C fractions are difficult to ignite in the low-to-medium temperature range under the compressed pressure of 20 bar, but they can be ignited at relatively higher top dead center (TDC) temperature ranges under the compressed pressure of 30 bar. Moreover, the logarithm of ignition delays and the reciprocal temperature clearly show a linear relationship, meaning that the reactivity of these two groups is poor. The results obtained with these surrogate fuels match well with the experimental results of each light fraction.