Isoconversional kinetic analysis of the combustion of heavy hydrocarbons

One method to access unconventional, heavy-oil resources is to apply in-situ combustion (ISC) to oxidize in place a small fraction of the hydrocarbon thereby providing heat to reduce oil viscosity and pressure that enhances recovery. ISC is also attractive because it provides the opportunity to upgrade oil in-situ by increasing the API gravity and decreasing, for instance, sulfur content. Experimental analysis of crude-oil oxidation kinetics provides parameters, such as activation energy, for modeling and optimization of ISC processes. The complex nature of petroleum as a mixture and multistep character of oxidation reactions complicates substantially the kinetic analysis of crude oil. Isoconversional techniques provide model-free methods for estimating activation energy and naturally deconvolve multi-step reactions. In this sense, they are superior to the conventional methods of analysis of crude oil oxidation kinetics. Isoconversional methods are also useful as a diagnostic tool to recognize the burning characteristics of different oils. Our work shows that different phenomena, such as "cool flames", can be identified by using isoconversional analysis. The combustion kinetics of three oil samples are reported adding to the knowledge base of crude-oil combustion and the applicability of isoconversional analysis to oil oxidation is tested experimentally. In addition synthetic examples are presented to show the diagnostic characteristics of the analysis.