Combustion analysis of Camurlu crude oil by isoconversional method

Abstract

The Camurlu field in Southeast part of Turkey contains 380 MMbbl of heavy oil with 10–12° API. Due to very low oil recovery, different enhanced oil recovery techniques have been evaluated for this field. In-situ combustion has been eventually considered to increase oil production in this field. The fundamental purpose of this study was to experimentally understand whether in-situ combustion would be a promising way of increasing oil production from this field. We conducted this study within three essential steps. The first step included the determination of some physical and chemical properties of sand and oil used in the experiments. Later, within the second step, we prepared the sample with sand and oil within certain ratios for kinetics experiments which were for characterizing combustion properties of Camurlu oil. Then, kinetics and combustion experiments were carried out and analyzed through isoconversional methods. Eventually, we calculated the activation energies of the reactions that took place during the combustion experiments and developed the chemical reaction models that are a good representative of the experiments. We found that the low temperature oxidation reactions (LTO) were realized by a rapid increase in the oxygen uptake rate. Later, we also observed high temperature oxidation reactions (HTO) with a second rapid increase in the oxygen uptake rate. In LTO region, both oxygen addition and combustion reactions took place simultaneously. In order to differentiate between combustion reactions and oxygen addition reactions, produced carbon oxides were subtracted from oxygen uptake. It was also found that there was a negative temperature gradient region in low and high temperature oxidation reactions. We concluded that there was a stable zone for the chemical reactions and found the ignition temperature being around 400 ℃. Next, we developed the chemical reaction model that composed of four different and consecutive reactions that took place during the experiments. Based on the developed model, molecular weight of Coke 1 and molecular weight of Coke 2 were found to be 20.64 g and 13.8 g, respectively. Also, activation energies of each chemical step through gas measurements were estimated. Finally, this study, to the best of our knowledge, for the first time, experimentally investigates the combustion characteristics of Camurlu crude and developed the chemical reaction model for the in-situ combustion of this field, also the results from this study form fundamentals for further experimental work and a pilot study in the field.