In-Situ Combustion Experience in Heavy Oil Carbonate

Abstract In-situ Combustion (ISC) has the potential to be the most effective enhanced oil recovery (EOR) method for heavy oil recovery. However, it is considered a high risk failure rate process since it is hard to predict the combustion reactions between complex crude oil and heterogeneous rock matrices. If the reservoir rock is reactive, like carbonates, the risk factor of ISC increases. This research studies the ISC performance for different rock matrices found in Alberta, Canada. The reaction kinetics analyses were carried out by Thermogravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC) on bulk oil, and its Saturates, Aromatics, Resins, and Asphaltenes (SARA) fractions at a constant heating rate (20°C/min). To better understand the combustion behavior of bulk oil, pseudo blends of SARA fractions were prepared and systematic TGA/DSC tests were run on these blends. Furthermore, the impact of reactive porous media on fuel formation mechanism was investigated by using clays and carbonates. The reaction kinetic analyses on bulk oil and SARA fractions suggest that asphaltenes, resins, and aromatics fractions go into endothermic reactions at elevated temperatures, still the asphaltenes fraction generates the greatest amount of heat. The two-component interaction of asphaltenes with other fractions produces less heat than the combustion of asphaltenes alone. The three- component pseudo blend prepared by mixing asphaltenes-resins-aromatics produced the highest amount of heat and we believe that in bulk oil combustion saturates by acting as an ignitor provides the necessary heat to initiate the reactions among aromatics, resins, and asphaltenes fractions. Moreover, the effect of reactive porous media on reaction kinetics of bulk oil were investigated at a constant heating rate (20°C/min). Carbonates and clays were used. Since the clays act like a catalyst, heat generation was observed lower with clays than carbonates and carbonates required more heat for successful combustion. While the heating rates during in-situ combustion are generated naturally, in TGA/DSC tests, a constant heating rate is applied. In this study, we used 20°C/min as the heating rate. If the same heating rate during ISC cannot be reached, then, the heat generation cannot be as high as reported in this manuscript. Thus, it is important to extend the systematic TGA/DSC analyses presented in this paper. Tests should be conducted at varying heating rates on different oil samples and on their SARA fractions.