The Role of Thermal Analysis Techniques in the ln-Situ Combustion Process

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Abstract
Summary: Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) studies were conducted on two Lloydminster region, Canada, heavy-oil cores, extracted oil, and mineral matter. Fig. 1 is a general schematic of the thermal process, such as evaporation, distillation, thermolysis, low-temperature oxidation (LTO), thermal cracking, combustion, coking, polymerization, and thermal alteration of mineral matter. Four core samples and their extracted oils were examined for propensity of coke formation under helium atmosphere. A two- or three-fold increase in the fuel content was observed in the cores compared with the extracted oil. This indicates a selective and significant contribution of the minerals to the coke-forming mechanism. The data from DSC and TGA experiments were used to calculate enthalpy values and ignition temperatures. These data suggest that heat generated by LTO reactions is significant during in-situ combustion. With the exception of Sand D, the thermal alteration of the mineral matter at 600 and 900°C [1,112 and 1,652°F] was significant. In Sands A and B, the percentage of fine particles, <2 μm, doubled at 600 and 900°C [1,112 and 1,652 °F] compared with that at 100°C [212 °F], Although kaolinite constituted between 15 and 75% of the fine particles in all cases, it was not detected in appreciable concentrations when the sand was heated at 600 or 900°C [1,112 or 1,652°F]. These results indicate that potential problems during oil production could arise from the migration of fine particles. The mineral-analysis data obtained from these core samples suggest that swelling of clays during wet combustion may not be sufficient to have a deleterious effect on air/water injectivity or oil production. The results from TGA/DSC experiments are complementary to those from combustion-tube tests and provide the kinetic, thermal, and mineralogical data required for numerical simulation, planning, and design of an in-situ combustion project.