Thermal Cracking of Heavy-Oil/ Mineral Matrix Systems

Abstract

Summary At temperatures and pressures encountered during thermal recovery, chemical reactions involving oil, possibly water, and mineral matrix may lead to significant changes in composition of the phases. This work focuses on thermal alteration of four crude oils with different geochemical compositions. The tests were performed in an autoclave at 350°C [660°F] for 200 hours. The oil was in the presence of water and a mineral matrix representative of reservoir rocks. The formation of significant amounts of insoluble organic material was observed in all tests. Gaseous hydrocarbons (mainly methane) formed by pyrolysis. CO2 evolution depended on oil and matrix compositions; moreover, water was found to be a reactant in the formation of oxygen-containing components. For crude oils investigated, the oil phase was significantly enriched in lighter hydrocarbons (mainly in saturates). However, aromatic content was less affected by the thermal treatment. On the other hand, asphaltenes and, to a lesser extent, resins were the main precursors of insoluble material. These results provide new insight on mechanisms of the cracking reactions involved in thermal recovery processes.