Upgrading of crude oil via in situ combustion

Crude oil upgrading is of major economic importance. Heavy crude oils exist in large quantities in the western hemisphere, but are difficult to produce and transport because of their high viscosity. Some crude oils contain compounds such as sulfur and/or heavy metals causing additional refining problems and costs. In situ upgrading could be a very beneficial process for leaving the unwanted elements in the reservoir and increasing API gravity. u combustion has long been used as an enhanced oil recovery method. For heavy oils, numerous field observations have shown upgrading of 2° to 6° API for heavy oils undergoing combustion [Ramey, H.J., Jr., Stamp, V.V., Pebdani, F.N., 1992. Case History of South Belridge, California, In Situ Combustion Oil Recovery, SPE 24200, Proc. 9th SPE/DOE EOR Symposium, Tulsa, April 21–24.]. During in situ combustion of heavy oils, temperatures of up to 700 °C can be observed at the combustion front. aper describes the changes caused by the various reactions occurring during combustion with emphasis on the upgrading potential for various oil types. We will first describe the in situ combustion process with an examination of the temperature changes and chemical reactions that can either upgrade or degrade the oil in terms of its API gravity and viscosity. In the second part, we present results from three combustion tube runs aimed at sulfur removal. We will end by discussing possible in situ upgrading strategies using combinations of in situ combustion and other improved recovery methods.