Insights into in-situ upgrading of bitumen in the hybrid of steam and combustion process: From experimental analysis aspects

Abstract

In situ combustion (ISC) has been evaluated as a follow up process in the steam injection process for heavy oil and bitumen recovery. Except for providing energy or heat to reduce bitumen viscosity, in situ upgrading of bitumen is another advantage of ISC process. In situ upgrading of bitumen through co-injection of steam and oxygen is evaluated in this work. Three different types of laboratory experiments, including one static thermal cracking experiment, one ramped temperature oxidation (RTO) experiment, and one combustion tube test, were performed to examine the produced oil properties and the potential of bitumen in situ upgrading. A comprehensive analysis of produced oil properties and gas composition was performed. Bitumen was significantly upgraded in the thermal cracking experiment at a temperature of 430 °C, in which Saturates fraction increased to 56%, while Resin and Asphaltene fractions reduced to 6.7% and 6.8%, respectively. The thermal cracking of Resin and Asphaltene contribute to the production of the light oil and gases, leading to the upgrading of the bitumen. Dynamic properties of produced oil were measured in the RTO and combustion tube test in terms of produced oil viscosity, density, boiling point temperature distribution, and produced oil compositions, etc. In the RTO test, the extent of bitumen upgrading is greater with the increase of temperature, further proving that the high temperature generated by the combustion front is able to effectively crack the bitumen. Furthermore, the lack of light hydrocarbon in the produced oil indicates light hydrocarbon participates in the high temperature oxidation reactions. Different from thermal cracking experiment and RTO test results, combustion tube test results indicated that the bitumen was slightly upgraded in late stage of the combustion tube test and most produced bitumen are similar with original bitumen. By examining the temperature distribution along the combustion tube, it is found that upgraded bitumen cannot be effectively displaced to the producer. This implies the limitation of in situ upgrading in the conventional in situ combustion process. Proper well configuration was recommended for the future field application of the hybrid steam and combustion process to achieve the high oil recovery factor and partial in situ upgrading of bitumen.