Abstract:

It is necessary to improve development efficiency of heavy oil reservoirs in the late stage of steam flooding. In this paper, considering the application of the technology of carbon capture, utilization and storage, and enhanced oil recovery （CCUS-EOR）, and taking the J6 block of Karamay oilfield as an example, four components of heavy oil were analyzed before and after CO₂ treatment, and the changes in saturation pressure, expansion coefficient, viscosity, and density were tested to investigate the regulation of CO₂ on physical properties of heavy oil. Parallel core physical simulation experiments were performed to understand the performance of CO₂-assisted steam flooding in improving oil recovery. The results show that the viscosity of heavy oil is mainly affected by the contents of resin and asphaltene. As the volume of CO₂ dissolved in heavy oil increases, the saturation pressure rises from 2.08 MPa to 11.11 MPa, and the expansion coefficient shows an upward trend, with an increase of 7.6%; meanwhile, the viscosity and density of the heavy oil decrease by 30.5% and 3.5%, respectively. This indicates that CO₂ can effectively improve the physical properties of heavy oil by optimizing the expansion coefficient, viscosity, and density while increasing the saturation pressure. In addition, the application of CO₂-assisted steam flooding enables the recovery of heavy oil to increase from 38.55% to 46.46% under the effect of CO₂ dissolution for viscosity reduction and demulsification, representing an increase of 7.91% compared to pure steam flooding. This study provides a theoretical and experimental basis for the application of CO₂-assisted steam flooding in enhancing the recovery of heavy oil, offering insights for similar heavy oil reservoirs.

Key words: J6 block of Karamay oilfield, heavy oil reservoir, CO₂, steam flooding, enhanced oil recovery, regulation of physical property, four-component analysis, physical simulation