Petroleum Reservoir Evaluation and Development ›› 2022, Vol. 12 ›› Issue (5): 794-802.doi: 10.13809/j.cnki.cn32-1825/te.2022.05.011

• Methodological and Theory • Previous Articles     Next Articles

EOR mechanism of viscosity reducer-CO2 combined flooding in heavy oil reservoir with low permeability

GUO Deming1(),PAN Yi1(),SUN Yang1,CHAO Zhongtang2,LI Xiaonan2,CHENG Shisheng2   

  1. 1. Southwest Petroleum University, Chengdu, Sichuan 610500, China
    2. China Sinopec Jiangsu Oilfield Company, Yangzhou, Jiangsu 225009, China
  • Received:2021-08-13 Online:2022-10-26 Published:2022-09-27
  • Contact: PAN Yi;panyiswpu@126.


The implementation of CO2 flooding in heavy oil reservoirs with low-permeability is currently the main comprehensive utilization technology for enhanced oil recovery. However, due to the low viscosity and high mobility of CO2, CO2 flooding in heavy oil reservoirs is prone to premature gas channeling. For this reason, the feasibility of low permeability heavy oil reservoirs with CO2-viscosity reducer to reduce viscosity and improve mobility ratio has been explored, and the mechanism of the combined flooding of CO2 and water-soluble viscosity reducer for low-permeability heavy oil reservoirs to EOR is obtained. The results show that the KD-45A water-soluble viscosity reducer can only emulsify the surface of crude oil to reduce the viscosity without external stirring. The viscosity reduction effect is poor, but the viscosity reducer slug can improve the mobility ratio caused by viscosity differences, which can effectively control the CO2 rushing along the airflow channel. The O/W-shaped emulsion transition zone formed by the emulsification of the water-soluble viscosity reducer has a viscosity close to the water phase, which can prevent the fingering of the water-soluble viscosity reducer, so that the viscosity reducer slug has a more obvious control and displacement effect on CO2, and the swept area of CO2 is larger. The dissolution of CO2 in the viscosity reducer will reduce the interfacial tension of the CO2-viscosity reducer system, which can give full play to the synergy between the two displacement effect. The formation of carbonized water after CO2 dissolves in the viscosity reducer can greatly reduce the influence of gravity and viscosity differences on the swept area, forming a relatively stable and continuous displacement interface. The displacement mechanisms of the combined flooding system are synergistic and superimposed, which can significantly improve the recovery rate of heavy oil.

Key words: low permeability reservoir, heavy oil, EOR, water-soluble viscosity reducer, CO2 compound flooding

CLC Number: 

  • TE357