Investigation of Polymer-Assisted CO2 Flooding to Enhance Oil Recovery in Low-Permeability Reservoirs

Xin Chen; Yiqiang Li; Xiaoguang Sun; Zheyu Liu; Jianbin Liu; Shun Liu

doi:10.3390/polym15193886

Investigation of Polymer-Assisted CO₂ Flooding to Enhance Oil Recovery in Low-Permeability Reservoirs

Polymers (Basel). 2023 Sep 26;15(19):3886. doi: 10.3390/polym15193886.

Authors

Xin Chen^{1

2

3}, Yiqiang Li⁴, Xiaoguang Sun⁵, Zheyu Liu⁴, Jianbin Liu^{1

2

3}, Shun Liu^{1

2

3}

Affiliations

¹ College of Petroleum Engineering, Xi'an Shiyou University, Xi'an 710065, China.
² Shaanxi Key Laboratory of Advanced Stimulation Technology for Oil & Gas Reservoirs, Xi'an 710065, China.
³ Ministry of Education Engineering Research Center of Development and Management for Low to Ultra-Low Permeability Oil & Gas Reservoirs in West China, Xi'an 710065, China.
⁴ State Key Laboratory of Oil and Gas Resources and Exploration and College of Petroleum Engineering, China University of Petroleum (Beijing), Beijing 102249, China.
⁵ PetroChina Coalbed Methane Company Limited, Beijing 100028, China.

Abstract

CO₂ flooding is a favorable technical means for the efficient development of low-permeability reservoirs, and it can also contribute to the realization of net-zero CO₂ emissions. However, due to the unfavorable viscosity ratio and gravity overriding effect, CO₂ channeling will inevitably occur, seriously affecting its storage and displacement effects. This paper conducts a systematic study on the application of polymer-assisted CO₂ flooding in low-permeability reservoirs. Firstly, the polymer agent suitable for low-permeability reservoirs is optimized through the viscosity-increasing, rheological, and temperature- and salt-resistant properties of the solution. Then, the injectivity performance, resistance-increasing ability, and profile-improving effect of the polymer solution were evaluated through core experiments, and the optimum concentration was optimized. Finally, the enhanced oil recovery (EOR) effects of polymer-assisted and water-assisted CO₂ flooding were compared. The results show that the temperature-resistant polymer surfactant (TRPS) has a certain viscosity-increasing performance, good temperature resistance performance, and can react with CO₂ to increase the solution viscosity significantly. Meanwhile, TRPS has good injection performance and resistance-increasing effect. The resistance increasing factor (η and η') of TRPS-assisted CO₂ flooding increases with increased permeability, the concentration of TRPS solution, and injection rounds. Considering η' and the profile improvement effect comprehensively, the application concentration of TRPS should be 1000 mg/L. The EOR effect of TRPS-assisted CO₂ flooding is 8.21% higher than that of water-assisted CO₂ flooding. The main effective period is in the first and second rounds, and the best injection round is three. The research content of this paper can provide data support for the field application of polymer-assisted CO₂ flooding in low-permeability reservoirs.

Keywords: CO2 responsive; EOR; injectivity; polymer-assisted CO2 flooding; profile control; resistance increasing.

Abstract

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