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© 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.

Abstract

CO2 flooding plays a crucial role in enhancing oil recovery and achieving carbon reduction targets, particularly in unconventional reservoirs with complex pore structures. The phase behavior of CO2 and hydrocarbons at different scales significantly affects oil recovery efficiency, yet its underlying mechanisms remain insufficiently understood. This study improves existing thermodynamic models by introducing Helmholtz free energy as a convergence criterion and incorporating adsorption effects in micro- and nano-scale pores. This study refines existing thermodynamic models by incorporating Helmholtz free energy as a convergence criterion, offering a more accurate representation of confined phase behavior. Unlike conventional Gibbs free energy-based models, this approach effectively accounts for confinement-induced deviations in phase equilibrium, ensuring improved predictive accuracy for nanoscale reservoirs. Additionally, adsorption effects in micro- and nano-scale pores are explicitly integrated to enhance model reliability. A multi-scale thermodynamic model for CO2-hydrocarbon systems is developed and validated through physical simulations. Key findings indicate that as the scale decreases from bulk to 10 nm, the bubble point pressure shows a deviation of 5% to 23%, while the density of confined fluids increases by approximately 2%. The results also reveal that smaller pores restrict gas expansion, leading to an enhanced CO2 solubility effect and stronger phase mixing behavior. Through phase diagram analysis, density expansion, multi-stage contact, and differential separation simulations, we further clarify how confinement influences CO2 injection efficiency. These findings provide new insights into phase behavior changes in confined porous media, improving the accuracy of CO2 flooding predictions. The proposed model offers a more precise framework for evaluating phase transitions in unconventional reservoirs, aiding in the optimization of CO2-based enhanced oil recovery strategies.

Details

Title
Computational Modeling and Experimental Investigation of CO2-Hydrocarbon System Within Cross-Scale Porous Media
Author
Chen, Feiyu 1   VIAFID ORCID Logo  ; Sun, Linghui 2 ; Bowen, Li 1   VIAFID ORCID Logo  ; Pan, Xiuxiu 1 ; Jiang, Boyu 1 ; Huo, Xu 1   VIAFID ORCID Logo  ; Zhang, Zhirong 1 ; Feng, Chun 3 

 University of Chinese Academy of Sciences, Beijing 100049, China; [email protected] (F.C.); [email protected] (B.L.); [email protected] (X.P.); [email protected] (B.J.); [email protected] (X.H.); [email protected] (Z.Z.); Institute of Porous Flow and Fluid Mechanics, Chinese Academy of Sciences, Langfang 065007, China 
 University of Chinese Academy of Sciences, Beijing 100049, China; [email protected] (F.C.); [email protected] (B.L.); [email protected] (X.P.); [email protected] (B.J.); [email protected] (X.H.); [email protected] (Z.Z.); Institute of Porous Flow and Fluid Mechanics, Chinese Academy of Sciences, Langfang 065007, China; Research Institute of Petroleum Exploration & Development, Beijing 100083, China; [email protected]; State Key Laboratory of Enhanced Oil & Gas Recovery, Beijing 100083, China 
 Research Institute of Petroleum Exploration & Development, Beijing 100083, China; [email protected] 
First page
277
Publication year
2025
Publication date
2025
Publisher
MDPI AG
e-ISSN
14203049
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
3159581429
Copyright
© 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.