Molecular dynamics of quantitative evaluation of confined fluid behavior in nanopores media and the influencing mechanism: Pore size and pore geometry

Zhao, Rixin; Xue, Haitao; Lu, Shuangfang; Greenwell, H. Chris; Xu, Yaohui; He, Taohua; Erastova, Valentina

Abstract

Understanding the potential mechanisms of reservoir fluid storage, transport, and oil recovery in shale matrices requires an accurate and quantitative evaluation of the fluid behavior and phase state characteristics of the confined fluid in nanopores as well as the elucidation of the mechanisms within complex pore structures. The research to date has preliminary focused on the fluid behavior and its influencing factors within a single nanopore morphology, with limited attention of the role of pore structures in controlling fluid behavior and a lack of quantitative methods for characterizing the phase state of fluids. To address this gap, we utilize molecular dynamics simulations to examine the phase state characteristics of confined fluids across various pore sizes and geometries, revealing the mechanisms by which wall boundary conditions influence fluid behavior. We use the simulation results to validate the accuracy and applicability of the quantitative characterization model for fluid phase state properties. Our findings show that the phase state features of fluids differ significantly between slit-like and cylindrical pores, with lower absorption limits in pore sizes of 2.8 and 7 nm, respectively. Based on pore sizes, we identified three regions of confined fluid phases and determined that the influence of the adsorbed state fraction on fluid phase state cannot be ignored for pores smaller than approximately 85 nm. Additionally, cylindrical pores interact with the internal fluids about 1.8 times stronger than slit-like pores.

Citation

Zhao, R., Xue, H., Lu, S., Greenwell, H. C., Xu, Y., He, T., & Erastova, V. (2024). Molecular dynamics of quantitative evaluation of confined fluid behavior in nanopores media and the influencing mechanism: Pore size and pore geometry. Physics of Fluids, 36(9), Article 092027. https://doi.org/10.1063/5.0226864

• Journal Article Type: Article
• Acceptance Date: Sep 5, 2024
• Online Publication Date: Sep 25, 2024
• Publication Date: Sep 1, 2024
• Deposit Date: Nov 4, 2024
• Publicly Available Date: Nov 4, 2024
• Journal: Physics of Fluids
• Print ISSN: 1070-6631
• Electronic ISSN: 1089-7666
• Publisher: American Institute of Physics
• Peer Reviewed: Peer Reviewed
• Volume: 36
• Issue: 9
• Article Number: 092027
• DOI: https://doi.org/10.1063/5.0226864
• Public URL: https://durham-repository.worktribe.com/output/3081110