Investigating fracture activation and CO2 migration in layered shale caprock: a phase-field approach

Authors

  • Yanji Fu College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China
  • Shaobo Qiao College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China
  • Huimin Wang College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China
  • Jia Liu State Key Laboratory of Eco-hydraulics in Northwest Arid Region, Xi’an University of Technology, Xi’an 710048, China
  • Zhihan Li College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China
  • Jinchang Sheng College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China https://orcid.org/0000-0002-6892-1661

Abstract

Although low-permeability layered shale has been regarded as a natural barrier for CO2 leakage, the accumulation of CO2 beneath the caprock may reactivate original fractures and even connect interlayers. This behavior significantly threatens the sealing integrity of layered shale caprock. Therefore, our study defines the "weak interlayer" as thin layer with low mechanical strength. Subsequently, we developed a phase-field framework to investigate initial fracture activation, fracture extension and deflection, and pore pressure dispersion within layers. The accuracy of the proposed model was validated through tensile experiments on 2D notched plates and hydraulic fracturing experiments conducted on specimens containing circular perforations. Simulation results indicate that while the increase in in-situ stress raises the threshold for activating original fractures, their extension tends to be along the vertical direction. Similarly, a reduction in horizontal stress accelerates the fracture extension in the vertical direction. Lowering the permeability of "weak interlayer" hinders lateral dispersion of CO2 pressure, promoting vertical migration through the caprock. Conversely, reducing the injection rate allows easier lateral migration of CO2 along "weak interlayer", thereby improving sealing efficiency. These findings provide practical guidance for site selection in geological CO2 geological sequestration, insights into fracture activation, propagation, and connectivity, and an assessment of layered shale caprock sealing efficiency.

DOI:

https://doi.org/10.46690/gs.2026.01.03

Keywords:

Layered shale caprock, weak interlayers, phase field method, CO2 pressure, sealing efficiency

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Published

2026-01-21

How to Cite

Fu, Y., Qiao, S., Wang, H., Liu, J., Li, Z., & Sheng, J. (2026). Investigating fracture activation and CO2 migration in layered shale caprock: a phase-field approach. GeoStorage, 2(1), 27–39. https://doi.org/10.46690/gs.2026.01.03

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Vol. 2 No. 1 (2026): March

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