Supercritical carbon dioxide (ScCO2) fracturing is a promising waterless stimulation technology for unconventional reservoirs, but the mechanisms controlling fracture-network evolution in naturally fractured formations remain unclear. In this study, a stress–flow–damage coupled numerical model based on the continuum–discontinuum element method (CDEM) was established to investigate hydraulic fracture propagation and natural fracture activation during ScCO2 fracturing. Water-based fracturing and ScCO2 fracturing were first compared under an identical symmetric natural fracture configuration. The effects of horizontal principal stress difference and natural fracture approach angle on fracture morphology, injection-pressure response, and fracture-width evolution were then analyzed. Finally, ScCO2-induced fracture-network development in a complex natural fracture network was examined under different injection rates and stress differences. The results show that water-based fracturing is dominated by rapid pressure buildup and relatively straight main-fracture propagation, with a peak injection pressure of 22.9 MPa at 0.075 s and a fracture width of approximately 1.0 mm at 8 s. In contrast, ScCO2 fracturing shows delayed pressure buildup, stronger pressure fluctuations, more pronounced natural fracture activation, and tortuous step-like fracture paths, while producing a smaller fracture width of approximately 0.44 mm at 120 s. A lower stress difference and lower approach angle favor fracture deflection and natural fracture activation, whereas a higher stress difference strengthens stress-guided main-fracture propagation. In complex fracture networks, a lower injection rate promotes more sufficient ScCO2–natural fracture interaction, while a higher injection rate enhances main-fracture extension. These findings provide a numerical basis for optimizing ScCO2 fracturing in naturally fractured unconventional reservoirs.
- Open Access
- Article
Numerical Simulation of Fracture Network Evolution in Supercritical CO2 Fracturing Based on the Continuum–Discontinuum Element Method
- Guopeng Huang 1,
- Fujian Zhou 1,*,
- Bo Zhang 2,
- Minghui Li 3,
- Yifan Hao 1 and
- Guangbo Lu 1
Author Information
Received: 13 August 2026 | Revised: 26 August 2026 | Accepted: 28 August 2026 | Published: 04 November 2026
Abstract
Keywords
supercritical carbon dioxide fracturing | natural fractures | fracture network | water-based hydraulic fracturing | continuum–discontinuum element method
References
- 1.
Gao, X.; Yang, S.; Zhang, Y.; et al. Integrated modeling and economic assessment of hydrogen storage with wellbore-reservoir-thermo-hydro-mechanical-diffusion coupling. Energy 2026, 353, 141065. https://doi.org/10.1016/j.energy.2026.141065.
- 2.
Hou, L.; Zhang, S.; Elsworth, D.; et al. Review of fundamental studies of CO2 fracturing: Fracture propagation, propping and permeating. J. Pet. Sci. Eng. 2021, 205, 108823. https://doi.org/10.1016/j.petrol.2021.108823.
- 3.
Middleton, R.S.; Carey, J.W.; Currier, R.P.; et al. Shale gas and non-aqueous fracturing fluids: Opportunities and challenges for supercritical CO2. Appl. Energy 2015, 147, 500–509. https://doi.org/10.1016/j.apenergy.2015.03.023.
- 4.
Li, Y.; Peng, G.; Tang, J.; et al. Thermo-hydro-mechanical coupling simulation for fracture propagation in CO2 fracturing based on phase-field model. Energy 2023, 284, 128629. https://doi.org/10.1016/j.energy.2023.128629.
- 5.
Chen, H.; Kang, Y.; Jin, W.; et al. Numerical modeling of fracture propagation of supercritical CO2 compound fracturing. J. Rock Mech. Geotech. Eng. 2024, 16, 2607–2628. https://doi.org/10.1016/j.jrmge.2023.11.043.
- 6.
Sun, Y.X.; Wang, X.L.; Meng, Y.Z.; et al. Fracture propagation mechanism and application of supercritical CO2 fracturing in shale: A review. Pet. Sci. 2025, 22, 1625–1652. https://doi.org/10.1016/j.petsci.2025.01.009.
- 7.
Huang, G.; Li, M.; Chu, J.; et al. Longitudinal propagation mechanisms of multiple fractures in heterogeneous multi-lithology stacked reservoirs: A continuum-discontinuum simulation study. Eng. Fract. Mech. 2025, 322, 111181. https://doi.org/10.1016/j.engfracmech.2025.111181.
- 8.
Huang, G.; Zhou, F.; Zhang, B.; et al. Visual experimental investigation on dynamic propagation mechanisms of multi-fractures in layered media. Int. J. Rock Mech. Min. Sci. 2026, 205, 106601. https://doi.org/10.1016/j.ijrmms.2026.106601.
- 9.
Huang, G.; Li, M.; Zhou, F.; et al. Numerical simulation of multi-fracture uniform propagation in naturally fractured reservoirs based on the continuum–discontinuum method. Phys. Fluids 2024, 36, 037111. https://doi.org/10.1063/5.0194485.
- 10.
Zhang, Z.; Yu, H.; Li, B.; et al. A multi-processes phase-field model for CO2 phase change fracturing. Int. J. Rock Mech. Min. Sci. 2026, 198, 106363. https://doi.org/10.1016/j.ijrmms.2025.106363.
- 11.
Zhao, H.; Wu, K.; Huang, Z.; et al. Numerical model of CO2 fracturing in naturally fractured reservoirs. Eng. Fract. Mech. 2021, 244, 107548. https://doi.org/10.1016/j.engfracmech.2021.107548.
- 12.
Zhao, Z.; Li, X.; He, J.; et al. A laboratory investigation of fracture propagation induced by supercritical carbon dioxide fracturing in continental shale with interbeds. J. Pet. Sci. Eng. 2018, 166, 739–746. https://doi.org/10.1016/j.petrol.2018.03.066.
- 13.
Dahi Taleghani, A.; Gonzalez, M.; Shojaei, A. Overview of numerical models for interactions between hydraulic fractures and natural fractures: Challenges and limitations. Comput. Geotech. 2016, 71, 361–368. https://doi.org/10.1016/j.compgeo.2015.09.009.
- 14.
Hu, Y.; Gan, Q.; Hurst, A.; et al. Investigation of coupled hydro-mechanical modelling of hydraulic fracture propagation and interaction with natural fractures. Int. J. Rock Mech. Min. Sci. 2023, 169, 105418. https://doi.org/10.1016/j.ijrmms.2023.105418.
- 15.
Zhou, J.; Zhang, L.; Braun, A.; et al. Investigation of Processes of Interaction between Hydraulic and Natural Fractures by PFC Modeling Comparing against Laboratory Experiments and Analytical Models. Energies 2017, 10, 1001. https://doi.org/10.3390/en10071001.
- 16.
Zang, Y.X.; Li, F.X.; Wang, H.Z.; et al. Effect of CO2 pre-injection on fracture propagation morphology in shale reservoirs under CO2 hybrid fracturing. Pet. Sci. 2026, 23, 2698–2712. https://doi.org/10.1016/j.petsci.2026.01.031.
- 17.
Jiang, C.; Chen, J.; Wang, H.; et al. Phase-field simulation of CO2 fracturing crack propagation in thermo-poroelastic media. Int. J. Rock Mech. Min. Sci. 2025, 187, 106052. https://doi.org/10.1016/j.ijrmms.2025.106052.
- 18.
Li, Y.; Hu, W.; Zhang, Z.; et al. Numerical simulation of hydraulic fracturing process in a naturally fractured reservoir based on a discrete fracture network model. J. Struct. Geol. 2021, 147, 104331. https://doi.org/10.1016/j.jsg.2021.104331.
- 19.
Huang, G.; Hu, X.; Zhou, F.; et al. A New Multi-Cluster Fracturing Simulation Model Coupled with Perforation Erosion: Based on the Continuous–Discontinuous Method. Rock Mech. Rock Eng. 2023, 56, 3887–3901. https://doi.org/10.1007/s00603-023-03256-9.
- 20.
Zhang, B.; Guo, T.; Chen, M.; et al. Research on fracture propagation of hydraulic fracturing in a fractured shale reservoir using a novel CDEM-based coupled HM model. Comput. Geotech. 2024, 168, 106170. https://doi.org/10.1016/j.compgeo.2024.106170.
- 21.
Zhu, X.; Feng, C.; Cheng, P.; et al. A novel three-dimensional hydraulic fracturing model based on continuum–discontinuum element method. Comput. Methods Appl. Mech. Eng. 2021, 383, 113887. https://doi.org/10.1016/j.cma.2021.113887.
- 22.
Ren, Q.; Zhao, Y.; Zhu, X.; et al. CDEM-based simulation of the 3D propagation of hydraulic fractures in heterogeneous Coalbed Methane reservoirs. Comput. Geotech. 2022, 152, 104992. https://doi.org/10.1016/j.compgeo.2022.104992.
This work is licensed under a Creative Commons Attribution 4.0 International License.
