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Description
When CO₂ is injected to induce fractures in rock, the resulting fractures tend to be more complex, and the breakdown pressure is generally lower than when water is injected. This study presents numerical experiments that reveal lower breakdown pressures under supercritical CO₂ injection and demonstrate that fracture paths are more strongly influenced by pre-existing weak interfaces due to CO₂’s low viscosity.
A fracture-propagation model for CO₂–water two-phase flow is developed based on a thermo-hydro-mechanical phase-field approach. The mass-balance equation is derived for each constituent (water and CO₂), accounting for capillary effects and the corresponding equations of state. In addition, the equivalent pressure from the two fluids modifies the potential-energy description in thermo-poro-elastic media compared with our previous micromechanics-based single-phase fluid model. The proposed model is verified against analytical solutions for one-dimensional incompressible, immiscible two-phase flow and for plane-strain hydraulic-fracture propagation, known as the KGD fracture.
| Country | Austria |
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