| Autor: |
Li, Wenfeng, Frash, Luke P., Carey, J. William, Welch, Nathan J., Meng, Meng, Viswanathan, Hari S. |
| Zdroj: |
Geophysical Research Letters; 12/28/2024, Vol. 51 Issue 24, p1-11, 11p |
| Abstrakt: |
Managing fluid‐driven fracture networks is crucial for subsurface resource utilization, yet the current understanding of the key controlling factors remains insufficient. While geologic discontinuities have been shown to significantly influence fracture network complexity, this study identifies another major contributor. We conducted a new set of experiments using a transparent true triaxial cell, which enabled video recording of the temporal evolution of fluid‐driven fracture paths. Using pseudo‐2D samples without macroscale structural discontinuities, we observed multiple occurrences of hydraulic fracture curving and branching under anisotropic boundary stresses. We proposed a theoretical model demonstrating that the stress parallel to the crack line in the solid matrix near the crack tip (i.e., the T‐stress) accounts for the observed fracture curving behavior. This finding suggests that T‐stress is an additional mechanism contributing to the complexity of fluid‐driven fracture networks in the subsurface, besides the geologic discontinuities. Plain Language Summary: The need to predict and manage fluid‐driven fracture networks in the subsurface is an important topic, yet questions remain regarding the factors that control these networks. This work presents surprising experimental observations of curving and branching of fluid‐driven fractures within samples lacking macroscale structural discontinuities and subjected to anisotropic boundary stresses. We propose a theoretical model to explain these observations. It is found that T‐stress (i.e., the crack parallel stress in the solid matrix near the crack tip) causes a local change in the direction of preferred propagation, leading to crack curving into a non‐optimal orientation. Eventually, continuing propagation in this non‐optimal direction becomes energetically disadvantageous, resulting in the reinitiation of a new crack that propagates in alignment with far‐field stresses. This process repeats and creates complex fracture structures. Therefore, T‐stress emerges as a new mechanism contributing to the complexity of fluid‐driven fracture networks in the subsurface. Key Points: Tests revealed curving and branching of fluid‐driven crack in rock analog without structural heterogeneity under anisotropic stressesA new customized transparent true triaxial (TTT) cell enabled video‐recording of fluid‐driven fracturing path in pseudo 2D samplesA theoretical model that accounts for stress parallel to crack line in the near‐tip solids (T‐stress) successfully explained crack curving [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
Plný text