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- Title
Rock Anisotropy Promotes Hydraulic Fracture Containment at Depth.
- Authors
Lu, Guanyi; Momeni, Seyyedmaalek; Peruzzo, Carlo; Moukhtari, Fatima‐Ezzahra; Lecampion, Brice
- Abstract
We report laboratory experiments and numerical simulations demonstrating that the anisotropic characteristics of rocks play a major role in the elongation of hydraulic fractures (HFs) propagating in a plane perpendicular to the rocks' inherent layering (the bedding planes in sedimentary rocks and foliation planes in metamorphic rocks). Transverse anisotropy leads to larger HF extension in the parallel‐to‐layers/divider direction compared to the perpendicular‐to‐layers/arrester direction. This directly promotes vertical containment of HFs in most sedimentary basins worldwide even in the absence of any favorable in‐situ stress contrasts or other material heterogeneities. More importantly, the ratio of the energy dissipated in fluid viscous flow in the fracture to the energy dissipated in the creation of new surfaces is found to play a critical role on fracture elongation, with fracture‐energy dominated HFs being the most elongated while the viscous dominated ones remain more circular. These results open the door to a better engineering and control of HFs containment at depth in view of the competition between material anisotropy (both elastic stiffnesses and fracture toughness anisotropy) and injection parameters (fluid viscosity and rate of injection). Plain Language Summary: The widespread application of hydraulic fracturing for unconventional hydrocarbon production has prompted concerns about fractures extending vertically to sensitive rock layers, highlighting the need to understand fluid‐driven fracturing for informed public discourse and improved industrial practices. Through numerical simulations and laboratory experiments on an analog transversely isotropic metamorphic rock, we show that the intrinsic anisotropic characteristics of sedimentary rocks lead to limited hydraulic fracture (HF) height growth across the bedding planes in the most common geological situations in unconventional reservoirs. Furthermore, we quantify the roles of elastic stiffnesses, fracture toughness, as well as the fluid injection conditions in shaping HF in transversely isotropic rocks. Our findings suggest that the HF is most elongated in the toughness‐dominated regime, and the impact of rock anisotropy vanishes when the fracture propagates in the viscosity‐dominated regime. Key Points: Intrinsic anisotropy of sedimentary rocks enhances the horizontal extension and hinders the vertical growth of hydraulic fracturesThe degree of fracture elongation depends on injection parameters and material properties through a dimensionless toughness coefficientElongation is larger for toughness dominated compared to viscous dominated fractures
- Subjects
ANISOTROPY; FLUID injection; HYDRAULIC fracturing; SEDIMENTARY rocks; AUTOMATIC control systems; METAMORPHIC rocks
- Publication
Journal of Geophysical Research. Solid Earth, 2024, Vol 129, Issue 4, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2023JB028011