Fracture behavior of transversely isotropic rocks with discrete weak interfaces

Celleri, Humberto M.; Sánchez, M.; Otegui, J.L.

doi:10.1002/nag.2849

Cited by 14 publications

(9 citation statements)

References 36 publications

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“…The solid solution scheme has been detailed in a previous work 31 . We solve the dynamics balance equation (Equation 1) with a penalty finite element formulation 22 with a focus on analyzing the deformation of rocks under compressing loads:

ρ_{0} \overset{φ}{true} = \nabla_{0} σ_{PK} + ρ_{0} B

where

φ

is the displacement field,

ρ_{0}

the initial density,

{boldσ}_{boldPK}

the first Piola‐Kirchoff stress tensor and

bold-italicB

are the externally applied forces.…”

Section: Numerical Frameworkmentioning

confidence: 99%

“…VTI materials require five independent elastic constants to characterize their elastic response. The stiffness tensor

bold-italicC

, in Voigt notation, represents the rigidity of the rock 31 . The compliance constants can be obtained from the engineering elastic parameters (Equation.…”

Section: Numerical Frameworkmentioning

confidence: 99%

“…Since fracture propagates through the finite elements interfaces, we have the possibility to define the interfaces strength properties independently from the rest of the anisotropic rock matrix. The mechanical strength is determined by a Modified Mohr‐Coulomb failure criteria with a softening cohesive law 31 . To establish its behavior, it is necessary to define the tensile critical strength

σ_{c}

, the cohesion

C_{0}

and the friction coefficient

μ

, as well as, the fracture critical energy per meter

G_{c}

involved in the de‐cohesion of the element.…”

Section: Numerical Frameworkmentioning

confidence: 99%

“…However, most shale rocks display certain degree of elastic anisotropy, with the elastic modulus in the horizontal direction, aligned to the shales bedding planes, generally greater than in the vertical direction (see e.g., 30 ). A common constitutive behavior for shale rocks is the well‐known Vertically Transversely Isotropic (VTI) model which requires five elastic constants to fully characterize its mechanical response 31 . Moreover, shale formations typically present heterogeneities in the form of solid concretions, calcitic veins, ash beds or other structures that affect the rock strength (see e.g., 32–34 ).…”

Section: Introductionmentioning

confidence: 99%

“…found both experimentally and numerically that the presence of weak interfaces has a strong influence on the fracture toughness measured in notched specimens. Celleri et al 31 . use a VTI anisotropic model with discrete weak interfaces to simulate fracture propagation in Brazilian tests (indirect tensile fracture).…”

Section: Introductionmentioning

confidence: 99%

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Hydraulic fracture propagation barriers induced by weak interfaces in anisotropic rocks

Celleri¹,

Sánchez²

2021

Num Anal Meth Geomechanics

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In the Oil&Gas industry, hydraulic fracturing is a technique that makes unconventional reservoirs economically viable. Despite the high impact of the stimulation processes on the productivity of the wells, hydraulic fractures are modeled assuming vertical and planar propagation in most cases. In Argentina, Vaca Muerta formation is the most important unconventional reservoir. It is predominately in a strike‐slip stress regime with areas in thrust regime, and has also strong elastic anisotropy with widely spread sub‐horizontal mechanical discontinuities such as calcitic veins or ash beds, that could act as preferential propagation paths. The effect of these heterogeneities on the fracture propagation, typically underestimated, is a key issue to model the hydraulic fracture geometry, to estimate the stimulated volume, and to optimize production under these complex mechanical conditions. In this work, we use a coupled fluid ‐ rock mechanics model that accounts for elastic anisotropy and weak discontinuities to study the fracture height growth. Fracture initiation and propagation are modeled using a Discontinuous Galerkin (DG) finite elements formulation with a softening Cohesive Zone Model (CZM). We analyze Vaca Muerta formation representative mechanical properties and provide some fundamentals on typical field problems like vertical containment induced by lamination and layering or horizontal fracture propagation with their consequent loss of productivity. We find, for typical Vaca Muerta formation conditions, that not only the weak bedding strength controls the height propagation of the hydraulic fracture but also the degree of anisotropy plays an important role under harsh stress regimes and high heterogeneity of the formation.

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ρ_{0} \overset{φ}{true} = \nabla_{0} σ_{PK} + ρ_{0} B

where

φ

is the displacement field,

ρ_{0}

the initial density,

{boldσ}_{boldPK}

the first Piola‐Kirchoff stress tensor and

bold-italicB

are the externally applied forces.…”

Section: Numerical Frameworkmentioning

confidence: 99%

“…VTI materials require five independent elastic constants to characterize their elastic response. The stiffness tensor

bold-italicC

, in Voigt notation, represents the rigidity of the rock 31 . The compliance constants can be obtained from the engineering elastic parameters (Equation.…”

Section: Numerical Frameworkmentioning

confidence: 99%

σ_{c}

, the cohesion

C_{0}

and the friction coefficient

μ

, as well as, the fracture critical energy per meter

G_{c}

involved in the de‐cohesion of the element.…”

Section: Numerical Frameworkmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Hydraulic fracture propagation barriers induced by weak interfaces in anisotropic rocks

Celleri¹,

Sánchez²

2021

Num Anal Meth Geomechanics

Self Cite

View full text Add to dashboard Cite

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Three‐dimensional discrete element simulation of indirect tensile behaviour of a transversely isotropic rock

Yin

Cheng

et al. 2020

Num Anal Meth Geomechanics

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SummaryThis paper presents the development of a three‐dimensional discrete element model using flat‐joint and smooth‐joint contact models to investigate the effect of anisotropy on the tensile behaviour of slate, a transversely isotropic rock, under Brazilian testing from both macro and microscales. The effect of anisotropy is further realised by exploring the influence of foliation orientations (β and ψ) on the tensile strength, fracture pattern, microcracking and stress distribution of the transversely isotropic rock. The variation of tensile strength with foliation orientation is presented. The cross‐weak‐plane fracture growth observed in laboratory is reproduced, and the criterion for which to form is also given from the aspect of foliation orientation. Furthermore, the proportional variations of microcracks well account for the effects of foliation orientation on the tensile strength and failure pattern. Finally, it is found that the existence of weak planes increases both the heterogeneity and the anisotropy of stress distributions within the transversely isotropic rock, with the degree of influence varying with the foliation orientation.

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