Comparison of Predicted Failure Area Around the Boreholes in the Strike-Slip Faulting Stress Regime With Hoek-Brown and Fairhurst Generalized Criteria

Lakirouhani, Ali; Bahrehdar, Mohammad; Medzvieckas, Jurgis; Kliukas, Romualdas

doi:10.3846/jcem.2021.15020

Cited by 9 publications

(3 citation statements)

References 35 publications

(43 reference statements)

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“…Figure 2 illustrates the problem geometry for a breakout wellbore. Breakout is shear failure caused by compressive stress that is formed symmetrically on both sides of the wellbore and along the minimum in situ stress ( ) h S [29][30][31]. Breakout failure expands episodically with the separation of crushed rock layers until it reaches stability.…”

Section: Breakout Wellboresmentioning

confidence: 99%

Impact of Wellbore Cross-Sectional Elongation on the Hydraulic Fracturing Breakdown Pressure and Fracture Initiation Direction

Jolfaei,

Lakirouhani

2024

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Investigation of breakdown pressure in wellbores in complex conditions is of great importance, both in fracture design and in wellbore log interpretation for in situ stress estimation. In this research, using a two-dimensional numerical model, the breakdown pressure is determined in ellipsoidal and breakout wellbores. To find the breakdown pressure, the mixed criterion is used, in which the toughness and the tensile strength criteria must be satisfied concurrently. In breakout boreholes, the breakdown pressure is lower than the circular wellbores; indeed, the ratio of the breakdown pressure of the breakout wellbore to the breakdown pressure in the circular wellbore is between 1 and 0.04, depending on the deviatoric stress and the width and depth of the breakout zone. In breakout wellbores, the fracture initiation position depends on the deviatoric stress. In small deviatoric stresses, the fracture initiation position is aligned with the minimum in situ stress, unlike circular boreholes; and in large deviatoric stresses, the fracture initiates in the direction of the major principal stress. In large wellbores, the breakdown pressure is controlled by the tensile strength of the rock; and in small wellbores, the breakdown pressure is under the control of the energy spent to create new crack surfaces.

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Section: Breakout Wellboresmentioning

confidence: 99%

Impact of Wellbore Cross-Sectional Elongation on the Hydraulic Fracturing Breakdown Pressure and Fracture Initiation Direction

Jolfaei,

Lakirouhani

2024

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“…In addition to physical models and laboratory studies on borehole breakouts, various theoretical and numerical models have also been conducted to investigate breakouts. Although the frst theoretical models presented for the breakout had simple assumptions, the episodic progression of the breakout was not investigated in them [7,22], but in the following, more complete numerical models based on the fnite element method and the discrete element method were presented, which are able to predict the breakout in a proper way [23][24][25][26][27][28][29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%

Effect of Eccentricity on Breakout Propagation around Noncircular Boreholes

Bahrehdar

Lakirouhani

2023

Advances in Civil Engineering

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Investigating the shear failure caused by the concentration of compressive stress around noncircular boreholes is important both in the field and in the laboratory. This article deals with the numerical analysis of elliptical boreholes under a nonisotropic in situ stress field using the Mogi–Coulomb nonlinear failure criterion. The purpose of the presented numerical model is to simulate the progressive shear failure (breakout) around the borehole and investigate the impact of the eccentricity of the borehole on the stability and depth and width of the failure area. According to the obtained results, the breakout is V-shaped and is formed along the minimum principal stress. As the eccentricity of the borehole increases, the final dimension of the breakout becomes smaller; in other words, the increase in ellipticity strengthens the borehole against shear failure. However, as the eccentricity increases, the stress concentration at the breakout tip increases. Another finding of the study conducted in this article is the significant relationship between the width and the depth of the breakout failure, which makes the idea of estimating both horizontal in situ stresses using breakout dimensions seriously doubtful. Also, the interesting result obtained is that the stress concentration factor at the breakout tip for boreholes with different eccentricities is the same at the end of the breakout.

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“…If the borehole is vertical, the breakout is created on both sides of the borehole along the minimum horizontal principal stress, i.e., where there is the highest concentra-tion of compressive stress (Bell & Gough, 1979;Gough & Bell, 1982;Zoback et al, 1985;Lakirouhani et al, 2021). Therefore, breakout can be an indicator to determine the direction of the in situ stresses (Bell & Gough, 1979;Hickman et al, 1985;Shamir & Zoback, 1992).…”

Section: Introductionmentioning

confidence: 99%

Failure Analysis Around Oriented Boreholes Using an Analytical Model in Different Faulting Stress Regimes

Lakirouhani

Ghorbannezhad

Medzvieckas

et al. 2023

Journal of Civil Engineering and Management

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One of the most important instabilities that may occur in a borehole is shear instability caused by high compressive stress in the borehole wall. The initial estimation of the width and depth of the failure zone around the borehole is very important in the field. In inclined boreholes, the shear instability or borehole breakout is affected by the in situ stress regime, the deviation angle of the borehole, the mechanical properties of the rock and the effect of the intermediate principal stress. In this article, an analytical model based on theory of elasticity is presented to find the breakout failure area around the inclined boreholes. Mogi-Coulomb shear failure criterion is used, in which there is also the effect of the intermediate principal stress. This model examines the failure in three-dimensional elements around the borehole for different in situ stress regime. The main finding of the analysis done in this article is that not only the deviation angle of the borehole but also the in situ stress regime has a great effect on the dimensions of the breakout. Also, the plane where the deviation angle of the borehole changes, affects the dimensions of the breakout.

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Comparison of Predicted Failure Area Around the Boreholes in the Strike-Slip Faulting Stress Regime With Hoek-Brown and Fairhurst Generalized Criteria

Cited by 9 publications

References 35 publications

Impact of Wellbore Cross-Sectional Elongation on the Hydraulic Fracturing Breakdown Pressure and Fracture Initiation Direction

Impact of Wellbore Cross-Sectional Elongation on the Hydraulic Fracturing Breakdown Pressure and Fracture Initiation Direction

Effect of Eccentricity on Breakout Propagation around Noncircular Boreholes

Failure Analysis Around Oriented Boreholes Using an Analytical Model in Different Faulting Stress Regimes

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