A simplified approach to directly consider intact rock anisotropy in Hoek–Brown failure criterion

Ismael, Mohamed; Imam, Hisham; Elshayeb, Yasser

doi:10.1016/j.jrmge.2014.06.003

Cited by 47 publications

(12 citation statements)

References 10 publications

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“…页岩的脆性是页岩气储层压裂改造所需要考虑的重要参数指标, 同时对井壁稳定性影响较大, 一般认为页岩的脆性越高越难确保井壁的稳定性 [25] , 但却更易被压裂, 越难以形成常规的双翼裂缝, 其裂缝的几何形态越复杂, 储层压裂改造的效果也就越好 [26] . 利用脆性指 [27] . 龙马溪组页岩的各向异性度略低于Tournemire页岩(k2=1.5), 而…”

Section: 龙马溪页岩的脆性unclassified

Anisotropic mechanism and characteristics of deformation and failure of Longmaxi shale

Xie

et al. 2017

Sci. Sin.-Phys. Mech. Astron.

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Section: 龙马溪页岩的脆性unclassified

Anisotropic mechanism and characteristics of deformation and failure of Longmaxi shale

Xie

et al. 2017

Sci. Sin.-Phys. Mech. Astron.

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“…Compared with the case of isotropic rocks, the anisotropic strength will influence the changes in the fracture initiation with well type, in-situ stress conditions, and other parameters, which are supported by experiments and analytical models [25][26][27][28]. The change in failure plane due to the anisotropic strength was the first to be analysed by developing two generalisations of the Coulomb-Navier criterion [29].…”

Section: Introductionmentioning

confidence: 94%

“…These studies were carried out based on the improvement in the fracture initiation model, but it was assumed that the rock was an elastic isotropic medium. This is contrary to the fact that the real rock is anisotropic, as the existence of bedding planes and laminations for sedimentary rocks, foliation and cleavage for metamorphic rocks, and even natural fractures will result in anisotropic strength [25]. Since oil shale is a typical sedimentary rock [9], it is required to establish the fracture initiation model by considering the influence of the anisotropic strength.…”

Section: Introductionmentioning

confidence: 99%

A Case Study on the Optimal Design of the Horizontal Wellbore Trajectory for Hydraulic Fracturing in Nong’an Oil Shale

et al. 2020

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A horizontal well with hydraulic fractures is key to forming a fracture network in oil shale for the generated hydrocarbon flows. By considering the influence of anisotropic strength, a prediction model is proposed for fracture initiation by studying different fracture initiation modes (FIMs) in oil shale: failure of the intact rock matrix and of the bedding planes. Through a case study on Nong’an oil shale, the influences of wellbore trajectory and bedding planes on the fracture initiation pressure (FIP), location (FIL), and FIM were analyzed and the induced changes in wellbore trajectory design were concluded. The preferred angle between the wellbore axis and the minimum horizontal principal stress was the same of 90° or 270°, when the lowest required FIP corresponded to the failure of the intact rock matrix. However, when the angle corresponded to the failure of the bedding planes, the preferred direction of the wellbore axis was away from the fixed direction and not corresponding to the lowest required FIP due to the fracture morphology. The error between the theoretical and experimental results ranges from 7% to 9%. This research provides a framework for the design of horizontal wellbore trajectories in oil shale, for easier fracture initiation and more complex fracture networks.

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“…For compressive strength of layered shale, the variation of uniaxial compressive strength in different inclination angles of the bedding is established using the empirical method by Hoek and Brown [21]. And the theoretical calculation method of compressive strength is revised and consummated by Rao et al [34], Ramamurthy et al [35], Saroglou and Tsiambaos [36], Ismael et al [37], and so on. However, there are few studies on the anisotropic tensile strength of shale.…”

Section: Mechanical Model Of Fracture Initiationmentioning

confidence: 99%

Fracture Initiation Model of Shale Fracturing Based on Effective Stress Theory of Porous Media

Jia

2018

Geofluids

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Unconventional oil and gas are important resources of future energy supply, and shale gas is the focus of the development of unconventional resources. Shale is a special kind rock of porous medium, and an orderly structure of beddings aligned in the horizontal direction where causing the strong elastic anisotropy of shale is easy. A new model has been established to calculate the fracture initiation pressure with the consideration of mechanical characteristics of shale and the anisotropic tensile strength when judging rock failure. The fracture initiation model established in this paper accurately reflects the stress anisotropy and matches well with the actual situation in porous media. Through the sensitivity analysis, the results show that σv/σH, Ev/EH, υv/υH, m/s, and A/B have a certain impact on the tangential stress when the circumferential angle changes, and there is a positive relationship between the initiation pressure and the above sensitive factors except for A/B. The results can provide a valuable and effective guidance for the prediction of fracture initiation pressure and fracture propagation mechanism under special stratum conditions of shale.

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A simplified approach to directly consider intact rock anisotropy in Hoek–Brown failure criterion

Cited by 47 publications

References 10 publications

Anisotropic mechanism and characteristics of deformation and failure of Longmaxi shale

Anisotropic mechanism and characteristics of deformation and failure of Longmaxi shale

A Case Study on the Optimal Design of the Horizontal Wellbore Trajectory for Hydraulic Fracturing in Nong’an Oil Shale

Fracture Initiation Model of Shale Fracturing Based on Effective Stress Theory of Porous Media

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