Comparison between analytical and 3D finite element solutions for borehole stresses in anisotropic elastic rock

Gaede, Oliver; Karpfinger, Florian; Jocker, Jeroen; Prioul, Romain

doi:10.1016/j.ijrmms.2011.12.010

Cited by 62 publications

(27 citation statements)

References 21 publications

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“…In this case, the stress field close to the borehole can be calculated from the stress concentration around a hole in an infinite, linear elastic, and isotropic plate (e.g., Zoback 2010). However, neglecting the anisotropy for any other orientation, as commonly done in drilling applications (Gaede et al 2012;Khan et al 2011;Birchwood and Noeth 2012), may result in significant errors of stress estimates (Blümling 1986).…”

Section: Introductionmentioning

confidence: 99%

Influence of Bedding Angle on Borehole Stability: A Laboratory Investigation of Transverse Isotropic Oil Shale

et al. 2014

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The stability of wells drilled into bedded formations, e.g., shales, depends on the orientation between the bedding and the borehole axis. If the borehole is drilled sub-parallel to bedding, the risk of borehole instabilities increases significantly. In this study, we examined the formation of stress-induced borehole breakouts in Posidonia shale by performing a series of thick-walled hollow cylinder experiments with varying orientations of the bedding plane with respect to the borehole axis. The thickwalled hollow cylinders (40 mm in diameter and 80 mm in length containing an 8 mm diameter borehole) were loaded isostatically until formation of breakouts. The onset of borehole breakout development was determined by means of acoustic emission activity, strain measurements, ultrasonic velocities and amplitudes. The critical pressure for breakout initiation decreased from 151 MPa by approximately 65 % as the bedding plane inclination changed from normal to parallel to the borehole axis. The finely bedded structure in the shale resulted in an anisotropy in elasticity and strength from which the variation in strength dominated the integrity of the thick-walled hollow cylinders.

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Section: Introductionmentioning

confidence: 99%

Influence of Bedding Angle on Borehole Stability: A Laboratory Investigation of Transverse Isotropic Oil Shale

et al. 2014

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“…It is worth mentioning that the equation (5) is only valid when the borehole axis is along the formation axis of symmetry. 32,33 The associated biasing strains in the transverse isotropic formation are similar to isotropic situation. 12 Associated biasing strain E r θ is the same with isotropic situation.…”

Section: Formulationmentioning

confidence: 65%

Acoustoelastic effects of Stoneley waves in a borehole surrounded by a transversely isotropic elastic solid

et al. 2014

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Stoneley wave in a fluid-filled pressurized borehole surrounded by a transversely isotropic elastic solid with nine independent third-order elastic constants in presence of biaxial stresses are studied. A simplified acoustoelastic formulation of Stoneley wave is presented for the parallelism of the borehole axis and the formation axis of symmetry. Sensitivity coefficients and velocity dispersions for Stoneley wave due to the presence of stresses are numerically investigated, respectively. The acoustoelastic formulation explicitly shows that the velocity dispersions of Stoneley wave depend on seven independent third-order elastic constants in presence of biaxial stresses and on six independent third-order elastic constants in the presence of borehole pressurization alone. Numerical results of both sensitivity coefficients and velocity dispersions of Stoneley wave show that at low frequency the velocity change of Stoneley wave is sensitive to c111 and c112. Stoneley wave velocity at low frequencies can be simplified by 3 independent third order elastic constants (c111, c112 and c123) instead of nine constants. In presence of biaxial stresses, at low frequencies the speed of the Stoneley wave is similar to White’s formula.

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“…Ryncarz (1989) studied the stress distribution around borehole drilled in a gas bearing coal seam with outbursts threat. Gaede et al (2012) compared the analytical solution with 3D Finite Element Method (FEM) for stress changes induced by borehole in anisotropic media. Aadnoy (1989) discussed stress characteristics around a horizontal borehole and the effects of anisotropy in sedimentary rock elastic properties on it.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Characterisation of mechanics and flow fields around in-seam methane gas drainage borehole for preventing ventilation air leakage: A case study

Zheng

Chen

Kizil

et al. 2016

International Journal of Coal Geology

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Coal Mine Methane (CMM) drainage via adopting in-seam horizontal boreholes is an effective way to decrease ventilation cost and production delay, ensure mining safety, reduce greenhouse gas emissions and increase the supply of energy resource.Ventilation air leakage into borehole, however, occurs frequently, which decreases the methane-drainage efficiency. Despite extensive anti-leakage method investigations, a very few studies have been focused on spraying air-proof materials on the roadway rib and optimizing borehole sealing along the borehole, along with taking the effects of sequential excavations of roadway and borehole into account. In this paper, based on data of a real coal mine, a fully coupled mathematical model was developed by incorporating coal permeability with coal mechanical properties and gas adsorption/desorption and was then implemented into a Finite Element software. This numerical simulation was used to analyse transient stress and dynamic air-leakage flow fields around the drainage borehole. Simulation results indicate that: (1) Four stress areas (І to IV) exist around the roadway based on different relief status of the tri-axial stress, and stress distributions around the borehole in those four areas are different from each other; (2) Based on different air-leakage degrees, on the roadway rib, there are four air-leakage levels around borehole. Meanwhile, there are four leakage areas along the borehole: FAA, SAA, HAA and VAA, and the optimal sealing length should be over 17m (exceeding HAA) to prevent air leakage. Air-leakage results in (2) are verified mutually with the mechanics outcomes in (1). Meanwhile, real data obtained from field experiments is introduced to validate the simulation results. All those outcomes can allow for the optimal design of the spraying area and order and borehole sealing, thus provide scientific basis for an integrated anti-air-leakage method including spraying air-proof materials on the roadway wall and sealing borehole effectively, to prevent ventilation air leakage and maximize methane drainage performance.

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Comparison between analytical and 3D finite element solutions for borehole stresses in anisotropic elastic rock

Cited by 62 publications

References 21 publications

Influence of Bedding Angle on Borehole Stability: A Laboratory Investigation of Transverse Isotropic Oil Shale

Influence of Bedding Angle on Borehole Stability: A Laboratory Investigation of Transverse Isotropic Oil Shale

Acoustoelastic effects of Stoneley waves in a borehole surrounded by a transversely isotropic elastic solid

Characterisation of mechanics and flow fields around in-seam methane gas drainage borehole for preventing ventilation air leakage: A case study

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