An Anisotropic Thermo-Mechanical Failure Criterion for Shale

Morteza Mohamadi, Richard Wan

In the proceedings of: GeoManitoba 2012: 65th Canadian Geotechnical Conference

Session: T1A - Soil Mechanics II

ABSTRACT: The prediction of the thermo-hydro-mechanical behavior of shales has attracted a lot of attention in thermal oil recovery processes and borehole stability problems over the past decades. A thermo-mechanical failure criterion is proposed to model the failure of shales considering their initial transversely isotropic structure. This criterion is based on a modification of Matsuoka-Nakai failure criterion in order to account for cohesiveness of the material and nonlinearity of the failure envelope in the meridional plane of the principal stress plane. The transversely isotropic structure was taken into consideration by incorporating a fabric tensor into the original isotropic formulation. Temperature effects were considered using a new scaling law which allows the separate description of thermal and mechanical characteristics of the material. The proposed criterion is versatile enough to capture both thermal-decreases and -increases of shale strength. The procedure for determining the various material parameters is elaborated for Tournemire shale. The results show that the proposed model gives well-matched predictions with experimental data.

RÉSUMÉ: -hydro-méthode thermique et dans des problèmes de stabilité des puits. Un critère de rupture thermomécanique pour argillites ayant un comportement isotrope transverse est ainsi élaboré. Ce critère est une modification du critère Matsuoka-Nakai pour inclure la cohésion et la non-principales. La structure isotrope transverse est décrite par un tenseur de texture qui modifie la formulation initiale isotrope. Ldissocier les caractéristiques mécaniques et thermiques du matéri au. Cette approche est assez flexible pour retrouver ssement de la résistance du matériau avec la température. Ainsi, les paramètres de bien avec le critère de rupture proposé.

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