Analytical and Experimental Investigations on Mechanical Properties of Weak Plane Bedding in Mudstone

Wellbore instabilities frequently occur in mudstone formation with weak plane bedding because of strong anisotropies. The mechanics parameters of weak plane bedding are of vital significance to the wellbore stability analysis for mudstone formations. The conventional method for determining the mechanics parameters is to fit lots of triaxial test data due to the blindness of coring. In this paper, an evaluation method of the mechanics parameters of weak plane bedding is proposed to improve the accuracy of weak plane bedding mechanical properties. The mechanics parameters of weak plane bedding are obtained by combing the single-weak plane failure criterion with the compressive strength of rock obtained by the triaxial test of cores with different coring angles. It is seen that the new evaluation method is simple and convenient. On the other hand, a validation method of the mechanics parameters of weak plane bedding is proposed to ensure their accuracy. The compressive strength obtained from the core with the special coring angle is compared with the theoretical compressive strength for verifying the accuracy of weak plane bedding mechanical properties. It is observed that the proposed evaluation and validation methods can be used to measure the value of weak plane bedding mechanical properties precisely. The proposed methods are general and can be used for measuring the mechanical properties of fracture weak-plane and joint weak-plane.

[1]  Y. Wang,et al.  Anisotropic fracture and energy characteristics of a Tibet marble exposed to multi-level constant-amplitude (MLCA) cyclic loads: A lab-scale testing , 2021 .

[2]  Guorong Wang,et al.  Wellbore Stability of a Deep-Water Shallow Hydrate Reservoir Based on Strain Softening Characteristics , 2020 .

[3]  Y. Meng,et al.  Multi-coupling stress field and evaluation of borehole stability in deep brittle shale , 2020, Arabian Journal of Geosciences.

[4]  Y. Wang,et al.  On the effect of stress amplitude on fracture and energy evolution of pre-flawed granite under uniaxial increasing-amplitude fatigue loads , 2020 .

[5]  Liu Yang,et al.  Hydrogeological characteristics and mechanism of a water-rich coal seam in the Jurassic coalfield, northern Shaanxi Province, China , 2020 .

[6]  Pathegama Gamage Ranjith,et al.  Hydro-mechanical behavior of sandstone with interconnected joints under undrained conditions , 2016 .

[7]  J. Daemen,et al.  Experimental and theoretical study of the anisotropic properties of shale , 2015 .

[8]  Yan Jin,et al.  Wellbore stability model for shale gas reservoir considering the coupling of multi-weakness planes and porous flow , 2014 .

[9]  Jincai Zhang.  Borehole stability analysis accounting for anisotropies in drilling to weak bedding planes , 2013 .

[10]  Harvey E. Goodman,et al.  A wellbore stability model for formations with anisotropic rock strengths , 2012 .

[11]  T. Popp,et al.  Influence of bedding planes to EDZ-evolution and the coupled HM properties of Opalinus Clay , 2008 .

[12]  Evert Hoek,et al.  HOEK-BROWN FAILURE CRITERION - 2002 EDITION , 2002 .

[13]  J. Shao,et al.  A modified single plane of weakness theory for the failure of highly stratified rocks , 1998 .

[14]  Jean-Claude Roegiers,et al.  Influence of anisotropies in borehole stability , 1993 .

[15]  B. Aadnøy,et al.  Method for Fracture-Gradient Prediction for Vertical and Inclined Boreholes , 1989 .

[16]  B. Aadnøy.  Modeling of the stability of highly inclined boreholes in anisotropic rock formations , 1988 .

[17]  B. Aadnøy,et al.  Method for Fracture Gradient Prediction for Vertical and Inclined Boreholes , 1987 .

[18]  M. E. Chenevert,et al.  Mechanical Anisotropies of Laminated Sedimentary Rocks , 1965 .

[19]  F. Donath.  EXPERIMENTAL STUDY OF SHEAR FAILURE IN ANISOTROPIC ROCKS , 1961 .

[20]  J. C. Jaeger.  Shear Failure of Anistropic Rocks , 1960, Geological Magazine.

[21]  M. Bott,et al.  The Mechanics of Oblique Slip Faulting , 1959, Geological Magazine.