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Title: Experimental Studies of Anisotropy on Borehole Breakouts in Mancos Shale

Abstract

Calculating the size and orientation of borehole breakouts is one of the key methods for determining the orientation and magnitudes of the in situ stresses in the subsurface. To better understand the effects of anisotropy on borehole breakouts, experiments were conducted on Mancos Shale, a finely laminated mudrock. A novel testing configuration was developed to conduct borehole breakout experiments in a standard triaxial vessel and load frame. Samples were prepared at three different orientations and deformed under 6.9 to 20.7 MPa confining pressure. The results show a variation of peak strength and breakout geometry depending on the lamination orientation. Samples deformed parallel to laminations failed at a higher maximum compressive stress than samples deformed perpendicular to laminations, which were stronger than inclined samples. These relationships are quantified by a cosine-based failure envelope. Observed breakout shapes in perpendicular samples are V-shaped and symmetric around the borehole, which advance as a series of fractures of increasing size into the sidewalls. In inclined samples, fractures form along weaker laminations planes and grow in an en echelon pattern towards the axial stress direction. In parallel samples, long fractures grow from the wellbore towards the axial stress direction. The observed geometries point to potential sourcesmore » of error in calculating in situ stresses from borehole breakouts.« less

Authors:
ORCiD logo [1];  [1]; ORCiD logo [1]; ORCiD logo [1];  [1]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1515201
Alternate Identifier(s):
OSTI ID: 1515791
Report Number(s):
SAND-2019-4347J
Journal ID: ISSN 2169-9313; 674787
Grant/Contract Number:  
AC04-94AL85000; NA0003525; DE‐NA0003525
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Solid Earth
Additional Journal Information:
Journal Name: Journal of Geophysical Research. Solid Earth; Journal ID: ISSN 2169-9313
Publisher:
American Geophysical Union
Country of Publication:
United States
Language:
English

Citation Formats

Choens, R. C., Lee, M. Y., Ingraham, M. D., Dewers, T. A., and Herrick, C. G. Experimental Studies of Anisotropy on Borehole Breakouts in Mancos Shale. United States: N. p., 2019. Web. doi:10.1029/2018JB017090.
Choens, R. C., Lee, M. Y., Ingraham, M. D., Dewers, T. A., & Herrick, C. G. Experimental Studies of Anisotropy on Borehole Breakouts in Mancos Shale. United States. doi:10.1029/2018JB017090.
Choens, R. C., Lee, M. Y., Ingraham, M. D., Dewers, T. A., and Herrick, C. G. Sat . "Experimental Studies of Anisotropy on Borehole Breakouts in Mancos Shale". United States. doi:10.1029/2018JB017090.
@article{osti_1515201,
title = {Experimental Studies of Anisotropy on Borehole Breakouts in Mancos Shale},
author = {Choens, R. C. and Lee, M. Y. and Ingraham, M. D. and Dewers, T. A. and Herrick, C. G.},
abstractNote = {Calculating the size and orientation of borehole breakouts is one of the key methods for determining the orientation and magnitudes of the in situ stresses in the subsurface. To better understand the effects of anisotropy on borehole breakouts, experiments were conducted on Mancos Shale, a finely laminated mudrock. A novel testing configuration was developed to conduct borehole breakout experiments in a standard triaxial vessel and load frame. Samples were prepared at three different orientations and deformed under 6.9 to 20.7 MPa confining pressure. The results show a variation of peak strength and breakout geometry depending on the lamination orientation. Samples deformed parallel to laminations failed at a higher maximum compressive stress than samples deformed perpendicular to laminations, which were stronger than inclined samples. These relationships are quantified by a cosine-based failure envelope. Observed breakout shapes in perpendicular samples are V-shaped and symmetric around the borehole, which advance as a series of fractures of increasing size into the sidewalls. In inclined samples, fractures form along weaker laminations planes and grow in an en echelon pattern towards the axial stress direction. In parallel samples, long fractures grow from the wellbore towards the axial stress direction. The observed geometries point to potential sources of error in calculating in situ stresses from borehole breakouts.},
doi = {10.1029/2018JB017090},
journal = {Journal of Geophysical Research. Solid Earth},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {3}
}

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Works referenced in this record:

Experiments with rock: Remarks on strength and stability issues
journal, June 2007

  • Labuz, J. F.; Biolzi, L.
  • International Journal of Rock Mechanics and Mining Sciences, Vol. 44, Issue 4, p. 525-537
  • DOI: 10.1016/j.ijrmms.2006.09.005