Experimental Study of Wellbore Instability in Clays
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 137, Issue 8
Abstract
This paper presents the results of an extensive program of laboratory model wellbore tests that have been performed to study wellbore instability in saturated clays. The tests were conducted on resedimented Boston blue clay (RBBC) anisotropically consolidated to vertical effective stresses up to 10 MPa by using two custom-built thick-walled cylinder (TWC) devices with outer diameters and 15.2 cm. The experimental program investigated the effects of specimen geometry, mode of loading, strain rate, consolidation stress level, and overconsolidation ratio (OCR) on deformations of the model wellbore measured during undrained shearing. Results indicate that for normally consolidated clays most of the change in cavity pressure occurs at volumetric strains less than 5% after which the borehole becomes unstable. Increases in outer diameter and strain rate led to a reduction in the minimum borehole pressure. Stress-strain properties were interpreted by using an analysis procedure originally developed for undrained plane strain expansion of hollow cylinders. The backfigured undrained strength ratios from these analyses for normally consolidated specimens range from . Overconsolidation greatly improves the stability of the borehole, and interpreted undrained strength ratios from the TWC tests are consistent with well-known power law functions previously developed for elemental shear tests.
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
This research was sponsored by BP America Inc., Houston, and by the BP-MIT Major Projects Program. The writers are grateful to Dr. Stephen Willson for his support and technical advice, and to Mr. Stephen Rudolph for his expertise in designing and fabricating the new TWC devices.
References
Abdulhadi, N. O. (2009). “An experimental investigation into the stress-dependent mechanical behavior of cohesive soil with application to wellbore instability.” Ph.D. thesis, Dept. of Civil and Environmental Engineering, MIT, Cambridge, MA.
Abdulhadi, N. O., Germaine, J. T., and Whittle, A. J. (2010). “Thick-walled cylinder testing of clays for the study of wellbore instability.” Geotech. Test. J., in press.
Ahmed, I. (1990). “Investigation of normalized behavior of resedimented Boston blue clay using Geonor direct simple shear.” M.S. thesis, Dept. of Civil and Environmental Engineering, MIT, Cambridge, MA.
Amorosi, A., and Rampello, S. (2007). “An experimental investigation into the mechanical behavior of a structured stiff clay.” Géotechnique, 57(2), 153–166.
Aubeny, C. P., Whittle, A. J., and Ladd, C. C. (2000). “Effects of disturbance on undrained strengths interpreted from pressuremeter tests.” J. Geotech. Geoenviron. Eng., 126(12), 1133–1144.
Bishop, A. W., and Henkel, D. J. (1962). The measurement of soil properties in the triaxial test, Edward Arnold, London.
Bishop, A. W., Webb, D. L., and Skinner, A. E. (1965). “Triaxial tests on soil at elevated cell pressures.” Proc., Int. Conf. of Soil Mechanics, Vol. 1, Montreal, 170–174.
Edwards, S., Matasutruyu, B., and Willson, S. M. (2004). “Real-time imaging of borehole failures.” SPE Drill. Completion, 19(4), 236–243.
Ewy, R. T., and Cook, N. G. (1990). “Deformation and fracture around cylindrical openings in rock: II initiation, growth and interaction of fractures.” Int. J. Rock Mech. Min. Sci., 27(5), 409–427.
Haimson, B. C., and Song, I. (1998). “Borehole breakouts in Berea sandstone: Two porosity-dependent distinct shapes and mechanisms of formation.” SPE/ISRM Rock Mechanics and Petroleum Engineering, Trondheim, Norway, 229–238.
Hoskins, E. R. (1969). “The failure of thick walled hollow cylinders of isotropic rock.” Int. J. Rock Mech. Min. Sci. Geomech. Abstr., 6(1), 99–125.
Kutter, H. K., and Rehse, H. (1996). “Laboratory investigations of factors affecting borehole breakouts.” Proc., Eurock 96, Balkema, Rotterdam, 751–758.
Ladd, C. C., and Foott, R. (1974). “New design procedure for stability of soft clays.” J. Geotech. Engrg. Div., 100(7), 763–786.
Ladd, C. C., Foott, R., Ishihara, K., Schlosser, F., and Poulos, H. G. (1977). “Stress-deformation and strength characteristics.” Proc., 9th Int.l Conf. of Soil Mechanics and Foundation Engineering, Vol. 2, Tokyo, 421–494.
Ladd, C. C., Germaine, J. T., Baligh, M. M., and Lacasse, S. (1979). “Evaluation of self-boring pressuremeter tests in sensitive clays.” Research Rep. R79-A, Dept. of Civil Engineering, MIT, Cambridge, MA.
Marsden, J. R., Dennis, J. W., and Wu, B. (1996). “Deformation and failure of thick-walled hollow cylinders of mudrock: A study of wellbore instability in weak rock.” Proc., Eurock 96, Balkema, Rotterdam, 759–766.
Nakken, S. J., Christensen, T. L., Marsden, J. R., and Holt, R. M. (1989). “Mechanical behavior of clays at high stress levels for wellbore stability applications.” Proc., Int. Conf. Rock at Great Depth, ISRM-SPE, Balkema, Rotterdam, Netherlands, Vol. 2, 141–148.
Petley, D. N. (1994). “The deformation of mudrocks.” Ph.D. thesis, Dept. of Geological Sciences, Univ. of London, London.
Santarelli, F. J. (1987). “Theoretical and experimental investigation of the stability of the axisymmetric wellbore.” Ph.D. thesis, Dept. of Mineral Resource Engineering, Imperial College of Science, Technology and Medicine, Univ. of London, London.
Santarelli, F. J., and Brown, E. T. (1989). “Failure of three sedimentary rocks in triaxial and hollow cylinder compression tests.” Int. J. Rock Mech. Min. Sci., 26(5), 401–413.
Schmidt, B. (1966). “Discussion of earth pressure at rest related to stress history.” Can. Geotech. J., 3(4), 239–242.
Sheahan, T. C., and Germaine, J. T. (1992). “Computer automation of conventional triaxial equipment.” Geotech. Test. J., 15(4), 311–322.
Sheahan, T. C., Ladd, C. C., and Germaine, J. T. (1996). “Rate-dependent undrained shear behavior of saturated clay.” J. Geotech. Eng., 122(2), 99–108.
Silvestri, V. (1998). “On the determination of the stress-strain curve of clay from undrained plane-strain expansion of hollow cylinders: A long forgotten method.” Can. Geotech. J., 35(2), 360–363.
Taylor, R. N., and Coop, M. R. (1993). “Stress path testing of Boom Clay from Mol, Belgium.” The engineering geology of weak rock: Proc., 26th Annual Conf. of the Engineering Group of the Geological Society, J. C. Cripps, J. M. Coulthard, M. G. Culshaw, A. Forster, S. R. Hencher, and C. F. Moon, eds., Balkema, Rotterdam, 77–82.
Whittle, A. J., DeGroot, D. J., Ladd, C. C., and Seah, T.-H. (1994). “Model prediction of the anisotropic behavior of Boston blue clay.” J. Geotech. Eng., 120(1), 199–224.
Whittle, A. J., and Kavvadas, M. (1994). “Formulation of the MIT-E3 constitutive model for overconsolidated clays.” J. Geotech. Eng., 120(1), 173–198.
Wu, B. (1991). “Investigations into the mechanical behavior of soft rocks.” Ph.D. thesis, Dept. of Mineral Resource Engineering, Imperial College of Science, Technology and Medicine, Univ. of London, London.
Information & Authors
Information
Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 137 • Issue 8 • August 2011
Pages: 766 - 776
Copyright
© 2011 American Society of Civil Engineers.
History
Received: Mar 21, 2010
Accepted: Dec 8, 2010
Published online: Dec 10, 2010
Published in print: Aug 1, 2011
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.