The Geotechnical Characteristics of Weak North Sea Reservoir Rocks

  • M. E. Jones
  • M. J. Leddra
  • A. Goldsmith
  • O. P. Berget
  • I. Tappel


Laboratory investigations of the deformation characterstics of chalks and weakly cemented sandstones from a number of North Sea reservoirs, and from outcrops, demonstrate that these materials are elastic under initial loading, but exhibit strongly non-linear deformation behaviour at higher stresses. This behaviour can be described by a characteristic failure surface in stress/pore volume coordinates. This paper presents a description of this behaviour. When reservoir rocks of this type are loaded, maintaining a uniaxial strain condition, the material, undergoes ductile yield at relatively low stress followed by significant porosity decrease at almost constant stress (pore collapse). The onset of pore collapse depends on the rock type, its pre-deformational porosity and the extent and nature of the cementing material. Eventually a hardening occurs that is a response to the increasing compaction and porosity decline in the sample. Reservoir rocks will mobilize maximum compaction drive if they yield in this manner, but may also suffer a permeability loss due to the decrease in porosity. Other detrimental aspects of reservoir compaction (well casing collapse and surface subsidence) may also occur. When subject to large shear stresses in the presence of high pore pressures, the materials investigated are observed to deform readily in shear. They may approach a liquefact stat. This aspect of the mechanical behaviour is interpreted as a possible mechanism for the rapid transfer of substantial volumes of reservoir solids in a well. This phenomenon has been reported to occur in a number of fields, generally, following rapid drawdown of previously “shut-in” well.


Effective Stress Triaxial Test Stress Path Reservoir Rock Uniaxial Strain 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Addis, M.A. (1987). Mechanisms of sediment compaction responsible for oil field subsidence. Unpublished Ph.D Thesis, University of London.Google Scholar
  2. Aam, K. (1988). Ekofisk subsidence: The problem, the solution, and the future. In: Proceedings of the International Conference on Behaviour of Offshore Structures, Trondheim, Norway, June 1988, p. 19–40.Google Scholar
  3. Atkinson, J. H. and Bransby, P.L. (1978). The Mechanics of Soils: An Introduction to Critical State Soil Mechanics, McGraw-Hill, London.Google Scholar
  4. Barton, N., Makurat, A., Harvik, L., Vik, G., Bandis, S., Christianson, M. and Addis A. (1988). The discontinuum approach to compaction and subsidence modelling as applied to Ekofisk. In: Proceeding of the International Conference on Behaviour of Offshore Structures, Trondheim, Norway, June 1988, pp. 129–142.Google Scholar
  5. Bishop, A.W. and Henkel, D.J. (1962). The Measurement of Soil Properties in the Triaxial Test. Edward Arnold, London.Google Scholar
  6. Bratli. R.K. and Risnes, R. (1981) Stability and failure of sand arches. Soc. Petroleum Eng. (April), 236–248.Google Scholar
  7. Farmer, I (1983) Engineering Behaviour of Rocks, 2nd ed. Chapman and Hall, London.CrossRefGoogle Scholar
  8. Goldsmith, A.S. (1989). Permeability decline and compressibility in sandstone reservoir rocks. In: V. Maury and D. Fourmain-traux (eds.), Rock at Great Depth, (Vol. 2), Balkema, Rotterdam, pp. 923–928.Google Scholar
  9. Janbu, N. (1985). Soil models in offshore engineering. 1985 Rankine Lecture. Geotechnique, 35 (3), 241–281.CrossRefGoogle Scholar
  10. Johnson, J.P. and Rhett, D.W. (1987). Compaction behaviour of Ekofisk Chalk as a function of stress. SPE paper 15872, SPE European Petroleum Conference, London, 20–22 October, 1986.Google Scholar
  11. Johnson, J.P., Rhett, D.W. and Seimers, W.T. (1988) Rock mechanics of the Ekofisk Reservoir in the evaluation of subsidence. Offshore Technology Conference, Houston, Texas, OTC5621, pp. 39–50.Google Scholar
  12. Jones, M.E. (1988) Determination of the Mechanical Properties of Reservoir Rocks using the Triaxial Test: Experimental Guidelines. Norwegian Petroleum Directorate, YA-524, Stavanger.Google Scholar
  13. Jones, M.E. and Leddra, M.J. (1987). Ground motions and seismicity due to fluid production from subsurface reservoirs. Mem. Geol. Soc. China, N.9. (December), 465–494.Google Scholar
  14. Jones, M.E., Leddra, M.J. and Addis, M.A. (1987). Reservoir Compaction and Sea floor Subsidence Due to Hydrocarbon Extraction. Offshore Technology Report, OTH 87 276. HMSO, London.Google Scholar
  15. Jones, M.E., Leddra, M.J. and Potts, D. (1989). Ground motions due to hydrocarbon production from the chalk. International Chalk Symposium, September. Preprint No. 59, Thomas Telford, London, pp. 341–347.Google Scholar
  16. Lambe, T.W. and Whitman, R.V. (1979). Soil Mechanics, S.I. Version, 2nd edn. Wiley, New York.Google Scholar
  17. Leddra, M.J. and Jones, M.E. (1989). Steady-state flow during undrained loading of the Chalk. International Chalk Symposium. Preprint No. 18, Thomas Telford, London, pp. 117–124.Google Scholar
  18. Leddra, M.J., Pederstad, K., Lønøy, A. and Jones, M.E. (1989). The influence of increasing effective stress on the permeability of chalks under hydrocarbon reservoir conditions. International Chalk Symposium, September. Preprint No. 19, Thomas Telford, London, pp. 125–131.Google Scholar
  19. Patillo, P.D. and Smith, M.B. (1982). The effect of formation flow on the integrity of perforated casing. SPE 11123, presented at the SPE Fall Meeting, New Orleans, September, 1982.Google Scholar
  20. Potts, D.M., Jones, M.E. and Berget, O.P. (1988) Subsidence above the Ekofisk Oil reservoirs. Proceedings of the International Conference on Behaviour of Offshore Structures, Trondheim, Norway, June 1988, p. 113–128.Google Scholar
  21. Risnes, R., Bratli, R.K. and Horsrud, P. (1982a). Sand stresses around a wellbore. Soc. Petroleum Eng. J. (December), 883–898.Google Scholar
  22. Risnes, R., Bratli, R.K. and Horsrud, P., (1982b). Sand arching — a case study. European Petroleum Conference, London October, 1982. Paper EUR 310.Google Scholar
  23. Ruddy, I., Anderson, M.A., Pattillo, P.O., Bishlawi, M. and Foged, N. (1988) Rock compressibility, compaction, and subsidence in a high-porosity chalk reservoir: A case study of Valhall Field. SPE paper 18278, SPE 63rd Annual Technical Conference, Houston, October, 1988, pp. 179–186.Google Scholar
  24. Smits, R.M.M., De Waal, A., and Van Kooten, J.F.C. (1986). Prediction of abrupt reservoir compaction and surface subsidence due to pore collapse in carbonates. SPE paper 15642, SPE 61st Annual Technical Conference, New Orleans, October, 1986, pp. 1-11.Google Scholar
  25. Teeuw, D., (1971). Prediction of formation compaction from labora tory compressibility data. Soc. Petroleum Eng. J. (Sept.), 263–271.Google Scholar
  26. Terzarghi, K. (1936). The shearing resistance of saturated soils and the angle between the planes of shear. International Conference on Soil Mechanics and Foundation Engineering 1, Cambridge, Massachusetts, Proceedings, Vol. 1, pp. 54–56.Google Scholar
  27. Terzarghi, K., (1943). Theoretical Soil Mechanics. Wiley, New York.CrossRefGoogle Scholar
  28. Uriel, S. and Serrano, A.A. (1973) Geotechnical properties of two collapsible volcanic soils of low bulk density at the site of two dams on the Canary Islands Proceedings of the 8th International Conference on Soil Mechanics and Foundation Engineering, Moscow, 1973, pp. 251–264.Google Scholar
  29. Vaughan, P.R. (1985). Mechanical and hydraulic properties of in situ residual soils. 1st International Conference in Geomechanics of Tropical and Saprolitic Soils, Brazilia, February, 1985.Google Scholar
  30. Yassir, N. (1989). Mud volcanoes and the behaviour of over-pressured clays and silts. Unpublished PhD Thesis, Universty of London.Google Scholar

Copyright information

© Norwegian Institute of Technology 1990

Authors and Affiliations

  • M. E. Jones
    • 1
  • M. J. Leddra
    • 1
  • A. Goldsmith
    • 1
  • O. P. Berget
    • 2
  • I. Tappel
    • 2
  1. 1.Department of Geological SciencesUniversity College LondonUK
  2. 2.OljedirektoratetStavangerNorway

Personalised recommendations