A medium with preferentially aligned fractures or cracks will exhibit seismic anisotropy. Evidence of anisotropy in fractured hydrocarbon reservoirs has the potential to be a powerful interpretation tool for characterizing the intensity and orientation of fractures. The presence of these fractures can dramatically improve production rates, most notably in tight formations. Seismic waveforms are very sensitive to the fracture density and orientation, which is valuable information for a drilling program.
Shell International Exploration and Production – Rijswijk, Netherlands
Total GRC – UK
BP – Houston, Texas; Stavenger, Norway.
SAIL – A consortium funded industrial project integrating seismic and laboratory observations of anisotropy in sedimentary basins.
Robust Fracture Identification (RFI) An industry funded project that linked geomechanical and seismic modelling. The work is focusses on the Clair Field and was a collaborative project between Heriot-Watt University and the Universities of Leeds and Bristol.
Fracture pattern map for the top of a chalk horizon inferred from azimuthal variations in amplitude versus offset patterns in ocean-bottom seismic data. The azimuthal variations are associated with fracture-induced anisotropy. Fault traces inferred from coherency analysis of seismic data are shown for comparison. There is a good correlation between the inferred fracture patterns and the large-scale faulting. (Figure from Steve Hall’s PhD thesis).
ReferencesTeanby, N., J-M. Kendall, R. H. Jones and O. I. Barkved, Stress-induced temporal variations in seismic anisotropy observed in microseismic data, Geophys. J. Int., 156, 459-466, 2004.
Hall, S. A. and J-M. Kendall, Fracture characterisation at Valhall: Application of P-wave AVOA analysis to a 3D ocean-bottom data set, Geophysics, 68, 1150-1160, 2003.
Hall, S. A., J-M. Kendall and O. I. Barkved, Fractured reservoir characterisation using P-wave AVOA anaylsis of 3D OBC data, The Leading Edge, 21, 777-781, 2002.
Hall, S. A. and J-M. Kendall, 2000, Constraining the interpretation of AVOA for fracture characterisation, in press Proceeding of the 9th IWSA, Houston, Texas.
Hall, S.A., Kendall, J-M., Barkved, O.I. and Mueller, M.C., 2000, Fracture characterisation using P-wave AVOA in 3D-OBS data: Proceedings of 70th Annual Internat. Mtg., Soc., Expl. Geophys., Expanded abstracts.
Hall, S.A., Barkved, O.I., Mueller, M.C. and Kendall, J-M., 2000, An approach for P-wave AVOA in 3D-OBS data, Proceedings of 62nd EAGE Conference and Technical Exhibition, Glasgow, Scotland, C-09(i-iv).
Kendall, R. R. and J-M. Kendall, 1996, Shear-wave amplitude anomalies in south-central Wyoming, Leading Edge, 15, 913-920, 1996.
Hall, S. A., R. R. Kendall, J-M. Kendall and C. Sondergeld, 2000, Analysis of anisotropic velocities in a core sample and AVOA from a fractured vuggy carbonate reservoir, in press Proceeding of the 9th IWSA, Houston, Texas.
R. R. Kendall, S. Hall, J-M. Kendall and C. Sondergeld, Anisotropy from aligned fractures and vugs in carbonate reservoirs and implications for AVOA analyses, Proceedings of 68th Annual Int. Meeting of the Soc. Explor. Geophys., New Orleans, 732-736, 1998.
Harwood, S., P. S. Rowbothom, I. Bush, P. R. Williamson, H. Houllevigue and J-M. Kendall, Analysis of AVOA for determination of fracture orientation, La Revue de l’IFP, 53, 60-64, 1998.
Hall, S. A. and J-M. Kendall, 1999. A methodology for ocean-bottom AVOA analysis using common-receiver data, 69th Ann. Int. Mtg., Soc. Explor. Geophys., Expanded Abstracts, 856-860.
Hall, S. A. and J-M. Kendall, 1997, Coverted phase AVOA effects over multiple fracture sets: application to ocean bottom surveys, proceedings of the 67th Annual Int. Meeting of the Soc. Expl. Geophys., Dallas, TX, SP5.1, 1195-1198.
Kendall, J-M. and S. P. Baker, 1997, P- and S-wave AVOA in fracture-induced anisotropic media, proceedings of 59th EAGE Conference and Technical Exhibition, Geneva, Switzerland, P011.