Seismic properties

Phase transition © iStockphoto.com/Grasko

Shale is extremely anisotropic, unlike sandstone and carbonates, which exhibit weak anisotropy. Any seismic data acquired over shale gas deposits will be affected by this strong anisotropy, and processing and interpretation of seismic data have to take anisotropy into account.

The BGS Edinburgh Anisotropy Project (EAP) is a world-leading research team that has pioneered the use of seismic anisotropy for characterisation of natural fractured reservoirs.

It is developing further innovative methods for fracture mapping using wide azimuth 3D P-wave data, 3D-3C land multicomponent data, and 3D-4C ocean bottom cable (OBC) data, with applications in mapping fracture patterns in shales.

The EAP produces guidelines for best practice, provides training courses and undertakes consultancy work.

For further information about induced seismicity see Fracking and seismic activity.

BGS capability includes:

Fracture mapping

Fracture mapping using wide azimuth 3D P-wave data, 3D-3C land multicomponent data, and 3D-4C OBC data:

  • azimuthal analysis P-wave attributes
  • shear-wave splitting analysis of multicomponent data
  • PS converted-wave analysis
  • singular value decomposition (SVD) inversion of fracture density using P-AVO
  • guidelines for best practice
  • training courses and consultancies

Rock physics modelling and inversion for shales

Analysis allows prediction of seismic properties of shales and shale gas deposits for given mineral compositions and total organic carbon (TOC). The rock physics model provides the basis for any lithological inversion using seismic data.

  • anisotropic properties derived from rock mineralogy, e.g. quartz, potassium feldspar, calcite, kerogen, clay
  • anisotropic properties derived from rock and matrix properties, e.g. porosity, permeability, number of fracture sets
  • analysis of wire line logs and laboratory measurements of shales
  • SVD inversion of shale's brittleness using PP- and PS-converted-wave seismic data

Anisotropic processing of P- and PS-converted-wave seismic data

  • shale anisotropic parameter estimation from pre-stack data
  • pre-stack anisotropic migration of P- and PS-converted-wave data
  • joint inversion of PP- and PS-converted-wave for Young's module and Poisson's ratio

Contact

Contact Ed Hough for further information or enquiries about BGS shale gas consultancy services