WELL LOGGING

• Well log is a continuous recording of geophysical parameters

• Logging : to determine petrophysical properties

TYPES OF LOGS

• LITHOLOGY LOGS

  • Gamma-ray logs - measure natural radioactivity , volume of shale

  • SP logs - measure DC potential difference, volume of shale fraction

• POROSITY LOGS

  • Density logs

  • Neutron logs - measure hydrogen concentration in the formation

    • Sonic logs - measure interval transit time, compressibility of waves

• ELECTRICAL LOGS

  • Resistivity logs

  • Borehole imaging

• Miscellaneous logs

  • Caliper log : borehole diameter

  • NMR : hydrocarbon saturation and permeability

Depth of investigation

Induction > Lateralog > Neutron > Gamma ray > Density > Sonic

• Magnetotelluric has highest depth of investigation

• Magnetotelluric > AFGAM > VLF > GPR

• GPR has highest frequency but less depth of investigation

• VLF - Measure angle

• TURAM - Measure phase