Porosity Logs Flashcards
Properties measured by Geophysical Logs (Wireline Logs)
- Electrical Resistivity/Conductivity
- Natural radioactivity levels in rock
- Acoustic wave propagation velocities
- Bulk Density
- Porosity
- Element Concentrations (e.g., Si, Fe, Ca, Cl, H)
- Magnetic properties (H relaxation time)
- “Visual” Images of the borehole surface
- Borehole dimensions
Resistivity/Conductivity Log
Good for fluid saturation.
Spontaneous Potential (SP) Log
Differentiate high and low permeability formations.
Gamma-ray Log
Lithology (shale) indicator. Detects decaying radiation within the elements of K, Th, U and if often found in clays/shales
Sonic Log
Good for porosity, mechanical properties. gamma source is emitted and scatter gamma is collected back at borehole
*pressed onto well bore via pad, only works in open boreholes
Bulk Density Log
Good for porosity, gas detection, mechanical properties.
Photoelectric Factor (PE) Log
Lithology indicator.
Neutron Porosity Log
Good for porosity, gas detection. neutrons are emit from sonde and slowed down by hydrogen atems. gamma rays are emitted when a slow neutron captures an atom
Elemental Capture Spectroscopy (ECS) Log
Lithology
Borehole Image Logs
To identify the presence, characteristics and orientation of bedding or fracture planes; Also good for borehole breakout analysis.
Caliper Logs
Cement volume analysis; hole quality indicator; borehole breakout analysis.
NMR logs:
For free fluid volumes, pore sizes, permeability estimation
Geophysical Logs: Advantages
than continuous coring
•Define geological contacts; basis for correlating between wells
•Unbiased & reproducible
•Provide basis for deciding where to collect samples
