Geology 449-University of Calgary

Petrophysical Techniques; Geology/Geophysics 449

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Questions on Petrophysical Log Interpretation will not appear in the following exam. Log questions are published under a separate section.

Go to: Midterm II | Well Log Interpretation

Geology (GLGY 449-UCAL) Midterm I

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Credits: Based on the excellent class notes provided by, Dr. Rudi Meyer during Fall 2014.
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Type
of tool
DOI Resolution Used for… Processes Notes
Caliper NA NA -Borehole size
and shape
Spring loaded
arms
2 arm = diameter
4 arm = shape, orientation
Gamma
Ray
10 – 15 cm ~40 cm -Lithology(vol. Shale/Sand often due to high K), geosteering,
facies, depth control
-Photoelectric effect (dom)
-Compton scattering
-Pair production
-Scintillation counter + photomultiplier
High (right kick):
-Shale line
-Organic content
-K-Feldspars
Low (left kick):
-Clean sand
-Carbonates
-Clean coals
Spectral
Gamma Ray
    -Radioactive anomalies
-Clay types
-Volume of shale(clay)
-Same as GR, but much better/larger scintillator  
Density
& Photoelectric Factor
< 10 cm 11 – 40 cm -Porosity, general lithology, min ids    
Neutron 15 – 25 cm ~50 cm -Fluid, porosity, density, cross-over gas effect
-Meassures porosity; used for calulating density
Hydrogen High (left kick):
-Shales and coals
Low (right kick):
-Gas breaing fm./rocks
Use Dphi & Nphi chart
*Decreased with increased permeability
Spontaneous
Potential
Depends Depends -Permeability(even small), lithology, facies, shale volume(not
so much)
Natural potential differences between fms. caused by:
-Diffusion
-Mambrane or shale potential
Important:
-Salinity of drilling fluid to fm.
-Conductive drilling fluid
-Constrasting permeability in adj. beds
-Surface electrode(earth)
No absolute scale(relatove +/-)
Positive kick (relative):
-Clean sand or sand stone, shaly sand
Negative kick (relative):
-Shale
*Decreased with increased permeability

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