Resistivity logging presentation prepared by me to present in a class.

1. Wireline Logging and Hydrocarbon Exploration
Presented by
Ziaul Haque
Department of Geology and Geography
Auburn University
Auburn, Alabama, USA

2. Outline:
Part-I
 Wireline logging
 Why logging
 Types of logging
 Uses of different logs
 History of logging.
 Tools
 Resistivity logs
Part-II
 Resistivity logs.
 Caliper logs
 Caliper logs tools
 Uses of caliper logs and Resistivity Logs
 Hydrocarbon determination.

3. Wireline Logging
 Continuous recording of a geophysical parameter along a borehole.
 The value of the measurement is plotted continuously against depth
in the well.
 May represent over 4 kilometers of readings continuously.

4. Things to remember: Why logging?
 Sampling during drilling ( cutting sampling) is imprecise recording of the
formations encountered.
 The results of coring is very precise and unequivocal but this is slow and
expensive.
 Logs fill the gaps between ‘cuttings’ and ‘cores’, and with experience,
calibration and computers, they can almost replace cores.
 Logging is precise but equivocal; needs high level of geological and
petrophysical experiences.
 A single log never tells about the subsurface condition.
 To identify the subsurface condition with certain degree of confidence we need
at least three different types of log.

5. History of logging:
In 1919 Conrad Schlumburger first use
logging measurement for hydrocarbon
determination.

6. Logging Tools:
Schematic Diagram of Wireline Well-Logging
Sonde

7. Uses of wireline logs:

8. Resistivity Log
 Off all the logging tools resistivity is the most archetypal. It was with
resistivity measurements that Conrad Schlumberger started his company in
1919.
 The resistivity log is a continuous plot of a formation’s resistivity from the
bottom of the well.
 Measures the resistance to the passage of electric current.
 Measured by resistivity tools.

9. Resistivity Logging Principle:
 Most rock materials are essentially insulators.
 Formation fluids that enclosed the rocks material is conductors.
 Hydrocarbons are the exception to fluid conductivity.
So when a formation is porous and contains salty water the overall resistivity
will be low and when the same formation contains hydrocarbons, its resistivity
will be high.

10. Formation Resistivity Factor (F):
Although rock plays no
active role but it has
passive role in the
resistivity or
conductivity. The
passive role is basically
dependent on rock
texture or more
specifically on the
geometry of the pores
and pore connection.
Schematic illustration of three formations which have the same porosity
but different value of F.

11. Next Class:
 Resistivity Measurement tools.
 Resistivity profiling.
 Resistivity of fine grained material.
 Caliper logging.
 Caliper log tools.
 Uses of resistivity and caliper logs
 Hydrocarbon determination.

12. Questions?

13. Thank You All
For Your Attention

14. Review of Part-I

15. Wireline Logging
 Continuous recording of a geophysical parameter along a
borehole.
 The value of the measurement is plotted continuously
against depth in the well.
 May represent over 4 kilometers of readings continuously.

16. Resistivity Log
 The resistivity log is a continuous plot of a formation’s resistivity from the
bottom of the well.
 Measures the resistance to the passage of electric current.
 Measured by resistivity tools.

17. Part-II
 Resistivity logs.
 Caliper logs
 Caliper logs tools
 Uses of caliper logs and Resistivity Logs
 Hydrocarbon determination.

18. Resistivity Measurement tools:
 The basic circuitry of the resistivity tools was established by the Conrad Schlumberger in
1927.
 Current electrode passed current through the formation and the potential drop is measured
between two potential electrodes.
 Two types of resistivity tools are used: Focused (Modern) and Non focused.

19. Resistivity Profiling at different depth:

20. Types of resistivity tools are used to measure resistivity
in different zones surrounding the borehole:

21. Why fine grains (Shale) material shows low resistivity:
 Rocks plays passive role in the resistivity or conductivity its not always true.
 When shale is present it plays an active role in conductivity and F is no longer
constant.
 Clays conduct electricity in two ways, through pore water and through the
clay itself.
 Clay is like an inverted electric cable; the inside is non-conductive while the
outside is conductive.

22. Caliper tools measure hole size and shape. The simple
mechanical caliper measures a vertical profile of hole
diameter. The more sophisticated geometry tools records
two simultaneous calipers and give an accurate borehole
shape and orientation.

24. Uses of Resistivity Log:
There are two types of use:
1.Quantitative use:
 Hydrocarbon saturation measurement
2. Qualitative use:
 Textures.
 Gross Lithology.
 Correlation.
 Facies identification.
 Compaction, Shale porosity and 0verpressure.

25. Qualitative Uses of Resistivity Log: Lithology

26. Qualitative Uses of Resistivity Log: Correlation

27. Qualitative Uses of Resistivity Log: Overpressure

28. Hydrocarbon Identification:
Negative separation: a good
indicator of presence of
hydrocarbon.
Fig: Resistivity over the gas/oil
bearing zone. MSFL shows very low
resistivity in the flushed zone(mud
fluid resistivity),LLS shows a little
higher resistivity(transition zone
resistivity) and LLD shows very high
resistivity(resistivity of virgin area).