well logging geology earth science

2. Electrical Logs
Self Potential log

3. * Definition.
* Units& Presentation.
* Applications.
* Theory and Principle of
measurement.

4. ObjectivesObjectives
To understand the physical principles behind
the operation of spontaneous potential (SP)
logging.
To learn how to interpret SP logs in terms
of lithology and petrophysical properties.
To understand what corrections needed to be
applied to SP log before using it for
interpretation.
Self (Spontaneous) Potential (SP) log

5. The SP is a measure and record of direct
current (DC) voltage differences between the
naturally occurring potential of a moveable
electrode in the well bore, and the potential
of a fixed electrode located at the surface.
SP logSP log ““DefinitionDefinition””

6. OROR
It is the measurement of natural potential
difference or self potential , between electrode
in a bore hole and reference electrode at
surface.
No artificial current are applied.

8. Units and PresentationUnits and Presentation
The SP log is recorded on the left hand
track of the log in track #1
It is measured in millivolts (mv).

9. Principle of MeasurementPrinciple of Measurement
1(Conductive fluid in the bore hole
2(Porous and permeable bed surrounded by
impermeable bed.
3(Difference in salinity between bore hole
fluid and formation fluid.

10. The SP log is used to identify
impermeable zones such as shale, and
permeable zones such as sand,
Detect boundaries of permeable beds,
Determination formation water
resistivity(Rw(,
Calculation the volume of shale in
permeable beds.
SP log “General Uses”

12. Theory of Measurement

13. THANK YOUTHANK YOU