The Self Potential (SP) log measures the natural voltage difference between an electrode in the borehole and a reference electrode at the surface without applying any artificial current. It is recorded in millivolts on the left track of the log. The SP log principle involves conductive fluid in the borehole creating a potential difference from formation fluids due to salinity variations. SP logs are used to identify permeable zones like sand and impermeable zones like shale, detect boundaries between permeable beds, and determine formation water resistivity and shale volume.

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