Lecture itemsLecture items- Electric Properties of Rocks.

- Factors affecting resistivity of reservoirs

- Electrical Logs

(Self Potential log, Conventional resistivity logs , Laterologs, Dual Laterologs, Microspherically focused logs, Induction logs).

Factors affecting resistivity of reservoirsFactors affecting resistivity of reservoirs

Salinity ∞ 1/RTemperature ∞ 1/RSaturation ∞ 1/RPresence of hydrocarbons ∞ RLithology plays an indirect role for

controlling resistivity

Electrical Logs - Self Potential log, - Conventional resistivity logs , - Focused resistivity Logs, - Microspherically focused logs, - Induction logs.

ObjectivesTo 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

* Definition.

* Units& Presentation.

* Applications.

* Theory of measurement.

-Shale-base line& Sand line

-SSP, PSP and SP log readings

* Factors affecting on log readings.

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.

The SP log is recorded on the left hand track of the log in track #1

It is measured in millivolts (mv).

SP log “Definition”

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”

Theory of Measurement