1. Lecture items Self Potential Log * Theory of measurement.
-Shale-base line& Sand line
-SSP, PSP and SP log readings
* Factors affecting on log readings.
* Applications.
Resistivity Logs
* Definition.
* Types
* Units& Presentation.
* Theories of measurement.

3. 1- Electrokinetic Potential (can be neglected)

7. 2- Electrochemical Potential
1) Membrane Potential
2) Liquid Junction Potential

14. Factors affecting SP log measurements
Rmf/Rw (Salinity effect) Fresh mud: negative SP, Saline mud: positive SP.
Shale or clay content Shale reduces SP.
Permeability
Presence of hydrocarbon
Bed thickness: SP decreases when bed thickness decreases.
Invasion: Reduces SP.
Mud filtrate: The magnitude and direction of SP deflection from the shale baseline depends on relative resistivities of the mud filtrate and the formation water.
Resistive formations

20. Clean Laminated Structural Dispersed

23. Rw calculation from SP

26. Applications Differentiation between shaly, clean and shale zones.
Differentiation between Permeable and non-permeable zones.
Calculation of Rw.
Determination of the volume of shale.
For correlation purposes
For sedimentological analysis and facies studies.

29. Notice how the shale baseline shows a distinctive drift with depth
Notice how the shale baseline shows a distinctive drift with depth. This characteristics is commonly caused by an increases in relative oxidation of the rocks that are close to the land surface. The highest sandstone in the well has a muted deflection on the SP log as compared with the lower sandstones. This contrast is an immediate indication that water in the upper sandstone may be significantly fresher than waters of the lower sandstone. In other wells it is not uncommon to see sandstone units where the SP deflection goes to the right of the shale baseline. In these instances, the drilling mud filtrate is salter than the formation water.

30. A good example of this phenomenon is shown in the figure attached
A good example of this phenomenon is shown in the figure attached. In the upper sandstone, "U", the SP log shows a deflection to the right, indicating formation water to be fresher than the drilling mud, while in the lower sandstone, "L", the deflection is to the left, showing the formation water to be more saline.

31. Flow chart from oil-industry log analysis to estimate formation water resistivity, Rw, in deep formations from the SP log. RMF is mud filtrate resistivity measured at temperatureTmf and recorded on the log header; Tf is the temperature of the formation, generally estimated by interpolating between the bottom-hole temperature (BHT) at total depth (TD) and mean annual temperature at the surface; SSP is the static self-potential measured on the log between the "clean line" and "shale line" in millivolts (mv) and with associated sign (positive or negative).