@gopigeo,
are you doing down hole or cross hole? Im used to doing a bunch of sondes down hole and having em all plotted.
EM and resistivity are induced nd SP is self generated.
Think about how the sonde for SP is made. (there are several styles , from induction to SP /SP.)
You have a decent knowledge of the theory behind your tools?
heres a quote from Conrad SChlumberger himself" re SP (in mv)
Quote:
Naturally occurring (static) electrical potential in the Earth. Spontaneous potentials are usually caused by charge separation in clay or other minerals, by the presence of a semipermeable interface impeding the diffusion of ions through the pore space of rocks, or by natural flow of a conducting fluid (salty water) through the rocks. Variations in SP can be measured in the field and in wellbores to determine variations of ionic concentration in pore fluids of rocks
Its measured in the hole with an e' and a reference electrode at the surface.
It is usually ALWAYS measured along with resistivity (in reciprocal ohms) and gamma and gmma gamma (Which are imprcious to the borehole and liners and mud infiltration.
We now use several other combined logs including gps -tilt and radar nd specific ions
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