Calculate Water Resistivity (Rw)- SP Log

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Water Resistivity (Rw)- SP Log

Water resistivity (Rw) can also be calculated from the spontaneous potential (SP) well log. This equation needs the values of mud filtrate resistivity, an SP measurement, and a constant K that depends on the formation temperature. The equation is the following:

Where:
• Rw = water resistivity
• Rmf= resistivity of mud filtrate at formation temperature
• K= constant
• SP= SP measurement

Calculate Water Resistivity (Rw) - SP
K:		Rmf: ohm-m
SP: mV

Constant K

For the calculation of constan K, formation temperature has to be known, and the expression is the following:

Where:
• Tf= formation temperature

Calculate Constant K - SP
Tf: °F

Made by Henry Herrera

Calculate Shale Volume Vsh - SP Log

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List of equations assignment

Shale Volume - SP

From the spontaneous potential (SP) well log, it is possible to calculate shale volume from 2 different equations. The first expression is the following:

Where:
• Vshale= volume of shale
• PSP= pseudostatic spontaneous potential (maximum SP of shaly formation)
• SSP= static spontaneous potential of a nearby thick clean sand

Calculate Shale Volume (Vsh)-SP
PSP: mV		SSP: mV

The other alternative to calculate shale volume is the following one:

Where:
• SPshale= value of SP in a shale (usually assumed to be zero)

Calculate Vsh - SP
PSP: mV		SSP: mV
SPshale: mV

Made by Henry Herrera