SP logs are used to distinguish permeable zones; which unit are they measured in?

SP logs are used to distinguish permeable zones; which unit are they measured in?

• A. mV
• B. API
• C. Porosity
• D. Flow Rate

Answer: (A)

Spontaneous potential (SP) logs measure a natural voltage difference that develops between the borehole fluid and formation water without any active energy input. This electrical potential is recorded in millivolts, so SP readings are expressed in mV. The SP response helps distinguish permeable zones because water-bearing formations with different salinity from the mud create noticeable potential differences, producing characteristic deflections on the log. Other options don’t fit because API is a crude-oil gravity unit, porosity is a property described as a fraction, and flow rate is a volume-per-time measure; none are the units used for SP log readings.

Spontaneous potential (SP) logs measure a natural voltage difference that develops between the borehole fluid and formation water without any active energy input. This electrical potential is recorded in millivolts, so SP readings are expressed in mV. The SP response helps distinguish permeable zones because water-bearing formations with different salinity from the mud create noticeable potential differences, producing characteristic deflections on the log.

Other options don’t fit because API is a crude-oil gravity unit, porosity is a property described as a fraction, and flow rate is a volume-per-time measure; none are the units used for SP log readings.