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Permalink Reply by Jack Straw on April 13, 2013 at 8:07am

What you were looking at was a Gamma Ray Well Log.

As part of the suite of well logs that can be run, the Gamma Ray Well Log is one of the most common.

The logging tool is run into the hole and measures the Gamma Ray radiation that is naturally emitted by the rocks in the subsurface. This is a passive logging tool, it simply measures the radiation present at various depths in the well. This radiation is related to the slow natural decay of radioactive minerals present (everywhere) in the subsurface.

Clean Sands emit very few Gamma Rays, Shales emit quite a few more. Some shales are "hotter" than others.

The Gamma Ray Well Log (when used in conjunction with other well logs) can provide valuable information about the types of rocks present and can assist in correlating the lithology (rocks) from one well to another.

For an explanation of a number of commonly used well logs (including the Gamma Ray Log), look here:

http://www.greatgeophysics.com/logginginfo.html#B._GAMMA_RAY

JS

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Permalink Reply by Don C on April 13, 2013 at 9:01am

Interesting.........Thank you

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Permalink Reply by The Hiker on April 13, 2013 at 8:22am

http://en.wikipedia.org/wiki/Gamma_ray_logging

Better explantation than I can give.

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