Gamma Ray Logs for the Clueless

Sample gamma ray log

When we happened not long ago upon some dumbassery at WiseGEEK.com about petroleum exploration, we tasked our house geologist – who has many years of experience in the “awl bidness” – to take a look through some of their related content. We based that on the assumption that, as often happened at Demand Media, freelancers would write several related articles because their research made them experts. She turned up several articles, including “What Is Gamma Ray Logging,” by B. Turner (now, for unknown reasons, at AboutMechanics.com).

Like not-so-wise geek Paul Reed, who penned the article about sonic logging that was our first WiseGEEK DotD, Turner demonstrates little knowledge of what gamma-ray logs are, and even less about how they’re used. Instead, Turner (as seems to be WiseGEEK’s pattern) simply reworded another source, perhaps at another content farm, managing in the process to filter out most of the useful information.

This “filtering” is especially true of anything remotely technical. Take, for instance, this passage from Turner’s opening paragraph:

“Gamma ray logging is a process used to measure naturally-occurring radioactivity below the soil. As certain types of rocks break down over time, they emit radiation in the form of gamma rays. There is a high correlation between gamma ray activity and deposits of sediment-rich rocks and clay called shale. The presence of shale often serves as a solid indication that oil and natural gascan [sic] be found nearby.”

Here to expand upon and/or correct Turner's content is our geologist:

• “Below the soil”? WTF does that even mean – in bedrock? Then say so!
• “Certain types of rocks”? No, idiot, minerals rich in elements that have unstable isotopes. For instance, potassium-40, common in shales and in the mineral feldspar, is unstable.
• “Sediment-rich rocks”? I don’t even know WTF that’s supposed to mean!
• “The presence of shale often serves as a solid indication that oil and natural gascan [sic] be found nearby.” Oh, dear lord, are people actually that stupid? Does this moron know that if you’re standing on a sedimentary rock, there’s a pretty good chance there’s shale under your feet. 

Turner also somehow came to the (mistaken) conclusion that,

“During gamma ray logging, geologists start by drilling a deep bore hole to access areas well below the surface of the earth. ”

That’s a monumentally stupid statement: That “deep bore hole” is an exploration well, usually for hydrocarbons but also for coal, minerals, or even water. The gamma ray log is a tool used to understand what the borehole has penetrated – not the reason that the hole was drilled in the first place!

Last, but not least, Turner claims that,

“…they lower a cesium or sodium iodide probe down below the surface using cables or ropes. The probe measures gamma rays at different depths, generally every few feet or meters.”

Again, a monumentally stupid statement, especially since Turner’s opening paragraph says that gamma ray logs measure natural radiation! Oh, and by the way? gamma-ray log measurements are taken at 6-inch intervals, not "every few feet or meters"!

Almost every assertion coming from Turner’s keyboard is misinterpreted, misleading, or just plain wrong. Half of what Turner wrote (anti-kudos to Turner’s “editor,” W. Everett) is just plain stupid. We can see a site-wide search for more output of the sort of output that has garnered B. the coveted Dumbass of the Day award.

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