Drill Cuttings for Dummies

Drill cutting analysis

Every once in a while, we wake up the Antisocial Network's geologist emeritus and toss him a nominee to chew on. It's dangerous work, since he's renowned for his curmudgeonliness, especially when the topic has something to do with the industry where he spent several decades working: the petroleum industry (or, as his former coworkers are wont to call it, the "awl bidness"). This morning, we slid one under his door, knocked loudly, and ran. A few hours later, he emailed us his comments about the WiseGEEK.com post, "What Are Drill Cuttings"? which Mark Wollacott tried (and failed) to answer.

This is one of those times that we'll give the answer up front, mostly because Wollacott's attempt was so doofus that you'll probably quit reading before the bottom of the page. All Mark had to do was visit the Schlumberger Oilfield Glossary to find a definition: "Small pieces of rock that break away due to the action of the bit teeth."
But no, Wollacott decided he had to... embellish his "answer," beginning with a series of bold misstatements in his first paragraph:

"Drill cuttings are shards of rock resulting from deep sea drilling [sic]. The cuttings are created when the teeth of a drill bit cut through the seabed in order to bore a hole. These boreholes are used to access oil and gas deposits below."

We hate to disabuse Mark of the notion that all cuttings are from "deep sea drilling," made when a drill cuts "through the seabed." No, Mark, cuttings are from drilling in general, and are made when the bit grinds its way through rock, making them sort of an analog to sawdust made when Daddy uses his cordless drill. But we digress... Wollacott righted his fact ship for a moment in the next 'graph, then went all wonky again:

"The majority of cuttings taken from a bore hole are sand [sic] and shale... Other cutting materials include barite, caustic soda KOH, potassium sulphate, sodium bicarbonate, and glycol."

Actually sandstone, limestone, and shale, but OK – until he started that bushwa about barite, etc: those are components of the drilling mud, not the cuttings! Wollacott then spent 300-plus words blathering about separating and disposing of the cuttings, but never mentioned that the cuttings are examined by geologists to determine the rock types encountered at depth and evaluate the possibility of a productive reservoir zone, No, according to Mark, all that's important is,

"After drill cuttings have been separated, the contractor must decide whether to dispose of the cuttings or make use of them."

Nope, no mention of using the cuttings for science. So now you know why Mr. Wollacott has just received his first Dumbass of the Day award. Something tells us it won't be his last, not if he tries to talk about science again.

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