I published a column from Debra Bac, one of our regular contributors, that claimed Wyoming bentonite topped everything else out there, specifically mentioning bentonites from west Texas. I didn't think much of it, because I've heard the same thing from drillers I've spoken to. But it touched off a discussion here at National Driller about where, exactly, the best bentonite comes from.
I did some mining. No, not that kind of mining. Digging around on the Internet to see what I could find.
First, a definition from the U.S. Geological Survey. Bentonite is:
"A soft, plastic, porous, light-colored rock composed essentially of clay minerals of the montmorillonite (smectite) group plus colloidal silica, and produced by devitrification and accompanying chemical alteration of a glassy igneous material, usually a tuff or volcanic ash."
That same site lists, state by state, the locations of bentonite formations and their characteristics. It includes the color, general makeup and the era during which Mother Nature laid down each formation (Mesozoic, Cretaceous, etc.). What it doesn't tell us is the quality. For more on that, I had to dig a bit deeper, where I found this document: Bentonite and Fuller's Earth Resources of the United States, USGS Publication 1522. It says:
"The best grade swelling bentonite occurs in the Mowry Shale of Cretaceous age in Wyoming and Montana. The most abundant nonswelling bentonite is found in Tertiary formations of the Jackson and Claiborne Groups in Texas."
Settled? Was Bac right? Not so fast. She says Wyoming bentonite is superior, because it's nearly pure montmorillonite. But, my digging shows that, among those who study clays, the words bentonite and montmorillonite generally get used interchangeably. It's also true montmorillonite comes in both sodium and, as back puts it, "inferior" calcium varieties.
So, what to make of all this confusion?
Miners unearth calcium and sodium bentonite clays all over the world, including in Wyoming, Montana, Texas, Arizona, California, Florida and France, where montmorillonite got its name. Yes, most of the U.S. supply of the best-swelling bentonite comes from Wyoming and Montana—about three-quarters by USGS estimate. But high-quality—drilling quality—clays come from all over.
Bottom line: If it works in the hole you're drilling, the location of the hole it came out of likely doesn't matter.
What do you think? Let me know in the comments or email me.
Stay safe out there, drillers.
In other news
All this talk of bentonite got me thirsty. I think I'll have a tall glass of drilling mud. Another fun fact I found in my digging: Bentonite has some popularity in the health food sector. People mix it with liquid and drink it, hoping it will rid their bodies of toxins. Good luck with that.
And, while we’re on the subject of drilling fluids, if you missed our recent webinar with Ashland about the company’s AquaVIS ETD Polymers, click here to replay it. That link is available for a limited time, so don’t dawdle. Users who didn’t register before the event may have to register to watch the replay.
