Drillers needing extra suspension have long reached for suspension enhancers to increase gel strength and keep the returns flowing. Every bentonite company has a slick brand name for them but, for the most part, they are xanthan gum-based products.
Xanthan gum is a polysaccharide secreted by the bacterium Xanthomonas campestris. PAC, guar, diutan gum, and welan gum are other common polysaccharides. Diutan and welan are non-ionic, like guar gum, whereas xanthan gum has an anionic charge. For the non-oil and gas side of drilling, xanthan proves to be the most cost-effective and job-specific suspension aide.
For our drilling purposes, xanthan is an easy mixing biopolymer used to control drilling fluid rheology. It is designed to enhance gel strength for improved suspension and aid in transporting normal cuttings as well as heavier gravel and cobble. Our goal is to always keep the hole open and transport the cuttings outward.
Xanthan gum is a byproduct of the bacterium that rots vegetables like cauliflower and cabbage; it turns them black. Greg Plutko in my lab added, “the bacteria naturally produces a polymer formed of repeating sugar molecules to help a colony adhere to the leaf and protect it from washing off.” In the 1950s, a researcher at the U.S. Department of Agriculture figured out how to turn this natural bacterial slime into a substance that you eat or use at home every day. In 1968, xanthan was approved for food use in the U.S. and many other countries. Salad dressings, gravy thickener, yogurt, gluten-free baked goods and ice cream are just a few items made better with xanthan. Along with being a drilling aid for both oilfield and non-oil drilling, other industrial uses include pastes, glues and inks. Xanthan gum is so versatile that it is in way too many products to list.
In drilling, several factors make xanthan gum a great tool for the jobsite:
- Suspension (gel strength).
- Filter-loss improvements due to the anionic charge on the molecule, which helps improve filtrate loss; whereas, non-ionic gums like guar will flocculate bentonite.
- Easy dispersal in drilling fluids.
Its ability to work in saltwater adds to its versatility. This is due to its short, three-sugar-long sided chains that prevent the polymer from coiling up in salty conditions. This is unique for anionic polymers, and really makes xanthan stand out from other polysaccharide types.
Most manufacturers sell their xanthan product in a powder. It can have a long shelf life if kept in a closed bucket and dry. In the field, we recommend you add it slowly through a hopper at maximum shear to avoid lumping and to minimize waste. Read your brand’s instructions, but a normal dose is one-half to 1 pound per 100 gallons of drilling fluid.