Mixology Is for Bartending and Drilling Fluids

Straying too far from the mixes, though, can cost time and money.

By Todd Tannehill

Drilling fluid companies put out mix charts and online calculators to make sure contractors use the correct
products for the soils they are drilling in. In fact, it’s not just a matter of using the correct products but also using the proper amount to go with the manufacturers’ products and get the best results for drilling contractors.

Figure 1. Soil identification. Source CETCO Vertical Drilling classroom presentation.

Inside a bag of high-yielding sodium bentonite are extenders and treatments that allow the drilling gel to work at maximum performance. Different companies use different treatments, and for that reason, using one brand for all products in the mix is important.

Once you decide on the manufacturer, the process of proper soil identification is next. Knowing if you have consolidated or unconsolidated soils is key when designing a mix. We also interchange terms with reactive and non-reactive soils. See Figure 1.

Saving Money

Reactive soils are reactive because they can absorb water and swell, become sticky, and create torque, bit balling, and even restrict annular flow. These soils have different degrees of stickiness, and thus, are treated differently.

A non-reactive soil is identified as sand, silt, gravel, and cobble. For these loose soils, we need to tighten the bentonite platelets up to reduce fluid loss to the surrounding soil, to maintain borehole stability.

Mixing charts and online calculators show basic mixes for single soils (Figure 2). These mixes are good starting points, but it’s possible to have clay and sand mixed in the same soil. Your “mud person” can design a mix to deal with your specific soil.

Figure 2. Online calculators assist in mix design. See www.mineralstech.com/cetco/drilling-products/tools-training/vertical-drilling-calculator.

Once the soil is identified, you can design a fluid mix that will maximize your drilling efforts and save money on the project. Save money? Yes, by knowing your soils and adding what works for that project, you can actually save by not overdosing the mix.

I was on a North American project a few years ago. The contractor and utility had a “mud engineer” on site to tweak the drilling fluids mix. When I arrived I asked, “What is in your mix?” My mouth dropped when he listed the nine products being run!

He had products in the mix that were actually working against each other to reduce results. When I pressed him on why he had certain products in the mix, he replied, “It’s working, and we are not sure what product is doing what, so we are running it all.”

I believe he only needed four products for the project: Soda ash (always), high-yield sodium bentonite, polyanionic cellulose polymer (PAC), and xanthan gum for suspension. That means there were five extra products—and extra cost in every tank of fluid!

As I stated previously, many times we have to set up for varied conditions, but that may add an additional one or two products to our mix. The simpler the mix design, the easier it is to replicate each tank.

When setting up for non-reactive soil (sand and gravel) with reactive soil (clay) present, it is recommended to set up for the worst condition. In this case, that is the sand. It makes sense that if you can’t control fluid loss to keep the hole open or suspend cuttings in non-reactive soils, then the additional clay product will not produce the desired results. Online calculators and mix charts will suggest optional products to add when clay is present.

Different companies use different treatments, and for that reason, using one brand for all products in the mix is important.

League of All Nations

The project I saw running the nine products had an additional issue. The project was “a League of All Nations.” This means it was a mix of products from different manufacturers. Adding different brands or combining mix charts can be a recipe for disaster.

When I add a suspension enhancer or xanthan gum to a mix, I know—based on my bagged bentonite—how much to add. Based on the branded mix charts, I know how it might change the viscosity or suspension capabilities. This is because different manufacturers add different additives (treats) to their high-yield bentonite bags.

One bag of your favorite brand’s high-yielding sodium bentonite drilling fluid comes pretreated with polymers and additives for fluid loss, suspension, and other general properties. But not all treats are the same and different brands have different mindsets on how to achieve the desired results. To prevent cross mixing, you should use the same brand polymers and additives when designing a mix.

All bentonite companies employ talented research and development professionals. These folks design mixes to be replicated in the field to optimize the efforts of drillers. Varying too far from these mixes can be costly in time and money.

Leave the mixology to the bartender and call your favorite “mud doctor” when you need assistance.

Todd Tannehill, based out of northeast Ohio, is the North American Director for the Drilling Products division of CETCO. Minus a brief hiatus, Tannehill has been with CETCO since 2005 and is well known in the industry for providing strong technical support to contractors, distributors, and engineers. He is a past board member of the National Ground Water Association and can be reached at todd.tannehill@mineralstech.com.