Knowing how to mix drilling fluids is an essential part of maximizing your horizontal directional drill’s efficiency. Properly mixed mud and fluid helps provide lubrication and cools downhole tooling and electronics, as well as maintains the integrity of the bore path and flush drill cuttings.

When you break it down, there are two main mud categories: liquid and dry. Which one should you choose? Both have pros and cons, making them each helpful for some drill sites and less helpful for others. Whether you use dry or liquid mud can depend on each specific jobsite and ground condition.
Here is a look at what that means.

Check your Water First

On every new job, you should check pH levels from your water source. Drilling fluid additives (bentonite and polymers) mix better with a pH level range between 8 and 9. Municipal water will typically measure around that range. However, if you’re using water from a pond or well, the pH level will likely fall below that range. Adding soda ash will help raise the pH levels and help you use less drilling fluid products.

When you’re ready to mix your additives with the water, powders (dry) like bentonite must be added to the hopper and liquids should be poured directly into the tank.

Liquid Drilling Additives

But before you pour any liquid additives into the tank, you should know more about them.
“Liquid additives, also known as polymers, are more commonly used in short bored and common ground conditions,” explained Vermeer training manager Dan Vroom.

Some popular liquid additives include PAC, PHPA and lubricants/detergents. One important note: these come in a dry version, as well.

They have both pros and cons to using them. Here are a few:

Pros:

  • They come in small packages, so they’re lightweight and easy to transport
  • They can be quickly added and mixed into your fluid/tank
  • They require minimal product training

Cons:

  • They can freeze
  • They’re limited to fluid characteristics of polymers
  • They have a shorter shelf-life
  • Most aren’t usable in recycling systems

If you plan to add a liquid additive, you’ll need to wait until the bentonite or powder is completely mixed in (about 10 minutes). Adding a liquid too soon or out of sequence can cause the bentonite to ball up in the tank, rendering it ineffective. If you’re not using bentonite with your liquid additives, you don’t have to wait 10 minutes; you can pour it right in.

“The biggest reason people choose liquid additives usually has to do with their skillset or comfortability with the liquids,” said Vroom. “One caution to that is to make sure that you’re changing your fluids to the drilling conditions that you’re in.”

No borehole or project is exactly alike, so knowing your soil and the right combination of fluids for each situation is key to successfully lubricating the downhole tooling and keeping the borehole open.

mud mixing

Dry Drilling Additives

There are also pros and cons to using dry products or powder, such as bentonite or dry polymers. Here are a few of each:

Pros:

  • They don’t freeze
  • They have a long shelf-life
  • There’s a non-polymer option (bentonite)

Cons:

  • They’re heavy and come in bigger bags or buckets
  • They’re dusty and dirty
  • They can require multiple steps to add “ingredients” to fluid
  • They require 10 minutes to hydrate in the fluid
  • They require more intensive product training

Every Vermeer fluid mixing system is equipped with a bag cutter next to the hopper to split and empty the whole bag of powder into the hopper at once. Doing it this way, instead of cutting it with a knife and slowly sifting material into the hopper, will help reduce dust levels and help prevent air from getting into the system.

If you’re adding bentonite, make sure it’s sent through the venturi and hopper at full throttle. You want to get the maximum implosion through the venturi to mix the product well. After enough bags of bentonite are added, keep the product mixing through the venturi for approximately 10 minutes until it’s thoroughly broken up and hydrated. Always make sure the person assigned to drilling fluid mixing is fully trained on the proper steps.

Another factor to consider is the size of the borehole. “If you’re drilling in a borehole that’s 10 in. (25.4 cm) or more, you should consider the range of options you have with liquid and dry drilling products,” said Vroom. “At that size, you’ll most likely need to use and mix a combination of liquid and dry, or go beyond using just one product.”

Use a Mixing System

The final step is to check the drilling fluid viscosity. If it’s too thick, add additional water or thinners; if it is too thin, add more drilling fluid additives.

“Whether contractors are buying bags of bentonite or have made the switch to liquid drilling additives in pouches, using a mixing system is crucial,” said Vermeer product manager for trenchless products Tod Michael. “With powders, you can see if an additive hasn’t been properly mixed. However, with the newest prepackaged liquid concentrate additives, sometimes people think they can pour it into the water tank with minimal stirring. Proper mixing and testing of your fluids should still be done for the best results.”

To help with the mixing process, manufacturers, including Vermeer, offer several mix systems, appropriately sized for the directional drill your crew is running. When you use dry or liquid additives, the important thing to consider is the water pH levels, your ground conditions, and the amount of mud you’ll need. That can factor into whether you use dry or liquid and can help keep your jobsite running efficiently.

Jon Hausler is a senior content marketing specialist at Vermeer Corp.