Proper drilling fluid mixtures stabilize the hole, cool the down-hole equipment and remove spoils. To help get the right mix, contractors should know the basic type of soil through which they’ll be drilling, as well as the water's chemistry.

David Wampler can understand why some contractors think drilling fluid products seem a bit like snake oil. “It looks like dirt in a sack, and you have this sales guy saying it’s good for you,” says Wampler, owner of Jackson Creek Enterprises LC, a directional drilling company located in Allerton, Iowa.

Wampler, who worked for five years as an international product specialist for Vermeer Manufacturing Co., knows from experience that having the right fluid mix can be the difference between success and failure on the jobsite.

“I’ve known contractors who have left thousands of dollars in the ground because they used the wrong fluid mix,” Wampler states.

Ed Savage, trenchless segment manager at Vermeer Manufacturing Co. in Pella, Iowa, says a common mistake contractors make is skimping on fluid mixes in order to try to save money. He adds that when costly equipment and material are at stake, attempting to save a few dollars per bag of bentonite may not be the best choice.

Wampler agrees. “I would say, on average, the fluid mix is only 5 percent of my total cost of a bore. That is a small amount when it helps guarantee a successful bore,” he adds.

In essence, drilling fluids are a mixture of water treated with drilling fluid additives. According to the North American Society for Trenchless Technology (NASTT), drilling fluid mixtures are beneficial because they stabilize the hole, which helps diminish the potential for hydrofracturing and allows product to be pulled in more easily. In addition, they cool the down-hole equipment and remove spoils from the hole.

There are some basic questions a contractor should ask in order to determine the right fluid mix for any given job.

What Is the Soil Type?

Savage explains that contractors should know the basic type of soil they will be drilling through. Sand, clay, rock and dirt have different characteristics that affect the drilling rig and tooling.

For example, clay can swell and become sticky when exposed to water, Savage says. This can increase machine torque and intensify drag on the material being installed.

Wampler adds, “If it increases the torque to the point that you can no longer rotate, or increases the drag on the pipe to the point that you can no longer pull, then you are done.”

Sandy soils can also stop a job or damage equipment. The porous nature of sand allows water to flow through it, limiting lubrication and the ability to remove cuttings. In addition, sand can be abrasive. “I have seen starter rods eaten up in 30 feet to 40 feet of sand using only water,” Wampler explains.

A fluid mix can help in each of these conditions.

Bentonite will break down into small platelets when mixed with water. “Imagine a bunch of playing cards that stack on top of each other,” Savage explains. The bentonite platelets shingle off the wall of the hole and form a filter cake around the circumference of the borehole. The filter cake keeps fluid in the borehole, which keeps tooling and product lubricated, and helps remove cuttings. Bentonite is best used in sandy or rocky conditions. When selecting a bentonite product, Savage suggests choosing one with a low sand content.

Polymers are synthetic drilling fluid additives that provide lubrication in clay-type soils. Often, polymers and bentonite are used in combination based on the makeup of the soil, which can vary drastically along the length of a bore.

What's in the Water?

The water source should be checked and adjusted to obtain a balanced pH level, Savage says. He explains that both bentonite and polymers perform better in water with a proper pH balance. A contractor can use a simple pH testing kit to get this reading. Contractors also should check the water for the presence of calcium, which can inhibit bentonite from mixing properly. Savage says bentonite will not mix in salt water; therefore, it should be avoided for this type of fluid mix.

Calculating the proper water volume also is essential. Fluid mix vendors can provide water volume calculators that will process the hole diameter, bore distance and soil conditions to determine the proper volume.

Fluid Monitoring on the Job

In addition to gathering geological information in advance of a project, NASTT advises testing soil extracted from the hole from time-to-time during the installation to verify that the proper drilling fluid mix and additives are being used. A contractor should also conduct a visual check by watching fluid flow at the hole opening or at the exit end of the installation.

Although selecting the right fluid mix takes some effort, Savage reminds contractors that it is time well spent. “Fluid mixes offer an added benefit that the bore can be completed successfully,” he adds. “That is the bottom line with fluids.”