Horizontal directional drilling (HDD) projects rely on more than just the drill itself. The quality of your drilling fluid, how efficiently you manage it, and how well you remove unwanted solids all play a major role in productivity, bore quality, and overall project costs.
Using a solids control or drilling fluid recycling system offers several advantages on rotary mud drilling projects. Recycling drilling fluid reduces water consumption, lowers fuel costs associated with hauling fresh water to the jobsite, minimizes transportation costs, and decreases the amount of wet drill spoils that must be disposed of after the job is complete.
Since many landfills only accept material that passes a paint filter test, disposing of wet drilling waste can become both expensive and time-consuming. Recycling drilling fluids also helps preserve valuable bentonite, polymers, and other additives, reducing product waste while minimizing the amount of material that must be transported on and off the jobsite.
Here are five important things every HDD contractor should know about solids control systems and drilling fluid recycling.
1. Choose a Recycling System That Matches Your Drill
Selecting the proper recycling system begins with choosing one that can process at least one-and-a-half times your drill's maximum pumping capacity. This allows the system to efficiently remove solids while keeping pace with drilling operations.
Hydrocyclones are one of the primary factors that determine a recycling system's capacity. As a general guideline, a 5-inch hydrocyclone processes approximately 80 gallons per minute. Multiply the number of cones by their processing capacity to estimate total flow, while remembering that hydrocyclones do not remove every particle in a single pass. Additional processing capacity is necessary for consistent performance.
Contractors should avoid undersized or overly compact recycling systems. Smaller screening decks limit throughput and often cannot utilize the ultra-fine shaker screens needed to extend drilling fluid life. Fine screens also help reduce abrasive wear throughout the entire drilling fluid circulation system.
According to the American Petroleum Institute (API), sand particles range from approximately 74 to 200 microns. A 200-mesh screen removes particles down to about 74 microns, while a 60-mesh screen only removes particles around 250 microns or larger. That difference has a significant impact on drilling fluid cleanliness.
As solids continue circulating through the system, they become progressively smaller until they enter the colloidal clay range. These ultra-fine particles increase plastic viscosity, create abrasive wear, and contaminate the drilling fluid without improving borehole stability or suspension characteristics. Eventually, the drilling fluid must be discarded and replaced.
2. Proper Screen Selection Makes a Big Difference
Your shaker screens are one of the most important components of any recycling system.
The scalping screen serves as the first stage of solids removal by capturing larger particles before they reach the hydrocyclones. If the screen opening is too fine, drilling fluid returns may overwhelm the system, causing valuable drilling fluid to flow off the end of the shaker instead of being recovered.
Another common issue is screen blinding. This occurs when cuttings become lodged within the screen openings, restricting fluid flow and reducing separation efficiency.
When this happens, stop the system and inspect the screens. Cleaning them may solve the problem, but sometimes switching to either a finer or coarser mesh is the better solution depending on soil conditions. Many contractors successfully run a coarse 30-mesh scalping screen while finishing with a 200-mesh screen for final solids removal.
Matching the correct screen combination to the jobsite helps maximize recovery while extending drilling fluid life.
3. Operator Technique Can Change Performance
Two experienced operators can use the exact same recycling system with identical screen setups and achieve noticeably different results.
A properly sized recycling system should allow drilling fluid to cascade through the clean compartments while the scalping compartment fluctuates with incoming returns from the exit pit.
One key to maximizing performance is controlling the fluid level within the scalping tank. Using the system's valve to maintain the compartment at roughly three-quarters full allows dirty returns to cycle efficiently while increasing the average solids concentration entering the shaker. This improves separation efficiency and helps deliver cleaner drilling fluid back to the drill.
The equipment is important, but the operator's understanding of the system often determines how well it performs.
4. Maintain Your Drilling Fluid Throughout the Bore
Even the best recycling system cannot replace proper drilling fluid maintenance.
Bentonite, polymers, and specialty additives are constantly consumed during drilling. They become part of the borehole wall to improve stability, reduce fluid loss, control reactive clays, and are also carried away with the drill cuttings.
Because drilling conditions change throughout the bore, drilling fluid properties should be tested regularly. Viscosity deserves particular attention since it directly affects hole cleaning, bore stability, and pumping efficiency.
Routine testing allows contractors to replenish bentonite, polymers, and additives before drilling performance begins to suffer. Many drilling professionals use bentonite consumption as a guide for determining polymer and additive requirements throughout the project.
Find all HDD fluids here: Drilling Fluids available at GUS
5. Select Additives That Work With Recycling Systems
Not every drilling fluid additive is compatible with solids control equipment.
High molecular weight synthetic polymers designed for reactive clay control can create a sheeting effect across shaker screens, reducing fluid flow and causing drilling fluid to bypass the recycling process. When selecting synthetic polymers for recycled drilling fluid systems, choose low-viscosity formulations specifically intended for compatibility with recycling equipment.
Products designed to aggressively break apart clay should also be avoided. While they may reduce larger clay particles, they often create extremely fine solids that vibratory shaker screens cannot effectively remove. These particles remain suspended in the drilling fluid, increasing plastic viscosity and contaminating the entire system.
On the other hand, poly anionic cellulose (PAC) polymers used for fluid loss control are generally well suited for recycling systems. Extra low-viscosity PAC products help maintain borehole stability in coarse soils while managing viscosity and reducing annular pressure.
Non-foaming detergents and surfactants should also be used carefully. To minimize aeration and prevent pump cavitation, keep the throat valve on the mixing hopper closed except while actively mixing drilling fluid products.
Ultimately, successful recycling depends on more than equipment alone. Proper training and knowledgeable system operation are just as important. Fortunately, many equipment manufacturers and drilling fluid suppliers provide training to help contractors maximize performance and extend drilling fluid life.
Get the Right HDD Drilling Fluids and Additives at Georgia Underground Superstore
Whether you're mixing fresh drilling fluid or maintaining a recycling system in the field, using the right products makes all the difference. Georgia Underground Superstore stocks a complete selection of HDD drilling fluids, bentonite, polymers, detergents, clay inhibitors, viscosifiers, lubricants, and specialty additives from trusted brands contractors rely on every day.
From everyday drilling conditions to challenging clay, sand, and mixed ground formations, our knowledgeable team can help you choose the right combination of drilling fluid products for your application. We also carry drilling fluid mixing equipment, tooling, and accessories to help keep your operation running efficiently from start to finish.
Visit Georgia Underground Superstore online or stop by one of our locations in Georgia, Texas, or Oklahoma to find the HDD drilling fluids and additives your crew needs to drill more efficiently, reduce waste, and maximize productivity.
Explore all HDD products here: HDD/Horizontal Directional Drilling Products for Utilities
If you have questions about your drill fluids, additives, or complete setup, reach out to our HDD team:
Texas:
- Mike Bearden - mbearden@georgiaunderground.com
- Jessy Mendez - jmendez@georgiaunderground.com
Oklahoma:
- Tim Allendorf - tallendorf@georgiaunderground.com
Georgia:
- Keven Hyatt - khyatt@georgiaunderground.com
Source: Adapted from "What to Know when Selecting Your Drilling Fluid Recycling System" by George M. Dugan, published in Trenchless Technology. This version has been rewritten and expanded by Georgia Underground Superstore with additional information on HDD drilling fluids, additives, and best practices.