Drilling fluid is essential for completing any horizontal directional drilling (HDD) installation. However, the cost and inconvenience of disposal is often the biggest pain point for contractors.
Commonly known as drilling mud, drilling fluid is specifically designed for the types of soil a bore path will pass through and includes varying combinations of water, bentonite and other additives.
There are three main purposes of drilling fluid. First, the fluid seals and stabilizes the hole and transports the cuttings out of the bore path during the bore. Without drilling fluid, any material removed by the drill bit will be packed into another location in the path, resulting in significant wasted downhole horsepower and greatly increasing the risk of a stuck or stalled tool.
Secondly, drilling fluid increases the longevity of the drill pipe and cutting head by providing the lubrication needed to maximize its effectiveness. Drilling into the ground creates a lot of heat, which can cause unwelcome wear and tear on the outer surface of the drill pipe. To avoid excessive wear, water and other fluids are a necessity on the job.
Finally, drilling fluid helps keep the electronics inside the housing cool. In the absence of a proper drilling fluid formula, the heat caused by the bore is intense enough to exceed the functionality of the components, leaving an operator without certainty of the bore’s location or its path and adding unforeseen replacement costs to the project.
Regardless of its benefits, drilling fluid is often overlooked on small HDD projects for a variety of reasons. Work being done in urban settings can leave contractors battling traffic congestion and traveling long distances between the jobsite and disposal site. That leaves contractors with trucks, vacuum excavators and CDL drivers tied up. In a business where time is money, contractors select the alternative method of substituting the minimum amount of water possible rather than the recommended amount of drilling fluid to cut dumping costs and travel time.
However, those who choose the less-expensive short-term option will likely find themselves with added expenses for damaged electronics, HDD tooling and drill pipe. Crews can better conserve limited resources and improve ROI on HDD projects by recycling drilling fluid and incurring less travel time to disposal sites, whenever possible.
Recycling and ROI
Historically, fluid recycling has not been a main focus area on smaller utility projects, which typically employ drill units of 30,000 pounds pullback or fewer. Fluid volumes required are small, compared to large projects, and conventional recycling equipment is too large for many utility work sites.
Today’s recycling systems are available from several manufacturers with designs varying by make and model. To assist in minimizing the costs associated with using drilling fluid, compact or micro systems allow HDD contractors on smaller utility jobs to recycle the drilling mud.
Recycling is a multistep process. First, fluid passes through shaker screens to remove large solid materials, then it goes to the second stage, where desander cones remove sand and finer particles, before a final shaker screen removes additional solids. Cleaned fluids are then reused and the cycle is repeated throughout the drilling process, reducing the volume of drilling fluid on a project. As a result, contractors will see a reduction in the cost of fluid additives, water transportation and disposal.
For example, after figuring in costs for disposal fees, miles driven to and from disposal sites, labor hours, mud and equipment, a contractor disposing of 8,000 gallons a week at 45 cents a gallon can cut yearly disposal and operating costs from $298,290 to $151,263.
Recycling systems are most effective in sand, gravel and rocky soil conditions. Clay-based soils present some unique challenges for HDD projects, as they are more likely to clog screens and reduce a unit’s effective recycling capacity. Operators must assess the jobsite to determine what method is ideal, though under most circumstances, micro-recycling system benefits often outweigh their limitations.
Utilizing the Right Drilling Fluid.
The correct mix and amount of drilling fluid depends on the equipment and the jobsite ground conditions. To maximize the effectiveness of the fluid being used on the jobsite, many mud suppliers provide drill fluid formulators to recommend a mix based on soil conditions. For utility contractors, that means fewer trips to haul water and dispose of fluids. Minimizing the cost of additives, water and disposal can help crews stay profitable on HDD jobs.
In addition to not having the proper mix, not using enough drilling fluid can lead to inadvertent returns just as much as using too much fluid. Not running the correct amount of drilling fluids can cause the bore hole to seal off, ultimately causing excess fluid pressure downhole, which can lead to inadvertent returns. To help avoid inadvertent returns, the bore must have an open path for fluids and cuttings to flow back to the bore pit.
When an inadvertent return happens, the jobsite may shut down and crews will be responsible for the cleanup. The nuisance of cleaning up inadvertent returns and potential fines can impact jobsite profitability significantly. By recycling drilling fluids, operators and crews can better monitor fluid volume and ultimately limit disturbance to the environment.
With the right fluid formula and proper recycling equipment, utility contractors can benefit from drilling fluids on small-scale HDD projects without having to compromise profitability. For guidance, operators can consult with their local equipment dealership, who are trained on proper drilling fluids and equipment for the jobsite.