A mobile centrifuge unit

Enhanced Fluid Recycling Saves HDD Contractors Time and Money

Drilling fluids play a crucial role in the ever-growing horizontal directional drilling (HDD) industry. Drilling fluids — also called “mud” or “slurry” — are a mix of water and additives such as bentonite. These fluids help remove cuttings, stabilize the borehole, and cool, lubricate and extend the life of equipment.

But with these benefits comes a drawback: Preparing and disposing of the drilling fluid can be costly, in terms of both time and money. For many drillers, an enhanced fluid recycling system could be the solution.

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On a typical job, a crew arrives early at the worksite, but drilling cannot yet begin. If the crew hasn’t brought water out in a water truck, they have to go out and find a source of fresh water. After they return, the drilling fluid needs to be mixed. The entire process takes up valuable drilling time. Then, at the end of the day, the drilling mud needs to be disposed of. While some areas permit mud to be dumped at the worksite, drillers are frequently required to dispose of the mud at approved waste facilities, per environmental regulations. Every single day, drillers spend money on transportation costs, fuel, water, and additives; by spending time on fluid preparation and disposal, crews spend less time drilling.

However, many of these costs can be reduced — or even eliminated — by incorporating an enhanced fluid recycling program. In a high-quality recycling system, suspended solids are removed from the drilling fluid, allowing it to be reused. As a result, disposal costs are reduced because less waste is generated, which lessens the environmental impact; in addition, less additives and water are needed for the preparation of the recycled fluid.

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While drillers may fear that such a system is cost-prohibitive, California Boring — a family-owned HDD company based in Anaheim, California — expects that its new enhanced fluid recycling system will pay for itself in less than 18 months.

Chemically flocculated solids

Chemically flocculated solids, demonstrating the successful coagulation and settling of drill solids for mechanical separation.

Concerned about high waste disposal and water costs, California Boring acquired a basic mud-recycling system three years ago. Using a basic shaker system, it was taking eight to nine hours to recycle one day’s mud, resulting in significant diesel costs to power the machine. In addition, because the standard recycling system wasn’t able to filter out enough of the finer silts, the California Boring team wasn’t able to get the high-quality mud it had hoped for. Although the basic system was working, the company decided it wanted to get more performance from its equipment.

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To upgrade its mud-recycling system, California Boring opted for an enhanced fluid recycling solution from M-I SWACO, a Schlumberger company, which features a high-volume decanter centrifuge and was installed in spring 2021 at its headquarters.

Within the first two hours of operation, the new system removed more than 400 lbm of fine silt. The enhanced recycling system also cuts the mud weight from 9.7 to 8.6 lbm/gal, which means that most drill cuttings are removed but significant bentonite is retained, resulting in a 35 percent reduction in bentonite consumption. The resulting fluid also requires less dilution, decreasing California Boring’s overall water usage by 15 percent. The entire process now takes only three to five hours a day, depending on the amount of fluid that needs to be recycled.

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The mud-recycling system allows California Boring to clean, mix and prepare drilling fluid at its facility, enabling the company to send its crews out to the job ready to drill, with everything they need for the day. There is no longer a need to secure city meter permits or spend time sourcing water or mixing mud at the worksite. Setup takes only five to 10 minutes, which saves both California Boring and its customers time and money.

An additional benefit is that California Boring’s clean mud prolongs its equipment life. The sandblasting effects of fine silts and sands significantly wear down pump seals and motors, particularly in small drills, which have small, sensitive pumps and can be finicky. By specifically targeting and removing these ultrafine solids, California Boring estimates that the high-quality mud will easily double the life of the company’s equipment.

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By reusing the fluid instead of simply disposing of it at the end of each day, the enhanced fluid recycling solution from M-I SWACO has reduced California Boring’s waste fluid by an estimated 32 percent, which has cut disposal costs and reduced the environmental impact. Because the system creates a drier cutting, the company has also been able to use dump trucks rather than water trucks to dispose of the waste, reducing trucking costs by more than 70 percent.

Looking to advance their operations even more, California Boring is currently testing M-I SWACO’s Dewatering Plus technology, which will allow the company to reclaim water for beneficial use. Separating the clear water will enable California Boring to retain and reuse even more additives, and ultimately, the dewatering system will save time and money.

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As environmental standards tighten and water becomes scarcer, particularly in the western United States, there will be a need for more efficient and cost-effective recycling solutions. For California Boring, the enhanced fluid recycling system has allowed it to reduce the amount of waste generated, prolong the life of its equipment, reduce emissions, use less water and additives, and add to their profitability — all with a single system — resulting in a win-win for both the company and its customers.

Jose Cerna is a mining and water well engineer and Kyle Tobin is business development manager with M-I SWACO, a Schlumberger company.

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