Reamer for Horizontal Directional DrillingThough the reasons for reaming a hole have not changed since the dawn of horizontal directional drilling (HDD), the tools used for the process have changed.

In the early days, the bores were smaller and at shorter distances and were drilled using a reaming bit attached to a 3-hp handheld air motors, so says Dick Melsheimer, president of Melfred-Borzall, a company Melsheimer’s father started in 1946.

The designs were not as plentiful in those days and a big hole was 10 or 12 in. Today, these reamers come in a myriad of styles and can be custom made to 48 in. and beyond.

“A 10-in. hole and a 12-in. hole in the 1940s is the same as it is today. The soil is the same. The rock is the same. It’s the horsepower of the machine that changed,” Melsheimer said. “This has caused the reamer to get much heavier, stronger and tougher.”

Logical Evolution

As size increased, both in bore diameter and drill rig horsepower, the management of the spoils coming down hole as reaming takes place became paramount.

“Originally, it was the intent to cut a bigger hole,” said Riff Wright, co-founder and general manager of Weatherford, Texas-based Radius HDD Tools. Enlarging the hole is still the No. 1 priority but playing into the success is spoil management and hole integrity.

“You’re taking out more material, so you have to not only think about how you’re going to take out that much material, but your tool has to be stouter, stronger and better engineered,” Wright said. “You also have to have the knowledge of what size fluid ports, where should they be and how will you mix the cuttings in a way that they can be floated out of the hole.”

When Wright started in the HDD world, many contractors focused on the smaller bores for fiber projects. At that time, the reamers were not traveling as deep or as far and the soil conditions were not that hard.

“In the last five to 10 years, obviously the pipeline business has picked up,” Wright said. “And it’s not just the large pipelines but also the distribution pipelines that are increasing the demand and expectations of hole opening tools.  Pipeline projects offer a completely different set of challenges than other HDD projects. Larger hole requirements and longer bores are two of those challenges.

Improved engineering has led to those stouter, stronger, tools that specifically address the longer, deeper, bores. In some cases, the project requires a custom design and those customizations often matriculate to a manufacturer’s product line.

For the last six years, Tony Torquato, president of Torquato Drilling Accessories, of Old Forge, Pa., has focused his reamer construction with polycrystalline diamond compact (PDC) cutters. Originally used by companies to drill oil and gas wells, the PDC reamers have gained favor with HDD contractors, as well.

The PDC reamers are ideally suited for drilling through what Torquato calls competent rock formations like shale, limestone and sandstone. Much of the area Torquato sells his products is on the eastern side of the country, which features such soil conditions.

A contractor recently finished a 700-ft ream, with an 18-in. reamer, in West Virginia, in what Torquato characterized as one-third of the time as a traditional roller cone or tri-cone reamer.

“The one comment that [the contractor] made to me was the fact that it was very smooth, the operation was smooth, it wasn’t a rough drilling that typically would be associated with the tri-cone reamer,” Torquato said.
It was smooth because the PDC cuts differently than a roller cone or tri-cone reamer, which chips, digs and crushes the rock. In the proper rock formations, the PDC shears the rock, which Torquato says is more efficient, creates less vibration and saves wear and tear on the drilling equipment.

As good as the PDC reamers are, Torquato cautions against using his products in gravel, broken rock or soft soils. In those conditions, he says it is easy to damage the reamer.

 PDC reamers are indeed a tool option in hard, solid rock, but such reamers are also cost- prohibitive on many HDD projects, according to Wright.

Whether using a PDC reamer, or an Ogre from Melfred Borzall or a Stack Plate Reamer from Radius, or a reamer from the countless other manufacturers, the companies interviewed all agreed that there is only one true way to tell if the product works as intended, and if improvements are required.

“To me, there is nothing more valuable than the input of a driller who uses this tool day in and day out,’ Wright said. “Those are the ones that can tell you what works, what doesn’t work and what needs to be done on the development end of things.”

A Contractor’s Needs

“Everyone would love to have one reamer for all types of ground conditions,” said Jose Mierzejewski, a design engineer at Melfred Borzall. “It just does not work that way.”

He went on to say that, contractors eventually realize that spending money on several reamers tailored to specific conditions is a better bet. For instance, in clay, an open style reamer with blades that can mix all of the stickiness and mud in there to be able to carry the cuttings out is better than a packer-style reamer.
When contacting a manufacturer, it is important that the contractor know what kind of ground they will be drilling. This generally falls into four categories: clay, sand, rock or mixed ground.

Wright sees no lack of creativity when it comes to reamer construction, most of which boil down to a cutter built around a shaft.

“In a lot of cases, that’s all you need, something that is designed and fabricated well enough to hold up while you’re cutting or enlarging the hole. Wright said.

The demand Wright sees from contractors is for casted-body fluted reamers for hard soil and chunk rock and barrel-style reamers for soft soils where the hole needs packing. An emerging market Wright said is the need for hole-opener reamers used in hard rock common with pipeline construction.

It’s when length, grade and larger diameters come into play that the reamer requires more design and engineering to work efficiently.

“Contractors may already have an idea of what style reamer they want or they just tell us, ‘I am in this type of ground condition’ and then we recommend a reamer,” said Eric Melsheimer, Dick’s son and chief engineer at Melfred Borzall.

30-in Hedgehog Reamer from Melfred BorzallAt Melfred Borzall, the open style Terminator reamer for clays and the Ogre, a fluted-style reamer, which can go through a variety of soil conditions, are the most popular.

In some instances, a contractor may need a combination of several reamers linked together. Melfred Borzall, for example, mated its Terminator reamer blades to the barrel style Turbo reamer.

“The more difficult the bore you are trying to do, the more important the correct reamer becomes,” Eric Melsheimer said.

As for sizes, Torquato’s reamers are custom manufactured in any size combination up to 30 in. Torquato says that generally getting to that size requires reaming a 6.5-in. pilot to 8-12 in. then 12 to 18 in. then 18 to 24 in. and finally from 24 to 30 in.

Radius ranges from 6  to 48 in. for reamers, with the 12- to 24-in. reamers being the most popular. Wright specified that hole opener sizes range from 16 to 36 in. but the company has manufactured up to a 72-in model.

“It certainly illustrates that the industry is moving into some very large projects,” Wright said.  “The business itself is changing in the fact that we are seeing, probably in the last three years, a 25 to 50 percent increase in tools for pipelines.”

Melfred Borzall’s models range from 4.5 in. for the smallest Juggernaut fluted-style reamer to 48 in. for a Sabertooth, barrel-style reamer, with all models available at larger sizes upon request.

Lately, a lot of larger diameter Melfred Borzall reamers — 24 in. and up — are heading to Colorado, Ohio, Pennsylvania and West Virginia for pipeline work.

Bang for your Buck

Unfortunately, no manufacturer has an answer to how long a reamer will last. Too many factors come into play that could shorten the life of the tool.

Once again, this is where proper research prior to purchase plays a role in longevity, as well as proper maintenance once purchased.

“In the case of a PDC reamer, typically the main element is the small diamond cutters. What you have to do is protect that,” Torquato said. “It’s not a tool that you want to just throw in the back of a truck. As long as it’s taken care of, they will drill 15,000 to 20,000 ft.”

Torquato Drilling Accessories Inc.Proper conditions include drilling in the aforementioned “competent rock formations” and making sure the reamers avoid gravel, sand or crumbled rock.

As for the maintenance, because the PDC reamers are built from a solid piece of machined steel, the operator does not need to look for damage to welds, but like any other reamer, pay close attention to the cutters, which can be replaced as needed.

Torquato, like his counterparts, suggested keeping up with hard facing the reamers at any point where it might encounter rock.

“Reamers as they come are fairly simple products. They don’t have a whole lot of moving parts so generally good maintenances and inspection will increase the longevity of the tool,” Wright said. “Look for cracks along the weld joints, replace teeth, make sure water ports are cleaned out so you get good flow during the next use and take care of the threads.”

All manufacturers stressed that the right drilling fluid mix, mating the reamer to the right drill rig and making sure the reamer is the correct style for the soil conditions plays into reamer longevity and the overall success of any HDD project.

“Using the correct back reamer is important but the interaction of that reamer with your fluids, the fluid for that ground condition and the flow rate you are pumping out, the rotation speed of that reamer, the pullback rate and even what you do during the pilot bore operation can really effect how successful you are on the pullback,” Eric Melsheimer said. “Getting the right reamer is an important part but there are a lot of other factors that fold in together to make a successful back ream.”

Mike Kezdi is assistant editor for Trenchless Technology.

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