By Jeff Davis (Product Manager, Ditch Witch Division)
From Dig Different
The game changed 25 years ago for the horizontal directional drilling industry with the introduction of a dual-pipe, rock drilling package. This All Terrain technology means operators have an option outside of powering the drill bit primarily with drilling fluid using a mud motor.
Mud motors are still a common tool found in the HDD industry. They take drilling fluids that are pumped downhole, through the drill string at high volumes, and into a rotor and stator, and they transfer that into mechanical power that drives the rotary bit on a mud motor. Mud motors are high-fluid volume downhole tools that can produce high drilling fluid pressures downhole and increase the possibility of inadvertent returns.
“Inadvertent returns happen when the drilling takes the path of least resistance to the surface, does not follow the designated path of the bore and makes its way through to the surface in unwanted areas,” says Jeff Davis, Ditch Witch’s HDD product manager. “Mud motors can often send much more fluid downhole than what is actually needed on the job.”
For example, a bore that requires 20 gpm of mud flow to efficiently flush the bore of cuttings could end up using an additional 180 gpm of fluid to run the mud motor. And, as the drill units become larger or the ground harder, mud motors can send as much as 10 times more mud downhole than what is needed to clean the borehole, according to Davis.
The additional drilling fluid results from inefficiencies of creating mechanical power. To accumulate enough energy for the drill bit, mud often flows over a 15- to 30-foot power section. “On average, only 50% of the power generated makes it downhole. In comparison, 95% or more of the HDD unit’s inner drive power is successfully transferred downhole using All Terrain systems,” Davis says.
ABOUT ALL TERRAIN TECHNOLOGY
A switch from powering the bit with drilling fluid to All Terrain technology helps operators minimize how much fluid is pumped downhole. All Terrain systems provide a way to use the HDD unit’s power more efficiently for driving the drill bit.
This is possible because of the dual-pipe technology offered by All Terrain systems. With an inner drive shaft that reaches back to the HDD unit, these motors physically control exactly how much horsepower is sent to the bit.
By reducing operator reliance on drilling fluid, All Terrain technology is an efficient power option. This direct connection to an HDD unit also reduces the overall size of an All Terrain system. Instead of a long power section, All Terrain systems are between 3 and 5 feet long. And by placing the electronic locating package in the middle of that system, the shorter length puts the package 1 to 2 feet behind the bit.
“Locators are then able to more accurately track the location of the drill bit’s cutting face, instead of predicting where the bit could be when the electronics package is embedded behind a mud motor’s 15-foot power section,” Davis says.
A small footprint is becoming a common requirement on HDD job sites. All Terrain technology generally provides a smaller job site footprint than mud motor-driven job sites, partially due to having to use less fluid. Large volumes of fluid usage on the job site comes with larger tanks and larger reclamation systems with a mud motor, according to Davis.
All Terrain technology is one of those technological advances that has the potential to generate a huge impact. The dual-pipe system lets operators control how much fluid is used on varying job sites. And, by keeping drilling fluid to a minimum, HDD crews can decrease the risk of inadvertent returns and stay efficient and profitable on any job site.