HDD Tech Talk: Managing Your Drill Pipe Investment
A Little Diligence Uphole Can Keep Your Dollars from Ending Up Downhole
Let’s face it, drill pipe isn’t the sexiest thing on your jobsite. It doesn’t have moving parts or horsepower or even the bite of a downhole tool. But it’s the lifeline of your job. A failed drill string means a failed — or incredibly costly — bore.
But making a good drill pipe investment, and protecting that investment, isn’t rocket science. A little knowledge, a little common sense, and a little insight from the pros can help ensure the success of your next job, not to mention your good name and your bottom line.
An Informed Investment
According to Hunting Trenchless general manager Klane Kirby, there are a few different drill pipe designs in the marketplace and some are better suited than others to withstand the rigors encountered downhole.
“It’s important to know how the pipe you’re buying was manufactured, and what that’s going to mean when you put it to work,” Kirby says.
Welded pipe, for example, is a three-piece stem, with the box and pin each welded to a tube using a conventional stick or mig welder. Friction or inertia welded pipe is also a three-piece design, with the box and pin welded to a tube using heat and pressure alone. Both types of welded pipe cost less to produce, and their price tag will reflect that.
The third type of pipe is one-piece forged. As the name suggests, this pipe is forged from one continuous piece of drill tube. Proponents of this design point out that, when connecting a drill string — as with any string of parts — the fewer manufactured connections the better. And any operator will tell you that the most common point for drill pipe failure is 12 to 18 in. from the heat affected zone (the point from where the tool joint and tube are welded together).
As Hunting Trenchless product design manager Greg Adkins points out, “It only takes one thing to shut an entire crew down. Understanding the manufacturing process of the components used in a drill string will help the drill operator know what to look for in regard to wear and tear on the drill pipe.”
Another point to consider before making a drill pipe purchase is the types of bores you commonly encounter. Are they long straight shots with plenty of room for setup? Or are they short runs in urban areas? The answer to these questions should determine the bend radius of the pipe you buy.
“The shorter the bend radius, the faster you will be able to level out and achieve your desired bore depth,” says Adkins.
And don’t forget the bend radius of the product you have to install. Adkins says it’s critical to plan for this, adding, “The bend radius throughout the bore must never compromise the product that will eventually be placed in the bore hole.”
Other factors that should be weighed before you make a drill pipe investment include warranty and dealer support. Most manufacturers warrant their pipe against manufacturing defects, and Kirby says it’s quality control that separates one manufacturer from the other.
“If the controls are in place, you will not see failures due to manufacturing defect,” he says.
As for support, any crew knows that having a good dealer on your side can make a big difference. “Being able to rely on a dealer’s industry experience gives operators the tools they need to keep their drill rigs running at peak performance,” says Adkins.
Protecting the Investment
We’ve all seen the pictures and heard the horror stories of drill pipe breaking off downhole, or even entire lengths of drill string twisting off and having to be excavated. Maybe you’ve even lived one of those stories yourself. But experts say most of this jobsite drama is completely avoidable.
The first thing to remember is that drill pipe is a wear item. And just like a rubber track or an air filter, sooner or later you’ll have to replace it. But good operator training along with day-to-day diligence can dramatically increase your turnover cycle and keep you profitable from one job to the next.
“Performing drill pipe maintenance really isn’t hard, and it doesn’t take a lot of time,” says Adkins. “I think most crews don’t realize the ROI you can get in the life of your drill string by investing just a couple of minutes a day.”
First of all, you know those plastic caps that come on each end of a new stick of pipe? “Don’t throw them away,” says Adkins. “They’re there for a reason.” In fact, they should stay on each stick of racked pipe until it’s time to drill, and replaced when the bore is complete.
According to Hunting Trenchless, joints racked without protectors can be damaged. Exposed thread compound on the pin and box connections can pick up road and field grit both during transport and on the jobsite. If dirt and fine particles are present when the joints are made up and broken out, the threads will wear out quickly.
“Threads can gall and literally wear out twice as fast if they’re dirty when you’re joining them up,” says Adkins.
Keeping joints lubricated with recommended thread compound is also important. Hunting recommends that you cover the entire area of the both the pin and box threads with compound before every make-up. Some brands of drills actually do this for you automatically. If yours doesn’t, just brush each joint with compound before it enters the drill string.
Also, make sure your thread compound is clean and free of dirt and other particles, and never use grease or Loctite on the joints.
When it’s time to drill, “the main thing operators need to remember is to pay attention and not get in a hurry,” says Adkins. “One-hundred percent of thread wear happens when you’re making up and breaking out.”
Because of this, Hunting Trenchless recommends torquing each joint properly, stabbing gently, and letting threads find their way, rather than driving the end of the pin against the box shoulder. During break-out, the same theory applies. Always come out of the hole slowly, and never pull back while unscrewing. Operators should use the same care when steering and never exceed the recommended bend limit of the pipe.
“Taking the slow and steady approach may take a few seconds longer, but it’s going to pay off tremendously downstream,” says Kirby. “Your drill string will last so much longer because of the cumulative damage you’re saving every day.”
Even with diligent, intentional operation, some damage can occur. If it does, try filing down the pin or box end to blend with the surrounding area. If the damage is severe, don’t use that joint.
“Any pin or box that is severely damaged is going to severely damage every stick of pipe that you make up with it,” says Kirby. “Just set it aside.”
When you do buy new joints, never introduce them into a used drill string, as this could damage the new pipe excessively and prematurely. According to Hunting, it’s better to replace the whole rack at once and always replace your saver sub or drive chuck at the same time. Matching up old tooling with new drill stem can minimize the life of your drill stem.
The Bottom Line
Drill pipe spends most of its working life downhole, where the conditions are tough. Making a wise investment uphole, and then taking the right steps to protect that investment, will keep you running longer and more profitably. And that’s really sexy.
Angie Lapaglia is principal/writer at EarthGirl Communications in Oklahoma City, Okla.