One thing we must all remember is that drill pipe is a wear item. And just like a rubber track or teeth on a backhoe bucket, sooner or later you will need to replace it. But good operator practices along with day-to-day due diligence can dramatically minimize your need to invest in new drill pipe, and keep you profitable from one job to the next.
Protect your Investment, and Know When to say When.
“Performing drill pipe maintenance really isn’t that difficult, and doesn’t take much time,” says Greg Adkins, product design manager at Hunting Trenchless. “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 each day.”
First of all, you know those plastic caps that come on each end of a new stick of drill stem? “Don’t throw them away,” says Adkins. “They’re there for a reason. Use them for storing the pipe when not being used.”
According to Adkins, both individual drill rods and complete pipe boxes of drill rod should be off the ground when being stored, and kept as clean as possible to prohibit contamination. “Threads can gall and literally wear out twice as fast if they’re dirty when you’re joining them up, and be cause for investing in new pipe,” says Adkins. “Clean and re-grease threads periodically to minimize road and jobsite grit.”
It is also important to also keep joints lubricated with recommended thread compound. Hunting recommends that you cover the entire area of the pin and box threads with compound before every make-up. Some drills do this for you automatically. If yours doesn’t, just brush each joint with compound before it enters the drill string. You will also need to make sure your thread compound is clean and free of dirt and other particles. Always use a copper based grease or in environmentally sensitive areas use a graphite or lithium based compound on the joints.
“One-hundred percent of thread wear happens when you’re making up and breaking out,” says Adkins. “So, the main thing to remember is to pay attention and not get into a hurry.”
Because of this, Adkins recommends torqueing each joint fully, 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 drill pipe.
Staking down the machine and keeping alignment of your drill rod is also critical. If the machine is allowed to move, you run the risk of galling or prematurely wearing or damaging the threads on your drill rod.
Always fully torque your drill stem to prevent pipe from unscrewing or breaking pins off during the bore.
“Taking the slow and steady approach may take a few seconds longer, but it’s going to pay off tremendously down the road,” says Klane Kirby, general manager of Hunting Trenchless. “Your drill string will last so much longer because of the cumulative damage you’re saving every day.”
Keep in mind though, that even with the diligent intentional operator, that 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 badly damaged, is going to severely damage every stick of pipe that you make up with it, says Kirby. “It is at this point it must be replaced.”
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 entire rack at once and always replace your saver sub or drive chuck at the same time. Matching up old tooling with new drill stem will reduce the life of your pipe.
Kirby also says to be cautious of mixing different manufacturers pipe. “A common theme we find when evaluating a failure is that some manufacturers of drill pipe do not hold critical tolerances as well as others, and the mixing of pipe can cause a failure in the drill string,” he says. “When these critical measurements are not maintained during the manufacturing process on pin and boxes of a drill pipe, the mating of pin and box may be incorrect and cause the connection to be flawed, leading to prematurely failing.”
Making an Informed Investment
According to Kirby, there are different drill pipe designs in the marketplace, and some are better suited than others to withstand the rigors encountered with downhole activity.
“It’s important to know how the pipe you are buying was manufactured, and what that’s going to mean when you place it on a drill and put it to work,” Kirby says.
For example, welded pipe 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 will reflect that.
Another type of drill pipe is one-piece forged, where the 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 and less manufactured connection the better. Any operator will also tell you that the most common point for a welded drill pipe failure is 12 to 18 in. from the heat affected zone – the point where the tool joint and tube are welded together.
“Keep in mind, it only takes one thing to shut down an entire drilling crew,” says Adkins, “Understanding the manufacturing process of the components used in drill string will help the drill operator know what to look for with regards to wear and tear on the drill pipe.
Another key point to consider when making a drill pipe purchase is the type of jobs you commonly encounter. Are they long straight shots with plenty of setup area? Or are they short runs in urban areas? The answer to these questions should determine the bend radius of the pipe you purchase.
“The shorter the bend radius, the faster you will be able to level out and achieve your desired bore depth,” says Adkins. He also adds that it is critical to plan for the bend radius of the product you are installing. “The bend radius throughout the bore must never compromise the product that will eventually be placed in the bore hole.”
The Bottom Line
Your drill pipe spends most of its working life downhole, where conditions can be very tough. Making a wise investment, and taking the right steps to protect that investment, will keep you on the job running longer and more profitable.
Jeff Smith is with Sentio Marketing.