By Jeff Davis
Efficiency is king. When on a job, operators are highly focused on efficiency and productivity above all else. After all, the return on investment of a horizontal directional drilling (HDD) project can hinge on the speed of deployment, especially when turnaround is tight. But sometimes moving quickly can distract operators from getting the most out of equipment.
One of the more expensive pieces on the job is HDD tooling, specifically the drill pipe. Replacement costs vary, but contractors can reduce overall costs by extending the life of their investment. For instance, high-quality steel and rigorous manufacturing standards help protect against fatigue, which can lead to a broken drill string downhole.
High-quality drill pipe is the first step to getting the most out of equipment. Even the best equipment, however, cannot withstand mistreatment. Proper use and maintenance helps operators confidently and efficiently complete a job on time and on budget. To increase drill pipe longevity and effectively complete job after job, operators should know the recommended bend radius, how to maintain correct torque and the proper use of drilling fluid.
The underground conditions ultimately determine the proper depth of a bore. Getting to that depth starts at the entrance point above ground. From the entrance point, HDD operators need to steer drill pipe down before leveling off at the correct depth. The space between the entrance point and deployment depth is often thought of as lost time and space, as operators prepare to install product.
Due to this impression, some operators exceed the recommended bend radius of their drill pipe when steering downward, in hopes of reducing the perceived lost time. Based on the metal’s ability to return to normal after being bent, the recommended bend radius should limit the angle an operator uses when drilling. When the bend radius is exceeded, the pipe is fatigued – thus reducing its useful life. Even if the drill pipe looks normal, the damage is done.
Costly replacement is not the only result of damaged drill pipe. When a drill string breaks downhole, operators need to plan a new route for product installation. If the job site allows, they’ll have to spend additional time and money unearthing the broken tooling.
To avoid costly repairs and replacements, be more efficient and extend the life of drill pipe, operators should become familiar with the recommended bend radius of their pipe. That begins with determining the proper entrance angle before digging begins. If unable to reach the recommended depth, the operator should set up and try again. While a second round of orientating the drill and creating a new entrance path might seem like unnecessary downtime, it will keep drill pipe working for its full life.
Exert appropriate torque
Proper torque also plays an important role in extending the useful life of drill pipe. All the effort of paying attention to the recommended bend radius will be lost if operators ignore their torque when making up or breaking out drill strings.
To avoid unnecessary wear on the threads of the pin and box, users should always apply the manufacturer’s recommended torque. For most HDD units, this is the maximum rig torque in low speed. By applying this recommended torque at each make-up cycle, the stress the thread encounters from the bending and drilling forces is evenly spread across all components of the thread. This helps prevent improper loading and excessive wear. If the joint is not properly torqued, the pin and box can result in not only galling and grinding of the threads downhole, but in the pin and/or box carrying more load than the other member, which in turn results in mushrooming and failure.
Before a project even begins, operators can avoid over-torque by matching drill pipe to the drill on the job site. If the drill has 3,000 pounds of torque, the drill pipe needs to be able to handle that amount.
Once on the job, operators can further reduce wear by bringing the pin and box together slowly, working up to the specific torque recommendation, versus quickly spinning a drill up to its maximum torque. Operators should guide the two threads of a drill string together instead of forcing them into place. This requires vigilance, tracking the drill’s gauges to make sure operators are not driving the pin too hard. The heat created when forcing a pin and box together will begin to embrittle the thread, which can lead to breaks or welding the threads of the drill string together.
Easing into the recommended torque may require more time than forcing a drill string together, but it will help improve the life of the threads.
Use drilling fluid to your advantage
Drilling into the ground creates a lot of heat, which can cause unwelcome wear and tear on the outer surface of the drill pipe. To avoid excessive wear, water and other fluids are a necessity. For example, drilling fluids, such as bentonite and polymers, can play an important role in keeping temperatures down and premature wear low, extending the life of drill pipe and tooling.
Without drilling fluid, operators increase the risk of the drill pipe breaking downhole. Drilling fluids are used to lubricate the components in the drill string as they slide along the bore walls, and carry the cuttings produced by the drilling tool out of the path of the string. Without these two critical functions, any material removed by the drilling tool is simply packed into another location in the bore. This results in significant wasted downhole horsepower and greatly increases the risk of experiencing a stuck or stalled tool.
The proper and correct amount of drilling fluid directly correlates to the equipment being used and the job-site ground conditions. For guidance, operators should consult with their dealers, who are trained on proper drilling fluids. They can also quickly check the Ditch Witch fluid formulator for advice.
Consistent maintenance practices also play a large role in getting the most out of drill pipe, especially when using new pipe. By investing a little time before each day on a job, operators will improve ROI and reduce the worry of downtime correlated to a damaged pipe or broken drill string. Common maintenance practices include:
Threading drill pipe together a few times before its first use on the job to break in threads.
Keeping threads clean if debris is present.
Thoroughly lubricating drill pipe before each use with the manufacturer’s recommended drill pipe thread compound.Inspecting drill pipe for sharp edges or any damaged thread, which indicates a string was previously forced together.
The normal wear and tear that occurs on a HDD job site does not have to cut down the useful life of drill pipe. Operators are encouraged to keep track of how they use their equipment, follow specified equipment recommendations, and properly maintain their equipment to increase drill pipe longevity. By following these practices, they’ll be able to reduce the risk of unplanned downtime and ultimately improve job-site ROI.
About the author: Jeff Davis is the Ditch Witch product manager for HDD tooling and drill pipe
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