In the field of drilling, extracting valuable resources from beneath the earth's surface is an important and complex task, and a drill pipe plays a key role. The drill pipe is a seamless pipe specially manufactured to withstand the harsh and challenging conditions encountered in drilling operations. This seamless design process ensures the longevity of the pipeline and minimizes the risk of weak points that could compromise the pipeline’s structural integrity. They come in a variety of sizes, strengths, and wall thicknesses. A key characteristic of a drill pipe is its hollow interior. The fact a drill pipe is hollow is essential for drilling because it lets fluid flow through the pipe.
Drilling pipes classification
After inspection, the drill pipes are divided into the following three categories:
Grade N (New Pipe): These are the sturdiest, newest pipes available and are generally in excellent or near-perfect condition.
Grade P (Premium Pipe): Premium pipes are one step below Grade N. They experience some wear and tear but are still fully functional.
C-grade (old pipe): C-grade pipe is further subdivided into C-1, C-2, and C-3, depending on the condition of the pipe. These include pipes that are heavily worn and those that are near the end of their useful life. The specific grade indicates the degree of wear and useful life of the pipe, so C-grade pipe is suitable for less demanding drilling tasks.
Improve the construction technology of drill pipe to increase its service life
(1) Standard operation: During construction, the drill pipes must be used strictly in accordance with the tension, torque and curvature diameter allowed by various drill pipes. For the construction enterprise, only by using the drill pipe according to the specification can the abnormal failure of the drill pipe be effectively avoided.
(2) During the process of hole expansion and pipe pulling, the radius of curvature of the drill pipe connected to the hole expansion drill bit is likely to be much smaller than the designed radius of curvature of the drilling hole), so that the drill pipe is subjected to greater cyclic stress under the action of rotation and tension, causing fatigue damage, and then cracks and breakage. This kind of fracture usually occurs between 0.3 and 0.8 m from the drill pipe male joint.
By connecting the transition pipe between the drill pipe and the drill bit, the small curvature transition between the drill pipe and the drill pipe can be borne by the transition rod, thus protecting the drill pipe. This function of the transition rod is often overlooked by users, but many seemingly inexplicable drill pipes break accidents are caused by this.
(3) Preventing the drill pipe from becoming unstable: The drill pipe is a slender rod in mechanics, which tends to become unstable under pressure. Therefore, during the pilot hole construction phase, the drill pipe in a free state must be constrained to prevent the drill pipe from becoming unstable and bending during the jacking process.
The drill pipe instability often occurs in the drill pipe section between the drill rig holder and the entry point. The length of this section should be shortened as much as possible, or appropriate restraint measures should be taken. To prevent the drill pipe from becoming unstable, the free section length of the drill pipe should generally be less than 20 times the diameter of the drill pipe.
(4) Use of thread oil: Good quality thread oil can effectively prevent the drill rod from sticking, reduce the torque of the unscrewing, and reduce the wear of the thread.
(5) Use of flushing fluid: When drilling in sand and gravel layers, high-quality mud should be used as flushing fluid. The mud forms a mud skin on the outer wall of the drill pipe, which acts as a lubricant, can reduce drilling torque, reduce drill pipe wear, and plays a very important role in protecting the drill pipe.
(6) Inspection of drill pipe: After the drill pipe has been used for a period of time, it should be checked for wear, bending, surface scratches, etc. The drill pipe with excessive wear, obvious bending and deep surface scratches should be promptly eliminated. In particular, the wear of the transition section should be carefully checked, as this is often the most susceptible to wear and tear.
Read more: How to Use Drill pipe and Precautions
