Frequent tripping of the drilling bucket on rotary drilling rigs makes disassembling the drilling tools very troublesome. The advent of telescopic kelly bars has greatly improved drilling efficiency and reduced the operator's labor intensity. How can we properly select and match drill pipes for rotary drilling rigs?
1. Determine the drill pipe diameter based on the rig's drilling capacity parameters, hole diameter, and drillable depth, using the empirical ratio D/d=4.5.
The maximum allowable length of the drill pipe for a rotary drilling rig should be determined based on the effective height of the mast and stability under self-weight conditions. Then, the number of drill pipe sections is determined according to the rig's designed hole depth and the effective working length of each drill pipe section.
2. Select the drill pipe based on the main design parameters, namely torque and feed pressure.
As we know, the drill pipe transmits torque through the meshing and extrusion of keys and keyways. Due to machining accuracy, material properties, welding quality, and other factors, it is impossible to ideally distribute the torque evenly across each key, and each contacting key cannot be uniformly loaded. Therefore, long keys often suffer local torsional failure. When selecting the design torque of the drill pipe for a rotary drilling rig, it must be greater than the rig's design torque.
The feed pressure of the rotary drilling rig is also a main external force borne by the drill pipe. When selecting the drill pipe, key design load capacity should be a key consideration, especially for mechanically locked drill pipes. More importantly, consider the diameter and wall thickness of the innermost and smallest drill pipe. It not only has the smallest torsional section modulus but also a small bending section modulus. The forces on the drill pipe in the hole are very complex, with tension, compression, torsion, and bending acting simultaneously. During stuck pipe incidents, the combined stress may exceed the drill pipe's fatigue limit and cause torsional failure. Externally, we cannot only consider the strength of the drill pipe. In reality, the working condition and nature of the drill pipe in the hole are unstable, so instability should also be considered when checking its bending strength.
3. Selection of drill pipe type for rotary drilling rigs
Drill pipes are divided into two types: friction-type and mechanically locked. The choice mainly depends on the formation conditions. For general formations such as soil, sand, gravel, and silt, friction-type drill pipes are selected. For cobble, boulder layers, hardpan sand, and hard rock formations, mechanically locked drill pipes should be selected. Mechanically locked drill pipes are also suitable for general formations. Enterprises or private companies with the means should preferably purchase both types of drill pipes for rotary drilling rigs.
4. Quality of drill pipes for rotary drilling rigs
When selecting drill pipes, it must also be considered whether the maximum pull of the main winch in the lifting system is compatible with the weight of the drill pipe, drilling bucket, and drill cuttings. This is because the drill pipe accounts for about 50-60% of the lifting weight. Special mention should be made of the effects of sudden braking during the lifting and lowering of the drill pipe and the inertial force when starting to lift from the borehole. The inertial force may account for 30-40% of the lifting weight, and its direction is the same as the lifting weight. Therefore, sufficient consideration must be given to the selection of the drill pipe weight.
Disclaimer: The content originates from the Internet and various platforms. The copyright of the article belongs to the original author. If there is any infringement, please contact us promptly for deletion. This website assumes no risk and accepts no disputes! Please be informed.
评论 （0）