Erosion fatigue damage
This type of damage is due to extensive damage to the drill pipe at this stage. Erosion is likely to cause more serious damage in various or multiple comprehensive damage methods (corrosion, wear, fatigue). Sometimes, several types of etching methods will be produced separately, but generally speaking, there has always been one type of etching method that has become a critical damage.
Notch fatigue damage
Defects on the surface of the drill pipe, whether it is produced by mechanical processing or the whole process of the metallurgical industry, will greatly harm the fatigue strength of the drill pipe. The degree of damage lies in the location, orientation, appearance, and a total number of the defect. If the notch is located on a part of the drill pipe that is not a critical stress function, the damage to fatigue damage is minor. However, if the notch is located in the range of 50 cm from the connector, because this part is where the drill pipe causes greater bending stress, it will become the key to fatigue failure.
Pure fatigue destruction
At this stage, the key reason for the fatigue failure of the oil well drill pipe is caused by the regular stress generated when the drill pipe rotates in the curved borehole. In a curved well hole, even if the drill collar has sufficient thickness, fatigue damage is still likely to occur, and the damage location is not necessarily. When the drill rod is bent, every time the drill rod rotates, its matching part will cause regular stress due to repeatable tension and force. The drill pipe close to the drill collar is likely to be bent. Because the drill collar has great rigidity and can resist bending, the bending will occur on the drill pipe above the drill collar.
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