Why Does Drillstring Fail? Basic Understanding of Drill String Failure

In drilling industry, it is common that drill string will fail while drilling. Two main factors causing drillstring failure are stresses and corrosion.

Stress Affects on Drillstring

Drillstring is exposed to the following stresses:

Tension – Suspended weight of drillstring sometimes can be several thousand pounds. Additionally, overpull weight while pulling out can be over drill string limit resulting failure (see Figure 1).



Figure 1 – Drillstring in Tensile

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Basic Understanding about Drill Pipe

Drillpipe is seamless steel pipe made up in the drill string and it is the major component of the entire drillstring. Typically, 90% – 95% of the total length is drill pipe. Thread connection of drill pipe is called “Tool Joint”. One end of drill pipe has a female end which is named as “Box” (see Figure 1).


Figure 1 – Box End of Tool Joint

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