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