Environmentally Assisted Cracking of Drill Pipes in Deep Drilling Oil and Natural Gas Wells

Corrosion fatigue (CF), hydrogen induced cracking (HIC) and sulfide stress cracking (SSC), or environmentally assisted cracking (EAC) have been identified as the most challenging causes of catastrophic brittle fracture of drill pipes during drilling operations of deep oil and natural gas wells. Although corrosion rates can be low and tensile stresses during service can be below the material yield stress, a simultaneous action between the stress and corrosive environment can cause a sudden brittle failure of a drill component. Overall, EAC failure consists of two stages: incubation and propagation. Defects, such as pits, second-phase inclusions, etc., serve as preferential sites for the EAC failure during the incubation stage. Deep oil and gas well environments are rich in chlorides and dissolved hydrogen sulfide, which are extremely detrimental to steels used in drilling operations. This article discusses catastrophic brittle fracture mechanisms due to EAC of drill pipe materials, and the corrosion challenges that need to be overcome for drilling ultra-deep oil and natural gas wells.