A sour service drill string with 110 ksi [758 MPa] yield strength has been developed. The NACE threshold stresses are above 90% of the specified minimum yield strength (110 ksiC758 MPa]) for the tool joint and the drill pipe and above 65% for the weld area. Also, the sulfide stress cracking (SSC) resistance of the drill string was totally evaluated by full-size SSC testing. The practicality was confirmed through finite element analysis (FEA) and full-size performance testing (gas leak, full-size fatigue, full-size tensile, overmakeup and make-and-break testing).

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