First Fully Sulfide Stress Cracking Resistant Drillpipe System

Abstract As the severity of sour drilling applications has increased, the requirement for drill stem materials resistant to sulfide stress cracking (SSC) has accelerated. Sour service drillpipe, traditionally manufactured with SSC resistant upset tubulars and tool joints, has been available for some time. Sour Service drillpipe metallurgy is not specifically controlled by NACE MR 0175/ISO 15156,1 however these tubulars and tool joints are often evaluated in accordance with the standard. The friction welds joining the upset tubulars and tool joints were not resistant to SSC and were not evaluated. This has been acceptable for many sour drilling applications since the weld is not the mostly highly stressed region of the drillpipe joint and because the operator has a certain degree of control over the environment through the drilling fluid properties and additives. As more severe environments with higher Hydrogen Sulfide (H2S) concentrations were identified for exploration and development, it became apparent that a fully SSC resistant drillpipe system including the friction welds was necessary. This paper presents the successful development and qualification of SSC resistant friction welds for critical sour applications. It describes the engineering and manufacturing philosophy employed, laboratory testing procedures with results presented and applications for the SSC resistant drillpipe. Since NACE MR 0175/ISO 15156 does not address friction welds the engineering team developed unique and innovative criteria together with testing procedures for the new weld technology. A new patent pending four-point bending test procedure and fixture were developed that employed unpolished samples that represent the surface finish of the product in service, in contrast to the polished samples used in NACE TM0177 testing. This paper provides background information on the evolution of sour service drillpipe and reviews case histories where sour service drillpipe has been successfully used including the new pipe with SSC resistant friction welds. The paper can benefit drilling engineers involved in critical sour drilling operations.