This paper provides a review of recent technology advancements and addresses practical considerations associated with drillpipe and drill stem components for extreme drilling applications. Ultra-high torque double-shoulder rotary connections are often employed in these applications. Recent developments and enchantments in these connection designs including new higher strength materials, advanced thread forms and associated improvements in torsional strength and fatigue performance are presented. Deepwater wells frequently require long, heavy casing strings to achieve the total depth objectives. High capacity landing strings capable of running these heavy strings with total hook loads approaching 2.5 million pounds have been successfully developed to address this well design challenge. The paper discusses the engineering solutions implemented to overcome the high forces, slip crushing concerns and material strength and toughness considerations for these critical applications.
Due to the dramatic increase in oil prices the industry has seen a re-emergence of deep and ultra-deep drilling projects that encounter H2S gas. The paper provides an update on the latest sulphide stress cracking (SSC) resistant drillpipe grades including the first fully SSC resistant drill pipe system with SSC resistant friction welds joining the drill pipe tubes and tool joints. Major operators have been using a drill pipe based riser system for intervention and completion work in the waters offshore Brazil, Australia, Africa and other deepwater basins around the world. The paper provides updates on design improvements of high pressure capacity connectors and advanced materials for these critical riser applications.
Deepwater wells often encounter abrasive formations, high side loads between the drill string and bore hole and other conditions that promote drill stem friction heating failures. The paper includes characteristic features of these failures along with case histories and prevention methods.
As the severity of sour drilling applications has increased the need for drill stem materials resistant to Sulfide Stress Cracking (SSC) has accelerated. This is especially true in the Middle East with some of the most severe H2S environments in the world. Sour service drillpipe, built with SSC resistant tubes and tool joints, has been available for some time. The friction welds joining the tubes and tool joints were not SSC resistant. This has been acceptable for many sour applications since the weld is not the high stress area of the drillpipe and because the operator has some control over the environment through the drilling fluid properties and additives. As more severe H2S environments were identified for exploration, it became apparent that a fully SSC resistant drillpipe system including the friction welds was necessary. This paper presents the successful development of SSC resistant friction welds for critical sour applications. It describes the engineering and manufacturing philosophy, laboratory testing procedures and results and applications for the SSC resistant drillpipe. Since NACE MR-0175 does not cover friction welds the engineering team developed unique and innovative criteria and testing procedures. A new patent pending four point bending test procedure and fixture were develop that employed unpolished samples that represent the surface finish of the product in service, unlike polished samples typically used in NACE TM-0177 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. A preview of some vital planning considerations for an upcoming world-class ERD well in Saudi Arabia with high H2S concentrations is also included. The paper can benefit drilling engineers involved in critical sour drilling operations in the Middle East and other world regions.