The torque requirement for sour service drill pipe connections has always been a drilling challenge. Operators and contractors face challenges when selecting the appropriate tool joints to use in a sour environment, especially when combined with deeper or longer wells.

Depending on the severity of the sour service environment, which is defined by the Association for Materials Protection and Performance (AMPP) [formerly National Association of Corrosion Engineers (NACE)] MR0175-2015 severity diagram, where environmental severity is defined in regions (0, 1, 2, and 3), several studies have been carried out to understand the actual limitations of the tool joints based on each connection design and tool joint material grade and not a "one-size-fits-all" approach (Plessis, 2022). A research and development (R&D) and industrialization test campaign was started to confirm the connection technology performances and limitations in each sour service environment.

Original equipment manufacturers (OEM) provided various tool joint material grades and connections technology to address drilling engineers’ specific needs for sour service environments. For example, a drilling engineer may require an increase in the maximum torque in the connection. This led to some exotic developments in double shoulder connections (DSC) technology, with thread designs other than the API standard for rotary-shouldered connections. Depending on the sour service region for the drilling operation, newer DSCs allow additional torque without compromising the sour service resistance features. The limited availability of high strength and sour service resistance standards added pressure on OEMs to innovate new grades. The drilling engineers demanded that these grades be able to drill deeper and longer wells. In addition, they wanted to customize tool joint grades to fit into the needed drill pipe.

As the drillstem technology leader, we saw an opportunity to drive this initiative and offer a sour service resistance suitable for each region, depending on severity. This allows operators to reach the maximum limitation a tool joint can offer based on its tensile strength and connection design.

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