connection development

Comprehensive design analysis, testing, and deployment verify the high-performance behavior that DUO was intended to deliver

Analysis & Testing

From the initial prototypes to production-ready drill pipe, the DUO connection family has undergone extensive analysis and testing to ensure that real-world performance meets the performance predicted through preliminary design calculations.

  1. Finite element analysis (FEA): CAD models of multiple DUO design configurations are put through simulated torsional load cases to evaluate localized stress levels, double-shoulder interaction, load-sharing between taper regions, and the overall expected deformation of the DUO design.
  2. Torsional stage loading: Prototype connections are subjected to increasing values of torque loads up to and beyond torsional yield with critical connection geometry measured between at each stage. The DUO connection design has proven to remain well within field inspection tolerances even at extreme torque loads.
  3. Cyclical torque loading: Connections are subjected to cyclical torque loads at makeup torque, evaluating the detrimental effects of repeatedly applied loads on connection geometry and threadform. DUO connections have demonstrated excellent galling and deformation resistance even being cycled well past the recommended makeup torque.

Correlated together, the above methods provide a clear picture of the raw torque capability of the DUO connection and validates the initial analytical calculations used in its design.

Field Testing and Beyond

The first field deployment of the DUO connection was performed in early 2018. A string of 4½” 400 DUO™ S135 pipe and HWDP was successfully utilized to drill a tough 2,300m lateral section which put the drill string through repeated bit & motor trips, providing for an excellent opportunity to evaluate the handling and spin up performance of the DUO connection. As expected, field personnel praised the rapid spin-up and ease of handling, while the operator and drilling contractor were more than satisfied with the DUO’s torsional capabilities.

The drill string was then sent back into service to drill an additional 4 planned wells, with a maximum total depth of 5,450m (18,000ft).

Following drilling, all connections were 3rd party inspected to the full extent of API and Complete Group’s specifications to evaluate and quantify any connection damage, and observe the effectiveness of the DUO’s unique landing pad thread design. The inspection resulted in:

  • 0.29% machine shop repair rate
  • Zero connections outside field inspection tolerances
  • A large portion of connections still within manufacturing tolerances

To date, there are now multiple strings of 400 DUO pipe sold and in use in Western Canada with more information and data being generated every day. Complete Group is looking forward to sharing more performance and inspection data as the DUO product line continues to grow!

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