• When drilling to total depth in subsea wells, pressures and operator’s requirements have continued to increase, making standard API drill pipe and rotary-shouldered connections unsuited to such operations. Completion tubulars were created to address the issue, but it was not until recently that a large-sized completion landing string (CLS) with a specialized connection technology was developed to be compatible with the large crown plugs of horizontal subsea well heads currently deployed on ultradeepwater rigs.

    The CLS was developed by NOV using 7⅝-in. pipe and MaXit™, which is a built-for-purpose, gas-tight, large-drift, pressure-rated, rotary-shouldered connection technology. The CLS underwent an intense research and development phase, where pressure ratings, maximum makeup torque and tool joint OD, and minimum drift diameter were established. Following this, a rigorous testing phase plan was created; both finite element analyses, to verify stress distribution in the connection, and full-scale physical testing, to verify connection performance, were conducted. Finally, a field trial and qualification of the 7⅝-in. CLS tubular were conducted onboard an ultradeepwater drillship to assure compatibility of the new, larger-sized tubular with the drillship’s pipe handling and running equipment and validate the connection’s performance under actual field conditions.

    The 7⅝-in. CLS has now been deployed on four completion in the Gulf of Mexico, with rig crews using the CLS confirming that the new string ran quicker and safer than the previous casing landing string. The new string allowed the operator to avoid the costs of using casing, tubular running services, and related equipment, and reduced the connection time by a minimum of 4 min. per connection, slip to slip, in comparison to the previous premium casing connection landing string, yielding time savings of 3.5 to 10 hours running the completion. 

    To learn more about our 7⅝-in. CLS and our MaXit connection technology, read our feature article in the August edition of World Oil here.






    Published Date: 2017-08-21
    Source: National Oilwell Varco