When conventional, manually operated riser-handling tools appeared incapable of fully supporting a particular drilling riser system, it was time to go back to the drawing board.

In response to a client’s need, Claxton Engineering Services Ltd. initiated an intense in-house development program to create an innovative hydraulic tool. The resulting design eliminates the need for scaffolding and manual handling and offers protection to the very expensive associated riser connector. It also can cut rig time and costs.

Need For Innovation

The limitations of the conventional heavy-duty segmented handling tool became apparent on this project when it could not hold the required internal pressure when attaching to the 18?-in., 49-ft (15-m) NT-2 tension joint. After exhausting all of the options, including changing the construction material and altering the segment design, engineers concluded that the client’s requirements could not be met with the existing design. A new approach clearly was needed.

Claxton’s innovative hydraulic riser-handling tool

Claxton’s innovative hydraulic riser-handling tool provides a means of fully supporting a drilling riser system during installation and recovery. (Images courtesy of Claxton Engineering Services Ltd.)

The engineering team set about re-engineering the conventional riser-handling tool. Over the course of the ensuing 10 months, they designed, manufactured, and tested a new multipurpose, hydraulically actuated running tool through a process that involved internal and client design reviews and third-party approval. Manufacturing and mechanical completion activities were in accordance with the Norwegian petroleum industry’s NORSOK standards.

This tool not only met the needs of the immediate application, but it also overcame the shortcomings of the manually operated variant. For one thing, the conventional tool requires the erection of scaffolding to reach the NT-2 joint. This adds time to the operation and introduces safety risks from the potential for dropped objects. Another shortcoming of the manual tool is that operating the tool is time-consuming because each of the 12 segments has to be manually secured onto the tool’s housing using a threaded stud and nut, which are tightened using a standard torque package.

Incorporating Hydraulics Into Riser Handling

In contrast, the new tool’s hydraulic operation means riser handling can be much quicker. Scaffolding does not need to be erected, and the tool hydraulically locks itself onto the NT-2 joint in seconds. A crucial step forward in terms of safety is that because the tool is hydraulically actuated, it can be operated remotely by means of a dedicated combined hydraulic power unit and reel, which reduces the risk of harm to personnel.

In its first real-world application, a Norwegian drilling operator used the tool to run and remotely pressure-test three 6,019-psi (415-bar) full riser systems. The tool cut 4.5 hours of rig time from each run and decreased the project costs by US $2.9 million.

The tool now is available as part of Claxton’s strategy of continuing improvements in efficiency and safety. The tool’s key features include its ability to:

Perform a wellbore pressure test to 7,000 psi while holding the tension at 308 metric tons (flanged and quick-connect systems are available to 12,200 psi);

Act as a contingency method for applying 400 metric tons of tension to the drilling riser system before BOP installation (with no internal bore pressure);

Interface with either a Grayloc 192 or 196 gasket seal profiled, 18?-in., 49-ft NT-2 pin by means of a removable adaptor housing the seal elements; and

Lift a drilling riser tension joint weighing up to 20 metric tons and measuring up to approximately 39 ft (12 m).

The tool’s vital safety features include visual indicator rods that show whether the tool is locked or unlocked and a manual override feature to lock and unlock the tool.

The Claxton tool is 11.5 ft (3.52 m) long, has a maximum OD of 45? in., and weighs 5.1 metric tons. It is DNV approved and is verified in accordance with DNVOS-E101 and API 16F, 6A, 8C, and 7G. The tool is supplied as a complete package with a DNV-2.7-1-certified container for transportation and storage and a combined ATEX-approved hydraulic power unit and umbilical reel to power all functions.

Claxton hydraulic riser-handling tool

The design of the new hydraulic riser-handling tool eliminates the need for scaffolding and manual handling and offers protection to the very expensive associated riser connector.

Operational Advantages

An important feature of the new tool is that it offers protection for the NT-2 riser connector. This expensive piece of hardware is at risk of being damaged by the riser when the crane is moving it. The key element of an NT-2 connection is the seal profile located at the top. When the tool is installed on the NT-2 joint, this seal region cannot be accessed because the tool envelops it and prevents damage through mishandling or from dropped objects.

The new tool also helps to safeguard against weather window issues, as it can apply tension if sea conditions worsen during the installation process. In such a situation, a manual tool could not operate to 400 metric tons without a specially designed tool mandrel and, more critically, could not maintain tension while being highly pressurized. This is not an issue with the new tool because it has been specifically designed to meet these parameters.

Designers also have eliminated some of the operational use restrictions. For instance, the manual version requires over-the-side scaffolding work, which cannot be undertaken at night on some rigs. The hydraulic riser-handling tool has no such operational restrictions and therefore does not impact decisions regarding when to run or pull the riser system during a drilling campaign.

Slimline Tension Rings

Further benefits can be realized from using a Claxton slimline tension ring, especially when more than one slot is being drilled at a given time and there is a need to “hop” the riser from one slot to the next. At some point, the tension joint needs to be pulled through the rotary table. By design, the slimline tension ring does not need to be removed to enable the tension joint to pass through the rotary table, therefore saving rig time. The tension joint can then be rerun through the rotary table to make further time savings.