Wellhead Load Relief (WLR) System

With SubseaDesign’s innovative wellhead load relief (WLR) system the cyclic bending moments that occur in the subsea wellhead during offshore drilling operations - potentially causing severe fatigue failure of critical components in the subsea well system - are efficiently reduced without compromising the operational flexibility.

The mechanism that provides pretension on the rope arrangement connected between the blow-out preventer (BOP) and the support structure is to be considered a pioneer, constantly evolving to reach even higher capacities and applications. The latest development of the tensioner mechanism, the Linear Rope Tensioner (LRT), has the capability to continuously pull excess length of rope before application of final tension. Thus, flexibility in adjusting length of rope required for each tension line is provided which overcomes the need to have several lengths of adjustment lengths and hence reduce the subsea rigging time.

The LRT can be equipped with two different configurations for initial tensioning, either by lift line from surface (snatch block) or by a hydraulic operated tensioning unit mounted on the LRT. The latter is fully ROV operated and ideal for use in shallow water or on locations where it cannot be reached from the rig.

The integrated load monitoring system ensures that the ROV can monitor and adjust tension force as required. The LRT enables easy interfacing on all types of anchor points, both on templates and seabed, and has a rotational range of 360 degree. Since the rope goes out of the LRT in upward direction, it will not be any clash with surrounding structures.

The WLR system consists of several LRT’s which are individually tethered to the BOP. The amount and anchoring coordinates of the LRT’s are decided based on analyses of the system to achieve the optimal WLR efficiency. Other optimization factors are loads on the existing infrastructure, well properties and soil conditions. The system is adaptable to different BOP designs.

Our WLR system is typically designed and supported, but not limited to, using the following:

  • WLR system drawings
  • WLR efficiency analyses
  • Geotechnical analyses
  • BOP attachment points for rope arrangements
  • Anchoring points (Tension supports, clump weights, suction anchors etc.)
  • Tensioning mechanism (LRTs)
  • Detailed installation procedures and operational support
  • Repair, maintenance, testing and storage of the equipment (WLR test jig with load test up to 105 T)

Specifications:

  • Pull-in capacity: 4 T
  • Pre-tension capacity @ 2700Nm torque: min. 30 T  
  • Design Load, ULS: 700kN 
  • ALS Load: 1050kN