Quad 204 - Wellhead Strengthening System

Our Experience


  • Scope of Work
    Extra Support Sleeve (ESS)
  • Project Operator

As part of their Schiehallion Quad 204 drilling campaign, BP employed a Generation-6 semi-submersible rig for the drilling operations. A need was identified for an Extra Support Sleeve (ESS) to be engineered and manufactured, to improve fatigue life of the existing subsea wellhead under the predicted loading conditions. A further need was identified to engineer and build a Torque and Alignment Structure (TAAS).

MMA was contracted to provide the ESS solution to support the wellhead. The ESS consists of a fabricated pipe which is welded onto a forged and machined ESS body. The ESS supports the wellhead from the outside and provides additional stiffness to the wellhead. The ESS is attached to a Torque and Alignment Structure (TAAS) which also accommodates cementing equipment.

The system was fully developed and delivered by MMA – 100% in-house design and optimisation. Eight systems were successfully deployed during the period of 2014 to 2016.

Our scope of supply included:

  • All elements of engineering and project management
  • All elements of engineering analysis and fatigue modelling
  • Qualification and validation testing for centraliser system
  • Factory acceptance testing and finite element model validation
  • Technical risk assurance process
  • Manufacture of every element of the ESS and TAAS wellhead integrity systems
  • Design and manufacture of wellhead lifting clamps
  • Management of third-party design verification and assurance process
  • Interfacing with client, OEM’s, technical authorities, assurance bodies and rig personnel
  • Offshore engineering and technical support with system installation and subsea deployment onboard Deepsea Aberdeen semi-submersible