This case study outlines the work that TDS carried out during the dismantling of the gas platform for Veolia Environmental Services from the redundant Frigg Field during 2008. The treatment & compression platform TCP2 was a concrete sub structure standing at a depth of 104m supported by three columns supporting the Main Support Frame (MSF).

TDS were proud to be awarded the contract to dismantle the TCP2 platform, it required an in-depth procurement process managed by Veolia Environmental Services, alongside Total Exploration & Production who were jointly engaged with Aker Kvaerner, as a main contractor, Veolia Environmental Services were subcontracted to Aker Kvaerner for the decontamination & deconstruction on land, of the Module Support Frame (MSF) to platform TCP2, including attached pancakes which was a framed module incorporated into the MSF.

Client: Total Exploration & Production

Contract: Demolition, structural dismantling & asbestos

Contract start/end date: 2008 – 2009

Total project value: £1,000,000.00

The MSF to TCP2 was lifted from its position at sea, then taken to a licensed facility at Greenhead base, Lerwick, Shetland on a transportation barge & positioned on the temporary support grillage on a concrete pad. Greenhead base is a facility constructed for the purpose of the handling & processing of oil & gas structures from the North Sea.

Technical Demolition Services were subcontracted to carry out the asbestos removal & structural dismantling of the 8,500-tonne structure.

Project Overview

  • Management of operations at Greenhead Base to a high standard of safety.
  • Surveys & documentation in respect of former process contamination, asbestos, paint & other materials plus substances & structural dismantling systems.
  • Notification & agreement of proposed systems with all parties.
  • Production of phased engineering plans for deconstruction.
  • Decontamination of the structure, including a dedicated asbestos removal process.
  • Disconnection & removal of plant items which were required for further use.
  • Selective disconnection & removal of redundant plant.
  • The safe dismantling, processing of scrap & waste materials of pancakes, MSF & associated redundant plant, electrical cables & pipelines.
  • The notification, consignment & disposal of segregated materials off site.

Scope of Work

Technical Demolition Services duties included:

  • Control & supervision of each category of their subcontracted works.
  • Asbestos removal including associated decontamination & certification, which was safely contained & labelled.
  •  Decontamination operations & the lifting of redundant plant items & attachments.
  • Safe dismantling of plant & internals from the pancakes by agreed sequence, this was completed with the use of an excavator & mounted shear, this was then followed by the dismantle of the perimeter frame structure & selected MSF frame by excavator shear & flame cutting.
  • The provision of personnel, equipment, plant & consumable stores for the dismantling of the MSF & integral structures.
  • The processing & segregation, of all arising salvageable scrap & waste materials.
  • Where plate thicknesses were beyond hydraulic shear capacity, flame cutting was used, piles of scalping’s were used to support sections & reduce impact concrete pad. 

Dismantling Operations

Prior to each dismantling stage, assessments were made to ensure the weight of the section was known & that the removal would not affect the stability of the structure on the grillage.

TDS prepared detailed method statements & risk assessments for each stage of the operation, these were assessed by all parties before issue as working documents. TDS planned engineered phases of work & issued photographs showing proposed cut lines in the structure to provide effective planning & operational techniques.

Live time risk assessments were also produced prior to work commencing, to ensure that all information was task specific, toolbox talks & pre start meetings were also held.

Analysis of the paint used on the structure showed it to be isocyanate based, therefore for all flame cutting operations, it was mandatory that burners wear battery powered respiratory protection.

The dismantling operations were split into specific phases in order to maintain the balance of the structure whilst sitting on its concrete supports.

Heavy plant items were removed from individual pancakes on the structure, followed by the removal of remaining items in the pancakes through the utilisation of the Liebherr 984, these items were brought to ground level for either segregation & processing or re-sale.

The Liebherr 984 excavator fitted with a powerful shear was used to cut deck sections of each pancake & was lowered to ground level for processing by other machines.

This process was repeated in a phased & engineered method until the only sections remaining were the main structural elements of the MSF.

Where the thickness of the steel within these structural elements was too great or where the complexity of the construction limited machine use, alternative methods were used, methods involved utilisation of the Liebherr Excavator to support the main structural sections, whilst flame cuts were made leaving small tags in place, the 984 machines then broke the tags & lowered the free section to ground.

Asbestos Removal

Detailed method statements were prepared following the type 3 survey. A resident Site Manager for asbestos removal works was in attendance throughout the asbestos phase, along with our team of skilled & experienced operatives who conducted the removal work to a great standard.

All operations were in accordance with ISBN 07176 62063 Work with materials containing asbestos & ISBN 07176 28744 the asbestos licensed contractors guide.

Completion Report

  • No accidents other than first aid were recorded.
  • The project was completed within the specified timescale.
  • Approximately 98% of materials from the operation were recycled.
  • Consumable usage was as predicted, but with increased flame cutting, due to the thickness of the structural sections.
  • All environmental controls were in place & maintained at all times.

Environmental targets for the contract were exceeded & no lost time or accidents were recorded.

Overall the project was a great success & showed that TDS can provide a professional solution to the challenges of the North Sea Decommissioning Market.