Longitude Engineering was contracted by PTTEP Thailand to develop the conceptual engineering for a fixed platform decommissioning asset via reverse floatover and jacket lifting.


  • Can accommodate the removal of 3 types of topsides and jackets
  • Up to 800 tons topside’s weight
  • Potential removal of 90 platforms for PTTEP
  • Heave compensated lifting and skidding systems integrated
  • Stand jack lifting system and locking system integrated for the lifting, upending, transport and disposal of jacket
  • 8 points position mooring system
  • Accommodation for crew and operation team for 60 POB.
  • Designed in line with ABS Class and DNVGL Guidelines for Marine Transportation

Longitude’s Scope of Work

The scope of engineering services included project management, conceptual naval design, facilities design, geotechnical analysis subcontracting, removal procedures, material take-off/cost estimation and platform decommissioning procedure. The naval design analysis included stability and longitudinal strength verifications using GHS software, motion analysis for the different operation stages (topside lifting, jacket pull-out, lifting, upending, transport and disposal) using MOSES software, mooring analysis for stand-by and operating positions, towing analysis and definition of the operational window for removal of the topside and the jacket. The associated drawings and layouts were produced.

The structural scope included the local verification of the primary steel using Finite Element Analysis software FEMAP, the design of reinforcements and additional steel comprising the lifting frame, topside interface, fenders, jacket lifting support, locking system using FE analysis software Staad.Pro and FEMAP.

The mechanical scope included the design of a heave compensated lifting system, a skidding system, the integration of a position mooring system and the integration of the jacket lifting and locking systems. In addition, the electrical scope covered the load analysis, the power system generation and distribution philosophy and the basic design philosophy of alarms and monitoring systems.

The scope also includes the marine system design, the underwater work definition and ROV spread definition and integration, the subsea connection screenings and design, the accommodation layout, deck layouts and philosophies covering aspects from the Health and Safety to material handling and Flag/Rules/Codes and standards analysis.

Finally, the procedures for transport, load-in via SPMT, topside lifting, jacket lifting, upending and disposal and overall decommissioning were produced for the client. In addition, several operation schedules scenario, HAZID sessions, CAPEX and OPEX costings, requests for quotation to potential fabricators, yards and suppliers were prepared and presented to the client to be incorporated in the decommissioning dossier.

Solution designed and engineered by Longitude Engineering is under Petty Patent Intellectual Property registration by PTTEP of Thailand.