UK-based engineering consultancy Longitude Engineering has developed a decommissioning barge concept for the removal of small oil and gas platforms for PTTEP, a subsidiary of the Thai state-owned oil company PTT.
Longitude said that the primary aim of the work was to develop an alternative to conventional ‘reverse installation’ through the use of heavy lift crane barges, for the removal of the topsides and jackets.
According to the company, the focus is the removal of 90-100 of PTTEP’s minimum facilities platform assets in the Gulf of Thailand, with topsides weighing up to 800 tonnes and jackets weighing up to 1,000 tonnes.
Under the contract, the company will deliver the conceptual naval, structural, mechanical, and electrical engineering, along with outline operational procedures, schedule, and capex & opex costing for the new removal concept.
Regarding the solution, it is a barge concept that utilizes reverse float-over and onboard lifting methods to remove both the topside and substructure utilizing the same vessel.
For the development of the primary float-off lifting system, Longitude partnered with German-based hydraulics specialist, Bosch Rexroth, to develop a heave compensated hydraulic lifting and skidding system.
The resulting vessel design can accommodate the removal of different types of topsides and jackets, without modifying the barge, from removal preparation stages, lifting, topside skidding, and securing to underwater disposal for the substructure and load in to a disposal yard for the topside.
PTTEP decom plan
PTTEP is currently in discussion with Thailand’s Department of Mineral Fuels (DMF), the government body regulating offshore oil and gas operations, which will sanction the decommissioning work, for the start of its removal program, due to begin in the coming years.
According to new decommissioning regulations, all concessionaires must submit the decommissioning plan with cost estimation to DMF for financial security placement at the first stage.
Longitude’s lead engineer, Jean-Baptiste Meier, said: “The South East Asian fields present many similar small platforms where innovative thinking can be used to make an economy of scale in the removal operations.
“It is crucial to define the standards and procedures for the decommissioning work in the Gulf of Thailand – to ensure that the solution is not only the most innovative and cost-efficient but also environmentally friendly. While pending approval from DMF, PTTEP has logged a petty patent for this solution.”