Vermilion Oil & Gas Australia (VOGA) required removal of their old Auxiliary Living Quarters (ALQ) from Wandoo B (WNB) to make way for new accommodation facilities. VOGA had little structural information on the old ALQ structures which had been installed in the fabrication yard and not designed for offshore lifting. VOGA required a safe method of removal of the two ALQ structures.
Cube Offshore was involved from concept through to removal of the ALQ units. Cube collaborated with VOGA to survey then develop and demonstrate a method whereby the ALQ units could be lifted safely from the deck onto a supply boat. The lift plan saved considerable offshore time by not requiring the ALQ units to be demolished offshore with debris removed in skips. Cube’s lift plan avoided using the existing padeyes which would have concentrated loads and stresses. Instead beams above and below the ALQ units were used to spread the load evenly thereby minimising the stresses induced in the ALQ structure. Cube’s responsibilities included risk assessments, lifting plans, designing the lift rigging and spreader frame as well as rigorous assessment of the ALQ using FEA.
ALQ lift off WNB deck
FEA of ALQ structure showing stress distribution in plated walls between door openings during dynamic lift off WNB deck
View of ALQ being lowered to waiting support vessel