Salvors could start pumping heavy fuel oil from a submerged tank on the container ship Rena as early as Monday night.
Hoses, ladders and pumps have also had to be set up so the oil can then be pumped to a bunker barge.
It has been a week since heavy fuel oil was pumped from the stricken vessel.
Maritime New Zealand's salvage unit manager Kenny Crawford says it will take about 100 hours to transfer the oil if all goes well.
About 750 tonnes of seawater has had to be pumped in so that the tank's 360 tonnes of oil will rise to the top and be able to be pumped to a bunker barge.
All of the ship's dirty oils have been removed from the engine room and clean oils such as lubricants are being transferred off the vessel.
