TAQA Bratani were unable to say how long the Brent pipeline that feeds oil from 21 platforms into the terminal would be closed, but they expect it to be a few days.
This is the second leak from a pipe in the same concrete leg of the 34 year old platform that is a lynchpin in the Brent pipeline system that currently supplies 50 per cent of oil to the Sullom Voe terminal.
On 15 January non essential personnel were evacuated from the rig when a leak was discovered, but it was repaired after two days.
The pipeline system took another four days to get back to full production of 80,000 barrels a day.
The latest leak was caused in a different pipe during an inspection of the same leg that reaches 150 metres into the sea, 110 miles north east of Lerwick.
Personnel were once again evacuated when the leak was discovered on Saturday morning.
TAQA has said that no oil has entered the environment from either incident.
On Tuesday a spokeswoman said only water was now leaking out of the latest fissure, but she could not say when it would be repaired.
The spokeswoman said that TAQA had invested £240 million in overhauling old infrastructure since they purchased the North Sea assets of Shell in 2008.
She said the current inspection was part of an 18 month programme of work at Cormorant Alpha.
“The leak was caused by the inspection work,” she said.
“The oil has been contained within the leg, nothing has gone into the sea. No oil is leaking from the site anyway, just water.
“We are still looking into the cause of the first leak.”
Concerns have been raised about rusty rigs working beyond their expected lifetime in the North Sea as the industry attempts to extract as much as they can from existing fields to feed the appetite for hydrocarbons.
TAQA’s spokeswoman said: “The integrity of our assets is one of the most important things that we are looking at. That is why we planned this inspection work.
“Sadly we didn’t get to the first leak in time, but the second leak we have been able to pin point.”
A Sullom Voe terminal spokeswoman said throughput had reduced by approximately 50 per cent, but this had no impact on terminal operations.