Two people were taken to hospital after the fire on February 16th, which was extinguished by crews on board the rig.
The Bravo rig, in Centrica's Rough field, 20 miles (31km) off Withernsea on the East Yorkshire coast, stores North Sea gas for UK consumption.
The platform can supply up to about 10% of the UK's peak gas demand.
In a statement, Centrica said: "The initial visual inspection of the scene would appear to indicate there was an apparent failure of a cooler unit in one of four dehydration units and an explosion occurred in that vicinity.
"Following this inspection we currently estimate that it is unlikely that Rough will be available for one month."
They said bad weather had restricted helicopter access and delayed restoring full power and other services to the platform, which was their first priority.
"Detailed examination of the equipment will continue over the next few days in parallel with the investigation of the cause of the incident and plans to restore safe operations," the company said.
There were 58 crew on board the rig when the fire broke out.
In addition to two staff being taken to hospital - one with burns and one with smoke inhalation - the remaining non-essential staff were evacuated to safety by RAF helicopters and support vessels.
(C) 2006 BBC Monitoring Newsfile. via ProQuest Information and Learning Company; All Rights Reserved
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