The drillship after already undergoing a lengthy upgrade programme in South Korea.
The Anglo-Dutch supermajor in January elected to call off a 2014 reboot of its mishap-filled 2012 drilling season after an unfavourable court ruling and exploration slimdown worldwide.
But Shell had already committed to a three-year deal for the rig starting in late February 2014 at a day rate of $368,000.
In its latest fleet status report, Noble Corporation said it was "notified by client of postponement of their 2014 drilling program offshore Alaska."
"After maintenance and upgrade project in South Korea, rig mobilising to Singapore in preparation for the client's future drilling program."
Neither Shell nor Noble immediately responded to a request for comment on the scope of the work.
The Discoverer had been in Korea under its prior Shell contract since March 2013 for maintenance and upgrades at a day rate of $244,000.
Upstream also previously reported that Shell had signed Transocean's semi-submersible Polar Pioneer to remain on standby in the event that a relief well or other measures were needed.
That unit is also booked on a three year contract at a rate of $620,000 during the July-October summer period and $589,000 during the off-season for the three years, according to Transocean fleet status data.