The drillship is called Kulluk, owned by Royal Dutch Shell. The US coastguard was concerned about any leak but overflights confirmed that no leak has occurred.
Coast Guard Captain Paul Mehler said the Kulluk had 143,000 gallons of ultra-low-sulfur diesel and 12,000 gallons of other oil products on board.
The grounding of the drillship, weighing nearly 28,000 gross tons and operated by Noble Corp, is a blow to Shell's $4.5 billion offshore program in Alaska.
The rig had been headed to Puget Sound for maintenance and upgrades when it broke away from one of its tow lines on Monday afternoon and was driven to rocks just off Kodiak Island that night. The 18-member crew had already been evacuated by the Coast Guard on Saturday because of risks from the storm.
With winds reported at up to 60 miles (100 km) an hour and Gulf of Alaska seas of up to 35 feet (11 m), responders were unable to keep the ship from grounding, the Coast Guard said.
Sean Churchfield, operations manager for Shell Alaska, could not explain why the Kulluk had been caught in the weather. "I can't give you a specific answer, but I do not believe we would want to tow it in these sorts of conditions."
Susan Childs, emergency incident commander for Shell, believed that a significant spill was unlikely because of the Kulluk's design, with diesel fuel tanks isolated in the center of the vessel and encased in very heavy steel.
Shell is waiting for weather to moderate to begin a complete assessment of the Kulluk.