Shell International spilled 13,000 gallons of oil and drilling fluids into the Gulf on Sunday while drilling an exploratory well near the site of last year's Deepwater Horizon accident, according to a federal report on the spill.

The area where the well was being drilled is about 20 miles from the site of the BP oil spill. Shell is working in water more than 7,000 feet deep. The well was being drilled by the Deepwater Nautilus, according to federal records. That rig is owned and operated by Transocean, the company that owned the Deepwater Horizon rig.

While a report Shell filed Monday morning with the National Response Center states that the company spilled 7,560 gallons of oil and 5,829 gallons of synthetic drilling fluids, company spokesperson Kelly op de Weegh said late Monday afternoon that no oil was spilled.

"Shell can confirm it has a loss of (13,398 gallons) of drilling fluid from a booster line, which provides additional drilling fluids and is separate from the wellbore itself," read an emailed statement op de Weegh sent Monday afternoon. "The leak was isolated, stopped and remedial action has been approved... which includes temporarily abandoning the well, pulling the riser and making appropriate repairs."

The Bureau of Ocean Energy Management, Regulation, and Enforcement dispatched inspectors to the scene Monday, according to a spokesperson.

The National Response Center report lists "equipment failure" as the cause of the spill. The report states that the release was caused by "a leak in the boost line," and describes the fluid spilled as a mix of drilling mud and "base oil."

A boost line is part of the blowout preventer located on the seafloor around a well head. Typically, the boost line is used to inject drilling mud into the riser to help carry rocks and other debris to the surface, or to help maintain control of pressure in a well. The report states that drilling was stopped and the well was secured.

(By Ben Raines, Al.com, 19/12/2011)