The Thunder Horse oilfield is an oilfield developed by BP (although 25% co-owned by Exxon) in the Gulf of Mexico, around 150 miles southeast of New Orleans, Louisiana. It is the largest producer in the Gulf, processing in excess of 250,000 barrels of oil per day and 200 million cubic feet per day of natural gas, and is also the largest deepwater field in the world. It is believed to hold in excess of 1 billion barrels of oil.

The Thunder Horse production platform is the largest moored semi-submersible oil platform in the world, located in 1,920 metres (6,300 ft) of water in the Mississippi Canyon Block 778/822, about 150 miles (241 km) southeast of New Orleans.

In July 2005, Thunder Horse was evacuated in the face of Hurricane Dennis. After the hurricane passed, the platform was listing badly. Inspection teams found no hull damage — Thunder Horse had not taken on water from a leak through its hull. Rather, an incorrectly plumbed, 6-inch length of pipe had allowed water to flow freely among several ballast tanks. That began a chain of events that caused the platform to tip into the water. The event boosted world oil prices because of speculation of further oil shortages. The platform was fully righted about a week after Hurricane Dennis, but BP announced that commercial production had been delayed. The platform was struck almost directly by Hurricane Katrina six weeks later, but was not damaged.

Designed to process 250,000 barrels of oil per day and 200 million cubic feet per day of natural gas, Thunder Horse is actually exceeding those goals. It is not only the largest producer in the Gulf, it is the largest deepwater producing asset in the world.

Located 150 miles southeast of New Orleans, the Thunder Horse field is one of the world’s most technologically complex, in part because of the challenging deepwater environment.

“First oil” at the world’s largest floating drilling and production platform came on June 14, 2008. Since then, Thunder Horse has steadily ramped up its production by bringing on new wells. In March 2009, Thunder Horse produced over 300 thousand barrels of oil equivalent (BOE) per day from just seven wells. Plans are in place to add two additional wells in 2009 to further develop the north end of the field.