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Oil and petroleum products explained Offshore oil and gas

Offshore drilling

The border of the United States extends 200 miles beyond the coastline. The ocean area between the border and the coast is called the Exclusive Economic Zone (EEZ) and includes areas administered by state governments and the federal government. Thirty basins in the U.S. EEZ have been identified as containing oil and natural gas reserves.

The first offshore oil well was drilled in 1897 at the end of a wharf, 300 feet off the coast of Summerland, California. Early offshore drilling occured in areas where the water was less than 300 feet deep. Oil and natural gas drilling rigs now operate in water as deep as two miles. Offshore oil and natural gas production is much more expensive than onshore (land-based) production.

Map of U.S. oil and natural gas fields showing onshore and offshore fields. Source: National Energy Education Development Project

Source: National Energy Education Development Project (public domain)

Offshore oil rig

Offshore oil rig

Source: Stock photography (copyrighted)

Offshore oil and natural gas wells are drilled from platforms that hold all of the drilling equipment, storage areas, and housing for work crews. Some drilling platforms stand on stilt-like legs that are embedded in the ocean floor. Floating platforms are used for drilling in deeper waters, including water depths of 10,000 feet or greater. These self-propelled vessels are attached to the ocean floor by large cables and anchors. After wells have been drilled from these platforms, production equipment is lowered to the ocean floor.

Offshore oil and natural gas producers are required to take precautions to prevent pollution, spills, and significant changes to the ocean environment. Offshore rigs are designed to withstand hurricanes. When offshore oil and natural gas wells are no longer productive enough to be economical, they are sealed and abandoned according to applicable regulations.

Nearly all offshore oil and natural gas leasing and development activity currently occurs in the central and western Gulf of Mexico, where thousands of platforms operate in waters up to 6,000 feet deep. A few platforms operate in depths of 10,000 feet or more. In 2021, offshore oil and natural gas production in the Federal Gulf of Mexico accounted for about 15% of total U.S. crude oil production and about 2% of total U.S. dry natural gas production.

Last updated: October 4, 2022 with the most recent data available at the time of update.