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Oil: crude and petroleum products explained Offshore oil and gas

What is offshore?

The coastlines of the United States are not the actual borders of the United States. The U.S. border is actually 200 miles away from the coastline. This area around the country is called the Exclusive Economic Zone (EEZ).

In 1983, President Ronald Reagan claimed the EEZ in the name of the United States. In 1994, all countries were granted an EEZ of 200 miles from their coastlines under the International Law of the Sea.

Image of a coastline

Image of a coastline

Source: Stock photography (copyrighted)

Map showing Exclusive Economic Zone around the United States and Territories

Map showing Exclusive Economic Zone around the United States and Territories

Source: National Energy Education Development Project (public domain)

The ocean floor extends from the coast into the ocean on a continental shelf that gradually descends to a sharp drop, called the continental slope. The width of the U.S. continental shelf varies from 10 miles to 250 miles (16 kilometers to 400 kilometers). The water on the continental shelf is relatively shallow, rarely more than 500 feet to 650 feet (150 meters to 200 meters) deep.

The continental shelf drops off at the continental slope, ending in abyssal plains that are 2 miles to 3 miles (3 kilometers to 5 kilometers) below sea level. Many of the plains are flat, while others have jagged mountain ridges, deep canyons, and valleys. The tops of some of these mountain ridges form islands where they extend above the water.

diagram of land and ocean overlayed with 3 miles of territorial sea, 200 miles of Exclusive Economic Zone, the Continental Shelf, and Continetal Slope.

Diagram of shore and ocean overlaid with territorial sea, Exclusive Economic Zone, the Continental Shelf, and Continental Slope

Source: National Energy Education Development Project (public domain)

Several federal government agencies manage the natural resources in the EEZ. The U.S. Department of the Interior's Bureau of Ocean Energy Management and Bureau of Safety and Environmental Enforcement manage the development of offshore energy resources by private companies that lease areas for energy development from the federal government. These companies pay royalties to the government on the energy resources they produce from the leased areas in the ocean. Most states control the 3-mile area that extends off of their coasts, but Florida, Texas, and some other states control the waters for as much as 9 miles to 12 miles off of their coasts.

Most of the energy the United States gets from the ocean is oil and natural gas from wells drilled on the ocean floor. Other energy sources are under development offshore. America’s first offshore wind energy project, the Block Island Wind Farm off the coast of Rhode Island, became operational in December 2016. Other wind energy projects are under consideration in several other areas off the Atlantic coast. Wave energy, tidal energy, ocean thermal energy conversion, and methane hydrates are other energy sources currently under development or exploration.

Last updated: August 28, 2018