Offshore -- Petroleum and Natural Gas Production

What is Offshore?
Offshore Petroleum and Natural Gas
Natural Gas from Methane Hydrates

WHAT IS OFFSHORE?

Question: When you are at your favorite beach in Florida or California, are you at the very edge of the country?

Answer: No. Although it might seem like the ocean is the border of the U.S., the border is actually 200 miles out from the land. This 200 mile wide band around the country is called the Exclusive Economic Zone(EEZ). In 1983, the President claimed the area of the EEZ in the name of the United States, and in 1994, all countries were granted an EEZ of 200 miles from their coastline according to the International Law of the Sea.

There is a lot of activity just beyond the beach. The beach extends from the shore into the ocean on a continental shelf that gradually descends to a sharp drop, called the continental slope. This continental shelf can be as narrow as 20 kilometers or as wide as 400 kilometers. The water on the continental shelf is shallow, rarely more than 150 to 200 meters deep. The EEZ is part of the US. The federal government manages the land under the sea on behalf of the American people. The United States Minerals Management Service (MMS) leases the land under the ocean to producers. These companies pay MMS rental fees and royalties on all the minerals they extract from the ocean floor. Individual states control the waters off their coasts out to three miles for most states and between 9 and 12 for Florida, Texas and some others.

The continental shelf drops off at the continental slope, ending in abyssal plains that are three to five kilometers below sea level. Many of the plains are flat, while others have jagged mountain ridge, deep canyons, and valleys. The top of some of these mountain ridges form islands where they extend above the water.

Most of the energy we get from the ocean is extracted from the ground. Oil, natural gas, and minerals all come from the ocean floor. People are working on new ways to use the ocean too. Solar and wind energy have been used on land, and now they are also being used at sea. Other energy sources that are being explored in the ocean are wave energy, tidal energy, methane hydrates, and ocean thermal energy conversion.

OFFSHORE PETROLEUM AND NATURAL GAS

Petroleum and natural gas are fossil fuels. They are derived from the remains of plants and animals that died millions of years ago, were buried and compressed. Petroleum and natural gas are nonrenewable energy sources because they take millions of years to form. In the Exclusive Economic Zone(EEZ), there are 30 basins that have been identified as containing oil and gas reserves. A few of these are already producing oil and gas. It is estimated that 30 percent of undiscovered US gas and oil reserves are in the Outer Continental Shelf (OCS).

The first oil well was drilled in 1859, and by 1897 the first offshore oil well was drilled. It was at the end of a wharf, 300 feet out into the Pacific Ocean in Summerland, CA . In 1953, individual states were given jurisdiction over lands within three miles of their shoreline, allowing the Minerals Management Service (MMS) to lease the rest of the EEZ and regulate recovery efforts. Early offshore drilling was generally limited to areas where the water was less than 300 feet in depth.

Offshore drilling looks very different today, supplying about 25 percent of the nation’s natural gas production and about 24 percent of its oil production. Drilling rigs can now operate in water as much as two miles deep. Some drilling platforms stand on stilt-like legs that are embedded in the ocean floor. These huge platforms hold all the drilling equipment needed, as well as housing and storage areas for the work crews. Floating platforms are used for drilling in deeper waters. These self-propelled vessels are anchored to the ocean bottom with huge cables and anchors. Once the wells have been drilled from these platforms, the production equipment is lowered to the ocean floor, sealed to prevent leakage. Wells have been drilled in 10,000 feet of water using these floating rigs.

Offshore oil producers are always taking precautions to prevent pollution, spills and significant changes to the ocean environment. Since 1975, drilling in the EEZ has had a safety record of 99.999 percent meaning that only .0001 percent of the oil produced has been spilled. Offshore rigs are even designed to withstand hurricanes. Offshore production is costly- many times as expensive as land-based production. When wells no longer produce enough to be financially worthwhile, they are sealed and abandoned. Nearly all current leasing and development activity occurs in the central and western Gulf of Mexico. There, more than 4,000 platforms are operating in waters up to 6,000 feet deep, and many rigs are drilling in waters approaching 10,000 feet. Right now most of the active wells and proved reserves are in the Gulf of Mexico. There are also 43 wells off California. Read about Energy Ant's visit to an offshore rig or learn about jobs in the offshore.

NATURAL GAS FROM METHANE HYDRATES

Within the last decade, research has shown that immense amounts of natural gas are concentrated in frozen, ice-like methane hydrates within the top several hundred meters of sediment in deep water on the continental margins of the United States , from the Gulf of Mexico to the Alaska arctic. Methane hydrates — molecules of natural gas trapped in an ice cage — are a fascinating substance that may provide inexpensive, plentiful, and clean energy. Once processed, the natural gas from methane hydrates is virtually identical to the natural gas we use at home.

Methane hydrates may be a great source of natural gas for the future. Worldwide natural gas resources are only about 13,000 trillion cubic feet and worldwide natural gas reserves are about 5,000 trillion cubic feet. Methane hydrates may represent about 742,000 trillion cubic feet of natural gas. In the United States alone, the U.S. Department of Energy estimates there to be 200,000 trillion cubic feet of methane hydrate deposits.

Last Revised: June 2008
Sources: National Energy Education Development Project, Ocean Energy, 2006-2007.