Offshore drilling

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Offshore drilling typically refers to the act of extracting underground resources which lie underwater near the shoreline. Most commonly, the term is used to describe oil extraction off the coasts of continents, though the term can also apply to drilling in lakes and inland seas.

Contents 1 History 2 Main offshore fields 3 Challenges 4 Effects on the environment 5 See also 6 References 7 External links

[edit] History

Around 1891, the first submerged oil wells were drilled from platforms built on piles in the fresh waters of the Grand Lake St. Marys (a.k.a. Mercer County Reservoir) in Ohio. The wide but shallow man made reservoir was built from 1837 to 1845 to provide water to the Miami and Erie Canal. The wells were developed by small local companies such as Bryson, Riley Oil, German-American, and Banker's Oil. The wells tapped into the Trenton limestone reservoir in the Lima-Indiana trend. Each well produced between 25 and 250 barrels per day. By 1901, over 100 oil and gas wells had been drilled in the lake. The discovery of highly productive onshore resource (such as Spindletop in 1901) undermined the economic rational for continued production from Grand Lake. By 1910, only a few wells in the lake remained active.

Around 1896, the first submerged oil wells in salt water were drilled in the portion of the Summerland field extending under the Santa Barbara Channel in California. The wells were drilled from piers extending from land out into the channel.

Other notable early submerged drilling activities occurred on the Canadian side of Lake Erie in the 1900s and Caddo Lake in Louisiana in the 1910s. Shortly thereafter wells were drilled in tidal zones along the Texas and Louisiana gulf coast. The Goose Creek field near Baytown, Texas is one such example. In the 1920’s drilling activities occurred from concrete platforms in Venezuela’s Lake Maracaibo.

The oldest subsea well recorded in Infield’s offshore database is the is Bibi Eibat well which came on stream in 1923 in Azerbaijan. The technique used here involved using landfill to raise shallow portions of the Caspian Sea. In the early 1930s, the Texas Co., later Texaco (now Chevron) developed the first mobile steel barges for drilling in the brackish coastal areas of the gulf.

In 1937, Pure Oil (now Chevron) and its partner Superior Oil (now ExxonMobil) used a fix platform to develop a field 1 mile offshore of Calcasieu Parish, Louisiana in 14 feet of water.

In 1946, Magnolia Petroleum (now ExxonMobil) drilled at a site 18 miles off the coast, erecting a platform in 18 feet of water off St. Mary Parish, Louisiana.

In early 1947, Superior Oil erected a drilling and production platform in 20 feet of water some 18 miles off Vermilion Parish, La. But it was Kerr-McGee Oil Industries (now Anadarko Petroleum), as operator for partners Phillips Petroleum (ConocoPhillips) and Stanolind Oil & Gas (BP) that completed its historic Ship Shoal Block 32 well in October 1947, months before Superior actually drilled a discovery from their Vermilion platform farther offshore. In any case, that made Kerr-McGee’s well the first oil discovery drilled out of sight of land.

[edit] Main offshore fields

Notable offshore fields today are found in the North Sea, the Gulf of Mexico, the Campos and Santos Basins off the coasts of Brazil, Newfoundland and Nova Scotia, several fields off West Africa most notably west of Nigeria and Angola, as well as offshore fields in South East Asia.

[edit] Challenges

Oil and gas production in the sea is more challenging, compared to land-based installations. Much of the innovation in the offshore petroleum sector concerns overcoming these challenges, including the need to keep manned facilities above sea-level. Manned facilities can be maintained with enormous constructions with their "feet" on the bottom of the sea, such as the Troll A platform standing on a depth of 300 meters. With height of 472 meters, it is the largest man-made structure ever to be moved. Other platforms may be floating, only anchored to the bottom of the sea. While the floatation cuts construction cost, extra security measures are needed, as well as mechanisms for nulling out heave from waves. In both cases, the ocean adds several hundred meters to the fluid column in the drill string. The addition increases bottom hole pressure as well as the energy needed to lift sand and cuttings for oil-sand separation on the platform.

The trend today is to conduct more of the production subsea, by separating sand from oil and re-injecting sand before it is pumped up to the platform, or even pumping it onshore, with no installations visible above the sea. Subsea installations help exploit resources at progressively deeper waters, locations which have been inaccessible, and overcome challenges posed by sea ice, such as in the Barents sea.

Offshore manned facilities also present logistics and human resources challenges. An offshore oil platform is a small community in itself with cafeteria, sleeping quarters, management, and other support functions. In the North Sea, staff members are transported by helicopter for a two-week shift. They usually receive higher salary than other industry workers do. Supplies and waste are transported by ship, and the supply needs to be well planned because floor area on the platform is limited. Today, much effort goes into moving as much of the personnel as possible onshore, where management and technical experts are in touch with the platform by video conferencing. An onshore job is also more attractive for the aging workforce in the petroleum industry, at least in the western world. These efforts among others are contained in the established term integrated operations. The increased use of sub sea facilities helps achieve the objective of moving more workers onshore. Subsea facilities are also more easy to expand with new separators or separate modules for different oil types, and are not limited by the fixed floor space of an offshore rig.

[edit] Effects on the environment

Offshore oil production involves environmental risks, most notably oil spills from oil tankers or pipelines transporting oil from the platform to onshore facilities, and from leaks and accidents on the platform.^[1] Produced water is also generated, which is excess water from well drilling or production and includes varying amounts of oil, drilling fluid or other chemicals used in, or resulting from, oil production. A platform is typically given a quota of produced water which may be emptied into the ocean. According to the organization Culture Change,^[2] a Gulf of Mexico rig dumps about 90,000 tons of drilling fluid and metal cuttings over its lifetime, with its wells also contributing with heavy metals.^{[citation needed]} The platforms themselves also present a problem when discontinued.^{[citation needed]} See ecological effects of oil platforms.

[edit] See also

• Offshore oil and gas in the United States
• Oil drilling
• Oil platform
• Subsea
• US offshore drilling debate

[edit] References

[edit] External links

• Center for Biological Diversity v Dept of the Interior 17Apr2009 DC Appellate Decision stopping offshore Alaska Oil Leases.