Offshore drilling
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Offshore_drilling".

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.

History

The first offshore drilling was done at the end of the 19th century in Baku at the Bibi-Eibat field and in 1896 at Summerland field on the California Coast^{citation needed}

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. It is thought that the oil and gas fields in the Barents Sea will become a major field in the future.^{citation needed}

Challenges

Oil and gas production in the sea is more challenging than land-based installations and much of the innovation in the offshore petroleum sector revolves around overcoming these challenges. This includes:

• Manned facilities need to be kept above sea-level.

This can be accomplished with enormous constructions with their "feet" on the bottom of the sea, such as the Troll A platform which is standing on a depth of 300 meter. With its height of 472 meter, 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 this cuts construction costs, extra security measures are needed, as well as mechanisms for nulling out heave due to waves. In both cases, the ocean adds several hundred meters to the fluid column in the drillstring. This increases bottom hole pressure as well as increasing the energy needed to lift sand and cuttings for oil-sand separation on the platform. The trend today is for more of the production to be done subsea, such as facilities to separate sand from oil and re-inject sand before it is pumped up to the platform, or even pumping it onshore, with no installations visible above the sea.

Sub sea installations further the goal of the petroleum industry of exploiting resources at progressively deeper waters, that have previously been inaccessible. It also circumvents many of the challenges related to sea ice, such as in the Barents sea.

• Offshore manned facilities present logistics and human resources challenges.

An offshore oil platform is a small society with support functions such as cafeteria, sleeping quarters and management located offshore. In the North Sea, people are transported in by helicopter, in for a 2-week shift. This in turn means a higher salary than for other industry workers. Supplies and waste are transported by ship and need to be delicately choreographed 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 an, at least in the western world, aging petroleum industry workforce. These efforts among others, are contained in the established term Integrated Operations. The increased use of sub sea facilities, of course, goes hand in hand with the goal of moving people onshore. Subsea facilities are also more easy to expand with new separators or separate modules for different oil types. It is not limited by the fixed floor space of an offshore rig.

Effects on the environment

Offshore oil production involves environmental risks, most notably oil spills from oil tankers transporting oil from the platform to onshore facilities, from pipelines doing the same, and from leaks and accidents on the platform.¹ There is also the impact of produced water, which is excess water from well drilling or production and which contain varying amounts of oil, drilling fluid or other chemicals used in or resulting from oil production. The platform is typically given an allowed quota of produced water that can be emptied in 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. The platforms themselves also present a problem when discontinued, see ecological effects of oil platforms

See also

• Oil drilling
• Subsea
• US offshore drilling debate

References