Offshore drilling

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Offshore drilling typically refers to the act of extracting resources, primarily oil, in an ocean or lake.

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

[edit] History

The first offshore drilling were 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.

[edit] Main offshore fields

Notable offshore fields today are found in the North Sea, Gulf of Mexico, the Campos and Santos basin off the coast of Brazil, several fields off west africa most notably west of Nigeria and Angola, as well as offshore fields in South East Asia. The oil and gas fields in the Barents sea is thought to become a major field in the future

[edit] Challenges

Oil and gas production in the sea is more challenging and more costly than for 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 its "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 cut 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.

Subsea 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 mean 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 e.g 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 subsea facilities of course goes hand in hand with the goal of moving people onshore.

[edit] Effects on the environment

Offshore oil production involve environmental risks. Most notably oil spills, both from oil tankers transporting oil from the platform to onshore facilities, pipelines doing the same and leaks and accidents on the platform. 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 ^[1] 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