Oil platform
is a large structure with facilities to extract and process petroleum and natural gas that lie in rock formations beneath the seabed.
Most commonly, oil platforms engage in activities on the continental shelf, though they can also be used in lakes, inshore waters, and inland seas.
However, in deeper water (more than 1,500 metres (4,900 ft)), the semisubmersibles or drillships are maintained at the required drilling location using dynamic positioning.
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.
In 1938, Humble Oil built a mile-long wooden trestle with railway tracks into the sea at McFadden Beach on the Gulf of Mexico, placing a derrick at its end – this was later destroyed by a hurricane.
In 1946, Magnolia Petroleum (now ExxonMobil) drilled at a site 18 miles (29 km) off the coast, erecting a platform in 18 feet (5.5 m) of water off St. Mary Parish, Louisiana.
But it was Kerr-McGee Oil Industries (now part of Occidental 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.
[6][7] The British Maunsell Forts constructed during World War II are considered the direct predecessors of modern offshore platforms.
It was noticed that the motions at this draught were very small, and Blue Water Drilling and Shell jointly decided to try operating the rig in its floating mode.
The concept of an anchored, stable floating deep-sea platform had been designed and tested back in the 1920s by Edward Robert Armstrong for the purpose of operating aircraft with an invention known as the "seadrome".
[13] The deepest operational platform is the Petrobras America Cascade FPSO in the Walker Ridge 249 field in 2,600 meters of water.
These platforms are built on concrete or steel legs, or both, anchored directly onto the seabed, supporting the deck with space for drilling rigs, production facilities and crew quarters.
[19] Concrete caisson structures, pioneered by the Condeep concept, often have in-built oil storage in tanks below the sea surface and these tanks were often used as a flotation capability, allowing them to be built close to shore (Norwegian fjords and Scottish firths are popular because they are sheltered and deep enough) and then floated to their final position where they are sunk to the seabed.
These platforms consist of slender, flexible towers and a pile foundation supporting a conventional deck for drilling and production operations.
Compliant towers are designed to sustain significant lateral deflections and forces, and are typically used in water depths ranging from 370 to 910 metres (1,210 to 2,990 ft).
Proprietary versions include the Seastar and MOSES mini TLPs; they are relatively low cost, used in water depths between 180 and 1,300 metres (590 and 4,270 ft).
Steel GBS are predominantly used when there is no or limited availability of crane barges to install a conventional fixed offshore platform, for example in the Caspian Sea.
The GBS contains production storage tanks and the remainder of the void space is filled with ballast with the entire structure weighing in at 1.2 million tons.
Royal Dutch Shell has developed the first Floating Liquefied Natural Gas (FLNG) facility, which is situated approximately 200 km off the coast of Western Australia.
Larger platforms are assisted by smaller ESVs (emergency support vessels) like the British Iolair that are summoned when something has gone wrong, e.g. when a search and rescue operation is required.
The crew will normally comprise: The nature of their operation—extraction of volatile substances sometimes under extreme pressure in a hostile environment—means risk; accidents and tragedies occur regularly.
[29] Agencies and military units responsible for maritime counter-terrorism in the US (Coast Guard, Navy SEALs, Marine Recon) often train for platform raids.
[30] On April 21, 2010, the Deepwater Horizon platform, 52 miles off-shore of Venice, Louisiana, (property of Transocean and leased to BP) exploded, killing 11 people, and sank two days later.
The United States and Brunei have active Rigs-to-Reefs programs, in which former oil platforms are left in the sea, either in place or towed to new locations, as permanent artificial reefs.
[32] On the US Pacific coast, marine biologist Milton Love has proposed that oil platforms off California be retained as artificial reefs, instead of being dismantled (at great cost), because he has found them to be havens for many of the species of fish which are otherwise declining in the region, in the course of 11 years of research.
[38] To reduce the amount of carbon emissions otherwise released into the atmosphere, methane pyrolysis of natural gas pumped up by oil platforms is a possible alternative to flaring for consideration.
[42] and the chemical engineering team at University of California – Santa Barbara[43] If not decommissioned,[44] old platforms can be repurposed to pump CO2 into rocks below the seabed.
Much of the innovation in the offshore petroleum sector concerns overcoming these challenges, including the need to provide very large production facilities.
The trend today is to conduct more of the production operations subsea, by separating water from oil and re-injecting it rather than pumping it up to a platform, or by flowing to onshore, with no installations visible above the sea.
Subsea facilities are also easier to expand, with new separators or different modules for different oil types, and are not limited by the fixed floor space of an above-water installation.
