functions of a production platform

7/22/2019 Functions of a Production Platform

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Functions of a Production Platform

Oil platforms are an industrial town at sea, carrying the personnel and equipment needed for

continuous hydrocarbon production. The most important functions are drilling, preparing water or gas

for injection into the reservoir, processing the oil and gas before sending it ashore, and cleaning the

produced water for disposal into the sea. Power is generated on the platform to drive production

equipment and support life. All production systems are constantly monitored for leaks, since oil and gas

are hazardous and extremely flammable.


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The top of each production well sprouts a branching series of pipes, gauges and valves called the

'Christmas tree' (see F97, page 55). At this point, crude oil is a hot, frothy, corrosive, high-pressure fluid

containing gas, water and sand. After separation, the crude oil is metered and pumped into the pipeline,or stored until sent ashore by tanker. The gas separated from the oil may be used for fuel, or

compressed and piped to shore or re-injected into the reservoir. Any gas that cannot be used or piped

ashore must be burnt in the platform's flare. Very little gas is now flared. Processing systems for the

gasfields of the southern North Sea are relatively simple. Any liquids dissolved in the gas are removed,

then the gas is compressed, cooled, dehydrated and metered before being piped to shore.

Production Platforms

Most oil and gas production platforms in offshore Britain rest on steel supports known as 'jackets', a

term derived from the Gulf of Mexico. A small number of platforms are fabricated from concrete. The

steel jacket, fabricated from welded pipe, is pinned to the sea floor with steel piles. Above it are

prefabricated units or modules providing accommodation and housing various facilities including gas

turbine generating sets. Towering above the modules are the drilling rig derrick (two on some

platforms), the flare stack in some designs (also frequently cantilevered outwards) and service cranes.

Horizontal surfaces are taken up by store areas, drilling pipe deck and the vital helicopter pad.

Concrete gravity platforms are so-called because their great weight holds them firmly on the seabed.

They were first developed to provide storage capacity in oilfields where tankers were used to transport

oil, and to eliminate the need for piling in hard seabeds. The Brent D platform (F87), which weighs more

than 200 000 tonnes, was designed to store over a million barrels of oil. But steel platforms, in which

there have been design advances, are now favoured over concrete ones.


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Several platforms may have to be installed to exploit the larger fields, but where the capacity of an

existing platform permits, subsea collecting systems linked to it by pipelines have been developed using

the most modern technology. They will be increasingly used as smaller fields are developed. For very

deep waters, one solution was the Hutton Tension Leg Platform: the buoyant platform, resembling a

huge drilling rig, is tethered to the sea-bed by jointed legs kept in tension by computer-controlled ballast

adjustments.

Alternatively, a subsea collection system may be linked via a production riser to a Floating, Production,

Storage and Offloading (FSPO) vessel (F88); either a purpose built ship or a converted tanker or semi-

submersible rig. The oil is offloaded by a shuttle tanker.


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Currently under fabrication for ATPs U.K. North Sea Cheviot field development is the OctabuoyDry Tree semi-submersible production platform. The Octabuoy, a dry-tree completion unit, can

accommodate both production facilities and a complete drilling/work-over rig, allows for

fabrication and installation flexibility, provides oil storage in the columns and is expected to be

more cost effective than other dry-tree floating production units. The unique feature of the


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Octabuoy is the shape of the columns, which provides more favorable motion characteristics

than other floating structures for dry-tree oil and gas production.

In 2007, due to lack of nearby accessible infrastructure near ATPs Telemark Hub project, ATPdecided to utilize a self contained floating drilling and production triple-column spar

structure. This is the first hull configuration of this kind. This versatile deepwater operating

concept, comprised of three columns linked by pontoons, offers higher variable load capacity

and enhanced stability over traditional single-hulled spars.

So, as one moves further offshore, then one might use aself-erecting tenderfrom a barge, but would

more likely move to something which could get the drilling floor stabilized and up above the waves.

These are the jack-up rigs.
http://www.onepetro.org/mslib/servlet/onepetropreview?id=00077232&soc=SPEhttp://www.onepetro.org/mslib/servlet/onepetropreview?id=00077232&soc=SPEhttp://www.onepetro.org/mslib/servlet/onepetropreview?id=00077232&soc=SPEhttp://www.onepetro.org/mslib/servlet/onepetropreview?id=00077232&soc=SPE


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Model of a jack-up rock (Stavanger Oil Museum)

Typically they have three legs, that are raised as therig moves around.Then when it has reached the

desired site, the legs are lowered to rest on the sea floor and the entire structure jacks itself up out of

the sea, and, hopefully,above the waves.(You can get apaper modelto cut out and assemble for thisrig). There is also ananimated videoshowing the installation of a rig at a site.

They can do this to work in depths to around 500 ft. The discussion aboutdamaged rigsgave links to the

different rigs that have been damaged, and some of these have photos of the rigs in better days.

As one goes out to deeper depths, then one will look for a more substantial vessel and so one comes to

the Semi-submersible.
http://www.shipsandoil.com/Features/Featjumv.htmhttp://www.shipsandoil.com/Features/Featjumv.htmhttp://www.shipsandoil.com/Features/Featjumv.htmhttp://www.rigzone.com/data/rig_detail.asp?rig_id=329http://www.rigzone.com/data/rig_detail.asp?rig_id=329http://www.rigzone.com/data/rig_detail.asp?rig_id=329http://papertoys.com/rig.htmhttp://papertoys.com/rig.htmhttp://www.youtube.com/watch?v=zLLqXaWL1Vkhttp://www.youtube.com/watch?v=zLLqXaWL1Vkhttp://www.theoildrum.com/story/2005/9/28/115151/818#morehttp://www.theoildrum.com/story/2005/9/28/115151/818#morehttp://www.theoildrum.com/story/2005/9/28/115151/818#morehttp://1.bp.blogspot.com/_udSTgadqhFc/SxMjWCd_ZII/AAAAAAAAA2Q/zZ8d454q45Q/s1600/jack+up+platform+2.jpghttp://www.theoildrum.com/story/2005/9/28/115151/818#morehttp://www.youtube.com/watch?v=zLLqXaWL1Vkhttp://papertoys.com/rig.htmhttp://www.rigzone.com/data/rig_detail.asp?rig_id=329http://www.shipsandoil.com/Features/Featjumv.htm


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Semi-submersible drilling rig (Stavenger Oil Museum)

These are built to either sail themselves, or to be towed out to the site, with the assembly floating, and

then fluid is pumped into the bottom tanks to partially submerge the vessel and thus stabilize it. One

can get some idea of the size of these from some of the photos shown where, (thanks to Ed

Ames),wikipediacovers the subject.

Semi-submersible rig off Brazil (Wikipedia)

Since these are floating there has to be a way of holding them in place. One way is to have them

dynamically positioned, usingthrusters to hold themin position, such as these.
http://en.wikipedia.org/wiki/Oil_platformhttp://en.wikipedia.org/wiki/Oil_platformhttp://en.wikipedia.org/wiki/Oil_platformhttp://en.wikipedia.org/wiki/File:Oil_platform_P-51_(Brazil).jpghttp://en.wikipedia.org/wiki/File:Oil_platform_P-51_(Brazil).jpghttp://en.wikipedia.org/wiki/File:Oil_platform_P-51_(Brazil).jpghttp://www.wartsila.com/Wartsila/global/docs/en/about_us/twentyfour7/Wartsilathrusters.pdfhttp://www.wartsila.com/Wartsila/global/docs/en/about_us/twentyfour7/Wartsilathrusters.pdfhttp://www.wartsila.com/Wartsila/global/docs/en/about_us/twentyfour7/Wartsilathrusters.pdfhttp://1.bp.blogspot.com/_udSTgadqhFc/SxMkowIsJPI/AAAAAAAAA2g/M1SbudECREg/s1600/Semi-sub+off+Brazil.jpghttp://4.bp.blogspot.com/_udSTgadqhFc/SxMkQxurASI/AAAAAAAAA2Y/xvs6LFYMFws/s1600/Drilling+platform+3.jpghttp://1.bp.blogspot.com/_udSTgadqhFc/SxMkowIsJPI/AAAAAAAAA2g/M1SbudECREg/s1600/Semi-sub+off+Brazil.jpghttp://4.bp.blogspot.com/_udSTgadqhFc/SxMkQxurASI/AAAAAAAAA2Y/xvs6LFYMFws/s1600/Drilling+platform+3.jpghttp://www.wartsila.com/Wartsila/global/docs/en/about_us/twentyfour7/Wartsilathrusters.pdfhttp://en.wikipedia.org/wiki/File:Oil_platform_P-51_(Brazil).jpghttp://en.wikipedia.org/wiki/Oil_platform


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Thrusters that go under the pontoons to stabilize a

semi-submersible (Wartsila)

Note that it takes about 3 years to build such a unit. The alternative is to have the rig attached to

anchors on the sea bed using cables, or tethers. (And for those interested in natural gas production,

note that thesame rigsare used for both).

Cables with controlled winches to stabilize a semi-

submersible rig (Stavanger Oil Museum)

The connection between the well and the platform now becomes more flexible and special connecting

pipes called risers are designed to reach from the blow-out preventer (BOP) at the top of the well, but

on the seabed, and the platform. These must allow the rig to rise and fall with the tides and somodelsof

behavior have to be written to design ways of allowing this.

An alternative is to use a drillship to do the exploration. The drillship has the rig mounted in the middle

of the ship, and can thus move around somewhat more easily than the others. It is generally held in

position by dynamic positioning while drilling. (Videohere).
http://www.wartsila.com/Wartsila/global/docs/en/about_us/twentyfour7/Wartsilathrusters.pdfhttp://www.wartsila.com/Wartsila/global/docs/en/about_us/twentyfour7/Wartsilathrusters.pdfhttp://www.wartsila.com/Wartsila/global/docs/en/about_us/twentyfour7/Wartsilathrusters.pdfhttp://www.naturalgas.org/naturalgas/extraction_offshore.asphttp://www.naturalgas.org/naturalgas/extraction_offshore.asphttp://www.naturalgas.org/naturalgas/extraction_offshore.asphttp://www.orcina.com/SoftwareProducts/OrcaFlex/Examples/http://www.orcina.com/SoftwareProducts/OrcaFlex/Examples/http://www.orcina.com/SoftwareProducts/OrcaFlex/Examples/http://www.youtube.com/watch?v=5rlLIOeIWXUhttp://www.youtube.com/watch?v=5rlLIOeIWXUhttp://www.youtube.com/watch?v=5rlLIOeIWXUhttp://1.bp.blogspot.com/_udSTgadqhFc/SxMln5tMfwI/AAAAAAAAA2w/9UEsV1jGEzM/s1600/dynamic+stabilizing.jpghttp://3.bp.blogspot.com/_udSTgadqhFc/SxMlK9PWj9I/AAAAAAAAA2o/iYyl66axExs/s1600/thrusters.pnghttp://1.bp.blogspot.com/_udSTgadqhFc/SxMln5tMfwI/AAAAAAAAA2w/9UEsV1jGEzM/s1600/dynamic+stabilizing.jpghttp://3.bp.blogspot.com/_udSTgadqhFc/SxMlK9PWj9I/AAAAAAAAA2o/iYyl66axExs/s1600/thrusters.pnghttp://www.youtube.com/watch?v=5rlLIOeIWXUhttp://www.orcina.com/SoftwareProducts/OrcaFlex/Examples/http://www.naturalgas.org/naturalgas/extraction_offshore.asphttp://www.wartsila.com/Wartsila/global/docs/en/about_us/twentyfour7/Wartsilathrusters.pdf


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Drill ship (Stavanger Oil Museum)

Once the field has been established, then a larger production platform can be brought out and placed

where it can, using directional drilling, reach the best places to extract oil from the field. It is these large

structures, such as that theOrlan platformfrom which Sakhalin Island oil finally began to flow recently,

or theThunder Horse,or Mars platforms. Although the former was due toproduce by 2005,it was

delayed by damage from Dennis and did not get up into major production untilthe end of last year,

while the Mars platform was extensivelydamaged by Katrina.it is nowback in production.

One of the problems with using these large platforms for Deepwater recovery is that they focus

collection and so when these two are disabled, for example, they take about 400,000 bd out of

production. And once they are damaged they are not so easily replaced. Back when I first wrote on this

subject,in 2005demand for rigs so strong that, as the International Herald Tribunereported
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