how fpso works

8/9/2019 How FPSO Works

1/15

Once oil moves from the reservoir into the FPSO and has been processed, the oil will be stored

within the vessel's 14 storage tanks. These tanks have a capacity ranging from over 50,000 barrels tonearly 78,000 barrels. The biggest tanks are 27m x 17m x 26m high.

The Terra Nova FPSO is double hulled - providing double containment. The oil cargo tanks arelocated within the inside hull, and are surrounded by a series of ballast tanks, which contain

seawater. The FPSO's storage tanks can store up to 960,000 barrels and have a heating system to

help prevent any build up of wax in the tanks.

To move oil to market from the Terra Nova field, oil is transported by a shuttle-tanker capable of

storing 850,000 barrels of oil. However, oil must first be moved from the FPSO into the shuttletanker via the vessel's offloading system - designed for wave 'significant' heights of up to about five

metres (16.5 feet).

When it is time to transfer oil, the shuttle tanker positions itself about 70 metres behind the FPSO.The FPSO then sends a messenger line toward the tanker. Attached to this line is a mooring line

known as the Mooring Hawser and an Offloading Hose - a hose 20 inches in diameter that transports

the oil from the FPSO to the tanker.


2/15

Once the offloading hose is securely connected to the tanker, and the vessels meet a series of safety

checks and balances, the transfer of oil can begin. Fuel is pumped from the FPSO's storage tanks into

two export pipes, through the export line to the Offloading Hose. Crude flows through theOffloading Hose at a rate of up to 50,000 barrels per hour.

During the transfer, the oil passes through what is known as the Export Oil Fiscal Metering Package.This allows the Terra Nova owners to calculate the amount of crude offloaded and available for sale

in the market.

It will take about 24 hours to transfer a full load of crude from the FPSO to the tanker.

The Terra Nova FPSO is a sophisticated ocean-going oil production installation. Fromdynamic positioning to fresh water generators, numerous state-of-the-art systems andfeatures have been designed into the vessel to make it as safe and efficient as possible.


3/15

Staying on station

A redundant Dynamic Positioning (DP) system is used to help the FPSO maintain position,monitoring the heading of the vessel, its side-to-side and fore and aft movements. Thevessel's location is constantly monitored by two independent global positioning satellitesystems, and a Hydro-Acoustic Position Reference (HPR) system, which receives locationsignals from six transponders on the seabed.

The vessel is equipped with five powerful thrusters (five megawatts each), which can beused to keep the FPSO within two to three metres of a given set point. This is especiallyimportant during operations to connect the FPSO with the spider buoy, and when offloadingoil to a shuttle tanker.

Maintaining balance

The FPSO's ballast system works in conjunction with its oil cargo system. The more oil thatis stored in the inner storage tanks, the less ballast water is kept in the outer hull, and vice-versa. Vessel Control Systems operators keep a close eye on the amount of oil and waterbeing stored and where it is located.

Terra Nova plans to keep the FPSO at an operating draught of between 12.5 and 18.5metres providing optimum stability to the vessel, as well as keeping the deck high out of thewater. When the FPSO is carrying a full load of crude, it will weigh approximately 200,000tonnes.

Closely related to the oil cargo system is the Inert Gas system. This system burns dieselfuel to produce an oxygen deficient air which can be stored on top of oil in the cargo tanks,providing an extra measure of safety by preventing the build up of combustible fumes in thetanks.

Generating power

The turbine generators are the main source of power for the FPSO. Each of thesegenerators can produce 40 megawatts of power, which is enough power for 50,000 homes.Shortly after first oil, the generators will be fueled by gas from the Terra Nova field. Thegenerators are also capable of running on any combination of field gas and diesel.

Converting salt water into fresh water

The FPSO uses between 20 to 30 cubic metres of water a day, mainly in theaccommodations complex for showers and for operations in the galley. While some of this

water will be loaded from supply vessels, the FPSO can provide its own water, through twofresh water generators that convert salt water into fresh water. The combined efforts ofthese generators can provide 50 cubic metres of water - about twice the daily amountneeded for the FPSO.

Heating the vessel

The FPSO also has a specialized Heating Ventilation and Air Conditioning (HVAC) systemthat provides temperature control and air circulation. In an emergency, the HVAC systemwill provide for internal circulation of air to the Temporary Safe Refuge (TSR) area for twohours.


4/15

The Terra Nova project is pioneering subsea technology on the Grand Banks. Advancesinclude the use of 'glory holes' - depressions in the seabed to protect subsea equipmentfrom scouring icebergs. It also has the world's largest disconnectable turret that will allowthe FPSO to halt production and leave the area if threatened by ice or icebergs.

Offshore interfaces

When the Terra Nova FPSO arrives at its offshore site, it will connect to the spider buoy,which is approximately 20 metres in diameter and weighs over 1 300 tonnes. The spiderbuoy is connected to a series of flexible pipelines, called risers, which will deliver oil, gasand water to and from the FPSO.


5/15


6/15

The Terra Nova FPSO has four main topsides modules - the M02 water injection module,the M03 separation and high pressure compression module, the M04 producedwater/glycol module, and the M05 separation and low pressure/ medium pressurecompression module.

In addition to containing modules that process and separate the oil, gas and waterproduced from the wells, the topsides structures also include the turret assembly, the flare

tower, the power generation module, the offloading reel, and the platform cranes.

Once reservoir fluids enter the FPSO, it moves up through the turret and into the topsidesmodules. In the separation and compression modules, the fluids are separated into oil,water and gas streams. The processed oil is then routed to the vessel's storage tanks, fromwhere it will eventually be loaded onto tankers and shipped to market.

The separated water and gas streams will undergo further treatment. The produced waterwill be cleaned and routed to the ocean. The gas may go back through the turret to be re-injected into the well or reservoir to aid in oil recovery. Additionally, some of the gas will beused to run machinery on the FPSO, such as the boilers and power generation modules. In


7/15

the event of a process upset or shutdown when the gas compressors are not running, asmall portion of the gas could be burned off through a flare tower located at the rear of thevessel.

Modules M02, M04, the flare tower and miscellaneous deck assemblies were built at theBull Arm Fabrication Site, where the power generation module was also assembled. TheM03 and M05 modules were constructed in Scotland. The modules, which weigh up to 2200 tonnes each, were lifted onto the FPSO at Bull Arm in late May and early June by the

heavy lift crane Asian Hercules II.

Terra Nova's flare tower is among the largest ever built, rising 100 metres from the reardeck of the vessel. In fact, a counterbalance was required to keep the flare structure uprightwhen it was being lifted onto the FPSO.

The turret is the mooring point for the FPSO as well as the interface between the subseasystems and the topsides modules. It serves as a connecting point between the FPSO andthe subsea systems, and is the pathway for getting oil from the reservoir into the vessel.Water and gas, used for injection into the reservoir, will also leave the vessel through pipesin the turret.


8/15

Weighing more than 4 000 tonnes with an overall height of 70 metres, the Terra Nova turretis the largest disconnectable turret mooring system ever built. Constructed to operate in theharsh North Atlantic environment to cope with hazards such as icebergs, it is composed ofthe upper turret, lower turret and spider buoy.

The spider buoy - approximately 20 metres in diameter and weighing over 1 300 tonnes,supports nine anchor chains and up to 19 risers.

When connected to the spider buoy, the Terra Nova turret is stationary. Specializedbearings allow the FPSO to rotate, or 'weathervane', around the turret, so that the front ofthe vessel is always facing into the wind. In an emergency situation, the FPSO candisconnect in about 15 minutes. If the FPSO must disconnect, the spider buoy settles into amid-water depth - ready to reconnect when the FPSO returns.

The lower turret provides the connection with the spider buoy and includes winches andother equipment needed to maintain the connection between the FPSO and the spiderbuoy.

The upper turret houses a collection of manifolds, hydraulic and electrical controlequipment, as well as the swivel stack. The swivel stack serves as the interface betweenthe subsea production system and the topsides processing and storage system. Theswivels form a series of fluid flow paths which connect to piping on the FPSO itself. Theseswivels allow fluids or electrical signals to move back and forth from the subsea to thetopsides while permitting the vessel to rotate around the turret.

Mooring Systems

A significant proportion of UKCS hydrocarbon reserves

are produced by turret mooredFPSOs which will remainpermanently on location for periods between five and 25years. Over the years, mooring line quality control hasimproved significantly and designs have evolved tominimise the consequences of possible failure.However, many different types of mooring system areused in UK waters today, and approaches to their inspection, repair and replacement canvary from company to company. UKOOA is keen to identify which management proceduresare the most effective, so that the highest standards of safety and operation may bepromoted across the whole of the industry.

In April 2001, UKOOA commissioned Noble Denton Europe Ltd to look into the design,construction and operation of mooring systems over the last five years, including seabedanchors, mooring lines, the turret interface and associated systems such as winches andthrusters. The work includes recommendations for improving mooring system integrity.

What is an FPSO?An FPSO is a Floating Production, Storage and Offloading unit and is just one of a range ofdifferent types of floating systems used by the offshore oil and gas industry today. It issimilar in appearance to a ship but is designed quite differently and carries on board all the


9/15

necessary production and processing facilities normally associated with a fixed oil and gasplatform, but with the addition of storage tanks for the crude oil recovered from the wells onthe seabed below. It is mooredpermanently on location and is connected to the wellsbelow by flexible risers.Click on the picture below to view it in full:

What different types of floating systems are there?As the name suggests, floating systems are not fixed permanently to the seabed but aredesigned to be moored to remain on station for long periods of time. There are manydifferent variants of these systems, and the terminology and acronyms vary too, even forthe same "system"!Some common abbreviations include:

FSOFloating storage and offloading system, often a ship or barge-shaped floating hullincorporating tanks for storage of produced oil, and a method of loading the oil into offtaketankers. These installations do not have any production or processing facilities. FPSOFloating production, storage and offloading vessel which includes, in addition to its storageand offloading capability, facilities for receiving crude oil from producing wells andprocessing it for export by separating water and gas.FPSFloating production system: a general term to describe any floating facility designed toreceive crude oil from producing wells and process it. It may not have facilities for storage,

in which case export would be by pipeline to shore or to a nearby FSO.FSUFloating Storage Unit; a floating facility intended only for storage of oil. Export may be bypipeline to an onshore facility rather than offloaded to shuttle tankers. Sometimes usedsynonymously with FSO.FPS units - which have production but usually nostorage facilities - can take many forms. They range insize from converted barges installed with separationequipment for small scale production of up to 25,000barrels of oil per day (b/d) to giant purpose-designedvessels with capacity for processing more than

200,000 b/d. Some may be converted drilling rigs orsemi-submersible and tension-legged platforms.FPSOs, which combine production, storage andoffloading facilities, are usually "ship-shaped" and maybe purpose built or converted from an existing hull,incorporating key modifications to increase the strengthor fatigue resistance in particular areas.Each design has its own advantages depending on the oilfield water depth, localenvironmental conditions and economic factors.


10/15

How many floating units are there?There are currently 15 FPSO and FPS units operating on the UK Continental Shelf and 70worldwide.

Why use a floating system?Across the world, oil and gas is being found andproduced in ever-deeper waters. Here, water depth,ocean currents and harsh weather conditions may

all influence the decision on which type ofproduction installation to use. A fixed installationmay not be technically feasible in a particularlychallenging location where a floating unit wouldoffer the best solution.Floating systems are also a cost-effective solution for developing smaller, satellite ormarginal fields in shallower water as they can be floated off when reservoirs are depleted,and re-used elsewhere. The benefits of "recycling" such facilities are not just economic butalso environmental.

How does an FPSO keep on station?

The offshore industry has developed highly sophisticated mooring and station-keepingsystems which enable oil production vessels to operate safely and reliably.In the UKCS, where weather conditions can be extreme, most vessels have a centralmooring arrangement located within the hull in a "turret", that allows them to rotate freelyaround the point of mooring in response to shifting weather direction. This is known as"weathervaning" and allows the vessel's bow always to point into the prevailing wind andcurrents, minimising the impact of nature's forces. Often thruster systems are also used tosupplement the station-keeping and control vessel heading.In countries with more benign weather, such an arrangement may not be required and thevessel is kept on station by an array of moorings and anchors, known as a spread-mooredsystem.

How does an FPSO recover oil and gas?The hydrocarbons treated on an FPSO or FPS are produced through wells that are locatedon the seabed. Untreated liquids are brought to the surface via subsea equipment on thesea floor including valves at the well (a "Christmas tree"), a manifold to connect severalwells together into one flowline, which is then linked to the vessel. These pipelines mustpass from the seabed to the floating facility at the surface - and are called "risers". Theymust be flexible to accommodate the heaving motion of the vessel above, and be veryresistant to fatigue.

What are the safety precautions on board an FPSO?

Safety on board any production facility has the utmost priority. Robust safety standardsmust be in place and rigorously enforced. In the UK, all operating companies must submit aSafety Case to the Health and Safety Executive, which:

demonstrates that the company has in place safety management systems; has identified risks and reduced them to as low as reasonably practicable; has put management controls in place; has a safe refuge for personnel in the event of an emergency and has made provisions for safe evacuation and rescue.


11/15

Features which contribute to the safe operation ofFPSOs are described below:The hull must be designed for at least the expected lifeof the field - often 15 to 25 years - and constructed tostandards that will permit it to remain at sea during thistime without access to dry docking facilities. Of specialimportance is how the vessel will survive a possiblecollision at sea. Normal maritime criteria are used such

that the vessel will be able to stay afloat with any twohull compartments flooded.Crude oil stage tanks, an integral part of the FPSO hull,are blanketed with inert gas to maintain a safeenvironment for loading and discharging crude oil.Oil and gas processing is controlled and monitored remotely. Shutdown systems are built into close off the flow and contain hydrocarbons under pressure in an emergency andallowing depressurisation via a flare stack.Protection against fire and explosion is provided in the form of protective coatings and blastor firewalls. Water deluge systems are installed in open areas and sprinkler systems inclosed areas. The accommodation block is mechanically ventilated and pressurised, taking

fresh air from a safe location remote from the process equipment, and is thus a safe refugefor personnel.Emergency evacuation is primarily by helicopter from a helideck situated directly above theaccommodation block, or by service craft. Other methods use lifeboats, life rafts andstandby service craft working in the field. Personnel are trained to respond to variousaccident scenarios relating to the process systems, including safe shutdown of operations,de-pressurisation and eventual evacuation. All personnel are provided with personal safetyequipment such as survival suits and life vests.

How is the oil taken ashore?In the UK, crude oil is normally transported to shore using dedicated off-take or "shuttle"

tankers specially designed for the weather conditions found offshore in Britain.For example, most shuttle tankers are now equipped with a bow-loading system, usuallyhydraulically operated. Bow loading was first introduced in 1975 and has proved to behighly reliable over the years. The method is well suited to the harsh conditions oftenexperienced in UK waters.Other features include emergency shut down equipment and dynamic positioning to keepthe tanker on station at a safe distance away from the FPSO or storage facility whileloading.Cargo is transferred by flexible hose or hoses which connect the installation with the tanker.The process of loading from the stern of the FPSO to the bow of the shuttle tanker is knownas "tandem loading"

What floating production facilities currently operateon the UKCS?There are currently 15 floating production facilities inoperation on the UK Continental Shelf. The most recentFPSO to arrive in the North Sea is Kerr-McGee's GlobalProducer III which has just left Swan Hunter's Newcastle-upon-Tyne ship yard for the Leadon field in the CentralNorth Sea. The first oil is due to flow by the end of 2001.Other recent start-ups using FPSO technology areAmerada Hess's Chestnut field, also in the Central North


12/15

Sea, which came on stream in July 2001and BG's Blake field which is linked by pipeline(known as a "tie-back" system) to Talisman's existing FPSO facility on the Ross field.Amerada Hess used FPSO technology in the North Sea with the commissioning of thePetrojarl I in the early 1990s to produce oil from the small Angus field. Interestingly, newproduction technology has given Angus a fresh lease of life and after lying dormant foreight years, it has been redeveloped and oil has once again started to flow. This time,production is tied-back by pipeline to another FPSO, the Uisge Gorm, which alreadyservices the Fife, Fergus and Flora fields 18 km away to the south east.

In the remote, deep waters to the west of Shetland, two floating facilities produce oil fromBPs' Schiehallion and Foinaven fields respectively, the only fields currently in production inthe Atlantic Margin.The following is a list of the FPSOs and FPS operating on the UKCS today:

Operator Field Type of floatingsystem

Installation Date

AGIP Balmoral FPS June 1986Conoco Banff FPS January 1999Texaco Captain FPSO December 1996Amerada

Hess

Chestnut FPS July 2001

Shell Curlew FPSO September 1997BP Foinaven FPSO November 1996Kerr-McGee Gryphon FPSO September 1993Kerr-McGee Janice FPS February 1999Kerr-McGee Leadon FPSO September 2001Conoco MacCulloch FPSO April 1997Enterprise Pierce FPS February 1999Talisman Ross FPSO March 1999BP Schiehallion FPSO July 1998Shell Teal, Teal South and

Guillemot AFPSO August 1996

Amerada Hess Triton - Bittern,Guillemot West &North West

FPSO March 2000

GIRASSOL LUANDA, ANGOLA

Girassol is located about 210km NNW of Luanda, Angola. It lies in 1350m of water. It willbe developed using a subsea facility tied back to an FPSO.

Girassol base-case reserves are estimated at around 700 millions of barrels (bbls).Production is expected to start by the end of 2000.

SUBSEA

The subsea production system will initially provide for 40 wells: 23 production wells, 14water-injection wells and three gas-injection wells.


13/15

FPSO - HULL

The bare hull was built in Hyundai Heavy Industries (HHI) shipyard in Korea and moved outof dry dock in July 1999. It will be able to store two million barrels of crude oil and supportprocesses with a capacity of 200,000b/d. It has an overall length of 300m, a mouldedbreadth of 59.5m, a moulded depth of 30.5m and a design draught of 22.77m. The design

life of the hull is 20 years without dry docking.

Current deadweight is 343,000t which includes 98% of cargo capacity and 50% of sloptanks.

The hull features a double-sided construction with 12 ballast wing tanks measuring 7mwide, as well as two fore-peak and two aft-peak ballast tanks. In total, it has 12 cargo tanks.

TOPSIDES

The main contractor, MAR Profundo Girassol - a joint venture between ETPM and

Buoygues - originally subcontracted to build the integrated deck at Fos-sur-Mer in France.It has since re-awarded the contract to Hyundai. This deck is 180m long by 60m wide. Itweighs approximately 20,000t.

It contains living quarters, oil treatment, storage, metering and offloading, gas treatmentand reinjection facilities.

The process deck is located 7m above the deck of the hull. It contains facilities forproduced water treatment at a flow rate of 180,000BPD as well as facilities for 3 millionm3/day gas lift, 8 million m3/d gas compression at 285 bars, and gas dehydration.

ACCOMODATION

The living quarters unit is located at the aft end of the hull and is designed to accommodate140 people in 80 cabins.

HOOK-UP

The integrated deck will be transferred to the hull, and the hook-up of the hull/topsides aswell as the pre-commissioning will be complete.

MOORING

The FPSO will be towed from Korea to the Girassol Field, offshore Angola, where the risersand umbilicals will be installed and connected ready for commissioning and for first oil.

The FPSO will be spread-moored with 16 lines, four at each corner. The anchor lines willbe a composite assembly of chains and cables connected to 16 suction anchors.

RISERS AND UMBILICALS


14/15

The east side of the FPSO will be designed to receive the umbilicals and risers from threeriser towers. Each of the riser towers will be connected to the FPSO by a riser. In addition,ten umbilicals will be connected to the base of the riser towers. The west side of the FPSOis designed to receive further risers and umbilicals if needed.

OFFLOADING

The FPSO is designed for two offloading systems, one for normal operation with a buoy,

one as back-up offloading, in tandem.

Both systems are located at the bow of the FPSO.

The main offloading system includes a loading buoy, located approximately one mile awayfrom the bow of the FPSO. This can accommodate tankers from 80,000 to 400,000DWT,with a nominal offloading rate of 6,000m3/h through two rigid steel catenary 16in lines.

The tandem offloading is a conventional system with a mooring hawser assembly andhandling system, and an offloading hose and its handling system. It is designed toaccommodate tankers up to 200,000DWT at a nominal offloading rate of 8000m3/hour.

The field will come on-stream in 2001.

The Girassol FPSO hull being completed at the Hyundai yard.

The Seaway Eagle will carry out most of the installation work on the Girassol field.

The Girasoll field layout diagram.


15/15

The riser towers and flowline bundles as they will be installed.

A CAD detail of the top of the riser towers.

A CAD detail of the top of the riser tower (left) and the riser tower on the seabed(right).

how fpso works

Documents