Platform utilities

person Finn Harald Sandberg, Norwegian Petroleum Museum
Utilities are a collective term for the systems required to operate a platform, other than those directly involved in oil and gas production. This definition embraces direct support for the production process, general power generation facilities, and systems which sustain life and work on the installation. The latter include safety, process control, heating and ventilation, and communication equipment.
— Cooling water pumps at Statfjord A. Photo: Shadé Barka Martins/Norwegian Petroleum Museum
© Norsk Oljemuseum

Chemicals

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Flotation cell and tank for chemicalies on Statfjord A. Photo: Shadé Barka Martins/Norwegian Petroleum Museum

Many different chemicals and chemical compounds are used on the Statfjord platforms for such purposes as separating oil and water. Other applications include inhibiting or breaking down oil droplets in the produced water (emulsions), which is separated from the crude oil flow. Chemicals also prevent or stabilise foaming, or inhibit hydrate (hydrocarbon ice) formation, bacterial growth or corrosion. These substances are shipped out to the platforms on supply vessels. Among the commonest are the following:

Methanol is used to prevent the formation of hydrate plugs in pipelines, which can halt liquid flow. When gas contains small quantities of water, ice-like clumps can form under special pressure and temperature conditions.

Glycol primarily serves an agent for removing water from rich gas because it acts as an efficient absorber of water. It is also used in coolant systems to reduce the freezing point to -12°C.

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Deck 8 in the utiliy shaft of Statfjord B is the deck for seawater intake. Photo: Shadé Barka Martins/Norwegian Petroleum Museum

Chlorine  can be added to seawater to prevent the growth of bacteria in pipelines and ballast water, seawater and fire water systems. Sodium hydrochlorite (NaOCI) or bleach is used to kill unwanted organisms.

Corrotion inhibitor is added to prevent internal corrosion in piping and tanks. The substances used are usually based on organic compounds which form a protective film on metals.

Baktericides are deployed to control the growth of bacteria in water and hydrocarbons. The most serious problem for oil and gas production is provided by the sulphate-reducing bacteria, which develop hydrogen sulphide (H 2 S). This substance is not only toxic but also both explosive and extremely corrosive.

Anti-foaming agents are used to prevent foaming in the main process, and are injected ahead of the separator tanks in order to ensure that separation of water, oil and gas is as efficient as possible.

Fuel

Statfjord C, hjelpesystemer, engelsk,
The bunker station at Statfjord C. Photo: Jan A. Tjemsland/Norwegian Petroleum Museum

Two types of fuel are needed on the platforms – helicopter (aviation) fuel and diesel oil for power generation and other specialised machinery.

Supplies are brought in by ships equipped with special tanks for helicopter fuel. These can also pump diesel oil directly via hoses to special storage tanks in one of the cells of the concrete gravity base structures (GBSs).

Lubricating oil

This system distributes various types of lube oil to the main systems through a permanent piping network.

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Lube oil, Statfjord A. Photo: Jan A. Tjemsland/Norwegian Petroleum Museum

From the filling (tote) tanks, they are piped via lube oil distribution tanks to the most important consumers – gas turbines, generators, water injection pumps and fire pumps.

Other types of oils/lube oils are also required on board, but the level of consumption does not warrant a fixed distribution system for them.

Water

A platform requires a lot of water for various purposes. The sea and service water system is designed to supply all the liquid required for drilling, injection and ventilation systems as well as for producing fresh water. Separate systems are installed for fire and ballast water.

Flushing water  is used to help wash sand out of the vessels used in the separation process.

Fresh water is produced from seawater with a maximum chlorine content of two parts per million (ppm). This is distilled in three evaporators. The resulting water is cooled down before being pumped through two units which regulate its acidity (pH value) and into storage tanks. The latter can also be filled with desalinated water or potable (drinking) water from supply ships. Most fresh water is used for drinking, with some also consumed by cleaning and cooling.

Statfjord A, hjelpesystemer, engelsk,
Pipes carrying drinking water at Statfjord A. Photo: Jan A. Tjemsland/Norwegian Petroleum Museum

Potable water is produced for use in the living quarters and selected areas of the platform. Desalinated water is pumped from one of the storage tanks via ultraviolet sterilisation units to consumer tanks located on the roof of the living quarters.

Desalinated service water is fresh water of secondary quality stored in a tank on the cellar deck and distributed by pumps for cleaning, drilling and refilling coolant water.

Coolant water  is used in coolers for gas and recovered oil. It is a mix of three parts fresh water from the distribution system for desalinated water and one part monoethylene glycol from the glycol system, giving a freezing point of -12°C. A small quantity of corrosion inhibitor is also added.

Warm water  is produced to provide a reliable heat source with a constant temperature for the following applications:

  • desalination of seawater in evaporators
  • heating and ventilation systems (except for the living quarters, which have electrical heating)
  • supplies of coolant water to the circulation pumps for hot medium.

Steam  comes from a generator at a pressure of eight bar for cleaning process vessels and for various other types of cleaning. The steam generator is a heat exchanger.

Heating, ventilation and air conditioning

These functions are split into two separate systems, covering the production area and the living quarters respectively. The system for the production area is designed to deliver air at a specified temperature and pressure to the platform’s modules. This is intended in turn to reduce risk and accidents in spaces where fire and explosion are hazards (see compressed air below). Provision of such air is crucial for safe operation of the platform. Should the system fail for any reason, the process plant must be shut down immediately. Heating and ventilation of the living quarters involve a completely separate system, which functions in the same way as an installation in a normal building on land.

Heating Medium System  serves as a heat source for:
the circulating hot water system for desalination of seawater and space heating, with the exception of the electrically heated living quarters

  • steam generation
  • superheating of sludge
  • sludge treatment
  • stabilising condensate
  • glycol distillation

The heat source is a refined paraffin circulated to the user sites, where it is heated in furnaces over an open flame and in three recovery units for waste heat.

The air conditioning system in the living quarters serves cabins, recreation areas and the galley. Located in the ventilation room on the service floor, it sucks in fresh air and delivers it at a predetermined pressure, temperature and humidity to the whole living quarters.

A helideck heating system keeps the deck free of ice, maintains the temperature of the fuel gas and the process gas piping to prevent formation of condensate and hydrate (hydrocarbon ice) respectively, and prevents the fire and injection water systems from freezing. Heating cables are located in channels under the helideck, with electrical heating strips installed externally on piping. These activate automatically if the ambient temperature drops below 5°C.

Compressed air

In a process facility where explosive gases could build up, electrical instruments and spaces containing such equipment must be kept at a pressure above the surrounding plant. This is intended to prevent gas from entering and being ignited by electrical sparks. A dedicated system provides a reliable source of clean compressed air for instrument and working atmospheres.

Sewage treatment

This system collects all sewage and waste water for treatment and subsequent discharge to the sea. Most of the sewage comes from toilets, showers, washbasins, kitchen sinks and washing machines in the living quarters. It is conducted by gravity and negative pressure to septic tanks. A filter removes solid particles, which are then sent to mills for grinding to a liquid sludge. All bacteria in the sewage – particularly coliforms – are killed by chlorine injection before treated waste is discharged to the sea 10 metres below its surface. If necessary, raw sewage can be discharged to a barge through a hose connection for disposal on land.

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Dish station at Statfjord B. Photo: Shadé Barka Martins/Norwegian Petroleum Museum

Hydraulic control system for the utility shaft

This ensure a fail-safe supply of hydraulic fluid to operate various valves. Three hydraulic power packs are installed in the utility shaft, supplying four systems.

Loading / Discharging

The loading/discharging system is designed to handle supplies brought in or taken away by sea.

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Containers being lifted onboard Statfjord A. Photo: Shadé Barka Martins/Norwegian Petroleum Museum

 

Cranes
Cranes on the platform are used for:

  • lifting from or discharging to supply ships
  • maintenance and construction lifting over the whole platform and in the equipment shaft
  • handling pipes and equipment.

Bulk handling
Equipment for bulk handling is used to transport, handle and store various liquids, powders, gases and chemicals required for the platform’s process system and utilities. These products are brought out by supply ships and transferred to the platform either in tanks or via hoses.

Tanks and other bulk containers are lifted by crane from the supply ship to the platform’s storage area on the open deck. Liquids used in large volumes are transferred via permanently installed piping to the fixed storage tanks. Empty tanks are discharged for transport to land.

Diesel oil, fresh water, barytes, gel and cement are transferred to the platform’s bulk storage tanks with the aid of hoses lowered to the supply ship.

Power supply

The electrical system on the platform provides all normal and emergency power supplies.

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Two workers servicing the main generator at Statfjord B. Photo: Shadé Barka Martins/Norwegian Petroleum Museum

Main electricity  is supplied by three 19-megawatt generators as 13.8 kilovolt, three-phase 60 Hertz current. The generators are driven by gas/diesel turbines.

Emergency power  is supplied by three 1.18 MW generators which start up automatically and connect to a 6 kV panel. If both main and emergency power systems fail, supplies of alternating and direct current will be maintained by batteries..

Electricity for the living quarters comprises the normal supply of alternating current, and emergency supplies of both alternating and direct current. The normal supply is used for air conditioning, galley equipment, heating, hot water, laundry, lifts, lighting, refrigerators, waste units and ventilation. Emergency supplies are used to maintain necessary lighting and electronic equipment.

Flaring and atmospheric ventilation

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The flare boom at Statfjord A. Photo: Shadé Barka Martins/Norwegian Petroleum Museum

Hydrocarbons are found under varying pressure and temperature on large parts of the platform. For practical and safety reasons, some of the gas can be led to a safe place for flaring.

This can involve process gases, pressure reduction as part of an emergency procedure, or removal of gases so that maintenance can be carried out.

In the event of a total pressure dump, large volumes of gas will flow out at the tip of the flare boom. This is burnt off immediately to prevent undesirable distribution.

Tanks containing volatile liquids, which vaporise easily under atmospheric pressure, must also be vented safely. They are not all in the same place, and accordingly have dedicated vent pipes led to the sides of the platform or to points at least seven metres above the upper deck.

Monitoring and control

Process control monitors and controls all systems on the platform to ensure that hydrocarbons can be produced as safely as possible. The main functions involve:

  • maintaining a check on data transmission between the production system and the control-room terminals
  • analogue operating commands
  • automatic switches and logical sequence control commands
  • alarm logging

All this information is monitored from a central control room. Printers and displays for alarms and trends are also concentrated there to provide the operators with a good and accurate picture of conditions at all times.

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Photo: Jan A. Tjemsland/Norwegian Petroleum Museum

Safety monitoring  is a system intended to handle “all” aspects of safety on the platform. Field instrumentation and sensors for fire and gas alarms monitor the whole process and every module.

The purpose of the system is to initiate emergency shutdown of production when the process monitoring system fails to handle the problems which might occur. In principle, it comprises two systems:

1.  The process shutdown system monitors the process and shuts it down if control is lost, and thereby prevents the plant being operated in a hazardous manner – under pressures higher than the tanks are designed to handle, for example.
2.  The emergency shutdown system, which reacts if hazardous conditions arise – such as a gas leak or a fire. This system receives signals from fire and gas detectors as well as from manual alarms.

The metering system for production and consumption  meters the quantity of gas and oil exported from the platform as well as the amount of consumption and fuel gas used internally. This system attracts great attention from all levels of the organisation, since its measurements form the basis for the revenues generated and the tax to be paid on output.

Safety and security

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Manual alarm at Statfjord B. Photo: Shadé Barka Martins/Norwegian Petroleum Museum

Systems in this category are required for notifying and executing actions to prevent or reduce major or minor damage. They also include systems for emergency evacuation or for retrieving people who have fallen into the sea.

Fire and gasdetection
All areas of the platform are fitted with fire and gas detectors. Should fires or leaks be registered, the following actions are initiated automatically:

  • fire pumps start
  • sprinkler/deluge systems are initiated (halon has been phased out)
  • fire dampers in the ventilation system are closed
  • emergency shutdown (ESD) of the platform is initiated.

Fire extinguishing system
This protects personnel, structures and equipment throughout the platform (including the shafts). Two types of system are installed:

  • wet, using water or foam
  • dry, using powder (and halon earlier).

The wet system is supplied by the fire water pumps installed on the service deck. Fixed foam extinguishers are positioned in areas with a high risk of oil fires. Halon
was originally used in technical spaces which contain much electrical and electronic equipment, but has been phased out. A large powder system has been
installed in connection with the helideck. In addition, fire extinguishers – both carbon dioxide and powder – have been positioned for quick response throughout the platform

Alarms
These are intended to warn of incidents which require a coordinated commitment by all personnel to saving life and maintaining platform safety. Alarms are given over the public address system, either as a signal or as a verbal announcement.

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The survival suits hanging outside the cabins. Photo: Shadé Barka Martins/Norwegian Petroleum Museum

Rescue/safety equipment
This is intended to permit speedy evacuation of personnel from the platform in an emergency, or to retrieve people who have fallen overboard. It includes:

  • covered free-fall lifeboats
  • covered rafts which inflate on contact with the sea
  • man-overboard boats (MOBs)
  • chutes for evacuation to the sea
  • personal survival suits.

Communication

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Modern equipment in the radio room at Statfjord C. Photo: Jan A. Tjemsland/Norwegian Petroleum Museum

Rapid advances have been made in this area since Statfjord came on stream. The following
thereby describes both the original position and the current systems.

External communication
These systems provide the necessary links between the platforms and contacts on land, at sea and in the air.

1980
The satellite system installed on Statfjord A was intended to the main carrying channel for communication between the field and the Norwegian mainland. Communication
to/from the B and C platforms was relayed over line-of-sight microwave links to Statfjord A for onward transmission. Were the satellite system to go down, VHF and MF radio communication would take over. An emergency phone system provided direct communication with land.

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The old radio room at Statfjord A. Photo: Odd Noreger/Norwegian Petroleum Museum

The radio shack on the A platform kept in touch with helicopters via VHF (AM) radio and with ships via VHF and MF communication. Crane drivers could communicate directly with ships using VHF radio-telephones operating on the marine frequency.

A telemetry system linking the platforms was designed for fail-safe operation during transfer of crude oil between the installations. The control room on each platform monitored and coordinated the oil pumps. This system also had a speech channel for communication between the control room and the loading buoy/shuttle tanker.

Walkie-talkies were used where phones were impractical. This system provided a back-up for the phone network, the public address system and ship-to-ship communication.

The internal phone system was operated from the radio shack. This was also the location for the telex system, which was operated via the satellite link.

2010
Microwave links (point-to-point by line of sight) installed on Statfjord A and B provide the two main carrying channels from Statfjord to Gullfaks and on via fibreoptic cable to the Norwegian mainland. Should one channel drop out, all communication is automatically transferred to the other. Communicationfrom Statfjord C is transmitted via microwave links to Statfjord A and B for onward transmission to land. An emergency system provides direct mobile phone communication with land via Gullfaks.

Communication managers on the platforms maintain contact with helicopters via VHF (AM) radio and with ships using VHF. Crane drivers also communicate directly with ships using VHF radio-telephones operating on the marine frequency.

A telemetry system linking the platforms is designed for fail-safe operation during transfer of crude oil between the installations. Changes to the loading buoys (see the separate article) mean that this system is now also used for communication between platform and tanker. The control room on each platform monitors and coordinates the oil pumps. A speech channel for communication between the control room and the shuttle tanker is also provided by the telemetry system.

Walkie-talkies and the internal telephone system function by and large in the same way as they did in the 1980s. The telex system is no longer in use.

Computer network
A revolution has taken place in computer technology since Statfjord came on stream. The platforms are currently equipped with a broadband network linked to Statoil’s computers on board and on land, and to the internet. This network is also used for videoconferencing between the platforms and the Statoil offices on land.

Internal communication
Internal communication systems have been installed to safeguard day-to-day operation and to protect important information flows in the event of a rescue or emergency.  Today’s systems have naturally been modernised, but still include a public addresssystem, intercoms, an internal telephone network, and sick bay alarms and call-outs. The original closed-circuit TV facility has been replaced today by an internal monitoring system based on video cameras, and the sickbay alarm is now provided by a pager. A significant contribution to secure communication is provided by the installation of a repeater system, which ensures radio communication coverage of the whole platform.

UHF radio communication is extensively used at present in day-to-day operation of the platform and, in the event of an alarm sounding, for search and rescue teams and the fire brigade.

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Main control room at Statfjord B. Photo: Shadé Barka Martins/Norwegian Petroleum Museum

Control room
The control room is placed in a secured area, where process operators monitor and control the various process and service systems. Two
separate monitoring and control systems are provided:

  1. a control and information system for safe operation and shutdown, with a duplicated control system for ballast tank level
  2. a supervisory control and data acquisition (Scada) system which monitors  and checks production, drilling, transport and other connected processes.

Process data are read off automatically by the system to provide the basis for dynamic process diagrams and tabulated reports presented to the operators. Possible changes to the status of a monitored process are presented as colour changes on the displays.

 

Published July 9, 2018   •   Updated January 3, 2020
© Norsk Oljemuseum
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The Statfjord B letter

person by Trude Meland, Norwegian Petroleum Museum
Preparations for building the Statfjord B platform were well under way in the autumn of 1976. But the Norwegian Petroleum Directorate, as the regulator responsible for offshore safety, had its own views on the project. It expressed these in a letter sent to operator Mobil on 11 November 1976, which came to change all the plans.
— Norway's most expensive letter, it was called, the letter that instructed the Statoil/Mobil group to change the structure of Statfjord B.
© Norsk Oljemuseum

At that time, contract negotiations had been pursued with Norwegian Contractors on building a four-shaft Condeep gravity base structure (GBS). They were at the point where a letter of intent was ready.

The recently established Norwegian Petroleum Consultants (NPC) joint venture had also signed a contract on project management and engineering design for Statfjord B. Read more about NPC in the section on Statfjord B – the first plan.

While the contract for building the platform topside and mechanical outfitting of the GBS shafts had yet to be awarded, an option agreement had been secured with the Aker group.

So all the main contracts for the project appeared to have been put in place. The Storting (parliament) had also approved phase II of the development plan in June 1976, and most people assumed that it was simply a case of starting to build.

Until the NPD letter arrived

The Vogt commission

New safety regulations for the Norwegian offshore industry had been adopted on 9 July that year. A key issue for Statfjord B and the field licensees was the introduction of a more restrictive attitude towards simultaneous drilling and production combined with living quarters on a single integrated platform.

The new rules had been developed by a commission of inquiry appointed by the government as early as 22 May 1970 with a mandate to propose regulations for the safety of production and storage facilities on the seabed and of exploiting petroleum deposits.[REMOVE]Fotnote: Norsk Oljerevy. (1976). no 2. Kontroll med sikkerheten fordelt på ni instanser. 

Work in the commission progressed slowly and its chair, Jens Evensen, asked to be relieved. He was replaced in November 1972 by director general Lars Oftedal Broch, who was replaced in his turn during May 1974 by Nils Vogt from the NPD.

The latter gave his name to the commission’s report, which was submitted to the Ministry of Industry on 12 July 1975. It was then circulated for consultation to affected companies and institutions.[REMOVE]Fotnote: Hanisch, T., Nerheim, G., & Norsk petroleumsforening. (1992). Fra vantro til overmot? (Vol. 1). Oslo: Leseselskapet: 324.

Adopted by royal decree of 9 July 1976, the new safety regulations were based on the recommendations of the Vogt commission and on comments received in the consultation process. One provision of the decree was that the NPD would bear primary responsibility for supervising fixed offshore installations.

Safety issues on Statfjord were viewed by the directorate through the prism of the new regulations. It kept the industry ministry informed about its work, and wrote the following in a letter dated 7 July 1976:

“Given the work being done on safety conditions, it has been found necessary to adopt a more restrictive attitude to those concepts which are based on combined drilling and production, where the living quarters are also placed on the same platform. The main intentions of the Vogt commission’s recommendations run counter to both combined activity and the above-mentioned placement of living quarters … The NPD would emphasise that combined drilling and production will only be accepted following individual analyses and assessments. The same applies to living quarters which it is proposed to place on a drilling/production platform. No final choice of concept has been made for Statfjord B, so no specific safety analysis has been submitted. Comments from the NPD will accordingly have to wait until it the actual conditions have been presented.”[REMOVE]Fotnote: Norsk Oljerevy.

In other words, the ministry had been informed of the NPD’s work and of its scepticism about the plans for Statfjord B. As the letter indicated, the regulator could not adopt a final position until the Statfjord Unit Operating Committee (SUOC) had approved the concept chosen for the B platform in late August 1976. Only then could the NPD conduct its own safety analysis.

The results of the latter were presented to the Statfjord licensees in the above-mentioned letter of 11 November 1976, where the NPD questioned the safety of an integrated platform and ordered the construction of a separate quarters platform:

“The NPD is currently assessing the concept for Statfjord B on the basis of a general evaluation of the safety rules on the field in the light of the new regulations (royal decree of 9.7.76)

“Statfjord B is expected to involve:

  • particularly complex and extensive production facilities concentrated on a single platform
  • a large number of producing wells with high capacity, along with water and gas injection
  • permanent living quarters for 200 occupants, which will be used by 400 people during the construction phase and possibly the drilling phase
  • possible simultaneous drilling and production.

“The total risk is characterised by the contributions from each of the activities and processes which include the examples given above. The NPD’s assessment is that the total risk associated with these conditions lies at too high a level.

“In the NPD’s view, the best way to reduce the total risk would be to reduce the number of people who are present on the platform at any given time. The NPD has accordingly concluded that a separate quarters platform connected to Statfjord B should be built.”

This safety assessment was not confined to Statfjord B. Questions were also posed about the A platform, construction of which was far advanced at the time. It was due to be towed out to the field in six months.

“The considerations mentioned above also apply to Statfjord A, if to a somewhat lesser degree. The NPD would accordingly, on the basis of the provisions in the royal decree of 9.7.76, request that the company undertakes a new overall assessment of safety conditions [on this installation] in relation to the planned drilling and production programme, with particular attention paid to the accommodation issue.”

This letter was signed by Gunnar Hellesen, chair of the NPD board, and director general Fredrik Hagemann.

New concepts proposed

Statfjord B was intended to be a virtual copy of the A platform, but with four support shafts instead of three. The process facilities would be equally large and complex, with a production capacity of 300 000 barrels per day, and the 200-berth quarters module was to be installed on the platform.

It was the last feature in particular that the NPD wished to prevent. The regulator took the view that cutting the number of people on the platform at any given time would reduce the overall risk.

As the letter indicates, the desirable solution was seen to be the construction of two platforms – one for production and drilling, and the other for accommodation. The NPD also emphasised the need for overall safety thinking, and wanted a separate safety study carried out before detailed planning began.

Statoil and Mobil expressed surprise at the letter, and claimed they had not heard that such assessments were being made. Arve Johnsen, then Statoil’s chief executive, described his reaction to the letter in his book Utfordringen (The Challenge): “As chief executive of Statoil, I received many kinds of letters … I have forgotten most of them, but I will remember one to my dying day … It sent a shock wave through the licensees in the Statfjord group.”[REMOVE]Fotnote: Johnsen, A. (1988). Utfordringen : Statoil-år. Oslo: Gyldendal: 202.

It might seem incomprehensible that the partners had failed to see this coming. They had long been aware that the NPD was looking at problems associated with simultaneous drilling and production, and the Vogt commission’s report had been through a consultation process. Comments in the latter as well as the report itself formed the basis for the new safety regulations.

Adopted in June, four months before the letter was despatched, the regulations specified that simultaneous drilling and production was prohibited without special permission. This should have sent certain signals that the plans for Statfjord B might be more difficult to implement than Mobil and Statoil thought.

As late as 12 October, section head Harald Ynnesdal had explained the NPD’s view on the issue in a speech he gave in Kristiansand:

“The new platform types are particularly complex and difficult to assess from a safety perspective with regard to these combined activities. As far as possible, fields should be planned with separate quarters platforms. The production platforms could then, with their combined activities, be assessed purely as industrial plants.

“In an assessment of simultaneous drilling and production in the Statfjord project, for example, the problem would have been much simpler if separate quarters platforms had been adopted. The cost of such platforms would have had little effect on profitability for this project, but would have meant a great deal for overall safety and the desire for an early start to production.”[REMOVE]Fotnote: Norsk Oljerevy. (1976). no 9. Statfjord – planer og virkelighet. On the basis of this letter, an extraordinary meeting of the SUOC was called on 26 November. It decided that all activities related to Statfjord B would be halted. The project would have to be re-evaluated, and extensive conceptual studies were to be carried out for every option from one to three platforms.

A meeting of the Statfjord field engineering committee (SFEC) – the technical project team – took place in January 1977. A 35-strong sub-committee was appointed to study and assess various conceptual solutions for Statfjord B, and came up with 39 variants for consideration.

When the SUOC met again on 18 March, Statoil expressed concern at the progress made. The project had a tight timetable, and order books at the Norwegian shipyards were empty. To speed up the process, the company proposed a separate drilling platform linked by a bridge to a combined production and quarters unit.

A drilling platform supported on a steel jacket, for instance, would be relatively cheap to build and could be ready for tow-out as early as 1979. Drilling of production wells could start as soon as the platform was in place, and continue while the associated production and quarters facility was under construction.

As soon as the latter had been installed, oil and gas could thereby begin.[REMOVE]Fotnote: Norsk Oljerevy. (1977). no 5. Industrien må fortsatt vente på Statfjord B.  This meant in turn that the original schedule set in the field development plan could be met.

Mobil and Saga were strongly opposed to this plan, but did not have enough votes to block it. Their interests added up to only 25 per cent, while resolutions in the SUOC needed 70 per cent support. The Statoil proposal was thereby adopted – against the operator’s vote.

Esso also proposed its own solution at the meeting, comprising an integrated production, drilling and quarters (PDQ) platform but with processing capacity halved to 150 000 barrels per day. This facility would be simpler, since only one process train was required rather than the original two, and overall safety would be improved.

Mobil supported the Esso proposal. The two companies were uncompromising in their opposition to two platforms, and maintained that this would provide no safety benefit. A factor in their assessment was the poor seabed soil conditions on Statfjord, which meant that installing two platforms so close to each other and linked by a bridge carrying high-pressure pipelines would pose a safety risk.

The thought of the substantial capital investment required for two platforms also worried the operator. On the other hand, experience from other North Sea projects suggested that a capacity of 150 000 barrels per day would be sufficient. Such a solution would reduce construction costs by simplifying the platform, and production could also start earlier.

Threats

A further meeting of the SUOC was held on 28 April, when Mobil proposed an integrated platform with a single process train and an average capacity of 180 000 barrels per producing day. This size had been chosen in the hope of avoiding a separate quarters platform.

The change to the original concept was so large that a completely new field development plan might have to be produced. According to the proposals approved the Storting in the summer of 1976, three platforms with a combined capacity of 900 000 barrels per day were to be installed.

Reducing the size of the process facilities on each platform would either require more structures to maintain the planned output, or a slower pace of production.[REMOVE]Fotnote: Norsk Oljerevy. (1977). no 5. Industrien må fortsatt vente på Statfjord B.  Fresh consideration by the Storting could delay the project further.

At the same time, Mobil vetoed a separate quarters platform.[REMOVE]Fotnote: Moe, J. (1980). Kostnadsanalysen norsk kontinentalsokkel : Rapport fra styringsgruppen oppnevnt ved kongelig resolusjon av 16. mars 1979 : Rapporten avgitt til Olje- og energidepartementet 29. april 1980 : 2 : Utbyggingsprosjektene på norsk sokkel (Vol. 2). Oslo: [Olje- og energidepartementet]. With strong support from Esso, the operator noted that it could not accept a solution which complied with the NPD’s principle that drilling and production should not take place simultaneously on the same installation.

Clear instructions had been sent from Mobil’s head office in New York that a compromise solution which would involve an acceptance of the NPD principle was out of the question. It feared that conceding this demand from the Norwegian regulator could lead to similar requirements on other continental shelves, which would have major consequences for both Mobil and its fellow oil companies.

A telex from New York emphasised that, the way things looked, concrete platforms on the scale of Statfjord A had outplayed their role on this field. Mobil was willing to renounce the operatorship for Statfjord B if a two-platform solution was adopted. This attitude took Statoil and the Norwegian government by surprise.[REMOVE]Fotnote: Norsk Oljerevy. (1977). no 5. Industrien må fortsatt vente på Statfjord B. 

Statoil explored the possibility of another operator, but none of the other partners was willing to take on the role without a reallocation of licence interests. Mobil and Esso had staked their prestige on the issue, and they finally managed to convince Statoil of the technical problems posed by a two-platform solution. The argument that this could affect later developments in deeper water was central to the Norwegian company’s change of mind.

The discussion on one or more platforms and the studies of various concepts were paralleled with the presentation of new seismic data for the field. These cut its estimated oil reserves from 3.9 billion barrels – equivalent to 527 million tonnes – to 3.2 billion or 432 million tonnes. That reduced the need for two process trains on Statfjord B.

Clarification

On 5 August, the SUOC approved plans for a platform with the capacity to process 180 000 barrels per day. It was resolved on 29 November to apply to the NPD for permission to build such a structure. The application, accompanied by a separate safety study, was submitted on 1 December.

Plans now called for Statfjord B to be installed in 149 metres of water at the southern end of the field. Seabed conditions were poorer there than over the rest of Statfjord, and the base area of the GBS accordingly had to be increased.

While Statfjord A had 19 cells, the B version would have 24. Planned topside space would expand correspondingly, from 5 200 square metres to 7 800. The platform would still have four shafts even though only one process train was to be installed. With the fourth shaft reserved for risers, space was freed up in the others.

Additional safety barriers were introduced by the decision to make the decks and modules open, reducing the danger of an explosion and possible damage from such an incident. The various functions would also be positioned in such a way that no hazardous operations were close to or beneath the living quarters. And the quarters modules would be protected by an additional fire wall. These plans were approved by the NPD on 19 December.

The project had been delayed by a year and incurred substantial costs through a number of conceptual studies and reports. According to Henrik Ager-Hanssen, deputy chief executive of Statoil, the letter from the NPD was the most expensive in Norwegian history and cost the project NOK 25 million per word.

Viewed from a different perspective, former Statoil staffer Bjørn Vidar Lerøen has noted that oil prices reached record levels over the next few years. That meant the letter became one of Norway’s most profitable.[REMOVE]Fotnote: Lerøen, B., Gooderham, R., & Statoil. (2002). Drops of black gold : Statoil 1972-2002. Stavanger: Statoil: 149.

Published May 23, 2018   •   Updated November 22, 2019
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Gas pipeline agreements

person By Håkon Lavik, former Statoil employee
The sale of gas from Statfjord made it necessary to connect the platforms with flowlines to gather gas for export via the Statpipe system. Oil flowlines also linked the platforms, but these had been installed as part of the field development.
— Statfjord field with associated gas pipelines. Source: Storting Report 39 1984–85
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A separate project, the Statfjord intrafield pipeline system (Sips), was established to engineer and install the gas lines. Once the work had been completed, Sips was taken over, owned and operated by the Statfjord Unit. In formal terms, Sips
forms part of the Statfjord Facilities – in other words, all the platforms, flowlines, wells and so forth which have been developed to operate the field.

Since the British licensees in Statfjord were not allowed to sell their gas to continental Europe, a separate UK Gas Offtake pipeline was laid as part of Sips from Statfjord B to the UK side of the boundary. There it tied into the Northern Leg Gas Pipeline (NLGP), a gas gathering line for fields north of Brent. The Statfjord Unit owns that part of the UK Gas Offtake line which lies within its boundaries, while the British licensees own the section to the west, including the NLGP tie-in. The UK government demanded the inclusion of a non-return valve in this line, so that British gas could not be conducted to Statfjord B.

This line was regulated by the Agreement for Installation and Tie-in of the UK Pipeline to the Statfjord B Platform and to the Northern Leg Gas Pipeline , which entered into on 1 February 1983. The UK Statfjord Gas Offtake Operating Services between Mobil Exploration Norway Inc and Conoco (UK) Ltd service agreement was also signed on 27 September 1985. A gas pipeline was laid from Gullfaks A to Statfjord C under a separate Agreement for Tie-in and Operation of the Gullfaks Pipeline to the Statfjord C Platform between the two sets of licensees,   dated 27 September 1984.

Gas from Gullfaks was carried via Sips before entering Statpipe until the end of the 1990s, when Gullfaks acquired a new tie-in to Statpipe south of Statfjord. Gas transit via Statfjord accordingly terminated, but the pipeline from Gullfaks is still intact and usable and the tie-in agreement remains operative.

Statpipe tie-in

Gassrøravtaler,
Statpipe map from Gullfaks brochure 1984. Illustration: Equinor

Although the Statpipe system starts from the field, it does not form part of the Statfjord Unit. A separate pipeline and transport company was established after the gas from Statfjord, Gullfaks and Heimdal had been sold in 1982.

The purpose of this joint venture was to install pipelines and build the Kårstø processing plant north of Stavanger in order to export gas from the Norwegian continental shelf (NCS) via Ekofisk to Emden in Germany. Where Statfjord was concerned, this meant that a contract was signed on 12 July 1984 between the Statfjord Unit and Statpipe concerning the tie-in of the pipeline to Statfjord and its subsequent operation.

 Statfjord B serves as the starting point for Statpipe, and the valve system on the seabed is operated from that platform. But it was Statfjord C, via Sips, which was responsible for maintaining pump pressure in the pipeline and ensuring that the gas flowed to Kårstø.
Statpipe later became part of the Gassled joint venture, and the section from Statfjord to Kårstø now lies in Gassled’s tariff zone 1. In connection with the Statfjord late life (SFLL) project, the connection between Sips and Gassled was severed in 2007. Statfjord B now provides the connection with Gassled.

Statpipe-Statfjord transportation agreement

Dated 30 September 1985, this contract secured transport rights in Statpipe for the Norwegian share licensees in Statfjord. The agreement still exists in principle, but was converted on 1 January 2003 to individual contracts for each licensee following the adoption of the EU’s gas directive. Each company accordingly has its own transport agreement. That was also the original position, but based on a single contract.
Similarly, each of the licensees in the Norwegian share of Statfjord had separate sales agreements for its proportion of the gas with the buyer consortium in continental Europe. These contracts were terminated in 2007, since the volume sold under them was deemed to have been delivered. Statfjord gas, including output from the SFLL project, is sold today to the UK.

Tampen Link

Gassrøravtaler,
Tampen Link. Illustration: Equinor

As part of SFLL, the decision was taken to lay a new pipeline from Statfjord to tie into the Far North Liquids and Associated Gas System (Flags) in the UK North Sea. The latter runs from Brent to St Fergus in Scotland.
Tampen Link is a separate company operated by Gassled. Dated 22 February 2005, the contract related to Statfjord has a long name: Agreement Between the Tampen Link Joint Venture and the Statfjord Group for the Installation and Tie-in of the Tampen Link Transportation Facilities to the Statfjord Facilities and the Operation of the Tampen Link Statfjord Facilities and the Operation of the Tampen Link Statfjord Facilities and the Transit Services at the Statfjord Facilities.
This agreement makes it possible to transport gas from Statfjord directly to Flags and the UK, and from other fields in transit via Statfjord to the same destination.

Crossing agreements

Since Statfjord is a hub for oil and gas exports from the northern North Sea, a number of pipelines large and small have been laid. Where these cross over each other, a crossing agreement has to be established. You cannot simply lay your pipeline over one belonging to somebody else and possibly cause damage. This must be regulated.

The following agreements have been established so far:

  • Crossing of the Statfjord B Pipeline and the Statfjord Control Umbilical by the Penguin Pipelines and Cable , dated 22 March 2002. (Penguin is a small UK field tied back to Brent.)
  • Pipeline Crossing and Laying Agreement Between Statfjord Unit and Sygna Unit , dated 14 April 2000.
  • Pipeline Crossing Agreement Between Statfjord East and Statfjord North Flank , dated 1 April 1999. (the north flank is the northernmost part of Statfjord, developed with subsea wells).
  • Pipeline Crossing Agreement Between Tampen Link and Statfjord Unit , dated 20 November 2006.

Published October 30, 2019   •   Updated February 18, 2020
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