Diving

person Norwegian Petroleum Museum
Underwater operations for installation, inspection, maintenance and repair of platforms, risers and pipelines are pursued year-round in the Greater Ekofisk Area.
— Leif-Tore Skjerven (venstre) og John A. Haugestad på dykkeoppdrag. Foto: Leif-Tore Skjerven/Norsk Oljemuseum
© Norsk Oljemuseum

All such work was originally done by divers, but simple remotely operated vehicles (ROVs) began to be used in the late 1970s.

Known as “eyeballs”, the first of these were used for visual inspection and for monitoring divers performing difficult assignments in order to improve their safety.

The ROVs became steadily more sophisticated and took over an increasing amount of subsea work. Most underwater operations today are done without diver assistance.

Divers

Divers have been an integrated part of the Ekofisk workforce ever since trial production began on Gulftide in 1971, where they carried out various assignments.

These included regular inspections of the seabed near the platform’s legs to spot erosion in good time and counter it with the aid of sandbags. Another job was to inspect the riser base plate for erosion.

During the early years, Ekofisk crude was carried to market in shuttle tankers. A regular diving job was to inspect flanges on the flowlines to the loading buoys and to make repairs.

The buoys themselves and their mooring systems also had to be checked, as did the anchoring equipment and loading hoses for the tankers. Hawsers and hoses floated in the sea in order to be retrieved by the tankers when they arrived to load. Almost every time gale-force or stronger winds had been blowing, this equipment was all tangled up and had to be sorted out.

Not infrequently, too, all or part of a loading buoy would have been torn free and had to be restored again as soon as weather and wave heights permitted.

The service vessels in the 1970s were called Imkenturm and Pagenturm, and took it in turns to provide standby on the field. Both were equipped for surface-oriented diving, while the first of them also carried a bell system.

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Diver ready for work, approx. 1980. Photo: ConocoPhillips/Norwegian Petroleum Museum

When substantial underwater work had to be done, a dedicated diving team was mobilised to Choctaw 1. This vessel carried its own bell system for deeper jobs.

However, the bulk of subsea assignments were performed as surface-oriented diving which could be used for water depths down to about 72 metres.

When diving support vessel Seaway Falcon arrived in 1975, saturation dives became even more common. Divers here were housed under seabed pressure in a chamber on deck.

They were pressurised to two different levels – 50-58 or 30 metres of water – depending on the work to be done. The diving bell was used for transport to the work site and to provide communication and breathing gas for the divers.

The diving supervisor instructed the men in the water what to do from the control centre. They usually spent about three hours outside the bell to do a job.

One diver always remained on standby in the bell while the other was out working. Once they had completed their time submerged, the bell was hoisted back to the surface.

The men remained in the pressure chamber between each bell run, with food and drink supplied via air locks. Video cameras permitted constant monitoring from the control room.

A saturation diver usually spent up to 16 days at a stretch under pressure. They would undergo decompression during their final 60 hours.

Continuous construction work characterised the first period on Ekofisk. Divers were assigned to conduct exact topographical and geotechnical measurements.  Irregularities in the seabed where a platform was to be installed might have to be levelled out. Other jobs included inspection, installation, equipment overhaul and welding.

Where pipelaying was concerned, divers usually carried out route surveys and topographical surveys as well as assisting throughout the operation. Positioning pipelines and using measurement equipment on them were other jobs.

Diving supervisor

The diving supervisor’s role on Ekofisk has changed in line with technological advances in this area. Until the mid-1970s, they also led the diving team on minor operations.

They were the immediate superior of the divers, with management responsibility for all the work done by their team.

While diving was underway, their place was at the controls (in the control room where one existed) where they directed the diver’s work over the communication link and otherwise operated everything relating to life support.

The latter included supplies of air/breathing gas and possible hot water. Depth, time submerged, descent/ascent speeds, decompression stops and so forth were managed in accordance with the diving tables when the diver was in the water, the bell or the pressure chamber.

arbeidsliv, dykking, dykker, rov-operatøt,
The ROV follows closely as divers often have to deal with very delicate and complicated equipment. The image that the ROV sees is shown to the dive manager and the specialists in the control room. Everyone involved can see the same image at the same time. At the top right is the ROV garage, from where the small submarine can "fly" approx. 90 meters. Illustration: Barry Pearson/Norwegian Petroleum Museum

From the controls, the diving supervisor also managed the activities of the diving support team on the surface – winching, umbilical handling, lowering/retrieving tools and so forth.

In addition, they served as the link between the diver and necessary heavier assistance when this was in use. That included crane operators, for example.

When no dives were being made, they were the team leader for inspection, maintenance and repair of its equipment, and were responsible for purchasing consumables – such as breathing gas and carbon dioxide absorbents – spare parts and so forth.

The supervisor was also responsible for all logging and other paperwork. They took their orders from and reported to their own diving company on administrative and technical matters, and from the contractor where work was concerned.

After specialised support vessels and saturation diving were adopted in the mid-1970s, the size, duration and scope of this work increased.

That made it natural to spread the diving supervisor’s duties between several different people – diving superintendent, camera operator, life support technician (LST), gas technician and so forth.

The basic job of today’s diving supervisor is still to be in communication with the divers and manage their work, lead surface support and act as a link between the diver and direct external assistance.

ROV operator

Phillips was the first operator on the Norwegian continental shelf to adopt remotely operated vehicles, or ROVs, to support underwater work.

Known as “eyeballs”, the first of these were very elementary and served basically as motorised cameras. They were operated from the control room on the surface ship via an umbilical cable.

Diving support vessels (DSVs) used these devices for visual inspection and monitoring of the divers in order to enhance their safety. Subsea operations on Ekofisk utilised two RCV225 eyeballs, one on each of the two DSVs which operated there.

More advanced ROV technology was adopted during the 1989 inspection programme on the field, with work done by two very sophisticated manipulator arms mounted on the vehicle’s front.

It could also carry sonar equipment, up to five underwater cameras for both panoramic and close-up photography, and various modules for jobs such as weld cleaning and anode installation.

Ninety per cent of all subsea inspection on structures and pipelines was conducted by ROV in 1989. But divers were still needed, and a project was launched to combine them with ROV use.

In order to simplify diving conditions, a platform was installed on either side of the ROV for the divers to stand on while they carried out their work.

In addition, a modular framework was developed with pumps and hydraulic connections for tools. This was installed under the ROV, enabling it to carry equipment down to the divers.

Another project was started in collaboration with Elf to develop an ROV able to conduct non-destructive testing (NDT) on steel structures. A dedicated manipulator arm, software and tools were produced for this purpose.

As a discipline, operating underwater activities remotely from surface control stations covers a number of different work areas using ROVs and remotely operated tools (ROTs). Operations, maintenance and repair are carried out on subsea installations and process facilities.

Such work is pursued particularly in the offshore petroleum sector on continental shelf areas around the world, and embraces the exploration, development, production and cessation phases.

However, the technology is being increasingly extended to other contexts and will be utilised to a greater extent in the future for aquaculture, for example.

Further potential areas of application include environmental mapping, work on military equipment, cleaning up environmentally hazardous waste and in hydropower generation.

Published 31. July 2019   •   Updated 30. October 2019
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Base operations

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All the supplies needed to ensure that the offshore platforms can do their job of producing oil and gas pass through the base at Tananger outside Stavanger. Warehouse operation at the base covers five main functions: goods reception, spare parts store, accounting, pipe store and goods dispatch.
— Phillips is about to establish themselfs at the Norsco base,1972 Photo: Norsk fly og flyfoto/Norwegian Petroleum Museum
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Dusavik base, 1966-73

The contract for Phillips’ first supply base in Norway was signed with Stavanger-based tanker company Smedvig Tankrederi on 25 April 1966.

It covered the hire of outdoor storage and quay areas as well as a new combined warehouse and office building which was modest by today’s standards.

Located at Dusavik just outside Stavanger, Phillips ranked as the first tenant at what was to become one of the two big offshore supply bases in the district.

The drilling operations which led to the discovery of Ekofisk were served from Dusavik. While the lease ran until 1981, it only functioned as the main base for the Stavanger area until 1973.

Rapid organisational growth made the premises in Dusavik too small by that year, and additional space was obtained by taking a clearly creative approach.

 

So Phillips secured premises in a soap factory, a Chinese restaurant and the bar and other areas of Stavanger’s Alstor Hotel. And many of those hired in 1973 are sure to remember that they were interviewed at the city’s Atlantic Hotel.

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Hotel Atlantic. Photo: Asbjørn Jensen/Norwegian Petroleum Museum

Phillips base, 1973-81

Some activity had been established at the Aker Norsco base in Tananger during 1972, but it was not until the autumn of 1973 that the headquarters for Ekofisk was transferred from Dusavik.

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The "H-building" (lower right corner), at Tananger. Photo: Unknown/Norwegian Petroleum Museum

That occurred with the occupation of the H Building at Tananger, where Phillips had signed a lease with the base company the year before.

This covered the hire of outside storage areas, quays, warehousing, a canteen and an office building – a complete supply base. All the buildings were purpose-built.

The lease gave Phillips an option to acquire the whole facility at a later date, which the company duly exercised in the summer of 1979.

To varying degrees since 1973, the operator has needed to lease both warehousing and offices from Aker Norsco – partly in temporary structures and partly in permanent premises.

From 1973 to 1976, exploration operations with the Ocean Viking rig continued to be run from the Dusavik base. The charter then expired, and remaining activities were moved to Tananger.

Lack of space at the latter premises meant that the training department was transferred to Dusavik and remained there until the lease expired in 1981.

Similar shortages meant extra premises had to be leased around Stavanger. This growing problem led to plans being laid from 1978 for a significant expansion at Tananger.

Phillips base since 1981

The new building was gradually occupied from December 1980 and formally opened in August 1981. Once it had been finished, the old H Building was completely refurbished to the same standard.

This expansion marked a significant improvement in working conditions for many employees, and helped to enhance efficiency by gathering much of the organisation under one roof.

The development was originally intended to meet all needs for office space, with the exception of the project department’s requirements.

However, it became clear even before the new building was occupied that this goal would not be reached. But it proved possible by and large to cease hiring space outside Tananger.

Løfteskipet Uglen i aksjon ved Norscobasen i juli 1980. Foto: NOM/Norsk Fly og Flyfoto Løfteskip, Uglen, Norscobasen,1980, phillips, sola, olje, inntekter
The crane barge Uglen in action at the Norsco base in July 1980. Photo: Norsk Fly og Flyfoto/Norwegian Petroleum Museum

To deal with developments in the supply services for Ekofisk, Phillips entered into a contract with Aker Norsco on the construction of a larger and more modern warehouse.

This building and associated offices were occupied in late 1982/early 1983, and were regarded as a model example for the purpose.

The waterflooding project on Ekofisk received a green light in 1983, which created the need for more office space to accommodate the project department.

Since a quick start was important, the new building in Tananger was ready three months after the contract with Aker Norsco had been signed.

Premises utilised by Phillips in the Stavanger area by 1988 comprised 20 000 square metres of offices, 10 000 square metres of storage space and 850 square metres of workshops. In addition came the offices at Munkedamsveien in Oslo.

Another new building opened at the Tananger base in July 1996, which meant the whole workforce was assembled on one site in two connected premises.

While the old offices covered 14 000 square metres, the new seven-storey building has an area of 11 300 square metres and provides 420 additional office spaces.

It also accommodates a 600-square-metre conference centre, as well as a gym and a swimming pool measuring eight by 12.5 metres in the basement.

The Tananger base was sold in July 1996 to Aker Base, including buildings, furniture and fittings, and the deepwater quay.

Activities at the base

The Phillips base at Tanager plays a central role in operating the Greater Ekofisk platforms. All necessary supplies allowing these installations to do their job pass through it.

Warehouse operation at the base covers five main functions: goods reception, spare parts store, accounting, pipe store and goods dispatch.

The spare parts store is managed with the aid of a comprehensive computer system with full information for offshore personnel to log on directly and check availability.

When goods are received at the warehouse, they are marked with a purchase number and all data concerning the order is entered. They are packed out, checked and sent for shipment offshore.

The workshop, located in the same building as goods reception, deals with such jobs as mechanical repair of diesel engines, pumps, valves, heat exchangers and compressors.

It also repairs base equipment, like forklift trucks, cranes and fire-extinguishing systems. In addition, the shop produces pipework, pressure tanks and other structural welding.

The head office for Phillips’ activities in Norway stands alongside the supply base for the platforms in the Greater Ekofisk Area.

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In November 2004 ConocoPhillips opened its OOC (Onsore Operation Center) at Tananger. Photo: Kjetil Alsvik/ConocoPhillips
Published 29. July 2019   •   Updated 22. October 2019
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The oil and gas terminals

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Oil and gas from the Greater Ekofisk Area is piped to Teesside in the UK and Emden in Germany respectively, where the pipeline terminals formed part of the field development. ConocoPhillips still operates the oil terminal in Teesside, while the facility in Emden has been taken over by Norwegian state-owned company Gassco.
— Gassterminalen i Emden. Foto: Husmo Foto/Norsk Oljemuseum
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Oil terminal in Teesside

Olje- og gassterminalene, engelsk,
Teesside terminal. Brian Henderson Thynne takes samples of refrigerated propane. Photo: Husmo Foto/Norwegian Petroleum Museum

The terminal at Teesside in north-east England receives oil and natural gas liquids (NGL) by pipeline from the Ekofisk field. It comprises stabilisation, NGL fractionation, storage tanks for crude oil and an export port.

After arriving through the Norpipe Oil line, crude and NGL are separated and the oil goes through a stabilisation process before reaching the 10 storage tanks, which each hold 750 000 barrels.

The NGLs go to the fractionation facility, with a daily capacity of 64 000 barrels, for separation into methane, ethane, propane, and normal and iso butane.

While the methane (natural gas) is used to fuel the plant, the other products (now known as liquefied petroleum gases – LPG) are made liquid by cooling and stored for export by sea.

One reason for the choice of Teesside as the landfall for the Ekofisk pipeline was the opportunity it offered to install deepwater quays.

The terminal has four of these, with those for crude oil able to handle tankers up to 150 000 deadweight tonnes. The LPG quays can accept carriers loading as much as 60 000 cubic metres.

Two of the crude oil quays lie on the main channel of the River Tees, while the others have been installed in dredged docks.

Gas terminal in Emden

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Photo: Husmo Foto/Norwegian Petroleum Museum

Gas arriving at the Emden terminal from the Ekofisk Complex enters nine parallel treatment trains for cleaning, metering and onward distribution to the buyers.

The North Sea gas is very clean, and needs only limited treatment to remove small amounts of sulphur compounds using an absorption process. Impure molecules from the gas accumulate on the surface of small particles, which act as filter spheres.

Each of the nine trains comprises four process columns and a process oven. The gas enters the top of a column and leaves through the base after passing through the filter spheres.

That leaves the gas ready for sale, and it is piped to the fiscal metering station before entering the buyer receiving pipelines and distribution network.

Three separate commercial pipeline systems connect to the terminal, operated by Ruhrgas, BEB and Gastransport Services (previously Gasunie) respectively. They pipe the gas away on behalf of the gas buyers.

The Norsea Gas Terminal in Emden was officially opened in September 1977 by Norwegian industry minister Bjartmar Gjerde and Phillips executive Gordon Goerin.

Ranking as the first gas sales deal for the Norwegian continental shelf, the Ekofisk agreement paved the way for later contracts covering other fields off Norway.

Regularity at the Emden terminal has been very high, with its own equipment never causing shutdowns. Maintenance takes place when other parts of the system are off line.

The terminal has a daily capacity of about 2.1 million cubic feet of gas per day.

Gas transport restructured

Norpipe AS owned the gas pipeline from Ekofisk to Emden until the transport system for the Norwegian offshore sector was restructured at 1 January 2003.

Norsea Gas A/S furthermore served as the formal owner of the Emden facility, with Phillips Petroleum and then ConocoPhillips as operator for both pipeline and terminal.

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Teesside gas terminal. Photo: Husmo Foto/Norwegian Petroleum Museum

Since 2007, Norway’s state-owned Gassco company has been responsible for technical operation of the facilities on behalf of their owners.

That included operator responsibility for the H7 and B11 booster platforms along the gas pipeline, which were shut down in 2007 and 2013 respectively and have since been removed.

The Gassled partnership is a project collaboration embracing 10 companies which collective own large parts of the gas infrastructure on the Norwegian continental shelf (NCS).

A substantial proportion of Norway’s gas deliveries to Germany continues to arrive at the Emden terminal, including the volumes piped from Ekofisk.

Preliminary planning for a new terminal in the German port began in 2011, with Gassled taking the investment decision for this development in the autumn of 2012.

Construction work began in the following year, with the new facility being built on an unused part of the existing terminal site.

The new terminal has not expanded export capacity. But its functionality is well adapted to future processing needs for fields in the Greater Ekofisk Area and other parts of the NCS sending gas through the Norpipe system.

It was officially opened on 24 May 2016 by Elisabeth Aspaker, the Norwegian government minister for the EU and the European Economic Area. That closed a chapter in Ekofisk’s history.

Source: ConocoPhillips Norge

Published 29. July 2019   •   Updated 12. October 2019
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Pipelines

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Two export pipelines run from the Ekofisk Complex. The one for gas has an external diameter of 36 inches and extends 443 kilometres to the German coastline. With an external diameter of 34 inches, the oil pipeline runs for 354 kilometres to Teesside in north-east England.
— Gas pipes at Ekofisk. Photo: Husmo Foto/Norwegian Petroleum Museum
© Norsk Oljemuseum

In addition to ConocoPhillips’ own production from Ekofisk, these pipelines carry gas and oil from the company’s fields in the UK sector and from other fields on the Norwegian and British continental shelves.

The three fields in the Greater Ekofisk Area are also tied together by pipelines.

Oil pipeline to Teesside

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Pipes and oil tanks at the Teesside plant. Photo: ConocoPhillips/Norwegian Petroleum Museum

The pipeline linking Ekofisk with the terminal for oil and natural gas liquids (NGL) at Teesside on the north-east English coast became operational in October 1975.

Pumps raise the pressure of the oil and NGL before they start their journey to land. Two pumping stations – 37/4 A and 36/22 A ­– originally stood along the pipeline to maintain this pressure, but have now been disconnected and removed.

The pipeline was installed with the ability to carry a million barrels per day. However, that much capacity has never been required.

In the UK sector, a 24-inch pipeline has been tied in with a Y connection to receive input from several British fields – including the J block developments operated by ConocoPhillips.

Output from the Greater Ekofisk Area is supplemented by crude from Valhall, Hod, Ula and Gyda heading for Teesside, optimising pipeline utilisation and thereby boosting value creation.

The pipeline is owned by Norpipe Oil AS and operated by ConocoPhillips.

Gas pipeline to Emden

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Sandbags and gravel were used to cover Norpipe to Emden. Photo: Unknown/Norwegian Petroleum Museum

This pipeline became operational in September 1977. The starting pressure of around 132 bar is provided by compressors on the Ekofisk Complex.

The 443-kilometre distance to Emden was split into three equal sections, with platforms B11 and H7 located at the intermediate points to provide boosting if required.

However, additional compression was seldom needed on the final stage to Emden. H7 was shut down in 2007 and B11 in 2013, and both have since been removed.

These two booster platforms were located in the German sector of the North Sea, while the pipeline also crosses the Danish sector.

The pipeline has been trenched or covered with sand. Its final section passes the island of Juist before making landfall on the coast of East Friesland to the north of Emden.

Its daily capacity is roughly 59.4 million standard cubic metres (2.1 billion cubic feet). In addition to gas from the Greater Ekofisk Area, it carries output from Valhall, Hod, Ula, Gyda and the Statpipe system (primarily Statfjord and Gullfaks).

Source: ConocoPhillips Norge

Published 29. July 2019   •   Updated 12. October 2019
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Embla 2/7 D

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This unmanned wellhead facility is remotely controlled from Eldfisk 2/7 S located 5.2 kilometres to the north, where oil and gas output from the platform is also processed.
Brief facts:
  • Unmanned and remotely operated wellhead platform
  • Installed in 1992
  • On stream 12 May 1993
— Embla 2/7 D. Photo: ConocoPhillips
© Norsk Oljemuseum
sokkelkart, illustrasjon, blokker, lisens, forsidebilde, engelsk,
Hand-colored map of the licenses of the first licensing round on the Norwegian continental shelf. Norwegian Continental Shelf Map, 1965.

The Phillips group was awarded block 2/7 as early as 1965, and the Embla reservoir lies in the southern part of this acreage. Drilling began there in 1974 to depths of 4 500-5 000 metres, but pressure and temperature in the wells were too high for testing with the available equipment.

The first production well was not drilled and tested until 1988, followed by a second in 1990. Both yielded very promising results, and the field came on stream in May 1993.

Embla comprises a sandstone reservoir at least 250 million years old. The other fields in the Greater Ekofisk Area comprise fine-grained carbonate rocks deposited about 70 million years ago.

The Embla reservoir has a temperature of 160°C compared with the 125°C normally found in the chalk formations 1 000 metres higher up, and its pressure is almost twice as high.

Fabricated by Heerema in the Netherlands, the Embla 2/7 D jacket (support structure) was installed by the M 7000 crane vessel. It stands 84 metres high and weighs 2 300 tonnes.

A 5.2-kilometre subsea umbilical from Eldfisk comprises three power cables for electricity supply and eight fibreoptic lines handling data transmission and telecommunication.

Eldfisk 2/7 S, embla,
Eldfisk 2/7 S. Photo: ConocoPhillips

The platform has six production wells and an average daily output of roughly 7 000 barrels of oil. All processing and metering took place on Eldfisk 2/7 FTP until 2015, and has now been switched to Eldfisk 2/7 S.

A 14-inch flowline linked 2/7 D with 2/7 FTP and runs today to 2/7 S. Produced at Wick in Scotland, this line was floated out to the field in one piece.

Topside equipment includes the wellhead area, helideck (built by Vindholmen Services in Arendal), crane, control room, workshop, test separator and glycol pump.

Normally unmanned, the platform is maintained as and when required and therefore incorporates a simplified accommodation module with lounge, mess, coffee room, galley, changing room, WC and 12 emergency beds.

Published 24. June 2017   •   Updated 25. October 2019
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