This is a combined production, drilling and accommodation platform which was installed during 1972 in 70 metres of water, 2.3 kilometres north of the central Ekofisk Complex. The platform came on stream in 1974.
Combined production, drilling and accommodation platform
Installed in 1972
On stream 1 October 1974
Also called Ekofisk Bravo and known for the Bravo blowout in 1977
— Ekofisk 2/4 B. Photo: Husmo Foto/Norwegian Petroleum Museum
Collision damage to one of the jacket legs delayed the installation process. It was not until May 1973 that the jacket had been fully piled and was ready to accept the topside modules.
However, progress was then rapid and all the modules were lifted on board during June-July. Three months of hook-up and commissioning followed before the first of the two derricks – rig 41 – spudded the first production well. The second derrick required more work, and first became operational in December.
A trial project for water injection in the Cretaceous formation began via well 2/4 B-16 in April 1981. The aim was to assess whether waterflooding across the whole field could improve oil recovery. Positive results from the trial led to a decision to adopt this approach.
In April 1985, it was also decided to extend waterflooding to the Danian structure using the same equipment as with the Cretaceous formation.
Ekofisk 2/4 K was installed alongside 2/4 B in 1986 to inject water in the northern part of the reservoir, and Ekofisk 2/4 W was installed on a bridge support south of Ekofisk 2/4 FTP for injecting water in the southern area.
Ekofisk 2/4 B and 2/4 K were integrated operationally in January 1995 as Ekofisk 2/4 K-B. Both platforms were thereafter run from the 2/4 K control room.
One of the 2/4 B derricks was removed first, followed by the second in 1997. The 68-bed accommodation module was taken away after 2/4 K had been installed. A bridge now connects the two platforms.
Three oil and gas pipelines of 10, 18 and 22 inches respectively connected 2/4 B to 2/4 FTP. An eight-inch Coflexip umbilical was laid to 2/4 C in 1985. The platform weighs about 12 000 tonnes.
An uncontrolled blowout of oil and gas occurred from 2/4 B in April 1977. Well B-14 needed a workover, which meant pulling out the 3 000 metres of production tubing. The blowout preventer failed during this operation, and it took a week to bring the well back under control. See the article on the Bravo blowout in the history section.
The process comprises two identical production separators (each 12.2 by three metres) in parallel and a test separator (6.1 by 2.1 metres). This equipment was designed with a view to supplying crude oil from the reservoir to 2/4 FTP.
Of the 24 well slots on the platform, 22 were drilled and completed for this purpose and two held in reserve. These wells delivered a mix of crude oil and natural gas through the production manifolds or a test manifold. Output was piped directly to 2/4 FTP.
With each of the 22 production wells, casing and production tubing was set from the wellhead and through the reservoir. Seated on the casing, the wellhead provided a system for controlling pressure in the tubing.
Driven by pressure either from the reservoir or provided by injection support, the crude oil and gas flowed up through the tubing to the wellhead.
On top of the latter was a set of production and work valves known as an Xmas tree, which controlled the wellstream as it flowed to the manifolds and was also used to shut in production.
Each wellhead was equipped with the following valves.
Downhole safety valve
This hydraulically operated ball valve stood far down in the production or injection well. It closed automatically (fail-safe) if the hydraulic pressure was lost.
A line for hydraulic fluid accordingly ran from the wellhead to provide the pressure required to open the safety valve. When the latter closed, the well was shut in and all equipment on the platform was isolated from the pressure in the well.
Faulty installation of such a ball valve was one of the reasons for the Bravo blowout in 1977.
Manual and automatic master valves
These sat in the vertical section of the Xmas tree. The automatic (upper) master valve was kept open by hydraulic pressure. Supported by the manual (lower) master valve, it formed the second barrier against pressure in the well. During the Bravo blowout, this valve was also incorrectly installed and was a direct reason why the well could not be shut.
utblåsning, blow-out, 1977, ulykke,
Manual and automatic wing valves
Flow wing valves for production were positioned in the four-inch horizontal section of the tree and connected to the choke. These are the valves normally used to shut down a well.
These were designed to cope with a substantial pressure drop. They were used to regulate oil flow and pressure to the production and test manifolds.
Kill wing valve
This allowed diesel oil to be injected into the wellhead in order to increase pressure in the production tubing above the downhole safety valve. It could also be used to inject various chemicals during maintenance of the wellhead and the main pipelines.
A pressure gauge was installed on the Xmas tree to measure well pressure.
Three manifolds were used on 2/4 B to integrate flows from the various wells for delivery to the main pipelines. Two had larger diameters in order to accommodate the main production stream, while the third was narrower since it received the flow from a single well for testing.
During normal operation, output from all the wells was conducted to the two production manifolds and on to the two main seabed pipelines connected to 2/4 FTP. The flow from a well being tested was diverted to the test manifold and through the platform’s test separator.
This system was designed to import gas by pipeline from 2/4 FTP. Its pressure was then raised for continuous injection into the wells in order to “lift” the oil and boost the production flow.
Two different operational settings were built into the system – initial compression and gas lift. The first was used to initiate lift and required higher pressure than the ongoing operation. Once initial compression was completed in a well, the latter switched to continuous gas lift. This required less pressure but more gas. The settings could be used simultaneously.
The system comprised two gas scrubbers to remove possible residual liquid, a four-cylinder compressor for raising gas pressure, a motor fuelled by natural gas to power the compressor, and separate manifolds for initial compression and gas lift.
Production from each well had to be tested to monitor reservoir/well conditions and to check separation/treatment. A good monitoring programme was also needed for waterflooding, so a permanent test separator was installed. Its design was based on a vertical cyclone principle.
Utilities on 2/4 B included systems for telemetry and communication, safety, hydraulics, electricity generation, fuel and lube oil, instrument and work air, and chemical injection.
Other facilities covered pig launching, seawater, jetting and fire water, untreated seawater and drinking water, gas flaring and venting, oil recycling, steam generation, and cranes and lifting.
Published 30. March 2019 • Updated 23. October 2019
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
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.
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.
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.
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.
Published 29. July 2019 • Updated 22. October 2019
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
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
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.
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