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
Kjersti Melberg, Norwegian Petroleum Museum. Based on an interview with Kristensen on 12 September 2019.
More than forty-five years of service on Ekofisk underpin Knut Ove Kristensen’s status as a pioneering leader on the Norwegian continental shelf (NCS). His involvement began in 1974 when he switched from a career at sea to become a process technician for Phillips Petroleum.
— Knut Ove Kristensen in conversation with process apprentice Fredrik Svindland Theissen (left) and operations manager Siri Friestad. Photo: ConocoPhillips
Early promotion and trust followed, and he served as an offshore installation manager (OIM) for more than 33 years in the Greater Ekofisk Area.
Kristensen recalls that he was a committed young man in the early 1970s – an open, curious and plain-speaking person who was not afraid to criticise health, safety and environmental (HSE) conditions.
The working style he encountered offshore suited him well, ready as he was to speak his mind. “I’ve undoubtedly been a loud-mouth. I’m used to having zealous people in the Family With grand-parents and a father who served as mayors, which is perhaps why I don’t quite know when to keep quiet.”
Thinking back to working conditions when he started in petroleum industry, he recalls living on Gulftide, Norway’s first production facility, and says it was fascinating.
“This was an old jack-up rig, with the helideck installed on planks. We were four to a cabin, and things were pretty shabby. Primitive conditions prevailed, to put it mildly.”
The workplace at the time was characterised by the presence of the Americans, and confusions frequently arose between them and those who were not particularly good at English.
“It was very unusual,” reflects Kristensen. “We were trained up by the Americans, of course – they were the ones who knew about this business.There were a lot of misunderstandings among the Norwegians, people who pretended to understand the messages they were given about what jobs to do. Both serious and funny situations occured. Those of us who’d been to sea undoubtedly had an advantage in that we knew the language a bit better. The rest were fishermen and smallholders and ordinary people from the Districts in Western Norway who didn’t speak much English. Offshore terminology wasn’t easy for people who didn’t have the language.”
He quickly grasped the ethos in this working environment. “The Americans often only gave you one chance. If you showed that you could cope withyour job, you won trust, new opportunities and more responsibility.”
Given his background in the Norwegian merchant marine, however, Kristensen reacted negatively to a number of the conditions which prevailed at the time.“I was one of the youngest then, and that wasn’t always easy because there were a number of older and more experienced people who felt they had a ‘monopoly of brains’,” he comments. “And quite a lot were pushy.“Working conditions weren’t orderly, with proper employmentcontracts like I was used to from my time at sea thanks to the Norwegian Seamen’s Union – unionisation and the like.”
He adds that he is grateful for everything he learned from the Americans, but that they at the time were not particularly keen on unions and the Norwegian concept of collaboration between employers and employees.“They thought it was enough to enter into agreements on a man–to–man basis or with the company, and saw no need to organise this via trade unions.”
Given his views, it is not surprising that he became involved at an early stage with the Ekofisk Committee by serving as secretary to Øyvind Krokvik, who was first head of this union.
Kristensen explains that he has been committed throughout his career to involvement and worker participation and to good collaboration between unions, the safety service and management.That was particularly important during the early years of the petroleum industry on the NCS, he emphasises. His experience of union work accompanied him into various senior posts on Ekofisk.
With a gleamin his eye, he says the following about his promotion: “Acquiring managerial responsibility early on may have had something to do with my involvement with the union.“Putting in place systems for worker participation and collaboration was particularly important in the early years of Norway’s offshore industry.
“I played a part in establishing the parameters which govern industrial relations out on the field today, with unions and the safety delegate service.
I became the country’s youngest OIM at the age of 24, and served as a manager out there for 41 years.
They may have thought ‘he’s more trouble than we need, so we’ll just promote him up and then be quit him’.”
Kristensen reports that he has been preoccupied throughout his managerial career with ensuring that “things are genuine” – that a manager must understand and personally be part of “the home team”.He explains that as the ability to understand a position from the standpoint of the various parties involved, and adds that he has thrived offshore with a living and working community.This he defines as one “where you get close to people, where everyone is seen and heard, and where they understand that they play an important role in reaching a common goal”.[REMOVE]Fotnote: Pionèr, ONS 2018: 8.
It did not take him long to learn how to adjust his management style to the offshore environment, but admits that this approach has developed over the years.“The leadership culture which dominated on the platforms during the early years undoubtedly influenced me a bit. I was probably very inflexible and saw things in black-and-white, but have become more judicious and considered over time.
“Nobody left my office earlier in any doubt about what I meant. I thought that saved a lot of time. But I can’t have been too bad, or I wouldn’t have held down the job for so long.”
Kristensen’s long service makes him uniqueon Ekofisk, and he has thought a lot about management. His expressed strategy has been to get people on side over HSE through commitment and integrity – and without any “second agenda”.
“Working in the Ekofisk Complex with 600-700 people is an unusual experience,” he observes. “I held the same job as the man in charge for 20 years. “That means you’re ‘on stage’ the whole time, and attend 10-12 HSE meetings every week. You’ve got to get people committed, drive a doctrine and sell a message.”This involves getting what people have to concentrate onimplanted in their hearts and minds so they can contribute to their own safety and that of others, he explains.
“You must be genuine, and your own integrity must be order. You have to build trust, and not least display respect for your audience.”
“What’s been a powerful help for me is that I’m on the home team. I’ve been a skilled worker myself and have been through most things.”
Kristensen emphasises several times that he regarded the unions, their elected officers and the safety delegates as a resource in this work.
“The tripartite collaboration pursued in the petroleum industry between government, companies and unions functions very well,” he concludes.“This is about informing and involving people, and ensuring that decisions aren’t taken over their heads. Our company has achieved that in a positive way.”
“The fact that Ekofisk is a mature field and ConocoPhillips is a mature company also has something to do with it. Cooperation with the Petroleum Safety Authority Norway and other authorities is also very good.”
Kristensen denies that union-management collaboration has become more strained during the downturns experienced by the petroleum industry.“Strained and strained – we must adjust to external conditions and try to protect thejobs needed tosafeguard the industry. But nobody’s ever been made redundant by this company. That’s worthy of respect. “
“Downsizing has been solved with severance packages. People have often been given early retirement. From that perspective, it’s been a privilege to work for an operator company.”
After almost 46 years with the company, Kristensen’s commitment to continuous improvement, good safety and high production regularity is as strong as ever.Recognising that substantial progress has been made in the HSE area over the years he has worked in the industry, he affirms that this issue is closest to his heart.
“We’ve staked out the path as we’ve advanced. We don’t accept incidents and accidents. We take a completely different approach to risk today. Accidents which do occur are used for all they’re worth in aneffort to say to ourselves: ‘this has actually happened, but it’s our duty to learn from it’.”
Kristensen has personally experienced accidents and injuries at close hand, and thereby knows the importance of preventive safety work to protect people, the environment and equipment.
He will never forget some incidents – and immediately mentions the Alexander L Kielland disaster in 1980 With 123 casualties. An article in local daily Stavanger Aftenblad as recently as 2012, with photos of all those who have died on duty on the NCS since 1966, made a big impression on him.
Britain’s Piper Alpha explosion in 1988, when 169 people were killed, is another major incident he recalls. His conclusion is that the petroleum sector has not been a Promised Land for all.
The former OIM proudly mentions a number of HSE improvements which have partlybeen the result of technological advances in the industry during his time.But he warns about hazards which still exist, such as vessels drifting out of control. A well-known incident on New Year’s Eve in 2015 made a particularly strong impression on him.
A 150000 tons, unmanned barge had come loose and was threatening to collide with installations on Ekofisk. Several hundred workers from this field and neighbouring Valhall were flown to safety and production was shut down.The barge passed the platforms at a distance of about one nautical mile, but Kristensen found the actual incident and the threat it posed frightening.
“Drifting vessels which come loose in rough weather, which can get pretty challenging out there, are perhaps the biggest hazard we now face. Luckily we have good procedures to handle such challenges.”
Such incidents and near-misses are regarded by Kristensen as a reminder that the petroleum industry is under an obligation to learn the necessary lessons.He points to the potential for learning from other industries, and emphasises the good collaboration which prevails across the company. Mechanical handling provides a good example, he says.
“Things can go terribly wrong. After fatal accidents in the 2000s, we established a work group which held monthly meetings. I took part as technical manager for these facilities.We involved everyone in the logistics chain on land, at the base and on the platforms. That attracted so much attention and such great improvements that we’ve now managed to prevent virtually all undesirable conditions in this area.”
Despite good systems and routines, colleagues on the installations are Kristensen’s most important reminder of the responsibility he has had as an OIM on Ekofisk.
“Experiences frommy early years meant that I have become particularly attentive to HSE – and I was involved in quite a lot, of course.But this mostly relates to the individual who gets injured on your watch and on your shift – in other words, the people you work with.They stood on the drill floor and worked so that the sparks flew around their ears. Having only two-three fingers used to confer ‘status’.”
He notes that improvements have a lot to do with technological progress. Much risk has been eliminated by automating a great deal of the work which used to be done manually.
“But we still have more than enough opportunities to injure ourselves. This has a lot to do with awareness – being present in the real world, making sure you’re focused. That’s actually expected for 12 hours at a time.”
A respectful attitude to his big responsibilities and duties was maintained by Kristensen to his last working day. “Emergency preparedness is like being at war – you do what you’re told.But you feel it. Although we’ve trained so long at this, you’re still conscious of being responsible for several hundred lives. Taking a wrong decision could …You must act on the basis of the information you’ve got, not what you know many months later. When you tackle it, however, you get a sense of mastery at solving the problem together with an outstanding emergency response organisation on land.Ultimately, though, you’re the skipper on your own ship.”
Time to reflect
Kristensen has finally retired from ConocoPhillips, giving him time to reflect over his own commitment and lifestyle offshore as it affected him and his family.
“For my own part, I must say that it’s had a price,” he admits. “I couldn’t get involved in politics or organisations, for example. I was only at home half of the time. I followed up the kids when I was at home, of course, but never felt I could be active in associations and so on, contribute the way I’d have liked.”
He has found the transition to retirement unaccustomed in many ways. “Simply remembering that I’m not going offshore is a big change, for example.I had to deal with so many challenges right up to my last day at work that it’s been impossible to prepare anything. I ought to have thought about and planned retirement a bit better, of course, but I’ll undoubtedly find something to do when I want to.”
Published 21. October 2019 • Updated 25. October 2019
The aim of this facility – an extension to the Ekofisk South project – was to increase waterflooding on the southern flank of the Ekofisk reservoir in order to maintain oil and gas production.
An amended plan for development and operation (PDO) of Ekofisk South was approved by the Ministry of Petroleum and Energy on 7 September 2017.
This involved installing a new seabed template with four water injection wells, and represented a continuation of the well-established Ekofisk production strategy based on waterflooding.[REMOVE]Fotnote: https://www.regjeringen.no/no/aktuelt/okt-utvinning-pa-ekofiskfeltet/id2570011/.
The template was installed in September 2017, with a technical solution similar to that used on the seabed facilities already installed – Ekofisk 2/4 VA and 2/4 VB.[REMOVE]Fotnote:Pionér, no 2, ConocoPhillips, 2018.
In addition to the structure itself, including wellheads and Xmas trees, the installation comprised control modules with umbilicals connected to the existing waterflooding system.
The 2/4 VC facility receives injection water from Eldfisk 2/7 E, while power and control signals come from Ekofisk 2/4 M. It is run from the Ekofisk 2/4 K control room.
When fully developed, overall injection capacity for this subsea installation will be 80 000 barrels per day through the four wells.
The water pipeline and umbilical to 2/4 VB were extended to 2/4 VC. Well operations on the latter began on 24 May 2018 with a view to starting injection before the end of the year.
Published 15. October 2019 • Updated 15. October 2019