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Topic 32: Decommissioning of aged Platforms and Pipelines in the North Sea - Risks and Challenges

victor.adukwu's picture

The North Sea’s aged offshore oil and gas platforms and pipelines is
approaching a new phase in its operations during which it will be necessary to
decommission some of them, many of which have been producing oil
and gas for over 30 years.


Frixos Karletides's picture

In upcoming years, offshore oil and gas
installations and pipelines in the North Sea are going to be decommissioned
since they came close to the end of their useful time. Decommissioning carries
the same risks and challenges as with marine construction, therefore special
consideration must be presumed in safety, the environment, economic and social
aspects. Some challenging tasks to be accomplished in decommissioning are:

The removal of heavy structures from complex working environments

 Ensuring stability of partially
cut structures

 The removal of pipelines

Handling and storage of potentially dangerous materials and components

In some cases due to safety reasons, some
structures might be allowed to remain in situ, like some concrete

Frixos Karletides

Frixos Karletides's picture

Due to the significance of an oil decommissioning
platform, the Department of Energy and Climate Change (DECC) has the
responsibility to ensure that a decommissioning practice must be accomplished
safely according to The Petroleum Act 1998. This Act is divided into five parts
having part 4 to be related to decommissioning. Part 4 highlights legislative responsibilities
with references where further guidance can be obtained. As a final point it can
be stated that maintaining compliance to decommissioning legislation is a significant
factor in order to minimize risks. Those responsible for decommissioning must
partner with experts that have the strategic knowledge and experience to carry
out this task. As with all legislations if the regulations are breached, then
there is probability of large fines and penalties.     

Frixos Karletides

Oluwatosin A. Oyebade's picture

Just to add to Frixos' point, I would like to make a few suggestions on the approach for assessing the risks associated with decommissioning of offshre facilities in the North Sea.

 With exploitation of oil and gas going on in the north sea for over 30 years and the production facilities reaching the end of their service life, there is need to close down and abandon the production area. The main target of decommissioning is simply to remove and dispose the production facilities to the largest extent feasible. For complicated and costly decommissioning activities it is beneficial, if not mandatory that all significant risks are identified and appraised on an overall and theroretical unified basis. A vital stage in planning decommissioning of an offshore production facility is to quantify the associated risks in terms of;

  • Risk to personnel
  • Risk to environment
  • Economical Risks

The ideal decommissioning option can then be chosen based on this assessment. But care should be taken in demonstrating and documenting the different options compared and the risks linked with the decommissiong to the different parties of interest. A clear illustration of this breach is the Brent Spar controversy which is an example of Risk communication gone wrong. As Risk Assessment is usually employed in providing decision support in connection with design, constrcution, installation and operation of offshore production facilities, it should also be benchmark in decommissioning activities. It should be performed by considering the individual activities isolated, and then subdividing it such that the structural reliability, process safety and operational risks, including human and organiszational errors are evaluated and assessed seperately.


Oluwatosin Oyebade.

victor.adukwu's picture

With many of the North Sea platforms and pipelines in their aging phase, making provision for the eventual decommissioning of offshore installations has assumed increasing importance for well operators. As the number of offshore platforms installed from the early 1970s and '80s are due for decommissioning, the need to get it right becomes more pressing. In the recent past, the issue of platform and pipelines decommissioning has brought up a considerable debate regarding issues of the environment, worker safety, technology and cost, especially when it has to do with the demands of dealing with the very large platform structures and scattered pipelines in the deep and unpleasantly rough waters of the northern North Sea.

Although decommissioning redundant offshore facilities is governed by a strict legal framework encompassing international, regional and national legislation, in the end it falls to the industry to develop approaches which enable these often conflicting factors to be balanced. The situation is not without its own irony. In the early periods when many of these platforms and pipelines were initially constructed, they were widely recognised as breakthrough in offshore engineering; today, the industry's technological challenge lies in removing them.


Menelaos Michelakis's picture

(Adding information to Frixos Karletides and victor adukwu's post) (Similar problems in other areas and possible solutions)

De-commissiong and abandonment of offshore installations is becoming a growing industry where old installations exist and must be removed. For example, in the Gulf of Mexico, there are more than 400 installations in excess. Obviously, aging of the North Sea english sector platform and pipeline system is not unique. There are also too many old installations in Indonesia and Middle East (similar problems)

When the installation is not huge and the jacket can be removed safely, (onshore installations or installations on shallow waters) then the jacket is cut and removed to the coast. This is a very common technique. Especially, for areas like the Gulf of Mexico, where the installations are not as big as the installations of the North Sea.

When the installation is too big to be removed safely, and in areas that are far away from the coast, the most common solution is detonation. Explosives are used, (after removing useful things), and the platform goes to the bottom of the sea, so it is not a problem for shipping and no dangers can occur for the company.

The solutions, i described briefly, are the most common used and much information can be added. In the North Sea sector,the situation is much different than the situation in the Gulf of Mexico. Platforms are much fewer and much bigger, something which favors detonations. But we have a project on this thing and and detonation is not a good idea to collect marks, we must seek for something innovative !

Ref : An.Mather, Offshore engineering - An introduction (second edition) 

Deinyefa S. Ebikeme's picture

Over recent years, decommissioning of platforms and pipelines have led to considerable debate regarding issues of the environment, worker safety, technology and cost, especially when it comes to considering the demands of dealing with the very large structures in the deep and inhospitable waters of the northern North Sea (1).

One thing we are sure of, is that the technology and experience required to remove these installations are available as done in shallow waters of the gulf of mexico with some scale-up needed to face the wild conditions of the northern North Sea(2). But among these challenges, cost of decommissioning which runs into billion of GBP as estimated notable economic analyst(2) take the centre stage of them all because the cost of decommissioning was not considered, planned for and included in the design phase of these mature oil and gas field installations (eg Brent spar oil storage facility)(3).

So this has lead to operators and merchanise (investors) looking for alternatives to optimise this cost such as reuse/ life extension as in the case discussed in the HSE Key Programme 4 which take a look on life extension base on the level of knowlegde (known) of these platforms and also technology transfer (geothermal energy extraction system).


  3. Brent decommissioning project Event: "Front End Engineering in the Decom World"

Deinyefa Stephen Ebikeme IBIYF

Ajay.Kale's picture


Dispose of the redundant will be the biggest challenge from Greenpeace despite having all regulatory approval.

The old installations in early 1970 - 80, are not designed to have a concept of reverse engineering (decommissioning)

so it is big challenge to decommission those installations.

The other challenge will be decommissioning of installation without any disruption of production if facility is connected to other oil small fields.

Shortage of required skill personnel to decommission offshore facility 

Hydrocarbon cleaning and disconnections of other facilities.

How to remove redundant subsea pipelines.

For GBS (gravity base structure) it is very difficult to decommission.


Negative reputation for the operator if some decommissioning work left which will cause a concern for environment.

If you leave behind some structure/pipelines (i.e GBS) of facility in at place then what is long term impact on environment

Chances of oil spill (Reputation damage for company) 

Lee Soo Chyi's picture

According to DecomNorth Sea news [1], The North Sea oil and gas industry is
forecasting a programme of decommissioning across the next 30 years, requiring
expenditures estimated at GBP 25 to GBP 30 billion. Indeed, this is massive
amount and demand. A billion dollar programme will require all available
resources, such as engineering contractors, operators, facilities, specialist services,
safety and environmental specialist and so on.  The challenges are safety, environment, cost
and technical. A cohesive approach is needed to ensure effective management and
mitigation of various risks.  ‘Reduce, recycle and re-use’, this is
the target that decommissioning project trying to achieve. If economic,
environmental and social factors can be satisfactorily balanced, re-use all or
part of redundant oil and gas production facilities would be an ideal option.







Soo Chyi, Lee

Adekola Obayomi's picture

Indeed, the challenges of decommissioning the old and heavy fixed offshore platforms as highlighted by most of the comments above are numerous and risky; this maybe one of the reasons why the use of Floating Production Storage and offloading (FPSO) vessels are becoming common.  Most of the installations associated with oil and gas fields where FPSOs are used are in modules and heavy lift vessels are not required to decommission these subsea equipment.

Also, The summary of the Ivanhoe and Rob Roy  fields decommissioning preparatory work in the North Sea submitted by Hess limited to the Department of Energy and Climate Change (DECC) [1] show that decommissioning of subsea fields tied back to non-fixed platforms can be more environmentally friendly than fixed offshore platforms.  The following are some of the advantages that can be seen from the proposed programme:

  •  Mooring chains can be recovered and recycled;
  •   Anchor piles can be cut to about 0.6m below seabed;
  •   Subsea Christmas trees can be removed for re-use or recycling;
  •   Wells can be plugged and the casing strings cut to about 3m below the sea bed;
  •   The non-fixed production platform can be relocated to another field.

In 25-30years time, when most of the shallow wells have been depleted and most oil and gas exploration installations have gone further and deeper, decommissioning costs will still be huge but they will be more practically achievable due to the increase in use of non-fixed platforms and reduced modular lift loads.


Maria Christou's picture

Yes decommissioning platforms has a lot of risks as my
classmates mentioned above. On the other hand, decommissioning platforms can be
beneficial in certain sectors.

 This process provides
people with jobs opportunities and most importantly it brings the potential to
develop various novel technologies. According to Mr. Duncan Griffiths, sales and marketing
manager of CUT UK:  ‘Innovative cutting technology was developed
specifically for the North West Hutton decommissioning project’.

Additionally, the California Resources Agency
(CNRA) and California Department of Fish and Game (CDFG) suggested cleaning up
the underwater area around the old rig platforms and converting them into artificial
reefs in order to
attract a large number of fish increasing the marine biological

Plus, as Soo Chyi mentioned above, recycling the
reusing the parts of a platform is also a great advantage.

These are just some of the many
advantages that decommission of the platforms offers.



Kyeyune Joseph's picture

Decommissioning is the process of dismantling of subsurface, subsea and surface equipment that had been installed during the exploitation and production of hydrocarbons. Process is necessary so as to meet the requirements of the operation licence and laws of the host country. Several risks and challenges are involved in decommissioning of pipelines and platforms in the North Sea. These may include:
Lack of data about engineering changes over the life of the assets is a serious issue. Some assets specifically in the North Sea have changed ownership over the course of their production lives. Lack of such information is a crucial issue yet it is vital in understanding the structural integrity necessary in planning effectively for lifting operations. Structural integrity poses safety and environmental risks. If asset contains hydrocarbons, this can cause pollution and if not fit for lifting, fatalities can result. Therefore, clear and concise information about structure is vital.
Wastes like asbestos and hydrocarbons either in pipelines or topside modules create not only safety risks but also environmental threats which if not well addressed can be disastrous.
Marine movement, breaking containment, use of cutting gases, working at heights, diving and scaffolding are all hazardous activities that are risky to personnel executing them and are capable of causing fatalities.
Fire outbreak during cutting operations, dropped objects during lifting operations and human factors like fatigue due to overwork are all hazards that are risky in nature can be fatal if not well planned for.
Challenges in the whole process can be classified as technological, operational, procedural and environmental. These may include  lifting and transportation of heavy sections, cutting of heavy steel walled structures, acquisition of necessary logistics on time (skilled manpower, equipment), minimisation of risks to personnel involved, acquisition of licence to cease production and decommission, as well as weather interference that usually leads to downtime commonly referred to as wait on weather (WoW) in the North Sea. These challenges and others need utmost attention for the project to remain on schedule.
In summary solving issues associated with numerous risks involved requires a sound hazard management strategy involving a clear risk management plan complimented with good HSE regulation. Additionally challenges need a clear project execution plan with good communication between all parties involved.


White, C. & Adams, G. 2012, "North West Hutton Decommissioning - a Major Challenge…..a Major Success"", International Conference on Health, Safety and Environment in Oil and Gas Exploration and Production 2012, SPE/APPEA International Conference on Health, Safety, and Environment in Oil and Gas Exploration and Production, Perth, Australia, 11-13 September 2012. SPE 156827

Monday Michael's picture

The decommissioning and abandonment of platforms and pipelines in the North Sea are guided by several national and international laws/policies/treaties. One common denominator with these laws is that they all favour the 3 principles of re-use, recycling and final disposal on land, as noted in the post by Lee Soo Chyi. This is the thrust of the OSPAR decision 98/3 [1]Safety is such a huge issue in the decommissioning and abandonment process, just as it is at the construction and installation stages because it involves lifting of heavy sections of the topside modules and pipeline sections. The outbreak of fire is another safety concern as the decommissioning process involves cutting large sections of topside modules and pipelines into smaller and manageable pieces. The sparks from the cutting process could come into contact with residual hydrocarbon and result in a fire. As an aside, a solution to this is the use of Diamond Wire Cutting System (DWCS) [2]The use of explosives to decommission platforms pose the risk of creating shock waves in the surrounding area and this could topple fishing vessels, ships or other platforms in the vicinity in addition to the wanton loss of marine life. Also there could be undetonated explosives which could pose an even greater risk in the future users of the area [3]
The main challenge in the decommissioning process is the environment, especially to coral reefs and fish. Whatever method used in the decommissioning process poses a huge strain on the surrounding environment and this will naturally incur the wrath of the host community/government and indeed environmental charities such as Greenpeace, Friends of the Earth, etc. For example when Shell planned to dump/sink the Brent Spar storage facility in the North sea after it was found to be of no use, Green Peace objected to it and occupied the site for weeks and the stand-off eventually paid off [4] [5]. Decommissioning and abandonment should be in line with article 60(3) of the guidelines set by the United Nations Law of the Seas treaty [6]
One positive that can be taken from the decommissioning process is the creation of artificial reef, which is a submerged structure deliberately placed on the seabed to mimic the characteristics of the natural reef [7]. This concept has been dubbed rigs to reefs and research has shown that fish levels around active platforms is 20-50 times higher [8]

[1] [5]


In case of subsea facilities, these are
should be retrieved first and then will be evaluated whether will be used for
re-use or recycle for any other purpose. We can see the detailed work process
for individual facility;

: As a well barrier, plugging well should be a first
job before retrieval. Once production tubing is retrieved and permanent
plugging is settled e.g. cementing in conductor. Tree could be retrieved and
well head also. Remained conductor should be leveled with certain height e.g.
3m below from seabed. If it is above seabed, trawl could be caught by them.

Manifold: Make the system with hydrocarbon-free and retrieve piping module
connecting with rigging first considering capacity of crane. If remained
foundation structure is not able to retrieved physically e.g. pulling-out suction
pile is required for enormous power, cutting structure makes the certain level of
height e.g. 3m below from seabed.

Pipeline/Umbilical: The method is categorized with 2 types, leave in situ and completely
remove from seabed
. Environmental impact on leave in situ is not significant
but cost for removal is relatively huge because of using construction vessels.

I wonder decommissioning concept ‘reuse’
could be applied for subsea facilities for a real project. As you know, subsea facilities
are required for high reliability because of high intervention cost. Anyway, it
could be evaluated by operator / vendor from factory test for retrieval facility.







sreehariprabhu's picture

As my friends commented, decommisioning have certain advantages like the invension of new technologies, more job opportunities etc but at the same time it is very challenging and involves high risk. When decommissioning, the technical attributes must be studied well and also measures must be obtained to carry out safely. If they are not studied well, it may lead to unfortunate incidents. One example is the blowout caused while Total decommossioned their Elgin platform. They where forced to evacuate 238 workers off the platform and the gas spew for more than 2 weeks while costing $2.5 million per day. This example shows how important it is to carryout decommissionig safely.

The major problems that decommissioning arise is the environmental issues. A gas leak or oil spill can cause a huge environmental issue and thus lead for a debate on decommissioning. Other problem will be Engineering hazards. Since a lot of huge structures has to be dismantled, atmost care should be taken that they are carried out safely. Any problem occured can lead to danger for personnel working on the platform. While decommissioning, it should be properly planned. The planned order in which the decommission is carried out helps to minimise risk and ensure safety. Many operations will be going on in the platform. This include dismantling of structures with heavy machineries. The picture below shows a heavy machine used during decommisioning. It can cause many risks including dropping of objects, clash with the structures etc. This shows how carefully a decommission activity must be carried out.

Offshore decommissioning contract in the British sector of the North Sea 

Reference :

Sreehari Ramachandra Prabhu

Ikechukwu Onyegiri's picture

All comments addressed on this issue shows that industries operating on the UKCS are in dying need of innovative technologies to create safer means of decommisioning aged non-econmical platforms.

The technicality in such processes as are included in decommissioning pose in a dreaded challenge which can be summarized as the non-transferability of engineering concepts and technologies used over 30 years ago to technology used today (reverse engineering principles). Most platforms face challenges such as weight and mode of installation. For example, gravity based concrete installations till date have no layed out methodology for removal without causing catastrophic damage in the process. Also a financial challenge is attached to these structures especially when located in marginal fields. While the North Sea area only includes about 7 percent of the total
number of platforms, these account for about 60 percent of the worldwide decommissioning costs. This is due to the weight and
complexity of those installations, as well as the severe weather conditions making removal and disposal operations time consuming and
difficult [1].

In the midst of these challenges, stakeholders have ventured into innovative technologies to reconvert these platforms to serve other purposes aiming at profit generation in the process. One can only hope that these new alternatives don't yield further safety and relability issues.


[1] Decommissioning Technology Challenges: Peter H. Prasthofer, Offshore Decommissioning Communications Project (ODCP)/ EXXON Offshore Technology Conference; Offshore Technology Conference,
4 May-7 May 1998,
Houston, Texas

Ikechukwu Onyegiri


Oil and Gas Engineering

Siwei Kang's picture

To date, decommissioning of offshore facilities have been progressively increasing the concern of oil&gas companies and government. In North Sea, many platfroms are aging and approaching the end of service. From 2008 and 2009, North West Hutton, the biggest fixed steel jacket being dismantled, was successfully removed. Based on the previous decommissioning experience in North Sea, some risks and challenges are still facing.

The challenges can be generally conclude as follows. Normally, all decommissioned platforms have been served more than 15 years. That means electronic data systems were not used when it's as built. As there had been engineering changes during its production, it is hard to get accurate data of platforms when decommission, which can be the biggest challenge. Actually, this problem is not only for North Sea, but also happened in other regions. Secondly, in North Sea, concrete gravity platform is another common installation except jacket. How to decommission concrete platform is still addressed. Many uncertaties like refloating are facing. 

As mentioned by my classmates above, many risks are need to be considered during decommission. Here I would like to condense into severals. Firstly, harsh environment is a big problem in North Sea. As far as I am concerned, decommission is harder than installation, especially the weight control for topsides during lift, and subsea cutting for jackets. These requires excellent operation weather. Secondly, HSE management is still hard to carry out because many activities are involved during decommission, like lift, scaffolding, diving and explosive equippment dismantle. According to Caroline White's report(BP), 3 fatalities across a number of decommission activities are reported between 1992 and 2003. 

In general, compared with other regions worldwide, decommission in North Sea is full of risks and uncertanties. 


Reference: Caroline White, North West Hutton Decommissioning, SPE conference paper, 2012


Uko Bassey's picture

Decommissioning of aged pipelines and offshore structures in the North Sea is a regulatory requirement which must be complied with as provided in the petroleum Act 1998. Like every other project, there is a decommissioning programme which contains all the activities to be done during the project and a comprehensive assessment must be carried out. Assessment proposal must submitted to the department for business, enterprise and regulatory reforms for approval, this proposal contains all the planning, schedule of activities, pre and post decommissioning surveys, monitoring, contractors and machineries/equipments to be used, cost implications, adequate environmental impact assessment, risks anticipated, amongst others. Different methods of decommissioning are available with various degrees of risks, costs, machines and advantages, etc.

Decommissioning has so many challenges which include but not limited to:

1.Risk to personnel – there is a serious danger of fatality and potential loss of life.

2.Environment materials management, CO2 emission, impact on aquatic lives, aesthetics, energy consumption, discharge to Sea, impact on free passage, littering, etc.

3.Cost - heavy cost implication which runs in multi million pounds.

The choice of the method to be used must be carefully selected after considering all the risks, advantages, disadvantages and cost to strike a balance. There are instances that the anticipated risks in the decommissioning are so high such that fully decommissioning of the structure becomes undesirable that only topside structures are decommissioned, in which case it must be justified and adequate approval granted as seen in the case of Total E & P, UK MCP-01 (Manifold and compression platform no. 1). 

Ref: (Assessed November 3, 2012)

UKo Bassey

Subsea engineering

Elvis.E.Osung's picture

 The cost of decommissioning oil and gas installations is quite humongous, the Brent decommissioning lecture gave me a different view to decommissioning costs of platforms. It’s easier as an organisation to allocate billions to the construction of infrastructure knowing that invested resources will be gotten back but spending billions to decommission is a different ball game.The issue of decommissioning cost makes it very pertinent to include cost of decommissioning in the initial planning of installations or better still come up with approaches that cost less to decommission which is part of the recent increase in the use of FPSO's.An alternative approach to reducing the cost of decommissioning pipelines is the reuse of pipelines in carbon capture and storage. The North Sea (Scotland) already has well developed oil & gas pipeline infrastructure which has served the oil and gas sector for several decades and offers significant potential for re-use in the development of CCS

Samira Bamdad's picture

Decommissioning is a time consuming activity consists of various
tasks including project management, engineering, inspection, planning and
offshore decommissioning activities and with each activity there are risks and
challenges attached.  

Inspections required prior to and alongside with the decommissioning
process of an offshore asset, is one of the important and expensive part of the
job. The purpose of inspection is typically to identify areas requiring further
material sampling, decontamination and waste removal.

But not always enough budget is available to carry out the
inspections up to the required frequency and it consequently increases the risk
of failure. It should be noted that many of offshore assets has been
abandoned for a few years before the decommissioning and it results in a
considerable lack of data and higher risk of decommissioning. Allocating sufficient
financial resources to achieve a safe decommissioning process is a real financial
challenge in a dying project. 

Ekaterina Pavlichenko's picture

  When these Oil Platforms where built it was clearly with the intention that they would be around for a very long time and obviously costs to the Operator for decommissioning these are going to be eye watering to say the least. However, this doesn’t need to be the case in all circumstances and following a process of ‘reuse and technology transfer’ may result in offsetting a greater portion of the costs associated with decommissioning activities. 

  With around half of the North Sea’s 600 old oil platforms being made of steel, it would seem that for the majority of these they will be cut up and shipped to shore when there time comes for them to retire, however some of these will be made of concrete or located in areas where this activity may be considered dangerous and other options, such as installing wind powered generators and using them either as off sea power stations or to power small desalination plants are both viable life extension concepts. In this we are only limited by our imagination and just because their original role may be over, it could indeed herald the start of a rebirth and a new life totally different from that originally envisaged. 

faizakhatri's picture

Decommissioning of platform in North Sea is vital as it has number of challenges  due to  complexity of  installation in a plat form of many equipment’s like  Rig, Compressor, instrumentation ,long distribution of Pipe bundles  which create picture more dangerous, removal of these aged platform is necessary but just  cut and removing and transport or disposal is not a solution as it has  many factors are associated like weather condition   and environment  consequences  ,technological and operational challenges , cost challenges which is the biggest challenge which needs   new idea to make it happen in near future  a balance with close collaboration  in engineering and planning and consideration HSE strategy and development  along with Material management  as we know mostly plat form made up to stell jacket  by  using method of  Recycle or reuse  as a  good option .

Faiza khatri M.Sc oil and gas engineering

Liu Yishan's picture

The Elgin platform which is operated by Total had an accident of gas leak in March this year. The problem of this platform is that it was reused by a decommissioned old well. The International Energy Agency (IEA) has warned that other operators in the UK North Sea may face the same difficulties as Total in further decommissioning platforms. The cost of this accident is very large that other companies have to deal with decommissioning fields in cautious. The risks of reusing decommissioning wells need to be concerned after the gas leak. Total's experience should be an alarm to other operators that reusing may be not a good idea for some aged platforms.


 Elgin-Franklin platform (Source: Total)



Emmanuel Mbata's picture

The decommissioning industry is in its infancy, but its future potential is evident. As it is with all indusriesm, its has its own unique challenges and risk. During construction of most platforms, there was no intention of removing the structure, this makes decommissioning activity an expensive and challenging activity.

 Besides the cost, so many risks are associated with this activity e.g risk of injury to personnel from subsea work, underwater cutting or structural collapse from overloading could exceed the normally accepted risk criteria, unless these operations can be very carefully controled.

Decommissioning and removal of a complex offshore oil and gas facility is complex and potentially risky opeeration. Any proposed decommissioning operation must seek to minimise the associated hazards and risks to personnel to a level that is as low as reasonably practicable. Such operations will be subject to detailed safety analysis and summarised in the abandonment safety case approved by the appropriate regulatory authorities. 

Adejugba Olusola's picture

This is the main challenge – completing the decommissioning safely and in an environmentally friendly mannner.

Decommissioning is a relatively uncharted territory for everyone including the operators, stakeholders, the regulatory bodies and governments. Environmental Impact Assessments and studies are being completed but there is no full understanding of the health and safety effects of whatever part of the structures are left on the seabed. There is not much experience available to operators – only a handful of decommissioning projects completed in recent history.

Reverse assembly, opposite to construction is a typical method but in some cases, structures will have dilapidated and deteriorated so much that lifting and rigging will be a major challenge due to structural members of offshore platform members/structures suffering from corrosion, wall thickness and reduced strength. There are also other challenges around managing stakeholders, waste management, meeting legislative requirements during and after decommissioning e.g derogation case etc.

Typically, a Dismantlement Safety Case will be produced and updated by the duty holder as per UK regulation to show evidence that all risks and specific hazards have been identified and this also details how those risks will be managed at each stage of the decommissioning process. Issue is that there is no right or wrong answer in decommissioning and all actions would and should be based on technical and economic evaluation of options so evaluations must be sound. E.g leaving structures of drill cuttings in-situ based on demonstrable or appreciable impact on the environment over an extended period of time.

To decommission safely, all options should be considered and decisions based on safety, technically achievable, environmentally sound, and financially responsible option{1}. 


1. Shell Brent E-News. Issue 9 – July 2012.

YAKUBU ABUBAKAR 51126107's picture

There are a lot of risk that are associated with the
decommissioning of an ageing subsea platform and pipeline, the most obvious one
is the health and safety concern of the personnel carrying out the activities like
lifting which is very programme risk due to the loading path and balancing issues,
hazardous substance from the hydrocarbon remain due to the hot work nature of
the operations.  A Lot of diving is involved
to carryout cuttings subsea, poor weather is also an issues to the personnel,
working at height etc.

Another risk has to be with impact on the environment as
decommissioning would involve some discharges to the sea environment that can
effect marine life, Subsea noise and disturbance to the habitant as a result of
rigorous decommissioning exercise, drill cuttings disturbances due to the evacuation
of the debris all of these activities can affect the physical behaviour of the
sea bed.

The major challenges of subsea decommissioning have to do
with the cuttings of large size of structure subsea and the piles. A lot of
times for complete decommissioning an excavation have to be carried out meters
below the mud line in order to cut down the jacket structure which can be a
serious job to do.

Generally decommissioning of structure and pipeline subsea
has a lot of risks and uncertainties associated due to the unfriendly environment

Yakubu Abubakar

Oil and Gas  engr.


JIEFU's picture

Decommissioning heightens risk of leaks
The UK North Sea's dwindling oil and gas reserves will make abandoning wells increasingly common, exposing operators to similar challenges facing French major Total when decommissioning work triggered a blowout, the International Energy Agency (IEA) said on Thursday

"The problem that Total encountered as it decommissioned an old well at the field is likely to portend difficulties at other mature fields in the medium term," the IEA said in its latest oil market report.

The blowout that led Total to hastily evacuate all 238 workers off its Elgin platform - 150 miles off the coast of Aberdeen - over two weeks ago is still spewing gas, while costing the company $2.5 million per day so far.

The next decade will see several fields and installations in the UK Continental Shelf cease production and commence decommissioning, the West's energy watchdog said.

A recent report by Deloitte and Douglas-Westwood says over the next 30 years, almost 500 platforms, 8,000 wells, 4 million tonnes of steel and several hundred subsea wells, manifolds and pipelines will need to be decommissioned in the North Sea area.

"Other companies are sure to look towards Total's experience as an indicator of problems that might occur when routine maintenance becomes problematic for an entire field complex," it said.

Output from fields and platforms surrounding Elgin also ceased following the leak due to safety precautions, including Shell's (RDSa.L) Shearwater platform three miles away.


Experts already believe the regulatory fallout from the ongoing leak will be far-reaching, binding North Sea operators to stricter licensing and safety requirements.

Rating agency Fitch on Tuesday said the European Commission may require explorers to segregate up to 10 billion euros to cover potential environmental liabilities before granting operating licenses in European Union waters.

"That in turn would seriously affect the credit ratings of companies operating in the North Sea and other EU territorial waters," it said.

The latest North Sea leak may bolster EU proposals to strengthen safety requirements for offshore drilling, Fitch said.

The European Commission first proposed requirements in October 2011 for licensing bodies in member states to ensure only operators with "proven sufficient financial capacities" to meet liabilities were allowed to explore for, and produce oil and gas in a marine environment.

The draft legislation could be approved by the European parliament and member states in a few months, despite opposition from UK authorities, Fitch said.

Independent operators will be hardest-hit by a new wave of regulations potentially forcing some to downgrade activities in order to cut costs, analysts from JBC Energy said.

"Such a move may be justified given the poor offshore track-record of the industry but will accelerate the depletion rates in the region, further drying up the liquidity of North Sea crude," including that of the global Brent crude oil benchmark, they added.

"Many of the rigs are decades old and on their last legs with operators reluctant to invest in them beyond the bare minimum," it said.

Evidence suggests that safety checks and maintenance in the UK North Sea are behind schedule, as declining production leads operators into deeper and more hostile terrain.



JIEFU's picture

in its infancy but its future potential is evident. According to some analysts there are over 600 offshore platforms in the UK, of which more than
half are over 15 years old. Approximately 50 of these platforms will cease production completely by 2016 whilst another 250 offshore installations are scheduled to be decomm-issioned over the coming years. Decom North Sea estimates that over the next 30 years all of this work could be worth up to £30bn which would ultimately see decommissioning rival oil exploration in terms of its size and overall impact on the wider
UK economy.
However, the primary challenge with decommissioning is that essentially it still remains a total cost burden for operators. As a result, the need to ensure that projects are managed as cost-efficiently as possible is paramount especially when you consider that recently cost estimates have increased significantly - in
2005 the industry's estimate was £10 billion which then rose to
£30 billion by 2010. In a relatively new business with little room
for error and few examples to follow the challenge facing the
North Sea is not insignificant yet if the region can get this right it will have an opportunity to export this expertise across the world.
To help assuage concerns around the cost burden associated with decommissioning projects, rig operators and contractors need to agree on a commercial framework that makes financial sense for both parties. Getting the right contracting strategies in place from the very outset is arguably the most important step towards reducing costs and risk on a decommissioning project.

JIEFU's picture

The North Sea decommissioning industry may be in its infancy but its future potential is evident. According to some analysts there are over 600 offshore platforms in the UK, of which more than
half are over 15 years old. Approximately 50 of these platforms will cease production completely by 2016 whilst another 250 offshore installations are scheduled to be decomm-issioned over the coming years. Decom North Sea estimates that over the next 30 years all of this work could be worth up to £30bn which would ultimately see decommissioning rival oil exploration in terms of its size and overall impact on the wider
UK economy.
However, the primary challenge with decommissioning is that essentially it still remains a total cost burden for operators. As a result, the need to ensure that projects are managed as cost-efficiently as possible is paramount especially when you consider that recently cost estimates have increased significantly - in
2005 the industry's estimate was £10 billion which then rose to
£30 billion by 2010. In a relatively new business with little room
for error and few examples to follow the challenge facing the
North Sea is not insignificant yet if the region can get this right it will have an opportunity to export this expertise across the world.
To help assuage concerns around the cost burden associated with decommissioning projects, rig operators and contractors need to agree on a commercial framework that makes financial sense for both parties. Getting the right contracting strategies in place from the very outset is arguably the most important step towards reducing costs and risk on a decommissioning project.




Hanifah N. Lubega's picture

Wow, a lot has been said about this, that by the time I was going through the last person's comment, I felt that there was nothing to add but then I thought i should say something. Several risks and challenges have been identified but how best can we overcome them to make the risk as low as reasonably practicable? Well, one may refer to regulations and their requirements, which could be true because there must be environmental impact assessments carried out, description of decommissioning procedures, safety risk analysis and hazardous waste handling among others and approval from the Authority before undertaking the activities but is the industry ready to implement them? It is easy to spend millions of pounds on something that will generate income (an investment) but decommissioning? Are the companies ready for it? Should they be made aware at the beginning of the project implementation? So that easier decommissioning procedures are incorporated in the platform design to ease dismantling?! 

This reminds me of the 98/3 OSPAR decision that gives platforms weighing more than 10,000t in air and concrete installation a derogation to leave the structures at sea. As we move deeper into the sea, these scenarios may crop up often. So in my opinion I think looking for alternative sustainable uses of these platforms like wind energy, flottels, geothermal Energy and carbon capture among others could be a better option of keeping them in use. Drilling technologies could also help in limiting the number of platforms offshore and hence minimising the decommissioning burden otherwise we might find more the big companies selling out to small companies to dodge the high decommissioning costs (don’t quote me on this!!). 

chukwuemeka uzukwu's picture

The E&P industry faces a major
challenge over the next 25 years in being able to decommission over 6000
platforms worldwide in an optimal manner which seeks to find the right balance
among health/safety, environmental, technological, and economic considerations.
This balance needs to be achieved within the confines of a tight regulatory
framework, while also being mindful of public attitudes and concerns. Various
options for decommissioning offshore structures and facilities exist. These
options are driven by environmental considerations, cost, health and safety,
available technology and politics

The costs
of decommissioning are not only the direct costs to the oil and gas industry,
but also involve direct and indirect impacts on the taxpayer and society.

decommissioning of some 6000 platforms worldwide presents a formidable
challenge. In addition to the technological and operational issues, evolving
international and national regulatory philosophy and guidelines, as well as
increased public focus have added to the complexity of this problem.

will continue to design, develop, and improve safe and cost effective offshore
installations, and will meet the required technological challenges. This also
necessitates the ability to assess decommissioning options on a case-by-case
basis, using science and reason, to ensure that the right

balance is
achieved among safety, environment, technical capability, and cost.


Oil and Gas Journal: Industry tackles offshore decommissioning, December 8,

FELIXMAIYO's picture

Decommissioning security and costs have become key factors in oil and gas development, financing and asset trade in the more mature oil and gas basins around the world. They present a particular problem in the UK oil and gas industry, especially in the North Sea. Decommissioning in the North Sea has legislation put in place to govern them. The decommissioning of UK oil and gas assets is primarily governed by Part IV of the Petroleum Act 1998 - this implemented OSPAR Decision 98/3, which was influenced by the Brent Spar platform controversy in 1995.
The UK continental shelf contains more than 500 oil and gas installations, 10,000 kilometres of pipeline and 10,000 wells, together representing estimated decommissioning costs of at least £25 billion. Decommissioning is taking place more slowly, as higher oil prices have meant that ageing equipment has remained in commission far beyond its originally intended shelf life. However, the effect has been to postpone the impact of an enormous burden for the industry over a period in which cost estimates have increased steeply. Decommissioning is an expensive affair hence the need for extension. We don’t know the impact it will have because of aging if proper analysis is not done? Another challenge is managing the environment because the like hood of a spill from the old platform is high. The impact all of us know how a spill can be devastating. Safety to the personnel is a concern too because they are exposed to risks in the process of decommissioning.


VICTOR ETIM's picture

Holistic safety approach is ultimate driver in the current
plan of decommissioning in the North Sea as well as the entire global oil and
gas sector [1].

Reviewing most of the comments on this issue inspires me to
make the following assertions [1];

Best safety 
practice in operations is of critical importance in decommissioning
project plan

Well-developed technological know-how and tested
mechanization that is governed by a “Responsible Safety Attitude” all levels of
the project will make Decommissioning an “attractive and sustainable industry”
which will create competition, promote competence, encourage and inspire viable
investments as well as technological advancements in the oil and gas industry

To attain the above points, all stakeholders
must demonstrate to the later their commitment in the comprehensive risk
assessment, strict housekeeping routes and be pro-actively manage them satisfactorily
through the decommissioning process and post-process in compliance to



[1] Bjorn Sjetnan, AF
Decom Offshore. “Ekofisk Cessation Project EPRD of Platforms,%20AF%20Decom%20Offshore%20AS.pdf;



51126236: MSc.

Giorgos Hadjieleftheriou's picture

Decommissioning of aged Platforms and Pipelines in the North Sea -
Risks and Challenges

Offshore oil platform must be
decommissioned after all the oil has been extracted. This is a costly task and dangerous.
New ideas and designs are nowadays taking place regarding decommissioning. An example
of that kind of new technology is the removal of jackets, the steel substructures
that stand in the sea and support the platform topsides containing the
production facilities. The method is simple but only in theory. It involves the
attaching of the buoyancy tanks to the four corner legs of the jacket and when
the legs are cut the jacket will float and then drugged to the land. Newer ways
and technologies will prevent any hazardous accidents.

OWB \l 1033 [1]





"ENGINEERLIVE," [Online]. Available:




Samira Bamdad's picture

Pontoon columns in the semisubmersible platforms were used
to store hydrocarbon that could have been either for the use of the platform or
part of the extracted product. Hulls in FPSOs used for the same purpose. Even
so those assets, subjected to decommissioning, are not in operation anymore and
the storage tanks are empty of fuels, inside the structures are covered with
hydrocarbon flammable vapour and it impose a high risk of explosion. Release of
hydrocarbon to the surrounding environment after decommissioning is another
risk associated with decommissioning of such structures. It should be either
thoroughly cleaned or the risks and consequences should be accurately evaluated
in advance.   

Neil Fraser James Carr's picture

at case studies of decommissioning,  I believe
the challenges and risk of Decommissioning are extensive especially at the
decontamination stages how ever as far as top side assets go there is a proven
track record of success in this area where skills are carried across from the construction
of these structures. Looking at a waste management company’s claims of 97%
recycling rates it is well worth the risk to re-use these assets and work
towards a greener environment, what I struggle to find is enough information on
the subsea track record of wells that have been left long enough to show the
success rate. It is of course always going to be a concern that after a long
enough periods there may be quite a real risk of pollution after abandonment
due to inadequate techniques or materials with varying levels of success
depending on technology’s used.




Joan.C.Isichei's picture


In summary of all the posts above, the North Sea is currently facing a major challenge in how to solve the decommissioning problem following the depletion of oil and gas resources. In addition to these posts, decommissioning in the North Sea poses the following risks and challenges:


1. Cost: The cost of decommissioning a field is often significant, usually about 10% of the cumulative CAPEX for the field. Different types of platforms such as; steel jacket, gravity structure, tension leg and floating platform, have different options for decommissioning. Therefore, type of platform consists of one of the major factors influencing costs, along with[1]

  • size,
  • distance from shore,
  • weather conditions
  • Difficulty associated with removal, including all safety aspects.

2. Decommissioning Strategy: The basic decommissioning options are as follows[2]:

  • Leave in place.
  • Partial removal, with alternatives:
  • o Emplacement/toppling on site
  • o Carry to shore for recycling or disposal as waste
  • o Deep-water disposal
  • o Artificial reefs
  • o Re-use/other uses
  • Total removal, with alternatives:
  • o Carry to shore for recycling or disposal as waste,
  • o Deep-water disposal
  • o Artificial reefs
  • o Re-use/other uses.



  • 1. Uncertain budget and timescale for completion[3]
  • 2. Limited decommissioning experience to date in the North Sea which has an direct effect of increasing HSE risks [3].
  • 3. Environmental impact due to the possibility of leakage of "known" hazardous substances to an acceptable level to areas surrounding the platform [4].


      1.     Decommissioning. Developments in Petroleum Science, Volume 55, 2008, Pages 419-425. F. Jahn, M. Cook, M. Graham.

2.     Decommissioning of petroleum installations—major policy issues. Osmundsen, Petter.; Tverteras, Ragnar. 

3.  Available at

4. Available at

Samira Bamdad's picture

Assets are expected to reach to the end of their fatigue
life towards the end of the design life.  Though calculations are done to consider the
fatigue strength of structures during the installation and operational periods,
the life extension during the decommissioning may not have been considered in
the first design. It should be noted that the structural bits are subjected to
extra loadings during the decommissioning process. The extra loading during
various stages of decommissioning such as cutting, lifting and transportation
requires an extension on the fatigue life of and it may threat the structures integrity
during the decommissioning and transportations. The ultimate consequence of
this is the risks for the personnel and environment. 

Kyle McFarlane's picture

The decommissoning of platforms is likely going to be made even more complex by the fact that many of the platforms on the UKCS are already fast approaching the end of their design life, however it is not likely they will all be decmommissioned as previously planned. It is more likely that these platforms will be maintained to ensure they are functional for as long as the potential to produce is still achievable. 


The HSE's key programme four (KP4) looks at  extending these platforms Aging life by raising awareness of the dangers these aging systems may hold. It is my belief that the dangers decommissioning holds will also be reduced by this programme as it highlights many of the factors that must be considered when removing a platform once it has exceeded its design life. 

Keqin Chen's picture


With numerous oil and gas fields started in
70s or 80s of 20th century have arrived their design life in North
Sea, the eventual decommissioning of theses offshore installations has become
more and more important for the operators.


A study in 2008 showed that more than between
£15bn and £20bn will be spent on the decommissioning of near 450 offshore
structures by 2030 in North Sea. [1]


In the inhospitable waters of the northern
North Sea, other than the challenge of cost, several challenges related to legislation
bounds, technology and environment will have to be faced directly, especially in
dealing with the very large structures and subsea production systems in deep
water in northern North Sea.

Legislation Bounds

To accomplish decommissioning offshore facilities
is limited by a strict legislation bounds including international, regional and
national aspects and the final execution have to balance the conflicts between


Technical Challenges

The industry has not developed enough
experience in decommission tasks, and most of jobs have been down are about
Fixed Jackets in shallow water area. More challenges will be caused when we
face to the removal of giant gravity based concrete platforms and subsea
production systems.


Environmental Troubles

A series of risks may do harm to the marine
environment, such as residual oil or drill cuttings spill, the disturbance
caused by subsea incision and removal etc.. Strict environment protection
procedures have to be established and executed in the whole process of decommissioning.
At the same time, reuse, recycling or final disposal on land after
decommissioning of the infrastructure has also become a puzzle for the operator
to acquire the approval of national authorities.


1.    Decommissioning the North




Keqin Chen

Msc of Oil and Gas Engineering

ID:51126368's picture

The decommissioned oil platforms are always the trouble of the oil company. For instance, Shell decided to sink The Brent Spar oil platform into the bottom of the North Atlantic. However, this action received the protest from thousands of people and several governments. Finally, Shell claimed that the platform would not be sunk into the sea any more. The only way to decrease the cost is that to try to transform it into other objects with on-going profit.

 Transform challengesThe first issue is that the platform is far away from the mainland, if we want to transform it, maybe some materials need to be transported to the platform. Thus, frequent utilization of transportation will increase the cost.The weather of the North Sea is changeable and the climate must be taken into consideration. When the platform is transforming and when the platform is put into practise, two different emergency systems should be set up. Furthermore, more money will be invested into the system.To find the potential clients is another issue. As a matter of fact, it is an urgent affair to find some customs to achieve continuous profit. Nevertheless, this issue probably will be quite difficult due to the uncertainty of the platform.The new and innovate technologies should be used which means we may put much money in the innovation. However, all the technologies may not be so feasible and sometimes, failure may occur. Hence, to choose the reliable and reasonable technologies will be the significant challenge.

Dike Nwabueze Chinedu.'s picture

Most of the asset in the North sea are approaching the end of thier design/useful life as they have served the purpose for which they were constructed and have now in some cases reached over 25 years. 

Decommissioning is the process of removing all offshore structures which has been used for the purpose of production in a way that is safe to life, the environment and associated property. Article 5 of the geveva convention was the first international regulation for the removal of marine structures, and was later superseded by the UNCLOS, the IMO published its first guidance on decommissioning in 1989 and another in 1998, the OSPRA 1992 also stipulates general requirements for offshore structures to be removed [1].

The first structure (platform) to be abandoned in the north sea was the piper Alpha following the catastrophic fire, the next was the decomissioning of the brent SPar in 1995, the next milstone was the removal of the maureen platform. The first subsea development to be abandoned in the north sea is the crawford field in 1991, the Blair 1992, Staffa 1996, Durward and dauntless 2000, frigg 2003, Ardmore 2005 [1].

In all of this, the following challenges characterised the decommissioning process: the complexity of the selection of disposal options, complying with the relevant regulation, political authorities, technical challenges involved in the process. The major risks are risk to personnel, technical risk and environmental risk. mission failure probability. The following consquencies are may be pertinent for decommissioning and should be avoided: Ubiquity, delayed effects, voilation of equity etc. some uncertainty factors also exist which could affect the process [2].

For subsea pipelines, studies and research is growing in the area of life extension of aged pipelines.

In summary, the decommissioning may be compared to an engineering and construction project (in this case deconstruction), regulations has made it equally important as the exploration and production and thus all high standards for safety, health and environment must be complied with as during operation of the field.



[1] MyAberdeen (2012), Introduction to subsea systems and networks, [online], Available from:

[2] Aven T, and Vinnem J. E (2007), Risk management with applications from the offshore petroleum industry, springer series in reliabilty engineering.

YAKUBU ABUBAKAR 51126107's picture

Because of the complex and sensitive nature of decommissioning
oil & gas platform and their pipeline, there are a lot of safety and health
concerns with potential risk to the personnel and the environment.

The challenges can be
enormous but few are mention below:

Hazardous substance: there is a risk of release
of hydrocarbons and other harmful chemicals from the operations and hot work
during the dismantling exercise of oil and gas platform.

Integrity: The platforms are old and because of
that there may be hidden structural flaws in it that can cause hazard to the

Lifting: Decommissioning is a complex operation
that involves cuttings and large lifting of components parts with a lot of uncertainties
in the load path and structural integrity.

Working at height: the nature of the operation
would involve working from different height that has of risk of dropping object
from any part of the platform.

Diving: a lot of divers would be involved to
help in the underwater cuttings and other operations, which is a very huge challenge.

The  health and safety  challenges in the decommission an offshore
platform in the north sea is quite immense, but there are mitigation strategies
to deal with the problem one the most important one is good quality tool box
talks and regular updating of the job cards to mention a few.

Yakubu Abubkar

Oil & Gas Engr.

REF: OIL & Gas UK Oct, 2012

Sineenat Kruennumjai's picture

Topic 32: Decommissioning of aged Platforms and Pipelines in the North Sea - Risks and Challenges

 Offshore decommissioning processes consist of plugging of the wells, removing of all or some parts of structure, and deposal or recycling of removed devices. The hazardous outcome or the risks occurrence as a result of man’s activities in this process is environmental risk, for example the chemical contamination which can result from drill cuttings (sometime contain hydrocarbon, drilling mug, toxic chemical). Moreover, the work-related injuries are also result from the decommissioning .It might risky for workers, who are working in subsea, to facing with the injuries from underwater cutting or structural collapse from overloading.
  So, the challenge for decommissioning is to develop the forward planning regime, that is concerned on the issues of minimal the environmental impacts, as well as mitigate the number of worked-related injuries.


Post by
Sineenat Kruennumjai
ID 51126536

Yaw Akyampon Boakye-Ansah's picture


Decommissioning becomes imperative when the producible oil and gas
reservoirs reach the end of their productive lives. Some platforms may be taken
apart and sent onshore with some of the parts reused, sold, remolded or
discarded as deemed fit by the state of the materials.

Due to the risks
involved in decommissioning oil and gas platforms, there are various
rudimentary stages one must go through so as to ensure that the risks are
mitigated. Some of the risks involved include deposition of the platform
in the offshore environment. The possibility for the platforms to sink is also
a major risk.

The North Sea area regulations does not allow for oil and gas
platforms to be cut and the remaining legs allowed to form reefs. The limiting
regulation is due to the OSPAR convention agreement signed by the operating
companies in the area.

“However, there have been concerns raised over the potential for
oil and other contaminants to be released into the marine environment from the remobilization
of cuttings piles due to disturbance from other activities, i.e. trawling and decommissioning
activities, and OSPAR is addressing the issue in the Assessment of impacts of
offshore oil and gas activities in the North-East Atlantic (OSPAR publication
2009/453)”.  The OSPAR Convention has
such laws as “the dumping and leaving wholly or partly in place of offshore
installations is prohibited.” 

Thus, to decommission in the North Sea area, one must have a
permit from the requisite authorities to undertake the project. This is seen as
a means to forestall any damage to the environment.



2.      ttp://

Yaw A. Boakye-Ansah


Omololu Oyebola's picture

The decommissioning of offshore oil and gas platforms is an issue of growing concern within the industry as many fields approach the end of their economic lives. Retiring of an offshore platform involves complex methodical and active challenges. Regulations exist which govern the requirements for the decommissioning of structures in international waters and they must be adhere to (Ruivo, Morooka 2001). 

Significant strides have been developed to standardize the decommissioning of offshore installation and several options for decommissioning of offshore structures exist in order to meet regulatory requirements (Anthony, Ronalds et al. 2000). 

These are:

Complete removal: This option requires the structure to be entirely removed by lifting either in one piece or in sections depending on the size of the jacket and the capacity of the lift. Structures totally removed and brought to shore are typically recycled where possible

Partial removal

Toppling: This option involves toppling the upper portion of the jacket in-situ

Reuse: Oppurtunity may arise to use jacket legs in other production facility but the integrity must be checked before they are deployed to this facility

Alternative use

All points raised on re-use are good, but I will like to ask how reliable components made from these 'scraps' will be? 


ANTHONY, N.R., RONALDS, B.F. and FAKAS, E., 2000. Platform Decommissioning Trends, SPE Asia Pacific Oil and Gas Conference and Exhibition, 16-18 October 2000 2000, Copyright 2000, Society of Petroleum Engineers Inc.

RUIVO, F.M. and MOROOKA, C.K., 2001. Decommissioning Offshore Oil and Gas Fields, SPE Annual Technical Conference and Exhibition, 30 September-3 October 2001 2001, Copyright 2001, Society of Petroleum Engineers Inc.

Justice J. Owusu's picture

Risk analysis and risk management have become very important issues in decommissioning offshore oil platforms. I believe this has been so probably because the process and procedure of decommissioning rigs were not considered at their design stages. Depending on the platform type, offshore decommissioning involve many different (very) high risks that include environmental risk, risks associated with rope access and scaffolding, dismantling work, lifting operations, etc. These risks can be reduced by critically examining the technology and method of decommissioning the platform. Understanding, assessing and managing the method and technology will lead to proper planning and measures to take to reduce the risks to a level as low as reasonably practicable (a Safety Case should then be prepared based on this understanding). It is legally required to present a Safety Case for the decommissioning to the Health and Safety Executive (HSE) – as prescribed by “The Offshore Installations (Safety Case) Regulations 2005.

Tilak Suresh Kumar's picture

Safety in marine contracting is a key issue. It is even higher on
agenda for removal work because of some of the unknowns. Contractors working on
decommissioning projects have needed to develop procedures and skills in:

  1. The use of explosives.
  2. Verification of complete severance
    of cuts carried out (perhaps by explosives and perhaps underwater) after
  3. Ensuring stability of partially cut
  4. The safe re-floating and towage of
    structures that have undergone changes since installation;
  5. The removal of pipe work and other
    components which have LSA (low specific radioactivity) in them;
  6. The handling and storage of
    potentially dangerous materials and components during removal and prior to appropriate disposal;
  7. Removal of ballast water and any
    other sources of contamination before disposal;
  8. Handling
    flexible flow-lines, pipelines and umbilical’s during and after their removal, particularly
    managing the potential hazards to equipment’s and personnel of the emission of
    hydrocarbons material that has soaked into the material of these porous
    flowlines, and may come out when the flow line is on deck and no longer has ‘over-pressure’,
    As it does on the seabed.



Connie Shellcock's picture

In Ekins et al study of decommissioning of offshore
oil and gas facilities, they describe a typical North Sea Large steel deep
water structure consisting of the following ; a topside, a jacket, the footings
and the drill cuttings, each of which need to be disposed of when they reach
the end. In this study it is concluded that each of these 4 major parts will be
treated differently when it comes to decommissioning. Topsides will have to be
ashore as it is thought that this has less environmental impacts compared
leaving in situ. This however is more expensive. The jacket will have the same
outcome, except that it is a lot cheaper to take the jacket ashore. The footing
however will possibly stay in situ as it is thought that removing them has
massive safety concerns and will also be detrimental to the environment.
However leaving them in situ may have negative effects on other industries such
as fishing. What to do with drill cuttings is still part of a controversial
debate as to what is financially feasible and environmental friendly. This
source and many previous posts on this blog illustrate that there is a great
deal of uncertainty in decommissioning activities.
(Ekins, Vanner
et al. 2006)

VANNER, R. and FIREBRACE, J., 2006. Decommissioning of offshore oil and gas
facilities: A comparative assessment of different scenarios. Journal of
environmental management,
79(4), pp. 420-438.


ZHANGYANAN's picture

Topic 32: Decommissioning of aged Platforms and Pipelines in the North Sea - Risks and Challenges

For this topic, we need to focus on the reuse of the decommission. As this is the decommission platform, we may transfer it into an useful area such as the the renewable energy and the travel place.

For a renewable energy, we can use the top of the platform to install the solar panels and the wind turbines to collect energy for using. On the bottom of the subsea, we may set up some tidal stream turbines for collecting the energy from the sea.

For the reusing of the pipeline under the sea, we may use them as the cover of electric grid.

That can give the stakeholder company a green reused project to bring continuous income.

Zhang Yanan   ID: 51233945


Leziga Bakor's picture

The major challenge in decommission old platforms in the North Sea is that when most of them were designed, decommissioning them was not considered. As such they were not installed in a way that will make it easy to decommission them. This challenge makes it difficult to decommission the platforms as their decommissioning has to be designed late in the life of the platforms. Another challenge is that decommission of platforms is not a common thing. It is fairly new and only a few platforms have been decommissioned. This means that there are not too many data on decommissioned platforms available.
One of the risks in decommissioning of platform in the North Sea is the risk that results from harsh weather conditions. The weather in the North Sea is harsh and this makes it risky carry out decommissioning in the North Sea.
There is also risk of technology. When a new technology is being applied that has not been used before, there is the risk that it won’t work or may develop serious problems.

Samira Bamdad's picture

I’d like to add an example to Leziga’s argument. As he has
mentioned, when most of platforms were designed,
decommissioning them was not considered
. Decommissioning the
platforms with suction piles is a good example.

The method to decommission such platforms is to overpressure
the suction pile. Hence, the piping inside the suction pile will be pressurised
to a pressure higher than what is has initially been designed for.

Therefor the piping should be thoroughly inspected, and
reassurance should be made that there is enough thickness available to take the
pressure. That eventually means that the piping should have stayed uncorroded
to allow for overpressure. Excluding the inspection prior to decommissioning in
such cases may result in failure and therefore the risks associated with that
should be accurately considered. 

amir masoud bayat's picture

I personally believe that in the near future, the activity of offshore decommission in the North sea will significantly increase since existing offshore platforms are going to the end of its life.

There are several decommissioning challenges such as the removal of heavy platform structure from an inhospitable environments. The physical process of removing pipeline and heavy offshore platform securely and safely is a sensitive and technicaly formidable challenge. Those who are responsible for entire decommission should partner with experts who have ability and skills and strategic strength to deliver it. What I would like to stress is that the majority of hazards and risk control measures which are involved in entire decommission and disposal of offshore platform are similar to those hazards which associated with maintenance or construction operation conducted in offshore platform.



Bassey Kufre Peter's picture

Yes Leziga, i agree
with you on fact that the harsh weather condition of the North sea is one of
the major risk that affects decommissioning in the North sea. This identified
risk always leads to an extension on the project duration which will in turn results
in cost uncertainty as we will have to spend more resources on the project to keep
our personnel on a stand by pending on when the weather will be suitable for
work to commence. Additionally, environmental safety is another major
challenge, the workers may get exposed to some hazardous hydrocarbon release.
Aquatic lives are also endangered by leakage of crude oil from an abandoned oil
and gas well during the cutting process.

 Bassey, Kufre Peter
M.Sc-Subsea Engineering-2012/2013
University of Aberdeen.

Kelvin Arazu's picture

To decommission is to remove after use. Basically when an existing field has gone off plateau, the subsurface, subsea and surface equipment used during the production and exploitation of the field will be removed. This is done in accordance to the procurement of an operating licence for that field.

Risk associated to Decommission

Lifting of steel and heavy equipments

Cutting columns and other equipment

Toppling of the top side facilities

Diving activities

Purging the platform off hydrocarbon can cause pollution onshore or offshore. Altering the sea bed through dumping and removal of subsea facilities poses a lot of risk to the environment.

In performing this task, the formidable technological and operational challenges are the top event. But there will be need to ensure that the right balance is achieved among health/safety, environmental, technological, and economic considerations [1].

In conclusion, if this operation is achieved within the requirement of a tight regulatory regime, while being mindful of public health and safety concerns. The risk and challenges associated to decommission could be reduced.    

[1] Peter H. Prasthofer, Offshore Decommissioning Communications Project (ODCP)/EXXON, OTCC paper 8785 Houston Texas, May 1996.

Mehran Vakil's picture

Over a span of oil and gas production, ultimately there has been a trend towards decommissioning of platform. Taking into account of the type of the rig, there are different approaches adopted in order to removal. For instance completely removal, partial removal and leave in situ are the most significant ones.
Albeit removal of rig’s equipments is inevitable, it has its own risks. It would be noteworthy to cite the hazardous consequences associated with environment.
From my point of view, the major risk that threatens environment is leaking the toxic chemical, oil and mud during cleaning and flushing the storing tanks before commencing of structure removal. Hence, the residual oil and gas accompanied with toxic materials spread along the sea. These substances contaminate the water and they have potential to have an impact on marine specious. Also, dropping cuttings during removal of structure may cause entering toxic material and polluting the environment(Adedayo, 2012).
Generally speaking, installation, operation and decommission of oil and gas platform are jeopardous for environment.

OFFSHORE OIL PLATFORMS IN NIGERIA [Online]. Available: [Accessed 5/12 2012].


Samira Bamdad's picture

As it has been mentioned above, control the cost of
decommissioning is one of the driving parameters of this task. There are lots
of inspections and analyses to be done before starting the process, one of
those is extra steel work and stiffening. Because of modification throughout
the asset’s life, not the modules that installed as one part can be
decommissioned as a part; and therefore extra steel work is required to
facilitate cutting, lifting and transporting.

In some cases doing analyses based on surveys’ and
inspections’ results can help to control the steel work cost. In addition to
cost saving, there will be a better control on risks associated with

Manuel Maldonado's picture

Decommissioning of facilities (installations and pipelines) have become an important area of operations and business in the North Sea. Decommissioning Operations have challenges related to business (costs) and safety risks management. Companies are creating joint ventures to carry out those types of projects. The use of contractors and the specialist involved in these types of operations make a very diverse environment of safety and operations cultures.

There have already been some operations carried out in the North Sea and some good learning being recorded from that experience. Some of them focusing on the definition of responsibilities and liabilities during those operations and some others related to main areas where the main risks remain. The contractors work on their technical expertise and are responsible for carrying out specific activities in a safest manners, while the operator is liable for those activities and the compliance of standards to ensure the rules and legislation is respected. On the other hand the main gaps observed during this operations are: clarity of roles an accountabilities during these operations, incomplete work packs for the project, appropriate cutting equipment, techniques and procedures for the job, continoues ROV monitoring and interventions to minimise the leaks caused by existing facilities, control e implementation of particular lifting plans specified for the job rather than generics and risks associated to manual handling, slipping and falling.

The big challenge in the oil industry is to overcome those risks by implementing adequate risks assessment and the implementation of effective safety management practices and the reinforcement of the rules, policies and legislation. However, because the decommissioning industry is still in the early days, further legislation and regulation need to be established aiming at safer operations.

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