BRENT FIELD OVERVIEW
The Brent Field was discovered in 1971 and production began in 1976. It is located 186km north east of the Shetland Islands. For almost 40 years it has created and sustained thousands of jobs. It has contributed billions of pounds in revenues and provided the UK with a substantial amount of oil and gas.
The field is made up of four platforms. Alpha is a steel jacket and Bravo, Charlie and Delta are all gravity based structures which are made of thousands of tonnes of concrete which has been reinforced with steel.
The Brent Delta platform reached cessation of production – meaning that it stopped operating – on 31 December 2011.
All of the platforms – as well as their associated infrastructure such as wells and pipelines – will be included in the decommissioning programme which will make recommendations for how to safely and responsibly decommission the Brent Field. Decommissioning work on the Brent Field is expected to last for at least the next decade.
Our goal is to find a way to decommission the Brent Field that ensures the safety of people working on the project, has minimal impact on the environment and ensures that the work is economically responsible.
The topsides are the main area of the platform positioned on top of the legs – they house the accommodation block, helipad as well as the drilling and other operational areas.
Also on board are huge kitchens to cater for over 161 personnel on the Delta platform as well as a cinema and gym.
How Tall are the Structures?
From the seabed to the top of the platforms above the sea, they stretch up over 300m – this is the same height as the Eiffel Tower.
Platform information and the people on board
Brent Delta has accommodation for 161 people on board at any one time, however each person has a back to back cover.
Over the four platforms in the field, there are thousands of people involved in operations and decommissioning.
TOPSIDE RECYCLING, ALLSEAS AND ABLE
Contracts to remove, transport, reuse and recycle the platform topsides* have been awarded.
Allseas will use a giant vessel - the length of five jumbo jets - to lift the topsides in one go. It will then sail with these onboard to Teesside where another contract has been awarded to Able UK to reuse and recycle the materials. Our target is at least 97% reuse and recycling for all topsides material.
* topsides are the main areas of the platform positioned on top of the legs
Jobs, skills and workforce
Over the years, the Brent Field has provided tens of thousands of jobs both onshore and offshore. It has a long history of providing supply chain opportunities to local people and businesses.
The Brent Field decommissioning will enable British companies and their supply chains to gain invaluable expertise, just as they did when the platforms were being installed and production offshore was starting. This knowledge and experience will give them a head start in future decommissioning projects, both in the North Sea and worldwide.
Three of these structures have large concrete 'legs' which support the platforms above the surface of the sea, and have clusters of large concrete oil storage cells at their base. These are called gravity base structures (GBS)
and each weighs several hundred thousand tonnes.
At the bottom of three of the platforms; Bravo, Charlie and Delta, there are clusters of tanks known as cells.
During production offshore, these cells were used for oil storage and separation and now, there is a layer of sediment within the cells which will be looked at as part of the decommissioning programme.
These cells are each 60m tall – higher than Nelson’s Column – and there are 64 in total in the Brent Field, 42 of which have been used for oil storage and separation.
attic oil removal
Attic oil is the name given to the accumulation of oil that is found in the top of the cells. As part of our decommissioning operations, this will be removed and taken to shore for treatment and disposal.
sea bed pipelines and drill cuttings
Also in the scope of decommissioning are 28 pipelines, several drill cuttings piles and some debris from operations such as scaffold poles.
Drill cuttings are shards of rock which were produced as drilling operations to make the wells were carried out. Some of these lie on the sea bed and others are around and on the bottom on the platform structures. Debris such as the scaffold poles which have been moved overboard in periods of bad weather can also be found in these piles.
A Comparative Assessment is a piece of work that will allow a company to look at options, rate them and then select the best outcome. This Comparative Assessment method will be carried out for all of these areas in the Brent Field such as pipelines, drill cuttings and debris to assess the options available and recommend the best solution.
Each pipeline will be looked at individually to ensure that the best option is selected for its decommissioning.
Regulation for drill cuttings comes under the OSPAR guidance and Shell will treat them in accordance with this.
All debris will be collected with the exception of that which is buried within drill cuttings piles so as not to disturb the cuttings piles.
In order to get the oil and gas out of the seabed, wells are drilled. This allows the oil to flow up to the platform and then be transported via pipelines to shore for use.
In the Brent Field, over 140 wells have been drilled. Each well is approximately 2km long which would stretch as far as 19 football pitches.
To date, all of the wells on Brent Delta have been securely sealed as part of our decommissioning work – this led to the platform being declared hydrocarbon-free meaning that there is no longer any oil or gas flowing onto the platform.
Work is ongoing to seal the wells on the other platforms in the Brent Field as they stop operating.
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