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Statoil Bressay Developmental Delay

In late 2018 a thirty-year adventure will begin 250 kilometres off Scotland’s north-east coast. That’s when the first oil tanker will leave the Mariner field, bound for the world’s energy markets. It’s been a long journey. Mariner is a sleeping giant, discovered more than thirty years ago. 


But because of the oil’s extremely high viscosity, previous operators were not able to extract it. In 2007, we acquired the operatorship, and with the experience gained from working with other heavy oil fields, we managed to solve the challenges. The Mariner project will be one of Statoil’s most innovative developments ever.

Discovered in 1981 on the East Shetland Platform, approximately 150 kilometres east of the Shetland Islands, the Mariner field is a daunting prospect for oil and gas producers. Mariner is a heavy oil field characterised by dense, viscous oil.

In December 2012, Statoil and its partners decided to take on the challenge and made the investment decision for the Mariner project, which entails a gross investment of more than GBP 4.5 billion. This was the largest capital commitment to the UK Continental Shelf (UKCS) in more than a decade.

The concept chosen includes a production, drilling and quarters (PDQ) platform based on a steel jacket, Mariner A, with a floating storage unit (FSU), Mariner B. Drilling will be carried out from the Mariner A drilling rig, with a jack-up rig assisting for the first 4 years.


The Mariner oil field consists of two shallow reservoir sections: the deeper, Maureen formation at 1492 meters and the shallower Heimdal reservoir at 1227 meters. The oil is heavy with API gravities of 14.2 and 12.1 and viscosities at reservoir conditions of 67 cP and 508 cP, respectively for Maureen and Heimdal.  

The development of the Mariner field will contribute more than 250 mmbbls reserves with average plateau production of around 55,000 barrels per day. The field will provide a long term cash-flow over 30 years.  Production is expected to commence in 2018.

Mariner A platform

Statoil on Wednesday announced it would delay the start of production from the Mariner field, in the UK North Sea, from 2017 to the second half of 2018. 

In addition, the Norwegian oil and gas giant said on Wednesday, in its 3Q 2015 results report, it would delay production start from the Aasta Hansteen project located in the Norwegian Sea.

According to Statoil, the sailaway of the topside modules for the Mariner A platform will be delayed by one year compared to the original plan, and production start-up is postponed from 2017 to 2018. Meanwhile, Statoil will initiate the pre-drilling of production wells in 2016 in order to have an increased well capacity available at start-up.

To remind, Statoil awarded a contract for the construction of Mariner topside modules to Daewoo Shipbuilding & Marine Engineering Co., Ltd. (DSME) back in 2012. The topside was initially scheduled for delivery in January 2016.

“Mariner is a huge and complex project with many components. While key parts of the project, such as the platform jacket and the subsea installation, are progressing well and according to plan, the construction of topside modules has progressed slower than agreed,” says Managing Director for Statoil Production UK, Tove Stuhr Sjøblom.

“As the topsides arrival will be delayed, we have decided to adjust our activity plans in order to improve production profiles and optimise resource management on Mariner,” she says.

Pre-drilling from autumn 2016

The steel jacket for the Mariner A platform was recently installed in the field. A project is now underway for the pre-drilling of wells through the jacket when the purpose built jack-up rig Noble Lloyd Noble arrives in UK waters in the second half of 2016.

“We aim to start the pre-drilling of wells next autumn. If everything goes to plan we should have four to six production wells ready prior to start-up in 2018. This will enable a quicker ramp-up to plateau production than that of our original plan,” says the Statoil MD.

Potential for increased recovery

Statoil said that the drainage strategy for the field was also under revision. Based on seismic data acquired over Mariner in 2012, Statoil has identified a reduction in resource uncertainty resulting in the potential to increase the expected oil reserves and reduce the number of development wells.

“We have a much better understanding of the Mariner reservoirs now than when the project was sanctioned. We see opportunities for more targeted drilling, potentially reducing drilling costs whilst accelerating and increasing recovery. A new drainage strategy is being developed and should be completed in 2016,” Tove Stuhr Sjøblom says.

No major changes are anticipated to the staffing plans in the Aberdeen office, but recruitment plans will be adjusted to fit the revised schedule, the company noted.

“We are disappointed with the delay in start-up but remain excited about Mariner and its significant potential. We have been encouraged by the flexibility and commitment demonstrated by our teams to pursue improvements and find good solutions when change is necessary,” Tove Stuhr Sjøblom concludes.

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Posted on October 28, 2015 with tags Mariner, North Sea, Statoil, UK.

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