The Maria Field
Wintershall and its license partners Petoro and Spirit Energy started production at the Maria field in December 2017, one year ahead of schedule and significantly below budget. The costs have been reduced by more than 20 percent compared to the original plan. The successful delivery of the project has been made possible due to good cooperation and the combined efforts of the Maria project team, host owner Equinor and competitive suppliers, especially along the coast of Norway.
Maria is the first own-operated field in Norway, which Wintershall takes all the way from exploration, through development and to production. The field is located in the Haltenbanken area of the southern Norwegian Sea, some 200 kilometres from the mainland. Recoverable reserves of the field are estimated around 180 million barrels of oil equivalent, of which the majority is oil.
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Get to know Maria
Maria is a subsea field, producing hydrocarbons via two underwater templates that link back to existing installations on Haltenbanken in the Norwegian Sea. The field is expected to produce for over 20 years. The subsea installations named Maria H and Maria G are 3 kilometres apart, and are connected to the nearby infrastructure with a total of 94 kilometres of pipeline. The templates weigh around 285 tonnes each and are each the size of a basketball field. Maria is primarily an oil field with some gas and condensate.
Innovative development solution
The Maria reservoir is linked via the two subsea templates to the Equinor-operated Kristin, Heidrun and Åsgard B production platforms. The Maria well stream goes to the Kristin platform for processing, while supply of water for injection into the reservoir comes from the Heidrun platform. Lift gas is provided from Åsgard B via the Tyrihans D subsea template. Processed oil is sent to the Åsgard field for storage and offloading to shuttle tankers. Gas is exported via the Åsgard Transport System to Kårstø.
1. Host installations
With the chosen development solution, a combination of hosts was required to provide all the services needed for production on the field. The water for injection into the reservoir is provided by the Heidrun platform about 40 kilometres north of Maria, while the produced oil is processed on the Kristin platform. Gas for the gas lift is provided by the Åsgard B platform, via the subsea facilities at the Tyrihans D subsea template.
Production flowlines connect the two templates and send hydrocarbons to Kristin for processing. Water for injection into the reservoir is provided via a dedicated pipeline from the Heidrun platform about 40 kilometres north of the Maria field. Flexible risers connect the pipelines via riser bases on the seabed to the Kristin and Heidrun facilities. The risers are supported by buoyancy elements that provide additional flexibility when the facilities are moving in the sea.
3. Subsea production system
The subsea production system consists of two 4-slot templates. The combined production and water injection templates have a total of three production wells, two water injection wells and one spare slot that can be used later in the field life if required. The system also includes the control umbilicals and control pods that make it possible to send signals to and from the Kristin platform and the subsea templates.
The export system consists of two main elements: oil export and gas export. The oil export takes place by transferring the processed oil via a flexible riser and a pipeline to the Åsgard C FSU (Floating Storage Unit) where it is offloaded with a shuttle tanker. The gas export system consists of a flexible riser and a pipeline tied into the Åsgard Transport gas line to Kårstø.
The reservoir in the Maria field is the Middle Jurassic Garn Formation. It is a well-defined horst block structure with moderate reservoir quality. When all the wells have been drilled, Maria’s 4-slot subsea templates will have a total of five oil production wells drilled approximately 4,500 meters below the seabed and stretching 2,000 meters horizontally into the reservoir. Water injection is provided to pressure-support the field, pumping water into the zone below the oil to help push the hydrocarbons up towards the well producers.
Project history & timeline
Wintershall as the operator in cooperation with the other license partners Petoro and Spirit Energy decided on a preferred development solution for Maria in 2011. This was the first of four so-called decision gates that are part of the Norwegian authorities’ guidelines to be approved for development and operation of an oil field. The partnership submitted their application in the spring of 2015 and received approval by the Ministry of Petroleum and Energy in September 2015. The approved concept was to connect the reservoir to the already existing, closely located infrastructure via a subsea tieback. The field started production only 2 years and 3 months after the approval.
What is a decision gate? Click to expand
Passing Decision Gate 1 (DG1) means the partners in a license must agree on at least one economical development solution and inform Norwegian authorities of their intention to continue with the project. Following feasibility studies for Maria, Wintershall and its partners agreed that both a subsea tieback to nearby host platforms and a stand-alone development using an FPSO could form the basis for further studies.
Maria passed DG1 in July 2011
This is the Select Phase, when the partners must narrow the project outlines to a single concept and submit the BOV Report (Decision to Continue) to the Norwegian authorities. After additional studies, it became clear that the most economical solution for Maria would involve a subsea tieback to multiple host facilities on Haltenbanken.
Maria passed DG2 in 2013
This is the decision to commit to financing the project. It follows further refinement of the chosen concept through front end engineering and development (FEED) and the establishment of robust cost and schedule estimates. These are included in a Plan for Development and Operation, which is submitted to Norwegian authorities. Once the PDO is approved, the Execution Phase of the project can start.
Maria passed DG3 and submitted the PDO in May 2015. The PDO was approved in September 2015.
This is the start of production which happens after all installations have been finalised and tested thoroughly.
The production on the Maria field started on 16 December 2017, one year ahead of schedule and 20 percent below budget.
Essential host support
Modifications were required on the Equinor-operated host platforms Kristin and Heidrun to enable production and operation of the Maria field. During the summer of 2016, two risers and most equipment linking Kristin to the subsea installation and wells was installed to facilitate transfer of hydrocarbons, and to control of Maria’s subsea and well instrumentation. A final riser, a meter to measure the oil and gas produced by Maria and a subsea control unit was installed in 2017. On Heidrun, a balcony was constructed and installed to accommodate a new water injection riser which. In 2017 the existing injection system was upgraded with a new sulphate reduction module before the field could start production.
The development project Scroll sideways to read more and see videos from the different steps in the development project.
Contracts & deliveries
Over 90 percent of the contracts for construction and installation of the Maria field were awarded to and delivered by companies in Norway. This included components for the subsea production system, covering templates, manifolds and x-mas trees. The templates were designed by FMC Kongsberg and assembled at Agility’s yard in Tønsberg. The pipelines that links the templates to the host fields were fabricated in 1500 meter lengths at Subsea 7’s facilities at Vigra and were also welded together here, and spooled onto 50 meter drums ready for the installation on the ocean floor. In total, contracts were awarded to contractors and subcontractors on three continents.
Wintershall laid 114 kilometres of pipelines and umbilicals on the ocean seabed, weaving away from corals in order to tie the subsea production system to Maria’s host facilities. Surveys were carried out to determine the safest route, and thousands of tonnes of rock were laid to prepare the seabed for installation of the pipelines. Long trenches were dug for the pipelines, and afterwards these were covered with rocks for protection so that fishermen can continue to trawl the sea above.
Template and pipeline installations
The two subsea templates were installed on the seabed some 300 meters below the ocean surface. A 26-kilometre production pipeline was built to transport oil and gas from the templates to Kristin. Running alongside this pipeline is a control umbilical that allows Kristin to control the Maria valves. A 43-kilometre pipeline provides water from Heidrun for injection into the Maria reservoir, while a 19-kilometre pipeline brings lift gas from Tyrihans D.
The rig Deepsea Stavanger from Odfjell Drilling started the drilling operation on the field in March 2017. Over the course of an estimated 570 days, the rig and its crew had the task to drill and complete five production wells and two water injection wells. The production wells will produce the oil and gas while the water injector will help keep the oil pressed up towards the surface. The production wells were planned for around 110 days, with a total length up to 6500 meters, but were completed way ahead of schedule. The high drilling efficiency on the field set new performance records for the area.
Production & operation
The Maria field is planned for production in late 2018. Wintershall is operator of the field but day to day operation will be handled by Equinor. The Norwegian company operates all four of Maria’s host fields making it the ideal service partner. Wintershall’s single point of contact for operation is Equinor's Stjørdal office near Trondheim. This is the office that manages the Kristin platform, which is the host that both controls the valves in the Maria templates, and receives the hydrocarbons that flow from the reservoir. From there, Equinor can also co-ordinate water injection from Heidrun and the lift gas that travels from Åsgard to Maria via Tyrihans.
Health, safety and environment
Nothing is more important to us than health, safety and environmental obligations. We are therefore thankful that we together with our suppliers have completed the project without any major problems or delays.
May Kristin Sviland, HSE Manager
Nothing is more important to us than health, safety and environmental obligations. We are therefore thankful to our team and supplier that the project was completed without any major problems or delays.
May Kristin Sviland, HSE Manager
People on the team
Delivering such a complex project as Maria ahead of schedule and below budget is a testament to Wintershall’s capability to deliver on development projects. The experience gained will serve as a blue-print for our future developments.
Hugo Dijkgraaf, Managing Director, Wintershall Norge