The Sillimanite is a cross-border offshore gas field spread across the UK and the Netherlands territorial waters in the southern North Sea.

The Netherlands-based oil and gas exploration and production company Wintershall Noordzee is the operator and holds a 39.7% interest in the Sillimanite field. Wintershall Noordzee is a joint venture between WintershallDea (50%) and Gazprom EP International (50%).

The other development partners of the field include the Dutch state-owned EBN(25%), Gazprom International UK (19.9%), ONE-Dyas UK (7.9%) and Neptune Energy (7.5%).

The Sillimanite field was discovered in June 2015 while the UK and Dutch governments signed a treaty for the Sillimanite field development in July 2018.

The final investment decision (FID) on the Sillimanite field development was reached in October 2018 and the field came on stream in February 2020.

Location and reservoir details

The Sillimanite field is located approximately 200km off the coast of Den Helder, Netherlands. The field spans across the block 44/19a of the UK continental shelf and the blocks D12a and D12b of the Netherlands continental shelf.

The Sillimanite field is producing gas from the sandstone reservoirs of the Carboniferous Age. The depth of the reservoir is approximately 3,700m below the sea level.

Sillimanite field development details

The Sillimanite field consists of two production wells and a normally unmanned platform. The first well D12-B1 started production in February 2020 while the second well D12-B2 commenced gas production in June 2020. Both the production wells are connected to the D12-B satellite platform.

The D12-B platform is reusing the topside of the decommissioned E18-A platform and a newly constructed 12km-long, 10in-diameter pipeline exports the gas from the D12-B platform to the Neptune Energy-operated D15-A production platform.

The natural gas is further exported from the D15-A platform through the Noordgastransport pipeline to the Uithuizen processing station in the Netherlands.

The D12-B platform and the D15-A production platform are located in the Dutch sector of the North Sea, while the Sillimanite field operations are monitored from Wintershall Noordzee’s Remote Controlled Operations (RCO)centre in Den Helder.

Contractors involved

Maersk Drilling was awarded a contract by Wintershall Noordzeeto to drill the wells in the Sillimanite and Sillimanite South fields. The Maersk Resolve drilling rig was deployed for development of the fields.

Fugro conducted the geophysical and geotechnical surveys for the D12-B well site, as well as for two proposed pipeline routes for the Sillimanite field development in April 2017. The survey was performed by M.V. Fugro Frontier survey vessel.

Enersea provided engineering consultancy services for the Sillimanite field development project.

Sillimanite South field

The production from the Sillimanite South field discovery well, D12-B3, started in January 2021. The Sillimanite South field, discovered in 2020, is located in the block D12a.The D12-B3 exploration well was converted into a production well as part of the Sillimanite South field development.

The D12-B3 well became the third well from the Wintershall Noordzee portfolio to start production during the year ending January 2021.The D12-B3 well is connected to the D12-B production satellite platform. The gas is exported from the D12-B platform to the D15-A production platform.

Wintershall Noordzee is the operator of Sillimanite South field and holds a 39.5% interest. The other field development partners are EBN (50%) and Neptune Energy (10.5%).