Decommissioning Insight 2019

DECOMMISSIONING INSIGHT 2019

CASE STUDY — STATFJORD

The Statfjord field was discovered by Mobil in 1974 in 149m of water, approximately 120 miles west of Bergen. Statoil, now Equinor, assumed operatorship on 1 January 1987. The field was developed using the Statfjord A, B and C concrete gravity base production platforms, all of which incorporate oil storage cells. Industry-leading recovery factors approaching 67 per cent for oil (4.3 GBO) and 78 per cent for gas (8.3 TCF) have been achieved and this means that the Statfjord A platform will shut down production in 2022, 43 years after first oil and after more than double its expected lifetime. Equinor has incorporated its own experience and lessons shared by others that have undertaken large offshore decommissioning projects, including commitment to start the decommissioning of the platforms 34 wells early such that these operations will be completed very soon after CoP. Post-CoP OPEX will be minimised and this will facilitate early transition to EPRD contractor led removal preparation and de-manning. As one of the largest platforms on the Norwegian continental shelf, the 48,000-tonne Statfjord A topsides comprise an 18,000-tonne module support frame supporting a large number of small modules, many of which were installed offshore. Equinor recognised that removal to shore of this very large topsides would present unique engineering challenges and therefore decided to engage contractors early todevelopoptimisedmethods and execution plans. This work formed the basis for a competitive tender process which concluded in early 2019 with an EPRD contract award to Allseas to use its record-breaking heavy lift and pipelay vessel “Pioneering Spirit” to remove the topsides in a single lift after 2022. The vessel’s revolutionarymotion-compensated topsides lifting system will be upgraded from its current 48,000-tonne nameplate capacity to account for weight uncertainty. Allseas has selected Kvaerner AS to demolish and recycle the topsides at its Stord disposal facility. Equinor completed Norwegion Public consultation of its Impact Assessment of its Disposal Plan in 2018, and is expected to progress regulatory approvals, including request for OSPAR 98/3 derogation, through 2019–20.

Credit: Harald Pettersen / © Equinor

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