Photo: The 48/29A complex - the main operating hub for Hewett field; Source: Eni

Eni hands in decommissioning plan for six North Sea platforms

Italian oil and gas company Eni has submitted its plans for decommissioning of six platforms on the Hewett field to the UK authorities.

The Hewett field is located in the Southern North Sea, about 22 km northeast of the Norfolk coast.

Five of the Hewett platforms (48/29A Complex, 48/29B and 48/29C) are located in UKCS Block 48/29, with the remaining platform (52/5A) located in Block 52/5.

The Hewett area contains the main Hewett field, consisting of five horizons vertically situated above each other, and six adjacent satellite fields: Big Dotty, Little Dotty, Deborah, Dawn, Della, and Delilah.

The main Hewett field, Big Dotty, Little Dotty, and Deborah are in a single unitised licence area.

The Hewett field infrastructure comprises six platforms, 32 platform wells, and a further eight subsea wells tied back to the platforms.

Under the plan, topsides and jackets for all six platforms will be removed and returned to shore for processing, recycling or disposal.

The earliest start date for decommissioning activities is in late 2021.

Hewett field layout
Hewett field layout; Source: Eni

Some preparation works are required prior to topsides removal including piece small removal of specific items and installation of lifting points.

Following this, the topside will be removed via several possible options. These include single lift removal by single lift vessel/monohull crane vessel; or modular/piece-large removal by heavy-lift vessel (HLV) for re-use/recycling/disposal or offshore removal ‘piece small’ for onshore reuse/disposal.

The jackets will be removed either in a single lift or cut and recovered in several pieces.

In addition to the topsides and jackets removal work, during 2020, Eni proposes to remove the vent stack and redundant compressor package on the 52/5A platform to clear any obstructions for rig access to facilitate the P&A of the platform wells.

Removal and transportation to the shore of this material will be managed by the current field supply vessel and disposal arrangements to Great Yarmouth or Lowestoft Harbour, minimising any environmental or societal impacts.