Lloyds List: Shell draws up blueprint to decommission five platforms: British government will scrutinise plans to decommission platforms on Indefatigable gas field, writes Martin Wingrove: Tuesday August 16, 2005

SHELL is preparing to submit a plan to the British government outlining how it will decommission five platforms on the Indefatigable gas field in the southern North Sea.

The Anglo-Dutch oil major intends to gather data on its decommissioning options and submit a plan to the Department of Trade and Industry this year. Shell has started discussions with contractors to find the most cost effective and safe method of decommissioning the wells, platform structures, associated pipelines and hose bundles from the Inde field.

The London-listed company's schedule is to use at least one jack-up rig in 2006 to abandon the 26 production wells on the five platforms. It is also looking to remove the five platform topsides and jackets in 2007 during two heavy lift periods.

This is one of the largest decommissioning projects to be undertaken in the UK sector and could provide considerable opportunities for British contractors. It involves the Inde platforms Juliet, Kilo and Lima, installed from 1970 to 1977, plus the more modern Mike and November platforms that came on-stream in 1985 to 1987. There is also some 21 km of gas pipelines and 6 km of hose bundles to decommission.

The largest of the platform complexes is Juliet, which includes a four-leg steel platform bridge-linked to a 10-leg structure with gas production topsides and a venting tower. The platform supports seven wells and has two helidecks, power generation systems, a crane and storage tanks.

Kilo is the second largest structure to be decommissioned, as a 10-leg steel jacket with a similar topsides arrangement to Juliet except there are no storage tanks and only five wells. The Lima platform has a six-leg jacket that is, uniquely, narrower at one end. There are six wells, plus gas production facilities, storage tanks, power generators and a crane. Mike and November are wellhead platforms supporting four wells and emergency accommodation only.

'There are five pipelines to be decommissioned in the Inde field. Three are inter-platform pipelines,' said Shell. 'The other two are main export pipelines that run from Juliet and Kilo to the receiving platform Inde 23AT, which is operated by others.'

Shell has made its well abandonment plans and needs to find a suitable jack-up rig and associated services. 'The platforms are scheduled to cease production in sequence. Following the cessation on each platform, well abandonment activities will commence,' said Shell. The options available for removing the platforms are more open to discussion and Shell hopes for dialogue with contractors to find the best solution.

Following the plugging and abandonment of the wells and the facilities being made safe, the platform topsides will need to be removed to shore.

Shell has highlighted four options it is considering, including reversing the installation process using a heavy lift vessel or doing this piece-meal. It is also considering an integrated removal using either a large semi-submersible crane vessel or any single-lift technology brought forward by contractors.

The jackets will need to be removed using either a heavy-lift vessel or a buoyancy aided system. Shell's options on the pipelines and hose bundles are either to leave them in-situ or removal by cutting and lifting.

'The exact method of decommissioning will be finalised and agreed with the successful contractor following detailed technical and commercial analysis of tenders,' said Shell. 'It is our desire to seek economies of scale and logistical synergies by providing flexible programmes for contractors interested in the decommissioning of these facilities.'

Once brought ashore, Shell may have options on how to dispose of the structures. It does not think there is much re-use potential for the topsides or jackets. But use could be made of some of the equipment, particularly the cranes and power generators.

'It is anticipated that the majority of the facilities can be recycled as they are predominantly steel, which has a high scrap value,' said Shell.

This is the first of the major southern North Sea decommissioning projects to be undertaken over the next 20 years and other operators will watch closely to see how Shell conducts the work. 

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