26-01-99 Phillips Petroleum in Norway appears to have pushed back its deadline to submit a report to the domestic authorities on how to decommission some of its Ekofisk field installations -- the biggest job of its kind in the world today.
What is called the field cessation plan was originally due to be handed over this July but the schedule has now been widened to the "second half of 1999", said an oil company spokesman, so the available options can be better assessed.

The platforms involved form part of the 29 platform Ekofisk complex which recently underwent a major revamp -- dubbed Ekofisk II -- which has resulted in 14 of the Ekofisk platforms either being shut or due to be closed.
In addition, there are two compressor platforms on the Ekofisk oil pipeline which runs to Teesside which have already been closed in.
Although these lie in the UK North Sea they also come under the cessation plan.
An additional two platforms may be added. Statoil is considering whether it would like its 2/4S gas riser platform to be included in the study while BP Amoco are mulling a similar proposal for its 2/4G riser platform.

The Phillips platforms range in complexity from small steel installations to the Ekofisk tank -- a huge concrete structure with 36,000 tonnes of topsides and surrounded by a concrete wall.
The tank was installed 26 years ago, with the wall placed in 1989 to protect it against the effects of subsidence at the field.

The cessation plan has 4 stages with implementation, if approved by the authorities, expected to take place at the start of 2001.
Two-thirds of the decommissioning costs will be borne by the Norwegian taxpayer.

Completed in the third quarter of last year, the first stage identified all feasible decommissioning alternatives and then evaluated them with particular attention paid to issues such as safety, environment, fishing, shipping, economy and public interest.
In all, more than 90 alternatives were considered, of which 52 were found to be unattractiveand 27 were selected for further study.
Twelve options covering continued operation or re-use of the facilities were handed over to an " investment recovery programme".
Some bizarre options were mooted such as using the platforms as prisons for dangerous criminals; a tourist destination; a launch pad for rockets or a conference venue. But these were discounted since no market existed.

Stage II looked at how the 27 alternatives could be applied to topsides, steel jackets, the Ekofisk tank and its concrete barrier, the tank sediments, buried pipelines, cuttings residues on the seabed and general seabed waste.
Five alternatives were found to be feasible.

In stage III, studies have been initiated covering these alternatives and which will rate them according to safety, environment, social consequences and cost.
This work covers such things as the type of sediment found in the tank and how the cuttings below the Cod, Albuskjell, West Ekofisk and Edda facilities are distributed and what they consist of.
Methods of recovering buried pipeline have also been discussed.

The fourth and final stage will collate all the information as a precursor to submitting a recommendation to the Norwegian authorities.

Early on in the cessation plan it had been established that the topsides of the 14 platforms will be brought ashore and that the seabed within the safety zone would be combed for waste to be removed after the platforms are decommissioned.
However, it is not yet known what will happen to the decks once they have been brought ashore or if there is a second-hand market available.
The first of the five scenarios for the jackets, tank and barrier involves converting the jackets into artificial reef sites, in situ, while the second is to place the jackets around the tank/barrier complex to form a super-reef.
A third option is to bring all the jackets ashore for metal recycling with the tank/barrier remaining in place. Alternatively, both the jackets and tank/barrier could be all brought to shore for recycling.
Finally, the jackets may be recycled ashore with the tank and its barrier being refloated and towed to a deepwater site to be scuttled. This begs the question of whether it is even possible to refloat this huge structure.

Engineers will also need to figure out if the buried pipelines should remain in place or be removed. They will incorporate findings from ongoing international studies. Other studies will try to identify the best solution for the petroleum sediments that have settled in the tank's nine storage cells. Samples will be collected this winter to find out exactly what they consist of and how they can be dealt with.

The issue of cuttings disposal is also a major one. These residues are being examined to determine the size and content of the mounds beneath each platform and how best they can be handled. Other proposals have been mooted including use for gas power production or as foundations for windmills. Phillips says that these studies have yet to reach a conclusion. but the windmill alternative is feasible for only a small number of the 14 platforms. With truly major platforms set to be decommissioned for the first time, the market looks ready for significant growth early next century.
The new Ekofisk complex consists of 11 platforms but 14 more remain to be decommissioned