From the North Sea (NT): Statoil’s choice of a remotely controlled unmanned wellhead platform as the concept for phase one of the Oseberg Future project reflects the swing it warned of last year from subsea back to surface installations as a means of cutting costs (SEN, 31/7).

‘The alternative was to place the wells on the seabed, but the cost of subsea wells has tripled during the last decade,’ explained Anders Opedal, senior veep, projects. ‘We have therefore chosen a jacket-based unmanned wellhead platform that will reduce costs by several hundred million krone.’

Dubbed ‘subsea-on-a-stick,’ the stripped-down platform - for which three different concept studies have been made - lacks living quarters, helideck and lifeboats.

These facilities will instead be located on the support vessel which, rather than helicopters, will transport maintenance crews to the platform. High-quality platform equipment should ensure that only two short maintenance campaigns are required per year - to be performed in good weather seasons.

New to Norway

According to Ivar Aasheim, senior veep, field development, the costs of subsea systems are still rising. While unmanned wellhead platforms without facilities represent a new concept in Norway, Statoil said, they are common elsewhere, including in the Dutch and Danish sectors.

Further pre-studies of the concept will be carried out, opening the way to an investment decision next winter.

‘Subsea-on-a-stick’ will presumably also be evaluated, along with subsea solutions, for a new Oseberg area tieback - Krafla-Askja (31/20). Following a fifth discovery on these fields, Statoil reckons it has confirmed reserves of 140-220mmboe, which it describes as ‘very substantial volumes for a mature area of the shelf.’

Krafla is expected to be developed as a 25km tieback to Oseberg South, possibly linking into the Stjerne subsea facilities, 16km to the northwest. Askja will likely be tied back 13km into Krafla. The project looks like another candidate for Statoil’s ‘fast-track’ portfolio.

The fifth discovery in the area was a modest find of 6-19mmboe, mainly oil, made with the Krafla North exploration well (30/11-10). The semi Transocean Leader then drilled an appraisal sidetrack (30/11-10A) into the Krafla Main reservoir, substantially lifting the reserves estimate to 50-82mmboe from 13-57mmboe, according to the NPD. The water depth is 105m. Discoveries have also been made on Krafla West, Askja West and Askja East (30/20).

Offshore