The vision of “subsea factories” on seabeds around the world is one that is slowly becoming reality. Although the jigsaw of competing technologies needed to give an operator a field development toolbox it can work with is complicated, it is now increasingly achievable.

The importance of having such options at their disposal – whether for subsea separation, boosting, or compression – clearly is recognized by all the industry’s major players.

The rewards can be dramatic when the business case is right. It is generally accepted that boosted wet tree developments can deliver between 5% and 20% higher recovery rates than dry tree developments, for example.

Statoil has made no secret of its goals for advancing subsea processing technologies to improve recovery from existing fields. On its Gullfaks South field, the company has worked with Framo Engineering since 2008 developing technology for compressing wet gas on the seabed. The field’s current recovery rate is already 62%, and the combination of subsea compression and conventional low-pressure production in later phases could lift the total recovery rate to an outstanding 74%, according to Statoil, which would increase production by 106 Bcf (3 Bcm) of gas – an additional 6%.

An artist’s rendering of the Snorre, Vigdis, and Tordis field operations. (Image courtesy of Statoil)

The standard industry solution has been to supply compression from a platform or onshore, but the closer compression is placed to a well, the more gas can be extracted. That’s why companies like Statoil want to place the compressor on the seabed nearer to those wells.

At the recent OTC Brasil show in Rio de Janeiro, the company stressed in a presentation that it sees subsea processing very much as an enabling technology for both greenfield projects (mainly those in northern, Arctic, and deepwater areas) and brownfield developments that may otherwise be abandoned without being exploited to the maximum. New technology development remains the key to opening the door to innovative ways of applying subsea processing.

According to Simon Davies, Statoil project leader for subsea technology and operations, the vision of a “subsea factory” could drive the application of more sophisticated gas processing on the seabed (gas sweetening and gas dehydration). Longer and more remote step-outs are driving interest in developing local, potentially renewable power generation concepts, he added.

Pumping and compression technology also will continue to evolve, Davies said, with more robust and simplified systems becoming available that are capable of greater pressure boost while handling liquids without the need for upstream scrubbing. Separation systems will become more sophisticated, and new materials – including nanotechnology – also will have an increasing role in tomorrow’s systems.

As the industry finds and develops oil and gas reserves in deeper, more remote, and harsher environments, the technological challenges, qualification requirements, and technical risks of deploying subsea processing will increase, Davies said.

“However, the business upsides will also increase, and there will almost certainly be areas where subsea processing becomes an enabling technology, without which fields cannot be profitably developed,” he concluded.

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