All-electric subsea starts its charge
  from: Offshore Engineer
  by: Darius Snieckus
  Thursday, April 03, 2008

For the all-electric subsea faithful, the future looks to have finally arrived, as installation of the world’s first ‘no batteries, no hydraulics’ subsea production system, the CameronDC, gets under way on Total’s K5F development in the Dutch North Sea. As final touches were put to the unit before transport to the field, Darius Snieckus visited Cameron’s centre of excellence for controls technology in Celle, Germany.

The September 2006 announcement by Total of plans to develop a satellite gas field in the Dutch North Sea might have excited only cursory interest from the majority in the offshore industry but for one fact: the beating heart of the operator’s K5F development is a pair of all-electric subsea production systems (SPS), the first in the world to be deployed on a greenfield project. This month, the units’ wellheads are to be installed on the development, located 104km from Den Helder, and in the coming weeks two 4in x 2in, 10,000psi WP trees fitted with electrically-actuated production and annulus gate valves, chemical injection valves, electricallyactuated insert-retrievable chokes, and fully redundant electric subsea control modules (SCM) will be lowered through 40m of water and hooked up. All going according to schedule, K5F will be onstream later this quarter.

The all-electric subsea production units have been more than a decade in the making at Cameron, the genesis of the technology traceable to the first take-up of electric actuators in the early-1990s. Starting with a core technology development programme that aimed to design, develop and qualify main systems components for the CameronDC, Cameron fashioned prototypes that were put through their paces in lifecycle, performance, function, shock and vibration, and insulation resistance tests. System assurance followed, with the contractor undertaking rigorous reliability evaluations and cost/benefit studies at Cranfield University in the UK, supported by BP and Total, to prove the capital and operational savings to be gained through the SPS use.

Next, two pilots were carried out. The first involved a 22-day operation in the fjord next to Cameron’s base in Stavanger, Norway, in 2003, the same year Total entered into a technology cooperation agreement with the contractor. The second, in 2004, took place on the BP Magnus platform, where the actuators successfully accomplished the equivalent of a 240-cycle, 20-year life. Most recently, the CameronDC moved through system qualification of the final product design, including testing of electric actuators for 5in, 2in and 3/4in gate values, electric choke actuator, electric SCM, power regulation module, and redundant channel systems. Now the K5F proving ground awaits.

‘CameronDC technology is something the industry has been looking for for a long time,’ states Robert Lopez, Cameron’s director for subsea electric systems. ‘And it’s been a long time in coming.We have worked with many operators now over the last dozen or so years to get to where we are today.We started with BP looking at reliability, cost benefit, value streams. Total joined the mix a little further on. Chevron has been very supportive. Petrobras, Statoil and other operators have also shown a real interest in this technology’s development and have given us a lot of really valuable input in the design of the system.’

The ‘voice of the customer’, he adds, has been highly influential, pushing Cameron to ‘go about as far as we could go [in] proving the concept, packaging the system, and assessing its functionality in the field and capability subsea.’

‘Everyone understands how risk-averse the industry is. So the ability to go in and assess the technology and the risk of applying the technology has been an area where the operators were of great help to us,’ Lopez continues. ‘I think we are under some scrutiny because everyone is watching us and that is not a bad thing. There is a continuing interest in allelectric technology for a very good reason and that is that it brings significant value.’

The CameronDC value proposition is far-ranging. To the contractor’s mind, the technology represents not only a stepchange in reliability and availability, with Total’s own independent tests returning a demonstrated 2.5% improvement in reliability in a ‘typical application’, but also an answer to the numerous shortcomings of electrohydraulics systems, including those linked to water depth limitations, long tieback distances, electrohydraulic component failures and environmental integrity. In the last instance, no hydraulics means hydraulic leaks and hydraulic-fluid disposal issues are removed from the production equation.

Enhanced functionality is another selling feature. Because power and signal transmission to the CameronDC are not dependent on hydraulics, control system commands can be sent in rapid succession, eliminating the lag time required for accumulator charging, while high-speed communication allows for ‘near-instantaneous’ communication with the system as well as feeding back data on subsea conditions. ‘Ultimately it is all about reliability,’ underlines Lopez. ‘And reliability means production availability – how functionable a system will be over the course of a field’s life.’

In operational expenditure terms, the CameronDC, when compared in a BP R&M report against a electrohydraulic system, was calculated to require 40% fewer interventions over the first year and an average annual reduction of 20% on a generic 20km step-out development in 1500m of water producing 100,000boe/d over a 12-year field life – uptime that translates into opex savings of $5 million/yr. Cash flow, the same report found, saw a 6% increase in year one, and an average annual increase of 3.5%. It is, says Lopez, a ‘very compelling opex proposition’.

Power play

Once into production, operation and control of the K5F’s SPSs will be handled from the K6 central complex, located 17km away. Subsea 7 took on installation of the development’s basic hardware – the manifold template and the 18km Ducosupplied umbilical that contains four power cables, chemical injection tubing, and – the one element still not fully electric – a hydraulic line to actuate the downhole safety valve. The umbilical will send 3000v of high voltage direct current via power regulation modules to the SPSs’ two SCMs, which will function on ‘independent channels’ affording the development full redundancy.

‘Full redundancy is one of the key features of the K5F system, with independent channels operating each tree,’ notes Lopez. ‘This is something you just cannot do with electrohydraulic systems, or at least not easily or economically.’

Production forecast to reach a plateau of 2.6 million m3/d from K5F will be conveyed along a new 10km long, 8in export line running to the existing K6N satellite platform, with tanks and pumps on K6 supplying the monoethyleneglycol needed to fight off hydrate formation.

A decision is to be taken this year by Total regarding longer term plans for K5F, likely to include as many as four wells on the development, another two on the existing template and a further stepout.

Cameron views its all-electric SPS as ‘an enabling technology with broad applications in many different scenarios’. Indeed K5F, as a shallow-water, shortdistance stepout development, is not its true calling. And so while Cameron eyes are focused on the CameronDC debut, investigations have already been carried out on behalf of other operators into possible installations in more hostile offshore environments.

Among the most ambitious would be Gazprom’s long-percolating Shtokman gas field in the Barents Sea, where a 640km stepout subsea-to-beach would need to be engineered to bring the development onstream. Tasked by three different operators with studies that addressed definition of a suitable system architecture, identification of technology gaps, and quantification of capex using an all-electric system, Cameron retuned findings including a 60% savings in controls umbilicals costs, both main and infield, an overall 23% reduction in capex, and expectation of ‘significantly higher availability’ due to the system’s higher redundancy levels.

‘There was no surprise here,’ suggests Lopez. ‘When you have an umbilical that is almost 400 miles long, anything you can do to minimise the complexity of the umbilical, taking out tubing in this case or hydraulic supply, brought out some dramatic savings. That 60% translates into a savings of around $80 million for the umbilical alone. Then there are further savings because you are doing away with all the equipment needed by hydraulic systems, hydraulic power units and so on.’

Installation, commissioning and testing of the simplified umbilical also becomes easier, representing a further cost reduction for Shtokman. And unlike with an electrohydraulic system, there is no requirement for a stored volume of hydraulic fluid subsea, ‘not only a cost saving but also in keeping with an environmentally responsible approach to development of a field in an area [the Arctic] that it is “zero emissions”,’ he notes. ‘We have high hopes for this technology in many different applications,’ Lopez continues.

‘We now have operators coming to us looking to apply the all-electric system in many different areas: the technology features and the benefits of reliability, fast response and accurate monitoring – all of which the all-electric system brings you – would certainly be applicable to subsea processing, a key goal of every operator today.’ High integrity pressure protection systems, chemical injection metering valves and BOPs are also all in the frame for the all-electric treatment.

‘When you remove hydraulic accumulation from the large stats, there are weight and space savings – significant capex benefits,’ he underscores. ‘And then there is subsea well intervention, which CameronDC is exactly right for too.’

Total, having adopted the mantle of ‘lead operator’ in moving CameronDC off the drawing board and down to the seabed, understand perhaps better than most just how wide a take-up the technology may well receive. Before K5F, the oil company had considered the system for use on a deepwater West Africa development. Now, as Total Deep Offshore project manager Laurent Bouquier, who was involved in bringing the technology to K5F, remarked recently, the operator has come to see myriad uses for all-electric units.

‘With all-electric systems, plans to add a new field to existing infrastructure will no longer be nearly as limited as with conventional hydraulic ones.With allelectric systems you have only electrical cabinets to add and on a platform where there is little room for new modules, as with most platforms in the North Sea, for example, this can be a serious advantage,’ he offered (OE December 2006).

Just how wide an appeal the CameronDC may have for asset teams in more mature oil and gas provinces is yet to be seen.

More certain, as Bouquier and Lopez both acknowledge, whether on Shtokman or some other frontier field development, ‘the greatest application of all-electric technology is yet to come’. OE

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