Cross-pollination stirs life on Pazflor
  from: Offshore Engineer
  by: Darius Snieckus
  Wednesday, March 19, 2008

On the surface, Total’s Pazflor development off Angola will bear a striking resemblance to its block 17 brethren, Girassol and Dalia, insofar as they each rely of a 2 million barrel FPSO for production, storage and offloading. Delve down 1200m to the seabed however and clear differences emerge. As the French operator awards the main contracts for its latest ‘pole’ megadevelopment, project director Pascal Girondon offers OE a first look at the $8.5 billion plans for Pazflor. Darius Snieckus reports from Paris.

In the beginning was the gamechanging deepwater Girassol development with its 2 billion barrel FPSO and trio of riser towers. Then came Dalia’s sprawling subsea city of 67 wells, first-of-a-kind integrated production bundles, and similarly large-scale floater. Now on the horizon – and fast building up steam – is Total’s latest offshore Angolan megadevelopment, Pazflor, a project once again fashioned around a floating production juggernaut but distinguished by the fact that the field’s wellfluids will travel topside for processing aided by the world’s first full-scale subsea separation and boosting systems. Forging an economically viable development concept for Pazflor, expected onstream in 2011 – 10 years after Girassol – may be the operator’s greatest feat yet, requiring an alloy of ‘many well-tried techniques’ matured on its block 17 predecessors and an array of technological advances tailormade for this ‘difficult deepwater field and its difficult reservoirs’.

Located in 600-1200m of water some 150km from the Angolan capital of Luanda and 40km from neighbouring field Dalia, Pazflor is actually four fields in one: Perpetua, Hortensia, Zinia – all heavy oil (17°-22°API) Miocene reservoirs – and Acacia – a lighter (35°-38°API) Oligocene structure. The development, budgeted at $8.5 billion, will cover an area of 600km2 with a north-south axis extending over 30km. Seen in the round, the seabed expanse at Pazlflor and the complex nature of its reservoirs – to say nothing of the water depths at the development – have thrown up an unprecedentedly wide range of challenges for Total.

Like Girassol (OE September 2001) and Dalia (OE October 2005) before it, Pazflor represents a brave new phase in block 17’s evolution.

‘Coming after the Girassol and Dalia developments, Pazflor, to my mind, constitutes a new frontier or technological step-change in the deepwater development adventure here,’ underlines project director Pascal Girondon. ‘And since I took on [project directorship of] Pazflor two years ago we have come to see that this development is not only a technical challenge – though it is certainly that – but is also a very tough economic challenge. The risks are stacked: technical, technological, economic.’

Underpinning these ‘stacked’ risks is a landmark subsea processing and production system that is being delivered by FMC Technologies under a $1 billion deal. Although there are two offshore projects presently using subsea separation units – the Troll C Pilot in the North Sea and the Vasps (Vertical Annular Separation and Pumping System) on the Marimbá field off Brazil – and one – Tordis (OE September 2007) – employing subsea separation with multiphase boosting and water reinjection, these are all employing the technology as an additional artificial lifting method for ageing fields. Pazflor, by contrast, is the first to incorporate subsea separation in its base case scenario, meaning, as Girondon notes, that the ‘stakes are of another size’.

‘As Miocene production, which represents some 70% of the total 200,000b/d or more of oil that will be flowing from the development at plateau, relies only on subsea gas-liquids separation, in the case of shutdown or degraded performance of the system the entire production of the associated line will stop,’ he states. ‘Whereas with the Troll C and Tordis systems production would carry on anyway, just at reduced flowrates or under degraded conditions. This clearly points to the criticality of the Pazflor system in terms of the overall success of the project, as well as its specificity as the main focus in the course of the concept selection, making robustness our leitmotif. Quite simply, without subsea processing the economics of Pazflor would not work.’

With Pazflor’s Miocene crude heavier and more than twice as viscous at that of Dalia, getting the technology to a satisfactory standard of robustness has meant testing, testing, and still more testing. Investigations into the gas-liquid separation efficiency of a technical solution for subsea separation and production from Pazflor began in the pre-project studies phase and led to a three-stage programme launched in 2006. First, tests with viscous synthetic oil were carried out in transparent downscaled units under atmospheric pressure at the UK’s Cranfield University to select a separation configuration (horizontal or vertical) and test different internals. Next, in early 2007, tests were run at the Institut Français du Pétrole’s Solaize facility with doctored Miocene crude – Dalia oil mixed with Sincor 80:20 to increase viscosity – and gas, again in a downscaled unit under pressure with vertical separation, in order to arrive at gas volume fraction (GVF) figures needed for subsea pump design.

‘Both stages explored extremely high viscosities, up to 2500-3000cPo, so that we would get the real behaviour of Pazflor during a cold restart at 4°C, as well as various flowrates, operating pressures, and different inlet piping arrangements,’ Girondon explains. ‘Following the first tests, a target of 15% GVF in the liquid was defined for the pumps design, with a pump back-up case consisting of multiphase pumps also added. The second set of tests confirmed this figure.’

Based on the 15% GVF figure, Total invited FMC Technologies and Aker Kvaerner Subsea to design suitable ‘hybrid’ pumps, the former developing a system around helicon-axial and centrifugal technology and the latter one that used a centrifugal unit with modified first stage impellers. The resulting pumps were put through their paces in qualification programmes that looked to define gas handling capacity under viscous flow, along with overall viscosity handling capabilities.With both pumps testing successfully under ‘severe conditions’ the technologies that emerged from this stage have formed ‘a key part of the solution proposed’ for Pazflor.

‘The results of these different studies were more and more convincing, so that eventually subsea separation and pumping was retained as the frontrunning solution despite the risks associated with its novelty,’ states Girondon. ‘A cost estimation exercise was performed internally and the recommendation passed successfully through Total’s internal validation process and received partner approval. [Block 17 concessionaire Angolan state oil company] Sonangol was also kept informed of the decision-making process through regular technical meetings.’

FMC, in the end, landed the grand prize for this aspect of the development: three subsea separation units (SSU), 49 subsea trees and wellhead systems, and three four-slot production manifold systems, production control and umbilical distribution systems, gas export and flowline connection systems, as well as ROV tooling. The contractor will also provide local support for installation and start up, with deliveries to be made over a ‘multi-year period’ starting in 2009.

Before that however, a third set of tests will be performed on the SSUs at IFP Solaize once sufficient volumes of Pazflor Miocene crude are available, ‘most probably during 2008’, according to Girondon. ‘This will constitute the ultimate test programme which will validate the concept before installation in two years’ time,’ he notes.

Solids handling is also central to Pazflor’s subsea separation solution. As the SSUs are foreseen to be permanently installed on the seabed for some 20 years and ‘not retrieved under normal operations’, Total has been keen to ensure that no sand accumulation finds its way into any part of the system. The choice of a vertically-orientated separator was informed by this development philosophy, as was a system design that features a conical base. To forearm the technology again ‘massive’ sand production – such as could result from a sand screen failure – that threatened serious cone clogging, an ROV connection to a jetting ring has been built in to the design. Sand plugs in the separator can also be ‘fluidised’ by backflushing from the liquid risers.

Benefits package

For Total, the wider benefits of using subsea separation on Pazflor include: elimination of gas-lift and separation of the associated gas form the liquids, meaning the wellstream comes well away from the hydrate formation zone at 23 bar and, in turn, a more stabilised flow regime in the risers can be achieved; location of wells can be optimised, shortening the drilling trajectory; and lowered gas compression requirements topside removes the need to build in pumps and heaters on the FPSO for dead crude circulation during shutdown. There is also a cost-savings on the seabed as subsea production and water injectors ‘tee’ into infield flowlines, each connected to a separation unit, cutting out manifolds and pigging loops and reducing spool pieces and insulation requirements.

Just as the development as a whole can be seen as a yoking together of the ‘classical and the novel’, Pazflor’s subsea layout is a combination of two distinct development architectures customised to the field’s two crude types. For Acacia’s lighter Oligocene oil, a conventional 80km flow loop with three manifolds similar to that used on both Girassol (OE September 2001) and Dalia, with reservoir pressure maintained via a combination of water and high-volume gas injection – the former into most of the Oligocene horizons and the latter into the upper Oligocene sands. To tap the ‘non-eruptive’ Miocene on Perpetua, Hortensia and Zinia, subsea gas-liquid separation and liquids boosting comes in to play, with production wells teed individually or in pairs into a single flowline connected to an SSU and liquids boosted by a duo of pumps to the FPSO and gas flowing naturally to the surface.

‘The SSUs are to be installed close to the first production well, in order to get a quick heat-up during cold restarts,’ Girondon outlines. ‘There is one main common umbilical per production line serving the producers by flying leads, and the injection wells by dedicated umbilicals. Each SSU has its own power and control umbilical. The entire subsea network is depressurised from a Christmas tree choke to the separator via the gas lines of the SSU. On both Oligocene and Miocene production wells, a multiphase flow meter will be installed for production allocation purposes and each producer will be equipped with a sand detector.’

Subsea gas-liquids separation vouchsafes ‘numerous advantages’ in producing heavy crudes and low energy reservoirs such as at Pazflor, ‘as long as the oil and field layout characteristics are favourable,’ offers Girondon, and the impact on the scope of supply is also ‘significant’: shortened flowline length, with lower thermal insulation and fewer spools, and reductions to the number of risers; a smaller compressor and first stage separator on the FPSO; and, operationally, an easier preservation sequence.

‘By reducing the scope of supply we expected a significant cost reduction compared to conventional schemes with loops and MPPs and gas-lift,’ he adds, ‘but when you take into consideration the present market situation – drilling rig availability, cost of Surf [subsea umbilicals, risers and flowlines] operations these cost benefits proved to be even higher than first calculated.’

A consortium made up of Technip and Acergy has been awarded the $1.86 billion contract to supply and install Pazflor’s subsea architecture. The French contractor is handling engineering, procurement, fabrication and installation of over 80km of production and water injection rigid flowlines, conventional flexible risers, and a ‘Dalia-like’ IPB, as well as engineering, procurement and fabrication of over 60km of umbilicals. Its UK-headquartered partner is taking responsibility for engineering, procurement, fabrication and installation of 55km of water injection, gas injection and gas exports lines, umbilicals and more than 20 rigid jumpers, along with installation of all manifolds, the three subsea separation units with associated umbilicals and the FPSO mooring lines, and overall pre-commissioning.

Technip will manufacture the umbilicals at the Angoflex plant in Lobito, Angola it runs with Sonangol, and flowlines and subsea structures at its spool base in Dande, Angola. All Acergy fabrication will be undertaken at the Sonamet yard in Lobito joint-owned with Sonangol. The two contractors will sail out vessels including Technip’s Deep Blue and Deep Pioneer and Acergy’s Acergy Polaris and Polar Queen to carry out installation on Pazflor, an assignment slated to start in mid-2010.

Stock float

Spread-moored three years from now on the field, the development’s 1.9 million barrel FPSO will bring the total installed production capacity on block 17 to over 700,000b/d, processing up to 220,000b/d of oil, 4.3 million m³/d of gas and 270,000b/d of water in line with the Pazflor’s present plan of 49 subsea wells – 25 producers, 22 water injectors and two gas injectors. South Korea’s Daewoo Shipbuilding & Marine Engineering has been selected to build the 325m x 61m x 32m vessel, and recently subcontracted Houston’s KBR to provide engineering, procurement and interface design services for the 32,000t topsides, which will have power generation of 165MW to run the subsea systems. Dresser-Rand will supply advanced turbomachinery including gas compression packages and centrifugal compression trains under a $44 million deal. Sailaway is scheduled for late-2010.

‘We kept a tight focus on basic engineering and this has meant there have been no major design changes proposed during the call for tender process for the FPSO,’ underlines Girondon. ‘Likewise, what we are really concentrating on this year are the long lead items and overall procurement for the development, it will be the detailed engineering and making sure we do not fall behind our schedule.We have 45 months before planned start-up, which is very aggressive for this type of project. On Pazflor, almost everything is on the critical path.’

Drilling, on the project timeline to get under way in 2009, presents its own raft of challenges, not least that 23 or the development’s 49 wells are called for at first oil – on both Oligocene and Miocene fields. Saipem will take on a five-year development drilling campaign at Pazflor using its S12,000 newbuild drillship, currently under construction at Samsung Heavy Industries shipyard in Korea, as part of Total’s longer-term plans to evaluate the potential reserves upside at Pazflor and its environs.

Among the many lessons learnt, going forward, from its first two block 17 projects – ‘Girassol, the world’s first giant subsea deepwater development, Dalia, more complex, with twice the number of Christmas trees’ – were those of cost control. Having seen Dalia fall prey to exponential cost escalations as steel prices rocketed over the course of its development, says Girondon, the Pazflor project team has worked hard to negotiate something more like fixed terms with its main contractors.

‘Speaking with the bidders, we all had to acknowledge that prices were already much higher than when the project started – and we have to accept those prices even if it is impacting on our economics,’ he underlines. ‘But what we want to avoid, as far as we can, is signing a contract and then seeing escalations of 30% in the price. So we have worked with the bidders using a kind of hedging mechanism to see to what extent we can secure prices from the start. And this is certainly a big difference from what we did on Girassol or Dalia.’

On Angola’s ‘floral’ block Pazflor is a new bloom, its name a hybrid derived from pasifor (Portuguese for ‘passion flower’) that references the development’s ‘beautiful but complicated’ Perpetua, Acacia and Zinia fields. Passion, if only to judge from the oil company’s development work on Girassol and Dalia, Total has. And passion it will need as it attempts that which has not been done before – a greenfield subsea separation and boosting technology based development, this time through grafting together the tried-andtested with the untried-until-now.

‘Like Girassol 10 years ago, I have no doubt that our success with subsea separation and boosting – making it possible to produce fields not obviously well-suited to subsea production because of viscous and heavy oil, low productivity index, low gas ratios and so on – will change the way the oil industry looks at many offshore areas of the world,’ Girondon concludes.

‘Achieving a good balance between the potential of such new solutions and the cost involved in pioneering them on a development such as Pazflor, that will be quite another story. And, ultimately, first oil in 2011 is really just the end of Pazflor phase one. OE

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