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Northern Lights

Written by  Elaine Maslin Thursday, 01 June 2017 00:00

Lundin believes the future is in the north. Elaine Maslin reports on the firm’s plans for the Alta Gohta development.

An artist’s impression: Alta Gohta. Image from Lundin.

Norway’s far north, in the Barents Sea, isn’t the easiest place to be a hydrocarbon explorer. It lacks infrastructure, is cold and very dark in winter (and the opposite in summer), has tricky reservoirs, and is subject to the same environmental regulation as in other parts of the North Sea.

The Barents Sea still has a prize to hunt, however. Half of the remaining recoverable undiscovered resources on the Norwegian Continental Shelf are estimated to be in the Barents, according to the Norwegian Petroleum Directorate. With project development experience (Edward Grieg) and Barents Sea exploration experience (Alta, Gohta, Neiden and Filicudi discoveries – all on the Loppa High) under its belt, Lundin thinks that it has what it takes to create a high north hub.

Lundin also has a trick up its sleeves. The firm is hoping to go all-electric on its Alta Gohta development, a project that can become a hub for further discoveries, such as Filicudi.

“We believe that the future in Norway is in the north,” said Lundin’s Tom Wideroe at the Subsea Valley Conference in Oslo in early April. “There is a challenge, the lack of infrastructure, and icing of structures. The Polar lows are hard to predict and it is dark in winter and light in summer.”

Exploration activities are also highly regulated and environment-related restrictions are tough. “Although there are no special environmental restrictions in the Barents Sea, we have to have high focus on it,” Wideroe says.

However, despite the cold and dark in this region, it’s not as bad as it could be. Wave height and wind are generally calmer than in the North Sea, water depth is generally less than 500m, and while icing is an issue, sea ice is not in this area of the Barents Sea, although conditions worsen as you go east. “We [will] maybe have ice every 10,000 years,” Wideroe says. “Johan Castberg is designed for some ice. Wisting [an oil field, discovered by OMV in 2013, in the Hoop area, further east] will have more ice. Korpfjell [further east again, close to the maritime border with Russia] has more ice than that. Temperature falls dramatically as you go northeast,” Wideroe says.

Even so, operators are targeting these areas, including Statoil. The Norwegian oil firm is planning to drill on the Korpfjell prospect, a huge four-way closure covering 800sq km in the very northeast of the Barents Sea, this year. Tim Dodson, executive vice president of exploration at Statoil, told Bloomberg earlier this year that he would be happy to prove up 500 MMbbl to 1 billion bbl in Korpfjell, while other estimates have suggested it could contain more.

On a Loppa High

Lundin made the Gohta discovery in 2013, followed by the Alta discovery in 2014. The two fields are estimated to contain 216-584 MMboe. Further exploration and appraisal drilling in the area found the Neiden (25-60 MMboe gross resource) and Filicudi (35-100 MMboe gross resource with “significant upside potential”) fields. Filicudi (also the name of an island off the north coast of Sicily) is 30km northwest of Alta and Gohta, while Neiden is 20km east of Statoil’s Johan Castberg field.

Lundin’s initial development idea for Alta Gohta is a floating production, storage and offloading (FPSO) vessel linked to a subsea production system comprising five subsea templates, two at Gohta and three at Alta, with injection (gas lift at Alta and water injection in Gohta) and production wells with 5in or 7in vertical Xmas trees. A pipe-in-pipe production pipeline could be used, not due to temperature considerations, but for stiffness because the seabed is complex, with craters from leaking methane and cracks from icebergs, Wideroe says.

While flow assurance, per se, isn’t a challenge, siting of the FPSO will be a consideration, due to having shallow seafloor in certain areas, which could cause issues around slugging. Winterization of the topsides will also be a significant factor in the design, Wideroe says.

DCFO

All-electric systems for subsea equipment have the potential to reduce costs, increase flexibility and lower the environmental footprint, Wideroe says.

Wideroe adds that DCFO (DC electricity and fiber optic) communications is an interesting alternative for subsea power and communication. This would see Lundin follow Statoil’s lead. The Norwegian major is pursuing a DCFO scheme on its Johan Castberg FPSO development (OE: August 2016). “We think the time has come for the all-electric system,” Wideroe says.

“DC takes the communication [cables] out of the umbilical and uses standard telecommunications cable. Everything will be standardized, cable and connectors can be bought more easily. Combine that with all-electric and you can take most of the umbilical out. This is really interesting and flexible and you have more reserves, in terms of available current [power].” Pursing this approach would be, “good learning for us and the rest of the industry,” Wideroe says.

Whether the FPSO would be powered from shore is yet to been seen, and different power solutions will be studied in accordance with guidelines from the authorities, Wideroe says.

Other options are being considered for the surface production system, which would be smaller than the Johan Castberg FPSO. Options include a cylindrical FPSO, a semisubmersible unit or even a concrete floater. “It could be interesting to build in concrete again,” Wideroe notes. Another option could be subsea storage, “which we think will be available,” he says. A tension leg platform could also be used if dry wellheads are needed. Finally, a spar buoy could be used, but the water depth might be too low, he says.

Karstified carbonates

One of the challenges on Alta Gohta is the subsurface. The Alta and Gohta reservoirs are in Karstified carbonate rock, which contain vugs (a cavity in rock lined with mineral crystals) and caverns created by fresh water dissolution. While this can improve permeability, it can be a challenge to drill through it. Alta and Gohta will be the first reservoirs of this type to be commercialized offshore Norway.

“We are doing a lot to minimize the risk of drilling,” Wideroe says. “We have implemented measures in the short-term to handle the appraisal drilling. We are also looking at what to do long-term. To put this in perspective, more than 50% of the world’s reserves are in this type of reservoir. But, this is the first offshore the Norwegian Continental Shelf.”

A version of managed pressure drilling (MPD) called pressurized mud cap drilling (PMCD) could be one technique that could help drill these reservoirs. Until recently, PMCD has not been a recognized drilling technique in Norway.

There are also uncertainties concerning what is in the reservoir, which also means uncertainty around how many wells are needed. This is why Lundin intends to build in flexibility. “We have an idea but… the drilling department is working on this. We might end up needing a solution with dry wellheads,” Wideroe says.

Seeing subsurface

New seismic will be shot over 1748sq km of the area this year. It will be the first time a new method called TopSeis will be used. Lundin’s geophysicists developed TopSeis with French geoscience firm CGG to better visualize the subsurface – not least the difficult to see Karstified formations in which Alta and Gohta sit. It means towing the receivers underwater, in a banana-shape with one vessel and a buoy, while a separate source vessel sails directly over them carrying the air guns.

Lundin also plans to conduct an extended well test, next summer [2018], to further reduce uncertainty. “We will have a horizontal section produce for a couple of months,” Wideroe says. “[Possibly] one on Alta and one on Gohta, for two months each. We need to do this before we can move on.” Lundin is also drilling two appraisal wells in the summer, one in the north of Alta, and one in Gohta.

Announcing the Filicudi discovery in February this year, Lundin said the find had 25% reduced the risk on two high-graded prospects within PL533: Hufsa, containing 286 MMboe gross unrisked prospective resource; and Hurri, with 218 gross unrisked prospective resource. No doubt there will be more to come from Lundin in the high north.

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