Statoil examines options for frontier gas-gathering system

Luva is in a harsh, remote location, presently devoid of production infrastructure.

It is also the northernmost discovery in the Norwegian Sea, with the nearest infrastructure 140 km (87 mi) to the south at Statoil’s Norne field, and the nearest point on Norway’s west coast about 300 km (186 mi) to the east. Water depth is around 1,250 m (4,101 ft), beyond the 850-1,000 m (2,789-3,281 ft) at Ormen Lange, which remains the deepest field developed to date on the Norwegian continental shelf.

Last year, the project reached decision gate one with the completion of a feasibility study which evaluated reservoir properties and local conditions. The conclusion was that there are no great hindrances to development in the subsurface. Reservoir pressure and temperature are within normal limits and the content of inert gases such as carbon dioxide is low. The current stage of work, which has a budget of NKr 213 million ($33 million), focuses on possible development concepts, including the issues of gas transport and power supply.

The partners are due to arrive at concept selection next spring, opening the way to decision gate two at the end of 2011, when they will decide whether to proceed to project sanction, Gjersvold says. Assuming the decision is positive, front-end engineering design will then be rolled out, covering the various aspects of the project in greater detail. This would allow a plan for development and operation to be submitted by the end of 2012.

All kinds of subsea solutions have been considered for Luva, but appropriate subsea processing and compression technologies have not yet been qualified. So a surface production facility with separation and compression capabilities is the preferred solution.

The choice of platform depends largely on whether the partners opt to export the condensate, which will be relatively small in volume terms, via offloading (in this case storage will be required), or through a pipeline, perhaps connected to Norne. If storage is selected, the preference at this stage is for a spar or buoy-shaped floating platform, or alternatively, a semisubmersible floater. Technip and Aker Solutions are performing studies for the spar option, with Sevan Marine working on a solution for a buoy-shaped platform. FMC is undertaking a study of the subsea requirements.

Technology new to Statoil – though not to the industry as a whole – will be required to some degree. For example, the company is looking at steel catenary risers as a lower-cost alternative to flexible risers, and fiber rope for mooring. There are no show-stoppers but a lot of smaller issues that add up to a significant challenge, Gjersvold says.

The power requirement will be in the range 40-50 MW. Statoil is evaluating how to bring power direct from the shore, which is a mandatory process for all planned field developments off Norway. Luva would require transmission over more than 300 km (186 mi) – the longest distance for the delivery of power from shore to date at present is 290 km (180 mi) on BP’s Valhall field. As at Valhall, the solution could entail delivery of high-voltage direct current, transformed into alternating current by a converter station on the platform.

Statoil would prefer to deliver Luva’s gas to the Nyhamna processing terminal, 500 km (311 mi) away, which currently serves the Ormen Lange field: there will be spare process capacity at Nyhamna by around 2016. Another option, the Åsgard Transport System some 250 km (155 mi) to the south, would not have availability until 2021.

Gassco, which operates Norway’s network of offshore gas trunklines, is also performing studies of gas transport solutions for undeveloped finds in the Norwegian Sea. Gassco is seeking a regional solution with an emphasis on both Luva and Shell’s Onyx discovery. Gjersvold stresses that the Luva partners are focused entirely on their own field at present, but he acknowledges that Statoil must think long-term, striking a balance between achieving the best solution for Luva while not limiting future opportunities for other fields.

Statoil itself has various other prospects in the area that it is looking to explore. It is also a participant in undeveloped gas finds such as Asterix, some 80 km (49.7 mi) to the west in 6705/10, which has estimated reserves of 16 bcm (565 bcf). And it is a partner in Shell’s Gro discovery (10-100 bcm), where an appraisal well was spudded in May, and Total’s Victoria (37 bcm).