Qualified system could be implemented in 2007
Statoil's search for an application for novel subsea technology has switched from the Norne complex to Tordis in the Tampen area of the North Sea. Here, it has identified a potential for implementing enhanced oil recovery, but realizes that this will depend on providing greater water-handling capacity, according to Eric Ulland, who works for the R&D depart-ment of Statoil's subsea increased oil recovery team.
The answer could be a subsea separator system with capacity to handle 200,000 b/d of liquids, separating out 150,000 b/d of water before delivering the remaining wellstream to the Gullfaks C (GFC) host platform 12 km distant. But first, such a system must prove itself to be technically feasible and more cost-effective than other options. By end-March, Statoil aimed to complete an option-screening exercise on the basis of which a preferred option would be chosen.
Screening procedure
The concepts included in the screening process involved combining lower arrival pressure at GFC with:
- subsea separation and reinjection of the water
- a new export pipeline
- existing pipelines with multiphase boosting
- increased water handling capacity on the platform.
If subsea separation is the selected option (to date this has only been implemented as a pilot project on Norsk Hydro's Troll Oil field) it will then undergo a technology qualification program geared to Tordis' needs. The process will take some time, and there are a lot of decision gates to pass through, Ulland warns. The earliest a plan for operation and development (PDO) could be submitted would be in 2005, and a scheme could not be implemented on the field before late 2007.
To date, Statoil's efforts to introduce this and other new subsea technologies have focused on satellite developments to the Norne field in the Norwegian Sea through the Norne Technology Project (NTP). Now it has decided that new technology is no longer needed on this project, as the handling volumes are below previous expectations, due to lack of success in locating additional reserves. Development of the first Norne satellites, Stær and Svale, both due on stream in 2005, will employ conventional subsea technology.
Shortlist
The NTP is now being wound up, with the final report likely to be delivered shortly. Initially five technologies were reviewed, of which two – subsea power supply and the integrated pipeline umbilical – were found to be too expensive or technically immature for application on Norne, and were dropped.
NTP then focused on qualifying the three remaining technologies, one of which was subsea separation. On Norne, this would have allowed taking production from the wells on a template, separating the water, and disposing of it down an existing injection well. Three vendors participated in a design competition – ABB/Framo, which developed the Troll Pilot; Aker Kværner, with the most compact system, and FMC Kongsberg Subsea (FKS), with a semi-compact system.
Qualification testing on the ABB and Aker Kvaerner systems has been carried out at Hydro's Porsgrunn research facility using the correct fluids on a small scale. A qualification program of the FKS system on a full-scale test loop built in Holland by the company's partner CDS was due to end in March. These tests included sand management, which would be a mandatory requirement on Norne. This project is supported by the Norwegian government's Demo 2000 program. Sand management is also being tested in both the ABB and Aker Kvaerner systems under separate Demo 2000 projects.
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Raw water injection
The NTP has also qualified two systems for the subsea injection of raw seawater (Norne is the only field in the Norwegian sector which already injects raw seawater), one based on a Framo pump and one on an Aker Kvaerner pump. Such a system would have the benefit of requiring a power line from the Norne FPSO, but no pipeline.
The third element in the NTP was a vehicle for removing hydrate plugs in pipelines, but according to Ulland, there was no application proposed beyond smaller flowlines. However, development of this technology is being extended in an Ormen Lange-related project run by Hydro, in which Statoil is also participating.
Subsea processing technology is entering a critical phase, in Ulland's view. As oil companies continue to select conventional solutions, vendors are becoming frustrated. They have invested a lot of effort and large sums of money in developing new systems, but see little sign at present of sufficient payback.
