Norwegian firms have chalked up yet another subsea first on the country's continental shelf.
Just weeks after Statoil brought the Aasgard subsea gas compression project online, on 17 September, Statoil has announced it has now also started production from the smaller Gullfaks subsea wet has compression project, in Block 34/10 in the northern part of the Norwegian North Sea.
Statoil says it is already looking at potential other candidates for the technology, developed with the help of multiple partners, including OneSubsea.
The subsea wet gas compression project project will help increase recovery from the Gullfaks South Brent reservoir by 22 MMboe and extend plateau production by around two years, according to Statoil.
Statoil has been keen to implement subsea compression, due to it having a bigger impact on recovery rates than conventional platform-based compression. It is also seen as an advantage that is does not take up space on platforms, as well as being a step towards Statoil's goal for the subsea factory.
The advantage of the wet gas compressor on Gullfaks, compared to Aasgard, is that it does not require gas and liquid separation before compression, thereby simplifying the system considerably and requiring smaller modules and a simpler structure on the seabed, Statoil says.
“We see great opportunities for wet gas compression on the Norwegian continental shelf. It is an efficient system and a concept that can be used for improved recovery on small and medium-sized fields. We are searching for more candidates that are suitable,” says Kjetil Hove, senior VP for the operations west cluster.
"The recovery rate from the Gullfaks South Brent reservoir may be increased from 62% to 74% by applying this solution in combination with other measures,” says Hove, senior vice president for the operations west cluster. The current recovery rate is around 59%, but Statoil has been striving to increase that to 62% through extended reach wells, new completion and sand control technology and water alternating gas injection. It is also possible to tie in other subsea wells to the wet gas compressor via existing pipelines. The station has already been prepared for new tie-ins.
The Gullfaks wet gas compressor system consists of a 420-tonne protective structure, a compressor station with two five-megawatt compressors totaling 650-tonne, and all equipment needed for power supply and system control on the platform.
The compressor station was installed in 135m water depth, 16km from the Gullfaks C facility, which they tie-in to, in early May by Seaway Heavy Lifting. On 26 June, the two 5MW compressor and cooling modules were delivered from OneSubsea's facility at Horsoy, near Bergen for installation.
Gullfaks first started production in December 1985, from Gullfaks A, with Gullfaks B coming on stream in 1988 and C in 1989.
Gullfaks is operated by Statoil, with 51% interest, with partners state-owned Petoro (30%), and Austrian firm OMV (19%).
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