Technical specifications

Basic infrastructures

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The Alwyn Area consists of the Alwyn North platforms, the Dunbar platform and a series of subsea fields tied back to these installations.

Alwyn North consists of two platforms, North Alwyn A (NAA) and North Alwyn B (NAB), which are joined by a bridge. NAA contains the drilling and accommodation facilities, while NAB contains processing facilities for both Alwyn and Dunbar. After processing, gas is exported into the Frigg UK pipeline (FUKA) and onwards to the St Fergus terminal. Oil is exported into the Brent System via Cormorant Alpha and onwards to the Sullom Voe Oil Terminal

Processing facilities

Alwyn has processing facilities for oil, gas and water separation together with facilities for gas lift and water injection and power generation. Click here to see an overview of its hydrocarbon processing facilities. These were designed to be able to accept third party business. Depending on third party effluent characteristics and production flowrate, tie-in locations could be studied on Alwyn, Dunbar or their associated subsea networks in order to process and export those effluents.

There are limited processing facilities on the Dunbar Platform. There is a production separator for Ellon fluids but all other production is pumped directly via multiphase pumps to the Alwyn North Platform for processing prior to export. Any future 3rd party tie-ins at Dunbar would require significant brownfield work.

In order for either the Alwyn or Dunbar platforms to process third party fluids, an acceptable specification would have to be developed following a detailed analysis of fluid composition in relation to processing capabilities.

Inlet hydrocarbon quality ranges will be considered on a case by case basis, in order that Alwyn platform facilities’ processing capabilities can be assessed with regard to redelivery of gas and stabilised crude.

Fluid facilities

Standard Platform Terms

Any party interested in using the existing plant should take the following basic parameters into account:

  • Alwyn platform has a limited capability to handle H2S;
  • Alwyn platform has no specific CO2 handling equipment and is constrained by the gas export CO2specification;
  • Low pressure system operating at 25 barg;
  • High pressure system operating at 50 barg;
  • Low, low pressure operating system (with minimal capacity) at 11 barg.

For non-processed transportation over the Alwyn Area platforms, the product stream must meet the oil and gas export specifications highlighted below.

Oil export specification

For oil export to Sullom Voe Oil Terminal via the Brent System, the True Vapour Pressure (TVP) should not exceed 115 psia at 100°F and the bottom sediment and water content should not exceed 5% by volume.

Gas export specification

For gas export to the St Fergus Gas Terminal, the following specification applies:

H2S 2.6 ppm Vol (maximum)
Total Sulphur 15.0 ppm Vol (maximum) expressed as H2S
Mercaptans Undetectable as measured in accordance with IP 272/71
CO2 3.8% mol (maximum)
O2 10.0 ppm Vol (maximum)