Shetland Gas Plant - Effluent Water Treatment
- Rachael Ferguson (Total E&P UK) | Brian Milne (Total E&P UK) | Oliver Bradshaw (Total E&P UK) | Simon Hare (Total E&P UK) | Cathy Fuchs (SUEZ Eau Industrielle)
- Document ID
- Society of Petroleum Engineers
- SPE Offshore Europe Conference & Exhibition, 5-8 September, Aberdeen, United Kingdom
- Publication Date
- Document Type
- Conference Paper
- 2017. Society of Petroleum Engineers
- 4.1 Processing Systems and Design, 4.2 Pipelines, Flowlines and Risers, 4 Facilities Design, Construction and Operation, 4.1.2 Separation and Treating, 4.2 Pipelines, Flowlines and Risers, 5.2 Reservoir Fluid Dynamics
- Effluent Water, Shetland Gas Plant, Water Treatment
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The Shetland Gas Plant (SGP) is a 500 MMSCFD capacity gas plant located at Sullom Voe on the Shetland Islands. It receives reservoir fluids, via twin 143km multiphase flowlines, directly from the Laggan-Tormore fields which are located 125km north-west of the Shetland Islands in approximately 600m water depth.
Fluids arriving at the SGP are separated into gas and liquid phases. The gas is processed and then exported to St Fergus gas processing plant via the SIRGE and FUKA pipelines. The liquid phases are separated and the condensate is exported to the BP Sullom Voe facility for stabilisation and export by tanker. The aqueous phase (rich MEG) is regenerated at SGP to produce lean MEG for reinjection subsea, a by-product of the regeneration process is produced water.
The produced water is then fed to the Effluent Water Treatment Plant (EWTP) for processing prior to being discharged to Yell Sound via a 3.75km pipeline. The effluent water treatment package was designed by SUEZ Eau Industrielle (patented design). The effluent water is required to meet strict discharge specifications as part of the operating consents, e.g. Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), MEG, Benzene, Total Suspended Solids (TSS), etc.
The Effluent Water Treatment Plant (EWTP) consists of 3 stages of treatment: physical, chemical and biological.
The physical treatment contains;
A Corrugated Plate Interceptor, which uses gravity to separate the free oil from the produced water;–
A Stripping Column, which removes BTEX (Benzene, Toluene, Ethylbenzene, Xylenes) and volatile hydrocarbons entrained in the water via transfer to fuel gas.
The chemical treatment contains;
A Dissolved Air Flotation Treatment Unit, to remove any residual free oil and TSS utilising flocculants and coagulants.
The biological treatment contains;
A Biological Aerated Flooded Filter (BAFF) Unit, which is an aerobic biological filtration process whereby a biomass (bacteria) give biological degradation of soluble organics while simultaneously removing suspended solids via filtration. The biological process removes the remaining MEG and BTEX and has the ability to handle varying loads of COD and BOD.
The EWTP has been in operation since the start up of the SGP in February 2016.
The paper will discuss:
The initial challenges faced during start up and the first year of operation and how these were overcome;–
Current operation of the process including ongoing challenges and areas of success.
|File Size||1 MB||Number of Pages||12|