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Lincolnshire Offshore Gas Gathering System

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Lincolnshire Offshore Gas Gathering System (LOGGS)
CountryUnited Kingdom
Regionsouthern North Sea
Location/blocks49/16
Offshore/onshoreOffshore
Coordinates53°23’27”N 02°00’13”E
OperatorsConoco, ConocoPhillips, Chrysaor
OwnerConoco, ConocoPhillips, Chrysaor
Field history
Start of production1988
Abandonment2018

The Lincolnshire Offshore Gas Gathering System (LOGGS) was a major natural gas collection, processing and transportation complex in the UK sector of the southern North Sea. It comprised five bridge-linked platforms about 118 km east of the Lincolnshire coast, which operated from 1988 to 2018.  

Background

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The development of the Audrey, North Valliant, South Valiant, Vanguard and Vulcan gas fields[1] across several North Sea Blocks (49/11a, 49/16, 49/21, 49/16, 48/25b respectively) required the provision of a central collection, processing and transportation hub to deliver the combined gas output to the onshore Theddlethorpe gas terminal. The LOGGS complex was built to meet these requirements and with provisions to collect gas from future fields.[2]

The LOGGS facility was principally owned and operated by Conoco, this became ConocoPhillips in 2002. Following cessation of production Chrysaor, a subsidiary of Harbour Energy, assumed ownership of LOGGS in 2019.[3]

The LOGGS installation

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The LOGGS installation was located in UK offshore Block 49/16, coordinates 53°23’27”N 02°00’13”E, the water depth is 21 metres.[4]

The installation initially comprised three bridge-linked platforms. These were North Valliant wellhead platform (PD), a Processing platform (PP), and an Accommodation platform (PA). These were commissioned in 1988. To allow lower pressure wells to produce gas a Compression platform (PC) was added to the complex. To cater for production from additional fields a Riser platform (PR) was added to the complex in 1993.[2]

The parameters of the platforms were as follows.[2]

The LOGGS Complex
Platform Function Legs Jacket weight, tonnes Topsides weight, tonnes
LOGGS PD Wellheads 4 1324 602
LOGGS PP Processing 8 2347 3950
LOGGS PA Accommodation 4 1444 2418
LOGGS PC Compression 8 2109 4752
LOGGS PR Import risers 4 1870 2499

Import and export

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The import and export pipelines connected to the installation were as shown in the following tables. Pipelines were connected to the PP and PR platforms only, there were no pipeline riser connections to the PC, PA or PD platforms.[2]

LOGGS Import pipelines
Pipeline number LOGGS Platform From installation Other connected installations Fluid Diameter Length. km Installed
PL456 PP Vanguard QD Well fluids 10” 7.5 1988
PL458 PP Vulcan RD Vulcan UR Well fluids 18” 16.0 1988
PL460 PP South Valiant TD Well fluids 10” 10.6 1988
PL470 PP North Valiant SP Well fluids 10” 4.3 1988
PL496 PP Audrey A WD Audrey VM, Audrey XW, Annabel, Ensign Well fluids 20” 4.3 1988
PL455 PP Theddlethorpe Methanol 4” 118.3 1988
PL854 PP Anglia YD Anglia YM Well fluids 12” 23.6 1988
PL947 PR Ann XM Ann A4, Alison KX Well fluids 12” 41.8 1993
PL1093 PR Ganymede XD Callisto ZM, Europa EZ, NW Bell ZX Well fluids 18” 19.1 1993
PL1692 PR Vampire OD Viscount VO Well fluids 12” 9.2 1999
PL2107 PR Saturn ND Mimas MN, Tethys TN Well fluids 14” 43.2 2005
PL2643 PR Viking BP All Viking satellites Well fluids 16” 19.1 2009
PL2811 PR Clipper South RL Well fluids 12” 15.1 2012


The export pipelines connected to the installation were as follows.[2]

LOGGS Export pipelines
Pipeline number LOGGS Platform To Fluid Diameter Length. km Installed
PL494 PP Theddlethorpe Gas & condensate 36” 118.3 1988
PL457 PP Vanguard QD Methanol 3” 7.5 1988
PL459 PP Vulcan RD Methanol 3” 16.0 1988
PL461 PP South Valiant TD Methanol 3” 10.6 1988
PL471 PP North Valiant SP Methanol 3” 4.3 1988
PL497 PP Audrey A WD Methanol 3” 16.5 1988
PL855 PP Anglia YD Methanol 3” 23.6 1988
PL1094 PR Ganymede ZD Methanol 3” 19.1 1993
PL1693 PR Vampire OD Methanol 3” 9.2 1999
PL2108 PR Saturn ND Methanol 3” 43.2 2005
PL2644 PR Viking BP Methanol 3” 19.1 2009
PL2811 PR Clipper South RL Methanol 3” 15.4 2012

Process facilities

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Upon arrival at LOGGS PP or PR the fluids from the satellite platforms and subsea completions were routed to their respective 3-phase Inlet Separators, where the fluids were separated into vapour, water/methanol and condensate.[5] Each of these streams was metered. The condensate and methanol/water streams were recombined and routed to a Condensate Surge Drum from where Condensate Pumps injected the liquids into the gas trunk line to Thedlethorpe. There were two condensate handling systems one on PP and one on PR.[5]

Platform PD was a wellhead platform for the North Valiant field designated North Valliant 1. Well fluids were routed across the bridge to PP and combined with fluids from North Valiant SP (North Valiant 2) and flowed to the North Valiant Separator.[5]

Each of the satellite gas streams could be routed to either the suction manifold, the interstage manifold or directly to the discharge manifold depending on the gas pressure. The compression facility had three trains of two stage compression. From the suction manifold gas flowed to the First Stage Suction Drum where liquids were removed. Gas was compressed in the First Stage Compressor and flowed through the Interstage Cooler where it combined with gas from the interstage manifold. The combined gas stream flowed to the Second Stage Suction Drum where liquids were removed. Gas was compressed in the Second Stage Compressor and flowed through the Aftercooler and then to the 36” trunk line to Theddlethorpe.[5]

Fuel gas for powering the compressor and electricity generation gas turbines could be taken from the interstage or the discharge manifolds.[5]

Throughput

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The gas throughput in million cubic metres per year (mcm/y) for some of the fields which flowed through LOGGS were as follows.[1] [6]

Field Peak production, mcm/y Peak year
Vanguard 437 1989
Vulcan 1,941 1989
South Valiant 1,294 1991
North Valiant 680 1991
Audrey 2,800 1990
Anglia 600 1992
Ann 500 1994
Ganymede 1,706 1996
Vampire 727 2000
Saturn 1,598 2007
Clipper South 587 2014

Terminal redevelopment

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As a consequence of the LOGGS development new gas reception and processing facilities were commissioned at the Theddlethorpe gas terminal. A second 30-inch line (Feeder No. 17) was laid from the Theddlethorpe terminal to Hatton Lincolnshire where it connected to the 36-inch National Transmission System Wisbech to Scunthorpe line (Feeder No. 7).[7]

Incidents

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In November 2012 there was a major gas release on LOGGS. ConocoPhillips were fined £3 million in the subsequent prosecution.[8]

In May 2016 the Low Pressure Vent Knock Out Drum became liquid locked which led to significant release of gas into the workplace.[9]

Decommissioning

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The Theddletorpe Gas Terminal closed in August 2018.[10] Gas export from LOGGS and its satellite ceased. The following installations were shut-down: Vanguard QD, Vulcan RD, South Valiant TD, North Valiant SP, North Valiant PD, Audrey A WD, Anglia YD, Ganymede ZD, Vampire OD, Saturn ND, a Viking BP. Subsequently their wells were plugged and abandoned and all structures above the seabed were removed.

Gas production from Clipper South, owned by Ineos, was rerouted via a new pipeline to Shell’s Clipped Complex and from there to Bacton Gas Terminal.[11]

In March 2021 Chrysaor submitted plans to decommission and remove the LOGGS installation. It envisages that the platforms would be removed in 2022-23, debris clearance would continue until 2024 and that close out would be in 2025-26.[2]

See also

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References

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  1. ^ a b Department of Trade and Industry (1994). The Energy Report. London: HMSO. ISBN 0115153802.
  2. ^ a b c d e f "Decommissioning Programmes LOGGS Installation & North Valiant PD, LDP5 LOGGS PR, LOGGS PC, LOGGS PP, LOGGS PA, North Valiant PD, & Associated Pipelines" (PDF). assets.publishing.service.gov.uk. 2021. Retrieved 25 November 2021.
  3. ^ "Chrysaor acquires ConocoPhillips' UK oil and gas business for $2.675bn". offshore-technology.com. 2019. Retrieved 25 November 2021.
  4. ^ "inventory of Offshore Installations". odims.ospar.org. 2017. Retrieved 25 November 2021.
  5. ^ a b c d e LOGGS Flow Diagrams, ConocoPhillips, 2005
  6. ^ "Production data". www.gov.uk. 2014. Retrieved 25 November 2021.
  7. ^ "NTS Maps". Retrieved 27 November 2021.
  8. ^ "CONOCOPHILLIPS FINED £3M FOR OFFSHORE GAS RELEASES". www.ioshmagazine.com. 2016. Retrieved 25 November 2021.
  9. ^ "ConocoPhillips hit with notice after "significant" North Sea gas release". www.energyvoice.com. 2016. Retrieved 25 November 2021.
  10. ^ "Conoco ends SNS production as Theddlethorpe reaches end of the line". energyvoice.com. 16 August 2018. Retrieved 30 November 2021.
  11. ^ Shell (2018). "First gas flows from Clipper South field into Bacton". Shell. Retrieved 1 December 2021.