Central Area Transmission System — BrandWiki

Central Area Transmission System

Overview

CATS pipeline

type	Natural gas
map caption	Location of CATS pipeline
country	North Sea, United Kingdom
operator	Kellas Midstream Limited
partners	BlackRock and GIC (via Kellas Midstream Limited), Eni, Harbour Energy
length km	404
discharge	1.7 billion standard cubic feet per day
direction	north-south-west, 210°
start	CATS Riser Platform (Block 22/10a) bridge linked to North Everest
finish	CATS processing terminal in Teesside, England
est	1993
through	Central North Sea
diameter in	36

The Central Area Transmission System (known as CATS) is a natural gas transportation and processing system that transports natural gas through a 404 kilometre pipeline from the Central North Sea to a reception and processing terminal at Teesside in the North East of England.

History

Plans for the site began from the discovery of BP's Lomond field in May 1972. In addition, other fields were discovered in the Central Graben Area of the North Sea.

The receiving terminal site for the system was built between 1990 and 1993. It was originally operated by Amoco.[1] The CATS pipeline was completed in 1993, receiving gas from two of Amoco's fields:[1] Everest and Lomond, now owned by Chrysaor.[2]

Together with the development of the Everest and Lomond fields, the project, which included the construction of an offshore riser platform and pipeline, was one of the largest construction projects ever undertaken in the UK, second only to the

CATS Terminal

The Central Area Transmission System Terminal is the reception and processing facility for the CATS pipeline.

It is located in Teesmouth (54°36’43”N, 1°11’45”W) at Seal Sands (borough of Stockton on Tees) on the North Sea coast, and occupies a 29-hectare site. It is situated in the middle of Teesmouth's petrochemical area, between an oil terminal to the north, and a chemical works and the former Teesside Oil Refinery (to the south).[3]

The facility processes the gas through processing trains that ensure that its quality meets the requirements for entry to the National Transmission System (NTS). Natural Gas Liquids (NGLs) are removed and the processed natural gas is fiscally metered before leaving the terminal and being fed directly into the NTS. The NGLs are then separated into propane, butane and condensate.

In 2024, CATS delivered 7.3 billion cubic metres of gas to UK markets, representing around a quarter of UK gas production.[3]

Gas processing

The CATS gas terminal has the capacity to process about 34 million standard cubic metres of natural gas a day in two parallel processing trains.[7]

The pipeline reception and gas treatment facilities[8] comprise:

The propane and butane are produced to the following specification.[6] Propane and butane are supplied to Norsea. Gasoline (C5+) is supplied to Navigator and Sabic.[7]

Inlet reception – pig receiver, slug catcher and filter. From the inlet reception fluids flow to the CATS or to the TGPP terminal.
Gas treating – mercury removal and hydrogen sulphide H2S/mercury treaters
Dewpoint control units – Joule-Thomson valve chilling then into separator vessel, gas is metered prior to export, liquid passes through a H2S removal vessel prior to metering and export
Gas dehydration (2 trains) – counter current contact with tri-ethylene glycol (TEG) facility which includes a TEG cold finger regeneration system
Cold separation – dehydrated gas undergoes Joule-Thomson valve cooling then flows to a low temperature separator, gas from the separator is heated and metered prior to export to the National Transmission System (NTS), liquid from the separator passes to the stabiliser column
Stabilization and compression – stabilizer overhead vapour (methane and ethane) is compressed and is routed to NTS, liquid from the stabilizer flows to the depropanizer
Fractionation – depropanizer overhead vapour (propane) is cooled, passes through a H2S removal vessel, and is metered prior to sale as propane, the bottom product from the depropanizer is routed to the debutanizer, overhead product from the debutanizer (butane) is cooled, metered and sold as butane, bottom product from the debutanizer is cooled, metered and sold as natural gas liquids (NGL).

Distribution

The purified natural gas is metered and enters the National Transmission System at an above ground installation (54°36’37”N, 1°11’48”W) in the south-west corner of the terminal site. The four-mile (6 km) spur of Feeder Main FM06 transports gas to a pigging and pressure reduction station at Cowpen Bewley in Stockton-on-Tees, where gas is delivered into the Regional Transmission System, there are also connections to the 24-inch Feeder Main FM06 from Little Burdon to Billingham and into the 42-inch Feeder Main FM13 from Cowpen Bewley to Bishop Auckland.

The site has two tall chimneys and one taller flare stack.[7]

The site belongs to the Teesmouth Industry and Wildlife Partnership.

Gas processing (CNS/CATS)

The CATS processing train uses turbo-expanders to reduce the temperature of the gas to remove natural gas liquids.[4] CATS gas is first dehydrated with TEG to remove water. The gas is routed to two turbo-expanders in series which chills the gas and condenses out the natural gas liquids, the product is mainly methane. NGL goes to the deethanizer fractionation column which removes ethane, this is mixed with the methane and is supplied to the National Transmission System. The NTS access point is the above ground installation (54°36’37”N, 1°11’48”W) on the CATS terminal site. NGLs from the deethanizer goes successively to a depropanizer and debutanizer which produce Propane and Butane and natural gasoline. The petroleum products are then transferred by pipeline either to liquid storage or to other petrochemical businesses based on Teesside for use as feedstock.[4]

Gas processing (SNS)

The Southern North Sea pipeline reception and gas treatment facilities include the following.[4]

A pig receiver and slug catcher. Vapour from the slug catcher is cooled and chilled in a gas-to-gas heat exchanger, then by a refrigerant system, and a Joule-Thomson pressure reduction valve before the, now two-phase, mixture passes to a separator. Gas is warmed in the gas-to-gas exchanger and flows through a filter and flow meter and is routed to the National Transmission System.[4]

Liquid from the cold separator is routed to a condensate separator which separates the liquid into monoethylene glycol MEG, which passes to the rich MEG storage tank, and condensate which flows to the 1st stage condensate separator which also receives liquids from the slug catcher. Gas from the 1st stage separator passes to the flash gas compressor, MEG is routed to the rich MEG tank, and condensate is heated and flows to the 2nd stage condensate separator. Gas from the 2nd stage separator passes to the flash gas compressor, and liquid is pumped through a mercury removal bed to the condensate surge drum.

MEG from the rich MEG storage tank is routed though the MEG regeneration plant where water is stripped out. MEG flows to the lean MEG storage tank from where it is pumped to the Breagh Alpha platform via a 3-inch pipeline piggybacked with the 20-inch gas line.

The NGLs from all the plants are transported by pipeline to petrochemical companies in the Teesmouth area.

Central Area Transmission System

History

Route

Technical description

Ownership

CATS Terminal

Gas processing

Distribution

Gas processing (CNS/CATS)

Gas processing (SNS)

See also

External links

References