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UK GAS-Spot prices drift lower on oversupply

* Within-day and day-ahead gas prices down slightly

* No new LNG cargoes expected, but new tankers possible

April 8 (Reuters) - British spot gas prices fell slightly on Friday on a slightly oversupplied network, while falling wind power output boosted demand for gas-fired electricity generation.

Within-day gas prices was down 0.10 pence per therm to 27.60 p/therm at 0808 GMT, while gas for Monday delivery was down 0.15 pence at 27.5 p/therm.

The UK gas market, which started the session undersupplied by 12 million cubic metres/day (mcm), moved into slight surplus in the morning, with demand estimated at 273.1 mcm/day versus supply at 274.3 mcm/day, National Grid (LSE: NG.L - news) data showed.

Imports from Norway via the Langeled pipeline, Britain's main import artery, rose by around 3 mcm/day to 55 mcm/day, while small gains in flows from the Netherlands through the BBL pipeline and some domestic terminals also helped support supply.

Further along the curve prices for May delivery rose 0.10 pence per therm to 26.52 pence.

Domestic gas output from the UK Continental Shelf is estimated at 153 mcm/day but a flow disruption into Shell (LSE: RDSB.L - news) 's Bacton terminal means physical flows are closer to 145 mcm/day.

Britain-bound liquefied natural gas (LNG) shipments are steady with no new cargoes announced, although the LNG Enugu tanker which has just departed Nigeria's loading port of Bonny is signalling the Milford Haven port in Wales as its destination.

However, the heading may simply be out of date given the LNG Enugu previously delivered a cargo from Bonny to Milford Haven.

The Qatari LNG tanker Zarga is currently sailing through the Mediterranean and may be heading for Britain, gas analysts at Thomson Reuters (Dusseldorf: TOC.DU - news) said.

In the Dutch gas market, the day-ahead price at the TTF hub fell by 0.23 euro per megawatt hour to 11.20 euro/MWh.

In the European carbon market, front-year EU allowances edged down 0.04 euro to 5.24 euros a tonne. (Reporting by Oleg Vukmanovic; editing by Jason Neely)