UK GAS-Prices slide as supply rebounds after outages

* Within-day gas price falls more than 7 percent

* Resuming supply, LNG and storage help create glut

Sept 7 (Reuters) - British wholesale gas prices fell across the board on Wednesday as the system struggled to clear a supply glut caused by recovering output after maintenance and strong liquefied natural gas (LNG) flows.

Gas for instant delivery fell by 7.54 percent to 25.75 pence per therm by 0826 GMT.

Thursday gas was down by 5.28 percent to 26 pence per therm, while 6.40 percent was wiped off the weekend contract which traded at 25 pence per therm.

Double-digit price swings have been a feature of trading activity in the past week as unplanned outages in Norway and Britain forced dealers to make sudden adjustments.

Britain's gas network was oversupplied by 21.3 million cubic metres/day (mcm/day), with demand forecast at 181.5 mcm/day and supply at 202.8 mcm/day, according to National Grid (LSE: NG.L - news) data.

"More than comfortable supplies on the return of UK Continental Shelf supply have seen prompt prices open the session lower... this is filtering out into near curve contracts," Marcel Boonaert, head of trading at Wingas UK, said.

Gas deliveries into the Bacton Seal terminal have recovered following an outage to 8 million cubic metres/day (mcm/day), with analysts expecting them to reach pre-outage levels of 14 mcm/day within 24-36 hours.

The resolution of an unplanned outage at the St Fergus Total terminal has seen flows rebound to 41 mcm/day.

With (Other OTC: WWTH - news) the arrival of two liquefied natural gas (LNG) shipments this week, flows from the South Hook import terminal in Wales remain strong in order to clear space in its storage tanks.

South Hook pumped around 50 mcm/day, while neighbouring receiving terminal Dragon flowed 4 mcm/day.

Further out on the curve, gas prices were dragged lower by weak spot market sentiment, overlooking limited gains on Brent crude oil markets.

The Winter 2016 contract fell 0.41 pence to 38.29 pence per therm. The Summer 2017 contract dipped 0.35 pence to 35.65 pence per therm.

In the Netherlands, the day-ahead gas price at the TTF hub fell 0.42 euro to 11.48 euros per megawatt-hour.

In Europe's carbon market, December 2016 allowances fell 0.04 euro to 4.09 euros per tonne. (Reporting by Oleg Vukmanovic; Editing by Alexander Smith)