SINGAPORE, Sept 21 (Reuters) - Uncertainty about the effect on crude production from a fire at Iraq's top oil field Rumaila rattled the Middle East market on Wednesday, sending the front of the Dubai curve into its steepest backwardation in at least two years. The premium of October Dubai swaps over November jumped to more than 70 cents a barrel, after a fire at a state-run gas compression unit at Rumaila on Tuesday killed one person and hit oil production, police and oilfield developer BP said. "We have stopped exporting gas that would have been exported into this compressor and this will have an impact on our production from Rumaila," BP spokesman David Nicholas said in London, without offering figures for the cut in oil output. Rumaila pumps almost half of Iraq's output and has some 17 billion barrels in estimated crude reserves. * NOVEMBER TRADE - Although the prompt market could become tighter with Rumaila, there was some pressure on values of November-loading cargoes as most Asian refiners were perceived to have covered the bulk of the month's requirements. - Abu Dhabi Murban was assessed at at a premium of 40 cents to the ADNOC official selling price (OSP), down 5 cents from Tuesday. Although Oman cargoes continued to be offered at premiums of about $2 to Dubai quotes, buying interest was unlikely to kick in at or above $1.90. - Narrowing crack spreads also contributed to expectations that premiums would fall further towards the end of the month. * DME OMAN - November Oman traded on the DME rose 6 cents to a premium of $1.96 a barrel to Dubai swap quotes at 0830 GMT, using the settlement price for DME futures, the ICE one-minute marker for Singapore and the Brent-Dubai EFS as calculated by Reuters. * EAST-WEST - The Brent/Dubai Exchange of Futures for Swaps (EFS) for November added 15 cents to $4.85 a barrel at 0830 GMT, Reuters data showed. The front-month EFS on June 15 touched $9.20, the highest intraday value since the spread reached a record of almost $12 in October 2004. * MARKET NEWS - Japanese refiner Showa Shell Sekiyu said its Toa Oil subsidiary permanently shut one of the two factories at its Keihin refinery on Sept. 20, as scheduled, due to declining Japanese demand for oil. - Showa Shell last year announced it would close the Ohgimachi factory, including its No.5 120,000 barrels per day No.5 crude distillation unit (CDU), by September 2011. - Qatargas wants to double its long-term liquefied natural gas (LNG) supplies to Asia from 11 million tonnes currently to more than 20 million tonnes, a company official said. - Inpex Corp , Japan's top oil and gas developer, has won concession rights for the Babar Selaru oil and gas block in Indonesia's first upstream bidding round this year, the energy ministry said. * CRACK SPREADS - Fuel oil's October crack widened 23 cents to a discount of $5.62 a barrel to Dubai crude, while the November discount was 11 cents weaker at $5.61. - Gas oil's October crack lost 46 cents to a premium of $16.51, while the November premium was 41 cents lower at $16.95 a barrel to Dubai crude. - Naphtha's October crack widened 68 cents to a discount of $5.57 a barrel, while November discount was 29 cents weaker at $4.68. * OUTRIGHT PRICES - October ICE Brent LCOc1 was at $110.73 a barrel at 0830 GMT, up 97 cents from Tuesday. (Reporting by Alejandro Barbajosa; editing by Jason Neely)

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