SINGAPORE, Aug 12 (Reuters) - Middle East crude values posted a small rebound on Friday as buyers of Oman and Qatari al-Shaheen crude paid smaller discounts than earlier in the week, though market sentiment remained sluggish amid a perception of ample supplies. Oman crude cargoes were discussed at a discount of about 20 cents to Dubai quotes on Friday, up from a 25 cent discount a day earlier. The discount of September Dubai swaps to October swaps narrowed to 16 cents from 19 cents, flattening a price structure known as contango. This weakening of so-called timespreads indicated expectations of a tightening market, with some traders expecting excess Oman cargoes to move to the U.S west coast. Also on the supportive side for prices, Taiwan's Formosa Petrochemical Corp is ready to start up its 540,000 barrel per day (bpd) refinery in stages after it was shut following a fire at a secondary unit at the end of July. The restart still awaits government approval. * OSPs - Iraq cut the official selling price (OSP) to Asian term buyers to a discount of $1.00 a barrel to the average of Oman/Dubai quotes for September from parity for August. * DME OMAN - September Oman traded on the DME rebounded 28 cents to a premium of 13 cents 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 September rose 25 cents to $5.35 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 - Indian firms have paid the first installment of their Iran oil debts, Finance Minister Pranab Mukherjee told reporters on Friday, adding the two countries have resolved the issue over payments. - A fall in China's gasoline exports is likely to accelerate in the second half of the year as growth in local demand and reduced refinery runs slash the volumes available for overseas sales. - OPEC, source of more than a third of the world's oil, is unlikely to become concerned about a slide in oil prices unless Brent crude falls towards $90 a barrel, OPEC delegates said on Thursday. - China's crude imports didn't bounce in July as had been forecast, but perhaps this isn't surprising as an analysis of buying trends shows the world's second-biggest oil user is more price sensitive than the market may expect. * CRACK SPREADS - Gas oil's September crack slipped 38 cents to a premium of $18.36, while the October crack weakened 36 cents to a premium of $18.24 a barrel to Dubai crude. - Fuel oil's September crack narrowed 60 cents to a discount of $5.34 a barrel. - Naphtha's September crack was 39 cents wider at a discount of $5.80 a barrel, while the October contract was also 32 cents weaker at minus $5.63. *OUTRIGHT PRICES - September ICE Brent LCOc1 rose to $107.73 a barrel at 0830 GMT, up 37 cents from the same time on Thursday. (Reporting by Alejandro Barbajosa, editing by Jane Baird)

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