* Profit falls 13 pct to C$635 million
* Oil output falls 5.2 percent
* Downstream profit nearly quadruples
* Shares rise 0.8 pct
CALGARY, Alberta, July 26 (Reuters) - Imperial Oil Ltd , Canada's No. 2 oil producer and refiner, said on Thursday its second-quarter profit dropped 13 percent due to weaker oil and gas prices and maintenance work at its refineries and oil sands operations.
Net income fell to C$635 million ($622.9 million), or 75 Canadian cents a share, from C$726 million, or 85 Canadian cents a share, a year earlier.
Imperial, 69.6 percent owned by Exxon Mobil Corp, is known for its national chain of Esso brand gas stations and is one of the largest investors in Alberta's oil sands. Along with a stake in the Syncrude Canada Ltd oils sands operation, the company operates the 155,000 barrel per day Cold Lake oil sands project and will open the first 110,000 bpd phase of its Kearl oil sands mine by year-end.
Imperial said it sold its output of bitumen from the oil sands at an average price of C$56.90 a barrel in the quarter, 17 percent less than it fetched a year earlier. Maintenance work at Syncrude and Cold Lake also cut into production.
As well, maintenance at three of its refineries during the quarter reduced throughput from its downstream operations but high refining profit margins in the quarter pushed earnings from the downstream operations up nearly four-fold to C$232 million.
"Overall the quarter was mixed as production was well short of expectations while the downstream posted another strong quarter despite meaningful downtime," Andrew Potter, an analyst at CIBC World Markets, wrote in a research note.
In the second quarter, Imperial produced 236,000 bpd from its oil sands and conventional oil and natural-gas liquids operations, down 5.2 percent from the year-before quarter.
Natural gas production fell to 195 million cubic feet per day from 257 mmcf a year earlier.
Refinery throughput dropped 3.3 percent to 384,000 bpd.
Imperial's revenue fell to C$7.51 billion from C$7.77 billion, in the year-earlier period.
Imperial shares were up 36 Canadian cents at C$42.77 at midmorning on Thursday on the Toronto Stock Exchange.