* Q2/13 net C$0.45 eps vs C$0.21 eps in Q2/12
* Oil production up 23 percent to 110,100 bpd
* Analysts expected C$0.52 eps
* Lowers annual production forecast
* CEO to retire at start of 2014
CALGARY, Alberta, July 30 (Reuters) - Canadian Oil Sands Ltd , which owns the largest stake in the Syncrude Canada Ltd oil sands project in northern Alberta, said on Tuesday its quarterly profit more than doubled on higher oil production and strengthened prices, though it lowered its annual production estimate because of maintenance issues.
Canadian Oil Sands, which has a 37 percent stake in the massive Syncrude tar sands mining and synthetic crude operation, said profit rose to C$219 million ($213 million), or 45 Canadian cents per share, in the second quarter from a year-earlier C$101 million, or 21 Canadian cents.
Analysts, on average, had expected a profit of 52 Canadian cents a share, according to Thomson Reuters I/B/E/S.
During the quarter, production averaged 110,100 barrels per day, up 23 percent from a year earlier, with operating costs averaging C$43.23 a barrel, compared with C$50.25 a barrel last year.
A coker at Syncrude has been shut for maintenance since June, reducing supply and pushing the average price of synthetic crude up to $4.89 per barrel above West Texas Intermediate over the quarter, compared with a discount of $1.85 per barrel below WTI during the same period in 2012.
The company warned that because the coker maintenance, a planned shutdown of another unit and unplanned work in other oil extraction units production, production this year would be less than expect.
It said it now expects the Syncrude operation to produce around 102 million barrels of synthetic crude this year, down from its prior estimate of around 105 million barrels.
Canadian Oil Sands also said Marcel Coutu, chief executive since 2001, will retire on January 1. The company has begun searching for his successor.
The company's cash flow, a measure of ability to pay for new projects, rose 40 percent to C$343 million, or 71 Canadian cents, from C$245 million, or 51 Canadian cents, in the year-before quarter.