* Horizon Dec. output drops 22 pct on coker maintenance
* Q4 output up 32 percent year over year (Adds details)
CALGARY, Alberta, Jan 6 (Reuters) - Canadian Natural Resources Ltd (CNQ.TO) said on Thursday that output at its Horizon oil sands project in northern Alberta fell 22 percent in December from the previous month as it shut down its upgrading plant to repair a coker unit.
The company, Canada's No. 1 independent oil producer, said Horizon's output averaged 83,700 barrels per day in the month, down from 107,800 bpd in November as it shut down the upgrader's coker unit for repairs. Upgraders convert bitumen stripped from the oil sands into refinery-ready synthetic crude.
The company says the unit was restarted last month.
Canadian Natural said Horizon's fourth-quarter production averaged 92,900 bpd, 32 percent more than the year-before quarter. It said its expects 2011 output to average between 105,000 and 112,000 bpd.
The company said last month that it plans to expand production at Horizon to 250,000 bpd through a series of small projects aimed at avoiding the hyper-inflation that plagued the development of oil sands projects before the financial crisis in 2008. (Reporting by Scott Haggett; editing by Peter Galloway)