Canadian Natural Resources said it is struggling to maintain stable production at its Horizon Oil Sands Project, one year after it started operations.
Production at the $9.4bn development has fluctuated since October 2009 because it has struggled with issues such as high clay content in the ore and mechanical problems at the upgrading plant, the company said.
In October, Horizon produced 71,000bpd and in subsequent months pumped 97,000, 42,000, 72,000 and 84,000bpd.
In December, production was affected by an equipment failure and difficulty in one of the coker furnaces, requiring the shutdown for an extended period.
Canadian Natural Resources president Steve Laut said that the company is working on operational kinks, equipment failures and compounding effects.
The company posted a 4% dip in adjusted profit while its net income for the fourth quarter fell 74% to C$455m, or C85¢ a share, from year-earlier C$1.77bn, or C$3.27.