* Nexen, Opti dealt with outages at Long Lake
* Cenovus hampered by pipeline, refinery issues
* Canadian Oil Sands said Syncrude had extended outage
By Jeffrey Jones
CALGARY, Alberta, Oct 28 (Reuters) - Canadian oil sands producers, including Nexen Inc NXY.TO and Cenovus Energy Inc (CVE.TO), struggled with operational problems in the third quarter, which pressured returns, prompting investors to pull their shares lower.
The issues were both internal and external, and highlighted the complexities of developing Alberta's oil sands, the largest crude oil source outside the Middle East.
Nexen, Canada's No. 5 independent oil explorer, earned C$534 million ($524 million), or C$1.02 a share, up fourfold from a year-earlier C$122 million, or 23 Canadian cents a share.
The profit included a net gain of C$522 million on the sale of Western Canadian heavy oil assets.
Cash flow, an indicator of its ability to fund development, rose 28 percent to C$485 million, or 92 Canadian cents a share, from C$379 million, or 73 Canadian cents a share.
Nexen, also known for shale gas development as well as offshore operations in the Gulf of Mexico and North Sea, said production for the year is expected to be in its forecast range of 230,000 to 280,000 barrels of oil equivalent.
However, the company struggled with outages at the processing plant at its Long Lake oil sands project, where it pumps steam into the ground to loosen up the bitumen so it can be pumped to the surface.
Steam generation was hampered by outages at its upgrading plant and power interruptions during August and September, which delayed the ramp-up of output by a few months, it said. Gross bitumen production at Long Lake is about 31,500 barrels a day, about half the capacity.
The equipment is running normally again, but Chief Executive Marvin Romanow was hesitant to say if output would climb into the 40,000 to 60,000 bpd range by year-end.
"I think that with the bumps we took last summer, that's going to make that target a bit more challenging," Romanow said. "But more importantly, I think when we see how our wells are responding when we provide them the constant steam ... we'll get back on the right ramp-up curve."
Nexen has a 65 percent stake in Long Lake. Opti Canada Inc OPC.TO, which has the remaining interest, reported a net loss C$46 million, or 16 Canadian cents a share, compared with a profit of C$12 million, or 4 Canadian cents a share.
Its CEO, Chris Slubicki, also lamented the operating woes, but cautioned investors to expect occasional interruptions at a large, new plant.
Opti shares were unchanged at 75 Canadian cents on the Toronto Stock Exchange. The company has spent the last several months weighing its strategic options.
Nexen was off 24 Canadian cents, or 1 percent, at C$21.38.
During the quarter, benchmark oil prices averaged $76.25 a barrel, 12 percent higher than a year earlier. However, Canadian producers were hampered by wide discounts on their heavy crude due to the shutdowns of two U.S. pipelines on Enbridge Inc's (ENB.TO) U.S. system.
That was one factor Cenovus, the second-largest energy independent, cited for lower than expected operating earnings.
Excluding one-time items, the company earned C$159 million, or 21 Canadian cents a share, down 63 percent from C$427 million, or 57 Canadian cents a share. Analysts, on average, had expected the company to earn 28 Canadian cents a share, according to Thomson Reuters I/B/E/S.
Cash flow fell 45 percent to C$509 million, or 68 Canadian cents a share, also due to a decline in gas production and lower cash flow from its U.S. refining joint venture with ConocoPhillips (COP.N).
"Weak natural gas markets, lower realized heavy oil prices due to pipeline outages, as well as disappointing refinery performance led to lower than expected results," CEO Brian Ferguson said.
Still, Cenovus's own operations, including the Foster Creek and Christina Lake oil sands project, were meeting or exceeding expectations, he said. Net production from the two averaged 58,107 barrels a day, up 25 percent from last year.
Shares in Cenovus, spun off by Encana Corp (ECA.TO) last year, fell 36 Canadian cents, or 1 percent, to C$28.73.
Canadian Oil Sands Trust COS_u.TO, the largest owner of the Syncrude Canada oil sands venture, is due to report its results later on Thursday. Last month, it cut its production target due to an extended processing unit outage.
$1=$1.02 Canadian Additional reporting by Scott Haggett; editing by Rob Wilson