The company lost C$728 million ($664 million), or C$1.49 per share, in the quarter, compared with C$78 million, or 16 Canadian cents, a year earlier.

Penn West, one of Canada's largest conventional oil producers, is revamping its operations after years of underperforming its rivals. New Chief Executive Dave Roberts has cut staffing by a third and put much of the company's widespread properties up for sale to concentrate on its three core regions.

The company said its loss consisted mostly of a C$742 million writedown of assets.

Penn West's cash flow, a measure of its ability to pay for new projects and drilling, dropped 27 percent to C$216 million, or 44 Canadian cents per share, from C$295 million, or 62 Canadian cents.

Production fell 19 percent to 123,995 barrels of oil equivalent per day as the company sold off properties.

Penn West shares rose 2.8 percent to C$8.94 by late morning on the Toronto Stock Exchange.

($1 = 1.0965 Canadian dollars)

(Reporting by Scott Haggett; Editing by Steve Orlofsky)