CALGARY - Canada's Enbridge Inc (ENB.TO) is eyeing opportunities to expand its pipeline network if the proposed Capline pipeline reversal goes ahead, providing access to the eastern Gulf Coast refining market for Canadian oil, the company said on Thursday.

Enbridge is Canada's largest pipeline company and its Mainline network moves around 2.5 million barrels per day of crude exports to the United States. Most of that is refined in the Midwest but producers are eager to ship more oil to the Gulf Coast, the world's largest heavy crude refining complex.

Capline operator Marathon Petroleum Corp (MPC.N) launched an non-binding open season last month to gauge shipper interest in reversing the pipeline to move 300,000 bpd of crude south from Illinois to Louisiana from 2022 onwards.

"It's early days on Capline, they have only just announced the potential reversal, but for sure it's one of the things we are pushing hard on," Enbridge Chief Executive Al Monaco told analysts on a third-quarter earnings call, when asked if his company would expand its pipelines feeding Illinois or partner with Capline owners to provide a path for oil sands crude to the Gulf Coast.

Calgary-based Enbridge posted a third-quarter profit on Thursday that fell slightly short of analysts' estimates, as a decrease in natural gas pipeline volumes offset gains from the assets it acquired in a deal to buy Spectra Energy last year.

Natural gas pipeline volumes averaged 1.53 million cubic feet per day (mmcf/d) in Canada, down 1 per cent, and Enbridge moved 1.64 mmcf/d in the United States, down 2.4 per cent

Enbridge's liquids pipeline business, its biggest, earned $976 million, on an adjusted basis, in the quarter, up from $941 million a year earlier.

The company is still waiting for approval from Minnesota for its Line 3 replacement project, which will double capacity on the line to 760,000 bpd. Enbridge expects that to come in the second quarter of 2018 and the line to start operating in the second half of 2019.

Earnings attributable to shareholders were $765 million, or $0.47 per share, compared with a loss of $103 million, or $0.11 per share, a year earlier.

Excluding items, Enbridge earned $0.39 per share, missing analysts' estimates by 4 cents as per Thomson Reuters data.

Enbridge shares were last down 3.6 per cent on the Toronto Stock Exchange at $47.60.