The estimated cost of the proposed Mackenzie natural gas project in the Northwest Territories is now $16.2 billion, more than double previous estimates, Imperial Oil said Monday.

The previous cost estimate for the project was $7.5 billion.

The Calgary-based oil and gas company also revealed that production will start no sooner than 2014, three years later than the previously scheduled startup date.

Imperial disclosed the costs and timing details in a filing with the National Energy Board and Joint Review Panel.

Despite the developments, the company believes the pipeline is economically feasible but it wants Ottawa to help improve its bottom line.

"We simply have to complete the work with the federal government, looking for a fiscal framework that makes sense for all parties," senior vice-president Randy Broiles said Monday. "So it's very much not on hold."

Imperial hopes to get a response from the government sooner rather than later, although it may take up to two years before it makes a final decision on whether to build the pipeline because it's working on obtaining permits.

Industry analyst Bill Gwozd of the Ziff Energy Group said that with $600 million already invested in the project, it would make sense for Imperial Oil to ask the government to share the risks and rewards.

It's "definitely a prudent matter to seek out alternatives, seek out ideas, seek out mechanisms to make the project go," he said.

A consortium led by Imperial wants to build a 1,220-kilometre pipeline along the Mackenzie Valley in the Northwest Territories to the Alberta border, where it would connect with existing pipelines and link to southern markets.

The consortium includes ConocoPhillips Canada, Shell Canada, ExxonMobil Canada and Aboriginal Pipeline Group.

APG president Bob Reid said he is already worried about the delayed project schedule. "Increased costs and a delayed schedule are simply not good news for the project," he said.

Imperial said in its filing with regulators that the massive project will cost an estimated $3.5 billion for the gas-gathering system, $7.8 billion for the Mackenzie Valley pipeline, and $4.9 billion to develop the gas fields to feed the project.

Shares of Imperial Oil finished down 42 cents, or one per cent, at $41.53 on the TSX.