The application is "considered to be one of the most comprehensive regulatory documents in the company's history," it said in a statement.
TransCanada will hold a simultaneous news conference in Toronto and Quebec on Thursday to discuss the application, which describes the environmental assessment process and provides preliminary information about the scope of activities.
The Calgary-based company will also provide an update on the $12-billion project, the statement said.
TransCanada wants to convert 3,000 kilometres of existing natural gas pipeline and build about 1,600 kilometres of new pipeline in Quebec and New Brunswick.
It is expected the west-east pipeline would transport 1.1 million barrels a day of crude oil from Alberta to the Irving Oil refinery in Saint John.
Also planned are new pumping stations, oil storage terminals and a joint venture with Irving for a new $300-million
deep-water marine terminal, according to the project description filed with the National Energy Board in March.