The misconception with 'west-to-east' pipeline proposals like Enbridge’s Line 9 or TransCanada’s Energy East is shipping western Canadian oil to eastern Canada means ‘Canadian oil for Canadian refineries.’ This assumption overlooks the fact eastern Canadian refineries cannot refine a certain type of Canadian oil - tar sands bitumen.
Bitumen is the heavy unconventional oil found in the Alberta tar sands (also called oil sands). Only a specialized refinery can process bitumen and turn it into refined products such as fuels. Few refineries in Canada can do it. None of the refineries in eastern Canada can refine large quantities of bitumen.
TransCanada and Enbridge claim their west-to-east pipelines will transport mainly conventional oil and only small amounts of bitumen. This is unlikely to be true in the long term as conventional sources of oil dry up in Canada and bitumen production continues to increase.
If no eastern Canadian refinery makes the massive investment to outfit their operation to refine bitumen, Line 9 and Energy East are destined to ensure more bitumen will flow to markets overseas, not Canadian refineries.