Could Western Canadian pipeline projects substantially hurt US Midwest refiners?

Today, the three surviving proposals to increase West Canadian takeaway capacity are Kinder Morgan's Trans Mountain Expansion (TMX), TransCanada's Keystone XL pipeline (KXL), and Enbridge's Line 3 Expansion. In total, these pipes represent approximately 1.5 million b/d of additional takeaway capacity. Western Canadian production, while forecast to increase, will likely be outstripped by takeaway capacity should all three pipelines come online. This poses the questions: how would the construction of these pipelines and the level of pipeline committed volumes affect the future WTI-WCS differential? What would be the potential financial exposure of heavy refiners in Western Canada and the US Midcontinent to a narrowing differential?