With pipelines full, crude shipped by rail has become the only real alternative left for producers to send excess oil out of the province. The region’s largest producers have been under mandatory production limits since January after rising production drove WCS prices as low as $50-a-barrel below WTI.

The heads of Canadian oil companies including Cenovus Energy Inc. and Suncor Energy Inc. are offering to boost crude-by-rail shipments in exchange for higher production limits.