Enbridge Inc. plans to shut a U.S. Midwest oil pipeline twice over the next two months to make repairs, the company said Tuesday, putting more pressure on Canadian crude prices.

Enbridge, the largest carrier of Canadian crude exports to the U.S., plans a five-day shutdown of the 290,000-barrel-a-day Line 6B starting around Feb. 7, and another of the same duration around March 7, spokeswoman Lorraine Grymala said.

Line 6B extends to Sarnia, Ontario, from Griffith, Ind. Last summer, Enbridge was forced to shut it down for nine weeks after a rupture and oil spill near Marshall, Mich.

“We’ve actually got a lot of maintenance work going on right now on 6B,” Grymala said. “These particular outages that we’ve got scheduled for February and March are related to replacing 14 segments along Line 6B.”

Western Canada Select heavy blend crude for February delivery was last heard at $23.25 a barrel under benchmark West Texas Intermediate light oil. That compares with January prices around $20 a barrel under WTI.

High shipper nominations after a series of outages and pressure restrictions on some lines have forced Enbridge to ration capacity throughout its system.

That has backed up large volumes of oil in Western Canada for the last month, pressuring prices.