U.S. imports of crude oil from Saudi Arabia plummeted to a near four-year low last week as West Coast refineries increase oil flows from Canada's Trans Mountain pipeline.

The $24.84 billion Trans Mountain pipeline expansion, which began in May, nearly tripled capacity to Canada’s Pacific Coast to 890,000 barrels per day, significantly altering global trade flows.

According to U.S. Energy Information Administration data released Wednesday, imports of Saudi crude fell to a mere 13,000 barrels per day (bpd) in the week ending Oct. 25. 

West Coast refiners, including those owned by Marathon Petroleum and Phillips 66, have significantly reduced their reliance on Saudi crude in favor of Canadian oil transported via the Trans Mountain pipeline.

“Increased TMX flows into the U.S. West Coast kept Saudi barrels away from those markets,” said Rohit Rathod, an analyst at ship tracking firm Vortexa.

However, Saudi Arabia is expected to continue supplying its Texas-based Motiva refinery on the U.S. Gulf Coast.