Canadian Oil Sands Maintenance to Squeeze US Refiner Supply in September
Rystad Energy puts the planned output loss at 300,000 b/d, hitting the US market's top crude supplier just as Asian buyers compete for Trans Mountain barrels.
Planned maintenance across Canadian oil sands operations will take roughly 300,000 barrels a day offline in September, according to Rystad Energy — a significant cut for US refiners that receive more than 4 million barrels a day of crude from Canada, making it by far their largest foreign supplier.4
Canada's position in US crude imports is structural, not incidental. The Midwest refining complex is configured around heavy sour Canadian grades with no direct Atlantic Basin equivalent, and with Gulf exports constrained by the ongoing Strait of Hormuz closure, finding replacement feedstock is not straightforward.4
The EIA flagged the broader context in its August Short-Term Energy Outlook, raising its third-quarter Brent forecast to $85 a barrel on account of continued severe constraints through the Strait of Hormuz. ICE Brent crude front-month was last quoted at $93.60 as of August 22 — already $8.60 above that revised ceiling, suggesting the market has run well past the agency's expectations.3
What makes the September timing harder for US refiners is intensified competition for Canadian supply from Asian buyers who had few alternatives before 2024. The Trans Mountain Expansion pipeline has been operating at double its nominal capacity of 890,000 barrels a day since launching. By 2026, 77% of total oil exports leaving the port of Vancouver have been flowing to Asia, up from 51% in 2024, Reuters data show.2
Japan illustrates how sharply buying patterns have shifted. Before the Hormuz disruptions, Japanese refiners sourced over 90% of their crude from the Middle East. In late July (2026-07-30), Japan's biggest refiner, Eneos, bought a rare cargo of Canadian crude — the first Canadian oil purchase by a Japanese company since 2025 — loaded onto an Aframax tanker carrying roughly 750,000 barrels, Reuters reported. Trans Mountain Corp. has since outlined plans to further expand the pipeline's capacity, potentially to 1.2 million barrels a day.2
The global inventory picture offers little cushion. Observable global oil stocks have fallen by a cumulative 246 million barrels since the conflict began — a 129 million-barrel draw in March followed by 117 million barrels in April, equivalent to about 3.9 million barrels a day of effective tightening, according to OGJ analysis. Barrels stranded in Gulf storage or unable to transit the Strait make the effective drawdown steeper still.1
Global refinery crude runs in 2026 are now expected to average roughly 82 million barrels a day, nearly 1.6 million barrels a day below 2025 levels, reflecting how severely feedstock shortfalls have constrained processing worldwide.1
US domestic production gives refiners some flexibility, and the country's crude export volumes have risen sharply as it displaces Middle Eastern barrels in global trade. But Midwest refineries built around heavy Canadian feedstock cannot simply substitute light sweet domestic crude without processing penalties and product slate changes. A 300,000 b/d shortfall does not constitute a crisis for a system that receives four times that volume from Canada daily — but it arrives with inventories already drawn down and replacement grades thin on the ground.4
September maintenance data from Rystad will tell refiners how long the squeeze runs. If Asian spot demand for Vancouver-loaded crude holds at its current pace as Canadian production recovers, US Midwest buyers may find the return of supply no easier than the outage itself.2