The study by energy consultancy IHS CERA says it agrees with the conclusions of the U.S. State Department's draft environmental review of Keystone released in March that says oil sands production is expected to continue at similar levels regardless of whether the project goes ahead.
Keystone XL, which would move oil from the oil sands of Alberta, Canada, to refineries along the U.S. Gulf Coast, is now under federal review at the State Department. The project needs a cross-border permit to complete the project's northern leg.
The department said in its draft review Keystone XL wouldn't substantially increase greenhouse gas emissions.
President Barack Obama in his June 25 climate address said the project would win approval only if it does not significantly exacerbate the problem of carbon pollution.
Environmentalists maintain Keystone XL would add to greenhouse gas emissions.
In the absence of the pipeline, IHS CERA's study says, U.S. Gulf Coast refiners would replace expected deliveries of diluted bitumen from Alberta with heavy oil from Venezuela, which has roughly the same emissions intensity as the Canadian crude.
"If gulf refiners cannot access Canadian heavy oil, the most likely alternative is Venezuelan supply, which is projected to grow based on ongoing investments," the study states. Currently the majority of supply on the U.S. Gulf Coast comes from Venezuela, followed by Mexico, it notes.
"Venezuelan heavy oil -- and Venezuela -- would be the No. 1 beneficiary of a negative decision on Keystone," the study says.
The study says in the absence of the Keystone XL, Canadian oil sands will still find a way to market, either through pipelines traveling exclusively through Canada and not requiring U.S. government approval, or through the increasing use of railcars to ship the heavy oil.
"Given sufficient investment, our view is that the economics for moving heavy oil sands crude by rail could improve further, even approaching pipeline economics," the study states.
"Consequently, even without the Keystone XL pipeline, we believe that oil sands production would grow at a similar rate. Therefore [greenhouse gas] emissions will be unaffected by the fate of Keystone XL."
"After five years and numerous studies, all pointing to the same conclusion, the White House and opponents of the Keystone XL pipeline project have exhausted all arguments," said Sen. John Hoeven, R-N.D., in a statement Thursday.
"It's time to stop delaying this critical infrastructure project, which will create jobs, help to grow our economy and help us achieve true North American energy independence," Hoeven said.