Chevron CEO John Watson on Monday warned that U.S. shale oil alone cannot meet the world's growing appetite for crude.
Global oil demand is growing by more than a million barrels per day each year. American producers are meeting much of that consumption growth after a revolution in drilling technology that has allowed them to unlock oil and gas from shale rock formations.
"Shale can help. Certainly between now and the end of the decade it will be a big contributor to meeting that million-barrels-of-oil-demand growth that's out there," Watson told CNBC's "Power Lunch" on the sidelines of the Milken Global Conference in Los Angeles.
"But ultimately oil fields decline, and we're going to need all sources of supply, including the shales, but also deepwater and other sources around the world," he said.
Investment in oil exploration and development — especially expensive projects like offshore drilling — has plummeted as oil companies slash spending plans amid a prolonged crude price slump. That could cause the market to become undersupplied in the future, the International Energy Agency warns.