Still, Mr. Sherman of Wood Mackenzie said settling the sea’s status could free up additional Caspian investment, though not on the scale of what has already moved into ventures like Kashagan, which produces about 300,000 barrels of oil per day. ExxonMobil is developing the field with Shell, Total, the Italian company ENI, the China National Petroleum Corporation, KazMunayGas and Inpex.
Rebecca Arnold, a spokeswoman for Exxon, declined to comment on the treaty’s significance for the oil business as the rules for dividing up the sea are “matters for governments to address.”
Also in the Caspian basin, a Chevron-led consortium is expanding its giant Tengiz oil field in Kazakhstan, at an estimated cost of $37 billion, to increase production by 260,000 barrels per day.
Companies have already invested about $40 billion into the southern corridor for natural gas, to ship fuel from the BP-operated Shah Deniz field in Azerbaijan’s territorial water to Italy. “We’re not starting from scratch here,” Mr. Sherman said.
The treaty allows Western energy companies, in theory, to push the southern gas corridor farther east, across the sea to tap Turkmenistan’s vast gas reserves and alleviate dependence on Russian gas.
Analysts see most of the benefit for oil companies in areas that might be freed from Iranian claims under the treaty, and where the United States Geological Survey estimates most of the undiscovered oil and natural gas lies. The agreement does not settle bilateral territorial disputes among Iran, Azerbaijan and Turkmenistan in the sea’s south, but lays out a formula for doing so. Iranian nationalists have already been objecting to the treaty, threatening to renege.
Oil and natural gas production from the Caspian is estimated at two million barrels of oil equivalent per day, depending on how the region is defined. This flow has helped cushion global oil markets from disruptions in the Middle East, the role advocates of Western investment in the region had long envisioned. The Caspian’s output, for example, is about equal to what disappeared from global markets during the Libyan civil war.
“For global supply,” said Mr. Elkind of Columbia University, “it has been a good thing.”