Orbital Insight uses algorithms to calculate how much oil is in tanks by examining roofs, which rise and fall depending on how much oil is being stored. (Orbital Insight/ satellite imagery: DigitalGlobe/Orbital Insight/ satellite imagery: DigitalGlobe)

One of the mysteries of the oil market is the question of how much crude oil China has squirreled away in commercial and strategic stockpiles.

Now a satellite-imaging firm called Orbital Insight claims to have an answer. It says Chinese inventories in May stood at 600 million barrels, substantially more than commonly thought and nearly as much as the U.S. Strategic Petroleum Reserve. Chinese storage capacity, which includes working inventory, is four times widely used estimates, Orbital Insight says, adding that the firm has not only counted storage tanks but has also used imaging techniques to figure out how much oil is in the tanks.

The issue could influence expectations in oil markets. If China has built larger reserves than previously estimated, that means much of what looked like oil demand over the past couple of years was not a result of higher consumption but of strategic planning. It would make OPEC’s task of cutting output to drive up prices­ more difficult. And it could provide a buffer for China in the event of a sudden disruption in imported supplies.

The new estimate comes from a firm founded by James Crawford, who formerly worked on Google’s book-scanning project. Crawford said that he recruited some NASA scientists and left Google to start Orbital Insight because the price of Earth-orbiting hardware was falling and the amount of satellite images was booming. He has received backing from the investment firms Sequoia and Google Ventures. The firm pays a percentage of its revenue to satellite-image providers.

“The broad vision is to take large volumes of satellite imagery and make sense of what we’re doing on the Earth and what we’re doing to the Earth,” Crawford said.

For its Chinese analysis, Crawford said the firm went back to images taken from 2010 to 2014 and counted the number of oil storage tanks built and destroyed and came up with a figure of 2,100 storage tanks, far more than the 500 tanks in the industry standard database in TankTerminals.com.

Orbital Insight also used its own algorithms to calculate how much was in the tanks by examining their roofs, which rise and fall depending on how much oil is being stored.

“As the reservoirs are filled and emptied, the roofs rise and fall, reflected in the crescent moon-like shadows from the walls of the reservoir,” the company said in a release.

Orbital Insight honed this technique on about 6,000 tanks in the United States, comparing its figures with those of the U.S. Energy Information Administration. Recently the firm said it could come up with statistics faster than the International Energy Agency, something that could be valuable to oil traders — customers the firm is trying hard to woo.

The firm, however, cannot discern whether there are underground storage facilities.

Orbital Insight’s estimate far exceeds the figure given in a rare glimpse of China’s oil supplies by its government. On Sept. 2, the state-owned Xinhua news agency reported that China had 287 million barrels of oil in strategic storage sites in eight cities as well as in commercial facilities at the beginning of the year. Started in 2004, the Chinese strategic stockpile would be enough to cover only 36 days of oil imports, Xinhua said, based on data from the China National Petroleum Corp.’s Research Institute of Economics and Technology. China’s goal is to have large enough strategic stockpiles to cover 100 days of imports, a target the government’s five-year plan said might not be completed by the 2020 goal.

The U.S. reserve is large enough to cover about 150 days of imports.

However, with low prices, China has been on a buying spree, many analysts believe.

Investment banks and other analysts have estimated that China has been importing 600,000 to 1.2 million barrels a day more than it needs for consumption. If China has just been bargain hunting, it could cut imports and help keep prices low. Or it could press ahead to reach its 100-day goal.

If Orbital Insight is right, that could be closer than anyone thought.