ALBANY — New York could see $11.4 billion in economic activity by 2020 and up to 18,000 new jobs by 2015 if the state allows gas companies to drill into the massive Marcellus Shale formation, according to a report released Tuesday by a conservative think tank.

The report, paid for by the business-backed Manhattan Institute for Policy Research, found that state and local governments would gain $1.4 billion in tax revenues alone over the next nine years.

The study’s authors — who also penned a report in 2009 that was partially commissioned by the natural-gas industry and released through Pennsylvania State University — also found that the typical Marcellus Shale gas well reaps about $4 million in economic benefits, while the environmental impacts come to about $14,000 per well.

Their study is based on a prediction of 330 horizontal wells in New York, which primary author Timothy Considine said is a conservative estimate. The number could expand five-fold, he said, if gas companies decide to tap into the Utica Shale — a much larger formation that lies below the Marcellus.

Both formations lie below large portions of New York, with the Marcellus region taking up much of the Southern Tier and part of the Hudson Valley.

“It could be much larger than the numbers projected in my report,” said Considine, a professor at the University of Wyoming. “The $11.4 billion number is based on a fairly limited development scenario in the Southern Tier of New York, like Broome and Chemung counties.”

The figures include both direct and indirect streams of economic activity, such as the spin off to other manufacturing, construction and retail industries. Considine said the financial estimates are based on activity that has taken place in Bradford, Tioga and Susquehanna counties in Pennsylvania, where high-volume fracking has been permitted since 2008.

Natural gas advocates hailed the report, which they said validates what they’ve said since the technique was first put on hold in New York in July 2008 so the Department of Environmental Conservation could review its environmental impact. That study continues, with a second draft due by July and high-volume fracking still on hold until a final review is complete.

“This study quantifies in real and remarkable terms the economic promise of natural-gas development in upstate New York,” said Brad Gill, executive director of the Independent Oil & Gas Association of New York.

The report’s authors, however, have faced criticism for their past work on hydrofracking, including the Penn State report.

A dean at Penn State said that report — which predicted a windfall of economic activity resulting from natural gas in Pennsylvania and spoke out against a proposed severance tax — should have been “more scholarly and less advocacy-minded.”

An initial version also did not disclose that it was partially funded by a gas-industry trade organization, but was later updated to include a disclaimer. The New York report was funded solely by the Manhattan Institute, Considine said.

David Gahl, policy director for Environmental Advocates of New York, said it’s important to look at the report’s source of funding, which he characterized as coming from “pro-gas people.” It’s not a coincidence that the report is favorable toward the gas industry’s intentions, he suggested.

“Just like Pennsylvania’s lax history of regulatory oversight for dirty gas drilling called hydraulic fracturing … you get what you pay for,” Gahl said.

Considine, however, said the funding had no impact on the results of the study, and that he has plans to submit it to several peer-reviewed journals for publication.

“I don’t see how it could have,” Considine said. “The work stands on its own.”

The Manhattan Institute report does make some policy observations, finding that New York’s “current shale gas drilling moratorium imposes a significant and needless burden on the New York State economy.”

The authors also found the risk of significant environmental damage is very low, and “in no way call into question the soundness of” hydrofracking.

The study found that 152 violations — such as spills, cases of stray gas and blowouts — have led to the contamination of 9.3 million gallons of water in Pennsylvania. That number is low, the authors said, if you take into account the state’s annual household use of more than 300 billion gallons.

“Our study finds the net economic and environmental benefits from shale gas development to be considerable, suggesting that the current moratorium is far costlier than its proponents, or even its opponents, realize,” the report reads.”

Gahl, however, said the report underestimates the concerns about hydrofracking.

“The pro-gas people paid for a report that claims natural gas is a fairy godmother that will save New York’s economy and — poof! — makes very real concerns about health and safety disappear,” Gahl said.