TRAVERSE CITY, Mich. — Michigan may have large natural gas reserves deep underground, but it will likely be years before they would be developed on a large scale, giving policymakers time to deal with the environmental and public health concerns associated with the extraction method known as fracking, according to a study released Thursday.

The University of Michigan analysis found that the industry has had a good safety record over the past six decades in extracting gas from shallow rock. More recently, companies have begun exploring shale formations more than 2 miles down, which raises questions about potential damage to water and air quality, and degradation of wildlife habitat, the researchers said.