U of M sees state fracking risks but says practice is too costly 6 (UPI) -- A University of Michigan report on fracking said the practice could pose a substantial risk but cost may inhibit a shale oil and gas boom in the state. U of M published a series of technical reports assessing the shale oil and natural gas potential in the state. The U.S. Energy Department said Michigan has the largest natural gas reserves of any state in the Great Lakes region. U of M said approximately 12,000 oil and natural gas wells were completed in the state since the 1940s using hydraulic fracturing without any contamination issues. Most of those were in shallow wells. The reports, published Thursday, said the potential impacts of hydraulic fracturing may be significant. Risks include erosion, chemical runoff, chemical spills and aquatic contamination. U of M researchers said surface spills were more likely than groundwater contamination. The report said the high cost of drilling deeper shale wells, the absence of new oil discoveries in the state and the low price of natural gas means the near-term threat is minimal. The Energy Department said Michigan's natural gas production peaked in 1997 at 305 billion cubic feet. Production in 2011, the last full year for which data is available, was reported at 138 billion cubic feet. The report said the gas extraction industry in the state is not enough to "make or break" its economy.