Louisiana's growing number of abandoned wells -- the state added an average of 170 per year from 2008 to 2013 -- highlight a problem expected to worsen the coming years in energy states, according to The Wall Street Journal.

Even though the state plugged an average of 95 wells per year over the same time period, the number of abandoned, or orphan, wells grew.

The Louisiana Department of Natural Resources told the Journal that regulators are looking to raise bonding fees, which cover the cost of plugging wells. A 2014 audit shows that 75 percent of Louisiana's wells had no bonding.

The minimal bonding requirements may actually provide an incentive for operators to abandon wells, since the bond is lower than the plugging cost, the audit says.

Louisiana is not alone. Several states and the federal government are struggling to clean thousands of abandoned wells. The wells were drilled years ago, but many producers walked away rather than pay to the thousands of dollars, or even tens of thousands, it costs to remove any equipment and plug the well.

The Journal reports that the shale drilling boom could generate vast numbers of abandoned wells. The horizontal wells in shales cost more to plug than conventional wells, and thousands have been drilled in shale formations.

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