"Hydraulic fracturing can cause nearby abandoned oil wells to leak methane, according to a study published on Tuesday in the peer-reviewed Water Resources Research journal, marking a potentially large source of unrecorded greenhouse gas emissions.

Researchers at the University of Vermont examined a part of New York state overlying the Marcellus shale gas reservoir to determine the chances that a newly fracked well there would intersect one of the state's thousands of existing wellbores.

'Average probability estimates for the entire region of New York underlain by the Marcellus Shale range from 0.00 percent to 3.45 percent,' according to the study, which suggested the results held broader national implications."

Richard Valdmanis reports for Reuters October 20, 2015. [2]