Ars Technica reports Measuring the heck out of shale gas leakage in Texas. Researchers tracked methane leakage from the Barnett Shale (around Dallas-Fort Worth). The results seems to be that overall leakage is low but higher than expected. Also, most of the leakage comes from a small number of "super-emitters".
"One group sampled 186 sites where a well or pipeline equipment was located. Just five percent of them accounted for over half of the total methane leakage. At 30 percent of the sites, on the other hand, their instruments detected no leakage at all."
That would seem to make it easier to address.