An interesting study relevant to the fracking controversy. I do not think most people realise that penetrating any shale body that has the slightest organic content will result in the release of limited amounts of methane. Any conductive faults through a shale body likewise provide a pathway for the escape of methane.
Most also do not realise that coal fired power stations release far more radiation that nuclear power stations. This is even more surprising when it is realised that coal has an extremely low gamma signature compared to most other rocks(apart from rocksalt- sodium not potassium)



https://phys.org/news/2018-05-three-year-relationship-methane-groundwater-proximity.html