Thermogenic gas, the kind of gas found in the Marcellus Shale, is the result of temperature and pressure
changes deep beneath Earth’s surface that change carbon matter into methane. It has a different chemical
signature than biogenic natural gas, which is produced by the metabolic decay of organisms close to Earth’s
surface. This study correlates a high percentage of thermogenic gas (as opposed to a mix of thermogenic and
biogenic gas) contamination with active gas drilling, but does not explain how the migration from deep rocks
has occurred. Migration pathways are difficult to trace, and no conducted studies have been able to confirm or
deny a fracture connection between deep gas and drinking water aquifers.