" in our study, we did several things. First, we documented the level of methane in the drinking-water wells. Second, we analyzed the isotopes in methane. The geochemical isotope is like a fingerprint in which you identify the source of the methane. And basically you can have two major sources of methane: one, thermogenic, is the methane exploited from deep shale gas and found in [drinking-water] wells. There is another type of methane that is called biogenic, which is formed in much more shallow depths."
Feel free to be the first
Please review the linked page for context.
If you can think of something better than this,
please add it to the database