thoughts on csg and energy for the future, page-31

db,

Methane does come out first, yes. The well will produce mostly methane for most of its life until you lower the pressure enough to hit the CO2 isotherm, and then all the CO2 will come out. So turn the well off when that happens.

Unfortunately it's not clear-cut, if you've got 30% CO2 content in the coal, you'll still get maybe 10% CO2 out from the start of the well's flow. Which is too high for most pipelines, so you either need a special pipeline or a CO2 scrubber. But if you've got 10% CO2 you might get away with production gas of 3% CO2, which is acceptable.

Interestingly there are biogenic processes that reduce CO2 to methane. So a potential use for microbially-enhanced CSG is to pump bugs into high CO2 areas and let them convert it to methane for you. Still a long way away though.