Coal Seam Gas vs Shale Gas ~ notes from the field

The following rant is taken from a bloke who left the CSG industry last week...reposted here for those who are interested in such things

There are 2 industries, and 2 VERY different legislators at play here.

ok, so what you saw in gasland was shale gas; that went largely unregulated and unchecked.

Shale gas, (and oil), reservoirs, like all conventional reservoirs, can be subject to all the conventional nasties, SBRs (sulphur reducing bacteria), mercury, heavies, condensates, hydrogen sulphide and other sulphates, benzene etc etc etc... this is, by and large, thermogenic gas.

In a coal seam, it is predominantly thought of as biogenic gas. Coal seams have varying amounts of gas adsorbed onto the carbon lattice depending on how much anaerobic digestion went on in laying down the coal, and how porous the coal is etc

To release the gas, all you have to do is drop the pressure, the easiest way to do this, is pump the water out.

Long story short, in a shale well, you have massive depths, high temps, and some corrosion accelerants down there that you want to deal with; which is by, as I understand it, they put some serious biocides down there, as well as some pretty nasty corrosion inhibitors.

In a coal seam, the coal will "skin up"and not allow the gas to move to the wellbore (which is essentially a water well with a pump in the bottom of it),so no coal seam gas operator with any nouse, will really want any hydrocarbons in their reservoir as it will bind the coal and essentially kill the well.

Fraccing is a process where high pressure formation water is pumped into the coal seam to "fracture" the coal to increase the permeability of the gas thus increasing your drill spacing to yield the reservoir. When I say pumped, they roll up with about 2000hp of turbocharged diesel pump to shift this water, its hardcore. Then a propant, which is either washed river sand, or a thermoset gel, like a guiar gum (the coagulant used in ice cream) Additives used in fraccing fluids in coal seams usually consist of some chlorine bleach, and some acetic acid to kill off whatever bugs may have been in the water that was sitting on the surface pre fraccing.

note:this is usually formation water, from the coalseam. The issue with fraccing in CSG is not the chemicals, its the hydro geology.

Here's the clincher, IF YOU DON'T HAVE GOOD GEOLOGICAL INTEGRITY YOU HAVE NO IDEA WHERE YOUR FRAC IS GOING! IF YOU CANNOT PROVE THERE WILL BE NO VERTICAL COMMUNICATION TO OTHER GROUNDWATER, YOU SHOULD NOT BE ABLE TO FRAC.

Technically, this is quite manageable, but it will be more expensive for the operator to do so.

Salinity on the surface from the evap dams and the R.O. plants needs some more planning, as does the effects of bulk movement of formation water (water out of the coal formation) and what effect that can have on the groundwater filtering out of other basins, into the coalseam then up into the dams. What effect this will have in 20 years if we try to pump 4 LNG trains out of Gladstone full of gas, is not yet well known enough. This is where the DERM needs to focus environmentally.

Socially, taking intensively farmed blacksoil, that is a whole nuther discussion...