[glompers]

> There are coal seam fires that have been going on for centuries and the pollution of these is just as bad as the pollution generated by human created coal mine fires (and that's truly awful, a significant source of carbon pollution).

Has CO2 fire suppression been unsuccessfully attempted in these seams? Since nobody is underground and we know how to inject CO2 into underground deposits at various pressures, it seems like it would be a good candidate. Plus, with rotary steerable drilling, we could come in laterally (from a safe location above ground) to as many depths of injection as necessary.

[a11r]

These are large coal seams with significant exposure to the atmosphere. See https://en.wikipedia.org/wiki/Jharia_coalfield for an example. That excavator in the picture is not trying to put out the fire, it is just mining coal that happens to be burning. Spray some water, put out the fire and ship it off to customers.

[recursivecaveat]

Apparently in mines they are sometimes extinguished with nitrogen. For less contained ones, injecting water or mud, while trying to seal off the ground with impermeable clay to halt oxygen and hopefully choke the fumes. Their scope can be huge though, and they generate a lot of energy which can cause subsidence to open up new passages. The Centralia fire in the US is apparently 15km².

[rkagerer]

I have a question on rotary steerable drilling. I gather we're only talking about a degree or less of deflection on the steering head. But how does the km's long rest of the stack behind the head snake through the curves? Is it like rail cars, with a little bit of angular bend allowed at the connection of each segment?