It's really no different than killing a wild well here in America's oil patch, assuming they set casing at the surface. You drop enough stuff down the hole until it gives up.
I'm not sure why this one would be any different.
The geothermal component?
No casing, all mud.
Good luck with that...
The stuff wants to get out. Wouldn't it just pop out somewhere else?
They only set surface casing and then continued to drill through overpressured mud to 9k feet, where they hit a high-pressure, high temp aquifer. That rocketed steam up the open hole and mobilized what could yet be years worth of plasticized clay formation 1k m thick. The cavern being created has got to be huge and has already resulted in substantial surface subsidence, so much so that two rigs working on relief wells were withdrawn. It will just flow until the system collapses on itself and snufs itself out. This baby could gush for years and the price tag is already well over $1 billion in damage. I guess sacrificing the goats and chickens to the mud gods has had no effect.