My understanding was the explosive was going to be put down the well or buried in a second well close to the leaking well. Nuclear bombs are more compact, for

My understanding was the explosive was going to be put down the well or buried in a second well close to the leaking well. Nuclear bombs are more compact, for equivalent yield, than chemical explosives which is why I assumed they were being proposed. As for your final point a fire needs heat, fuel and oxidiser. The oxidiser should be absent so no fire.