You cannot have ignition without oxygen.
If free oxygen was already in the field, the methane and other hydrocarbons would oxide with it producing CO2, H2O etc over the millions of years.
Some of that does happen, but by the time we get to producing a field, that is already long gone.
I only asked because of coal mines/seams burning underground for years.
Having witnessed this first hand the word ‘nuke’ raised an eyebrow.
Thanks for the reassurance. :)