Natural gas in well water is not necessarily or even usually due to fracking.
More likely it is a result of the slow release of natural gas through existing fissures in the earth. Eventually some of this natural gas could dissolve in water deep underground. When the water is pumped up to the surface the dissolved gas will bubble out, just like a carbonated drink. If the gas is allowed to collect in a well cistern, it could ignite or explode if exposed to the air and a spark.
It would not surprise me at all if such water well explosions have occurred in the past, but it would very much surprise me if any such occurrence could be linked in any way to “fracking”.
Exactly. It’s reminiscent of the way oil seeping up naturally from the ocean floor and washing up on beaches was used to ban offshore drilling in California.