genesis of gas at these depths, page-6

SSkim the situation exists because of the immense pressures exerted on the once orgainic material due to the buildup of rock on top of it and the heat radiated from the earth at sufficient depths. The majority of the gas/oil is not formed until the pressure is applied. Thus, you have time for salt traps to form and limestone to set before the process begins.

Once those are in place, and with increased pressure being gradually applied from above, the gas can form and become immediately trapped - permanently trapped by the salt until shifts in the earths crust (earth tremors etc) allow small pockets to seep through - which is why there have been shows all the way up.

The real question is how much of the original gas has remained trapped. It should be substantial given the size of the salt trap, but nothing is to be taken for granted in this game.

This is my view, but I am no "expert".