It means what it says,free gas. They drill a well on your property you might own a certain percentage or all of the mineral rights,,part of that deal might be free gas,might even be a deal like that made if pipeline was run through your property.Filtering,they seperate the water from the gas at well before you would get it,,it'll burn just fine,,just need regulators,high and low pressure,,put a tap on the pipe line somewheres with a valve,regulators,gas line,,might need a drip or two,[something to catch extra water in low spots so it don't freeze],,maybe even a heater,,,but you got free gas.I've had it at least in three places I've lived,,all of these from very old wells,,not enough gas to make it profitable to sell but plenty for one or two homes for 100 years or more. Hooked up several taps when hooking up new wells,[some authorized some not],,,,don't know how much its done nowadays but in the old days it was common,,,,,,lotta gas wells in ohio,w.va.,pa. areas,,lotta people getting free gas too. thingy