Giant airships to transport nat gas would not involve liquifaction. Nat gas is roughly half as dense as air so it would act as the lifting gas of huge blimps. The blimps would be filled at the artic gas field, flown south using a protion of the gas as fuel, then deflated at a southern pipeline terminal.  The deflated blimps would return to the gas field by ship or plane to repeat the cycle.
But the surface area displace would be huge. If not pressurized or liquified, you have problems with push a surface area like that through the air. You need power to push that area, and you have a static charges building up. So there are two problems to deal with.

H2 is still 7 times as lighter. Than methane and will provide much less surface area.

Who in their right mind would want to pilot or man the crew on one of those things?

Remember the Zeppelin!!!