Natural gas is perhaps 80% +- 15% methane. The rest is a variety of gasses, some of which constitute useful fuels in themselves, like propane and butane: these

Natural gas is perhaps 80% +- 15% methane. The rest is a variety of gasses, some of which constitute useful fuels in themselves, like propane and butane: these may be incorporated into the finished product (which is why we don't sell it as "methane"), or fractionated out. Historically, one saw 'stranded natural gas' flared from oil wells that produced too little natural gas or were in too remote a place to make a pipeline economical. Compressed natural gas is so low-energy-density that it's rarely economical to transport it outside the context of a pipeline - though this has changed in the last few decades with the adoption of liquified natural gas tanker ships and terminals to serve them; Still, the percentage of the value consumed by transportation is an order of magnitude higher than for oil tankers.