Methane: The Gas and Its Properties
What methane is, where it is found in oil and gas operations, and the properties that make it both a hazard and a climate concern.
8 min
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Methane is the simplest hydrocarbon. One molecule has one carbon atom and four hydrogen atoms, so its chemical formula is CH4. It is the main part of natural gas, the product that many oil and gas facilities produce, process, transport and sell.
The share of methane in natural gas changes from field to field. Sales gas is often more than 80% methane by volume. Raw gas from a well can also hold ethane, propane, heavier hydrocarbons, carbon dioxide, nitrogen, water and sometimes hydrogen sulphide (H2S). Oil wells produce associated gas, which is gas that comes out of the crude oil as its pressure falls.
So methane is present almost everywhere in an upstream or midstream facility: in wells, separators, compressors, pipelines, tanks and flare systems. Wherever gas is under pressure, some of it can escape.
Two reasons to keep methane in the pipe
For many years the oil and gas industry treated methane mainly as a safety issue. A gas leak can create a flammable cloud, and a fire or explosion can follow. Gas detectors, hazardous area classification and permit-to-work systems all exist partly for this reason.
Today methane is also treated as a climate issue. Even a small leak that is far below any flammable concentration still releases a powerful greenhouse gas into the atmosphere. A leak can be safe in the sense that it will not ignite, and still be harmful to the climate and costly to the business.
Because methane is invisible and has no smell, people often do not know a leak exists. Special instruments, such as infrared cameras and gas analysers, are needed to find most of them.
Why can a methane leak go unnoticed by people working nearby?