Billion cubic metres of natural gas
Billion cubic meters of natural gas (non SI abbreviation: bcm) or cubic kilometer of natural gas is a measure of natural gas production and trade. Some definitions cite volume, others energy content. Dependant of implied standards, this measure may represent different value of energy content. According to the standard defined by the International Energy Agency, it corresponds in average to  of energy in the case of Russian natural gas and  of energy in the case of Qatar's natural gas. Volume based definitions
According to the standard defined by the International Energy Agency, the gas physical volume is used, which is measured at the temperature of  at atmospheric pressure. According to the Russian standard, the gas volume is measured at . That means that 1 billion cubic metres of natural gas by the International Energy Agency standard is equivalent to 1.017 billion cubic metres of natural gas by the Russian standard. Energy based definitions
Some other organizations use energy equivalent-based standards. BP uses a standard which is equivalent to  per billion cubic metres. Cedigaz uses a standard which is equivalent to  per billion cubic metres. References

Natural gas
Units of volume
Units of energy
Non-SI metric units
International Energy Agency
BP