Dependant of implied standards, this measure may represent different value of energy content.
[1] According to the standard defined by the International Energy Agency, the gas physical volume is used, which is measured at the temperature of 15 °C (59 °F) at atmospheric pressure.
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.
BP uses a standard which is equivalent to 36 petajoules (1.0×1010 kWh) per billion cubic metres.
[2] Cedigaz uses a standard which is equivalent to 40 petajoules (1.1×1010 kWh) per billion cubic metres.