Associated petroleum gas (APG), or associated gas, is a form of natural gas which is found with deposits of petroleum, either dissolved in the oil or as a free "gas cap" above the oil in the reservoir. Historically, this type of gas was released as a waste product from the petroleum extraction industry. It may be a stranded gas reserve due to the remote location of the oil field, either at sea or on land, this gas is simply burnt off in gas flares. When this occurs the gas is referred to as flare gas.
The gas can be utilized in a number of ways after processing: be sold and included in the natural gas distribution networks, used for on-site electricity generation with engines or turbines, reinjected for enhanced oil recovery, be converted from gas to liquids producing synthetic fuels or used as feedstock for the petrochemical industry.
Russia is the world leader in the flaring of APG, and flares 30 per cent of the total APG flared globally.
The flaring of APG is controversial as it is a pollutant, a source of global warming and is a waste of a valuable fuel source. APG is flared in many countries where there are significant power shortages. In the United Kingdom, gas may not be flared without written consent from the UK Government in order to prevent unnecessary wastage and to protect the environment.
The World Bank estimates that over 150 billion cubic metres of natural gas are flared or vented annually. This amount of gas is worth approximately 30.6 billion dollars and is equivalent to 25 percent of the United States's yearly gas consumption or 30 percent of the European Union's annual gas consumption.