Gas flaring and gas venting

In an oil field, oil is almost always associated with a certain quantity of natural gas: newer oil wells are equipped for the recovery of both oil well gas and crude oil and hence the gas is an additional resource of the oilfield. However, the recovery of this gas presumes that there are the transportation infrastructures required to move it to the points of consumption: these infrastructures, which are both costly and often difficult to implement, are not finalised when the quantity of gas recovered from the oilfield as a “secondary” product is limited, since the potential revenue would not cover their cost. Hence the problem arises of what to do with the associated gas.
The term gas flaring indicates the combustion of gas (without energy recovery) in an open flame that burns unceasingly at the top of flare stacks in oil production sites. This practice has resulted in the burning of large quantities of gas with the consequent production of huge amounts of carbon dioxide together with sulphur dioxide and nitrous oxide, which have contributed substantially to atmospheric pollution. In order to better understand the scale of the problem, it is sufficient to observe nocturnal images of Earth from space: the gas flaring activity in regions corresponding to the major petroleum-producing areas are a proof that cannot go unnoticed! Consider that in Italy today (where the practice of gas flaring is limited not only because there are fewer oil fields respect to gas fields, but also because Italy attempts to use all the natural gas produced) one million tonnes of carbon dioxide are produced every year as a result of gas flaring, while in Nigeria, where this practice is still greatly utilised, hundreds of millions of tonnes are produced!
Besides the practice of gas flaring, there is also that of gas venting. Gas venting is the discharge of unburned gases into the atmosphere, often carried out in order to maintain safe conditions during the different phases of the treatment process. During venting operations methane, carbon dioxide, volatile organic compounds, sulphur compounds and gas impurities are released. In many cases gases that are being vented could be burnt rather than dispersed into the atmosphere; this would partially reduce the environmental impact in terms of greenhouse gases, because the gases would be oxidised to form carbon dioxide, which has a global warming potential 21 times lower than methane.
Currently, the above-mentioned practices are subject to strong restrictions, both for economic (the gas produced could be sold and consumed rather than wasted!) but especially for environmental reasons. Under the Kyoto Protocol, there are incentives for the construction of plants that have minimum environmental impact and which, at the same time, do not waste precious resources. In more developed countries, this practice has been almost totally abandoned because it is a waste of an important resource and the infrastructures required to utilise the gas in situ are not difficult to implement. On the contrary, in many developing countries the gas is often not required at the production site and the costs of transportation are very high. For this reason, there are incentives to implement practices that are more feasible and less costly such as, for example, natural gas reinjection into the reservoir to increase its pressure and consequently its efficiency, small-scale natural gas liquefaction plants on the production site, the generation of electricity in situ, the distribution of natural gas to neighbouring urban areas, its use for transportation, etc. while costly operations, such as the construction of pipelines, are carried out only when the natural gas extracted justifies the high costs.

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