Energy

Environmental problems

Be they conventional or non conventional hydrocarbons,problems related to the use of fossil fuels are unfortunately well known. Also in the production and upgrading phases there are serious environmental problems. In the case of oils recovered from oilfields, the problems are similar to those of the conventional type of production, but there are also other different problems, which are perhaps even more serious, created by the use of tar sand and shale. In this case besides the problems that are strictly related to the “oil production”, there are also problems that are typical of extraction processes in open pits or in mines: since the extraction is mainly from open pits, the consequence is the devastation of the landscape and environment of large areas. In these cases, and in case of the use of the CHOPS technologies, for the production and extraction processes, large volumes of rocky or sandy material are obtained, that must be disposed. Generally, this consists of inert (or almost inert...) material, and disposal of this material is not “dangerous”, but, as in the case of the mining debris, the need arises for delicate interventions to rearrange the landscape. However also mud, known as slurry, is produced. It consists of a mixture of clay, sand, heavy oils and chemical emulsifiers of various types that cannot be disposed of in the environment, but need special treatment for disposal and particular stocking. The slurry and mud from the perforation and extraction processes may be re-injected into the depths of the oilfield to increase their productivity, or stocked in the reservoirs that have been emptied, or in underground salt rock caverns.
The sites must be chosen and studied with great care, to avoid dangerous contaminations, especially of the ground water table. In the case of tar sand extraction, the problem of CO₂, emissions is very severe, for an equal amount of extracted oil, the emissions are approximately 4 times greater than in the case of extraction from the wells. And water too is a very sensitive problem, in order to extract a barrel of oil from the tar sand, 3-5 barrels of water are necessary. The water is then returned with a considerable content of polluting agents of the hydrocarbon and the emulsifying substances that are extremely toxic. These waters cannot be dispersed in the environment and cannot even be stocked in open pits, because they are extremely toxic for the fauna (particularly the water fowl) and a potential source of pollution of the surface water and ground water. Besides large quantities of CO₂, the upgrading processes also produce harmful gases, like S or N. With the modern technologies it is possible to almost totally eliminate the latter two (it is only a problem of costs and a “political” will) but the production of CO₂ is a big problem. Sulphur obtained from the oil desulfuring processes may be used for industries, but at present it is an excess product, and must therefore be stabilized and stocked in special underground deposits, from which it may be extracted again in the future if the need arises. Also coke produced in the upgrading processes is a problem. Its direct utilization as fuel has been very limited up to date due to its very high content of S and other impurities, and the problem of stocking or destroying it has been examined; however the advent of clean coal technologies may allow its future utilization for the production of electric power. It is evident therefore that also the non conventional fuels are not a clean source of energy, and they entail environmental problems that are even greater than the conventional hydrocarbons (which are already not exactly “ecological”). Also in this case regulations and technologies shall be applied, so that their utilization is as eco-compatible as possible, even if this will mean additional costs for the oil companies, so that the price to pay for the environment will be as limited as possible.