Threats to the environment in the areas of abandoned extraction of hydrocarbon deposits.
Czesław Rybicki, Tadeusz Solecki, Bogumiła Winid
Vol. 32, no. 1 (2015), s. 103-119, 
The environmental problems in past mining areas, where the production process was ended, are connected with contaminations coming from past extraction processes and the risks relating to the abandonment of wells and deposits. The risk could be variable depending on such factors as the geological formation and hydrogeological conditions in the analyzed area, and the condition of abandoned wells. The main source of contamination could be improperly sealed abandoned wells and unplugged abandoned oil and gas wells. The environmental problems could be particularly concern on the area of old historical extraction sites. There are some hydrocarbon deposits, where production i s endedand still it is possible to see places of wells and remains of an old oilfield infrastructure. Unplugged or improperly sealed wells can result in stray gas migration or contamination of soil, ground and surface and ground waters. The end of well exploitation may cause the risk associated to the restoration of formation pressure. This could be the reason of uncontrolled discharge of gaseous and liquid hydrocarbons into shallow depths. Returning to the extraction from some deposits could reduce the formation pressure and constrain uncontrollable leakages of hydrocarbons. This option seems to be environmentally friendly. Authors of the paper made efforts to evaluate the scale and the range of mentioned disadvantageous phenomena.