Groundwater contamination by hydrocarbons and chemicals used during drilling and hydraulic fracturing is thought to be probably the most significant environmental risk of shale gas extraction. Natural occurring vertical fractures in the rock formations, changes of hydrological regime due to intensive pumping of water into the wells, failures in integrity of wells casings and casings cementing, leakages of fracturing fluid and drilling cuttings on the ground surface are among the causes of potential groundwater contamination.

The main types of potential groundwater contamination due to shale gas extraction include migration of gaseous hydrocarbons (methane, ethane, propane) in aquifers, groundwater pollution by chemicals used in hydraulic fracturing due to surface spills or technological errors during hydraulic fracturing and penetration of contaminants (salts , heavy metals) from the deep layers into the aquifers.

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