Study of Some Potential Environmental Impacts of Hydraulic Fracturing Related to Unconventional Hydrocarbons in Hungary

Recoverable amount of the already discovered and even prospective unconventional hydrocarbons in Hungary supposedly exceeds 1,500 million tons of oil equivalent, but according to modest estimates, the 30-year perspective of the recoverable amount can reach only 100 million tons by current available technology. The unconventional hydrocarbon extraction is mostly the production of tight gas, but there is a great chance of unconventional shale gas and shale oil exploration and extraction as well. Nevertheless, in Hungary the hydraulic fracturing is a precondition for the exploitation of unconventional hydrocarbon resources.

The environmental consideration of hydraulic fracturing is contradictory; therefore, its regulation and official licensing are sources of conflicts not only in Hungary but all over in Europe. We show a case study of successfully fractured tight sand exploitation in Derecske Trough (E Hungary) in order to emphasise the importance of the analyses of local circumstances and the regulatory steps determined based on those. The study focuses on the two most significant risks specific to fracturing, namely, the effect of hydraulic fracturing on groundwater and the risk of induced earthquake based on a 3D geological model of the area interpreting the real geological conditions. The main conclusions are that (1) the spatial extension of induced fractures is extremely small in the prevailing continuously subsiding geodynamic conditions; and (2) it is almost excluded that a fracturing operation would release so much energy that would cause the development of a new, significant permeable fault (or the reactivation of an existing one). (3) There is at least 2,000 m mostly impermeable and ductile sedimentary succession between the uppermost fractured zone and the bottom of the deepest thermal aquifer. It concludes that (4) the risk of a possible pollution spreading along the communication between formations does not exist and (5) the dissipation capability of young sedimentary formations is able to absorb the energy released by induced seismicity, which in case of the most disadvantageous technical and tectonic circumstances can trigger most likely earthquakes with a magnitude of ~1.8 in Hungary. Such an activity practically cannot be perceived by humans on the surface.