DBPapers
DOI: 10.5593/SGEM2014/B51/S20.041

EXPLOITATION OF SHALE GAS BY HYDRAULIC FRACTURING - A METHOD WITH POSSIBLE MIDDLE AND LONG TERM CATASTROPHIC CONSEQUENCES

M .Ticleanu, R. Nicolescu, A. Ion
Wednesday 1 October 2014 by Libadmin2014

References: 14th International Multidisciplinary Scientific GeoConference SGEM 2014, www.sgem.org, SGEM2014 Conference Proceedings, ISBN 978-619-7105-17-9 / ISSN 1314-2704, June 19-25, 2014, Book 5, Vol. 1, 299-306 pp

ABSTRACT
In the hydraulic fracturing method the main quantity of fracking fluid (50-90%, waters with noxious additives) remains in the underground of the exploited areas, at various depths. The exploitation is more advantageous as the quantity of fracking fluid refluxed at surface is smaller. But in the same time, the greater the quantity of this fluid remained underground, the greater the possibility of a future contamination. These toxic fluids are quartered in the mother rocks affected by fracturing, represented by argillaceous rocks rich in organic matter. Nevertheless the fracking fluids can reachthe surface during medium or long periods of time by various ways and because of various causes. For this reason it is important to stress on the fact that the hydraulic fracturing surely disturbs the dynamic quilibrium of the rocks covering the mother rocks attacked by fracturing, especially in the case of unconsolidated rocks (sands) and carbonaceous rocks (limestone). This disturbance is caused mainly by the great number of microseisms resulted from the fracturing process. Subsequently, after the end of the exploitation, surface instability phenomena become probable because of large quantities of gas or oil extracted from underground. These phenomena are wellknown even after classical oil or gas exploitations. One way for the contaminated waters to reach the surface is the natural fault systems existent in the deposits above the exploited productive horizons. These faults are sometimes very difficult to detect, but they are always present, even in the platform areas in which the productive formations generally are to be found. Along these faults the toxic solutions and the methane gradually enter the permeable rocks i.e. deep aquifers and, closing to the surface, the phreatic waters and finally the hydrographic network. The natural seismic activity produced after the ending of exploitation can facilitate the access of the contaminated waters or methane towards the surface, especially in the situation of powerful seisms. After various periods of time, at surface, in the areas previously exploited by this method, it can appear contaminated waters springs which can more or less directly put in danger human, animal and vegetal life on large or even huge areas if the hydrographic network is contaminated. Also the closed wells, previously used for this type of exploitation, become contamination sources because of the continuous degradation in time of the cement isolation. All in all this method is dangerous for the natural resources of drinking and industrial waters (as strategic resources), connected with deep aquifers, phreatic waters or stream systems. In many zones there are valuable natural resources of mineral or geothermal waters that can be compromised. It is also important to mention that in the areas exploited with this method, the future drillings (whatever their purpose is) can be dangerous no matter if they reach the productive horizon or remain in the formations above. If they will open aquifers above the productive horizon they may find already contaminated waters and may facilitatetheir access to surface. From this perspective we consider the aggressive exploitation of the underground deposits by hydraulic fracturing as a planting of an ecological bomb with delayed effect, which will cause in the future at least catastrophic ecophenomena at regional scale.

Keywords: fraking fluids, pollution, mother rocks, flow-back , fault sistems, dynamic
equilibrium, microseisms.