Shale gashas recently received a high level of attention due to the potential negativeimpacts that it might have on the surrounding environment. However, ameticulous understanding of the methodologies used in order to extract the gasand the preventive measures available is necessary in order to assess thelevels of risk involved. A very common concern about shale gas development isthat hydraulic fracturing operations might lead to fractures that extend beyondthe target formation to water aquifers allowing contaminants to migrate fromthe target formation into drinking water supplies.
With the exceptions ofAntrim and New Albany Shales, thousands of feet of rock isolate gas-bearingshale formations from the aquifers’ base that contains drinkable water. Contaminationis highly improbable to take place in deep shale formations duringwell-designed fracture jobs. The reason for this is that contamination ofunderground sources of drinking water due to hydraulic fracturing requireshydrofractures to spread several thousand feet beyond the upward boundary ofthe target formation through many layers of rock. Water used for hydraulicfracturing is usually fresh water that is extracted from groundwater or surfacewater resources. In several countries, the average annual water volumesreported for hydraulic fracturing were less than 1% of the estimated annualvolume of readily available fresh water. With some exceptions, hydraulicfracturing relatively uses a small percentage of water when compared to thetotal water use at large geographic scales.
Water management strategies can aidin reducing the severity of impacts on drinking water resources due tohydraulic fracturing. Another concern with hydraulic fracturing is its effecton the seismic activity. The hydraulic fracturing process results in a highnumber of microseismic events, or micro-earthquakes. However, it is importantto note that the magnitudes of these are too small to be detected at thesurface. Therefore, seismic monitoring of hydraulic fracture jobs is crucial inimproving the understanding of how underground injection might result in anunexpectedly high magnitude seismic activity. Additives usually make up thesmallest portion of the overall composition of hydraulic fracturing fluids.However, additives have the greatest potential to affect the quality ofdrinking water resources compared to proppant and base fluids.
Additives can bea single chemical or a mixture of different chemicals. Additives are added tothe base fluid in order to change its properties such as adjust pH, increasefluid thickness, or limit bacterial growth. The properties and features of therock formation assist in making a choice regarding which additives to use. Thelaw does not currently require disclosure of chemicals stored in smallerquantities and access to MSDSs can often be limited. Several efforts areongoing in order to obtain greater disclosure of fracturing fluids.
Effortsinclude a provision in draft climate legislation introduced by Senators JohnKerry (D-MA) and Joe Lieberman (I-CT) in May 2010. This provision would amendEPCRA to mandate the disclosure of all chemicals used on public websites.