Hydraulic Fracturing Implications: Forensic Ambiguity, Science and Rhetoric
Environmental and public concern about potential impacts on drinking water resources from oil and gas industry hydraulic fracturing practices have led to a surge of media attention that has implicated the practice for “fugitive” methane and shallow groundwater contamination from hydraulic fracturing chemicals.
In February, the EPA released a plan of seven case studies to assess the potential impacts of hydraulic fracturing on drinking water and groundwater. The case study sites were chosen where natural gas resources are geographically extensive. The chances of naturally occurring gas in domestic water wells is also highly probable in these locations. Information from the Raton Basin, one of the EPA retrospective case study locations, is presented to demonstrate some of the potential problems and limitations of the proposed EPA study.
The EPA is using the same analyte suite for all study sites. The analyte suite includes compounds and stable isotopes that are selected as potential markers for hydraulic fracturing due to possible occurrence in hydraulic fracturing fluids or possible presence in natural gas bearing formations. Many of these same constituents can be naturally occurring in domestic water wells or present in common disinfection and rehabilitation chemical mixtures used by water well contractors. Consequently, potential markers for hydraulic fracturing identified in the EPA study cannot be considered a “fingerprint” or unique identifier of contamination by hydraulic fracturing operations. The word “fingerprint” is often used when addressing stable isotopes of carbon and hydrogen in methane and insinuates a unique identifier. However, this is not the case and isotopes only provide a marker for a general classification subject to deviations associated with processes such as mixing and oxidation.
Correlations drawn in media “exposes” may be linked but not causative. Areas are targeted by gas exploration because the potential is high, which often correlates with naturally occurring gas in aquifers which may supply domestic water wells.
Well logs, well completion and maintenance records, and baseline data need to be evaluated along with specific compounds and stable isotopes observed in injection and produced water fluids and in monitoring and domestic water supply wells to evaluate potential impacts due to hydraulic fracturing.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California