ENVIRONMENTAL IMPACT EVALUATION OF HYDROCARBON EXTRACTION FROM SHALES

Hydraulic fracturing technologies in shales and/or tight rock have allowed increased hydrocarbon recovery from organic rich units throughout the US and the world. With the recent increase in production, there has been pressure on government agencies to establish a regulatory framework for hydraulic fracturing.

An Environmental Impact Analysis, an approach used for other planned human disturbance activities, such as mines and landfills, could be used. Within the broad EIA process, pre-drilling baseline monitoring data of site-specific conditions of air, water, land, biota, and social environment are collected. Once data are collected and compiled, associated impact analysis can be performed and ultimate short and long term monitoring proposed. One of the biggest risks identified related to hydraulic fracturing is potential impacts to existing shallow aquifers and ground water wells. To address this, site specific hydrologic and geochemical conditions of existing and possibly newly installed wells would need to be characterized.

In this study, a literature review of 11 organic-rich shale plays across the US shows site specific challenges related to water quantity, quality, and disposal. Shales evaluated include the Antrim, Bakken, Barnett, Eagle Ford, Fayetteville, Haynesville, Marcellus, New Albany, Niobrara, Utica, and Woodford. These organic rich shales exposed to oxygen and containing pyrite have the ability to produce acid rock drainage, although high carbonate content in many of the shales limit degradation of water quality. Changing the oxidation/reduction conditions in the shales can potentially increase mobility of different constituents (i.e., uranium). Waste water disposal practices, whether using injection or treatment, are another potential risk to receptors and would be thoroughly evaluated during an EIA process. Review of available data for these 11 shales reveals that site-specific major and trace element data on the surface, ground, and flowback water as well as aquifer characteristics are sparse, making the evaluation of risk to human health and the environment challenging to understand and quantify. Increased efforts to collect more extensive site-specific hydrogeologic and geochemical data should be made to help in the evaluation of risk to human health and the environment.