SusChEM: Geochemical Characterization and Evaluation of the Environmental Impacts of Hydraulic Fracturing Fluids

Duke University, Durham NC

Investigators

Abstract

Broader significance. The development of unconventional oil and gas resources through hydraulic fracturing and horizontal drilling has increased energy production in the USA and is expanding globally. Yet, this rapid development has triggered an intensive public debate over the environmental implications of this technology. One of the environmental risks associated with unconventional shale gas development is the contamination of water resources. Hydraulic fracturing fluids (HFFs) are highly saline and contain elevated levels of toxic elements such as barium along with high levels of naturally occurring radioactive materials. Yet the ability to directly identify hydraulic fracturing fluids and their release in the environment is not known. This NSF project seeks to develop novel and diagnostic geochemical tracers that are inherently connected to the hydraulic fracturing process. The environmental forensic approach will enable us to distinguish hydraulic fracturing fluids from other forms of contamination, including naturally occurring saline groundwater and the legacy of past conventional oil and gas exploration that can mask attempts to delineate water contamination sources and evaluate the net impact of shale gas development. The methodology developed in this NSF project could be applied universally to other unconventional reservoirs as hydraulic fracturing expands globally. Technical description. This study will use an extensive collection of flowback and produced waters from shale gas and conventional oil and gas exploration (total 80 samples) to establish a comprehensive geochemical database that includes major and trace elements, combined with multiple isotopic fingerprints (d18O,d2H, d13C-DIC, d11B, 87Sr/86Sr, d7Li, 206Pb/208Pb) and radionuclides (228Ra/226Ra, 210Pb/226Ra). Based on preliminary data, it is hypothesized that the novel multi-isotopes tracers will enable us to characterize and identify the geochemical fingerprints of HFFs, providing the basis for evaluation of their origin and possible impacts on the environment. It is proposed to investigate already collected HFFs? samples in addition to new collection of water resources in areas of shale gas development in WV and PA. In particular, the study aims to (1) integrate geochemical and isotopic data for reconstruction the origin and evolution of produced and flowback waters in shale formations as compared to produced waters from conventional oil and gas wells; (2) evaluate possible contamination of surface water by HFFs upon disposal of inadequately treated wastewater, spills, or leakage from HFFs? ponds; (3) simulate reactions of HFF with sediments and mixing with other water types through laboratory experiments and thermo-kinetic modeling; and (4) evaluate groundwater contamination in areas associated with shale gas development in WV. This project is being jointly supported by the NSF Geobiology and Low-Temperature Geochemistry program, the NSF Sustainable Chemistry, Engineering and Materials (SusChEM) initiative, and the NSF Environmental Sustainability program.