Paula Mouser/ Desiree Plata Ohio State University/Duke University
Advancements in horizontal drilling and hydraulic fracturing techniques have recently made it possible to extract large volumes of energy resources from coal bed and methane shale formations. Currently, shale energy development is occurring at a rate that is outpacing both regulatory policies and research on the potential environmental and health effects of these techniques. Public concerns include the potential contamination of drinking water resources through the mishandling of fracturing and flowback fluids (e.g. borehole leaks, surface spills), as well as the fate of injected fluids that remain unrecovered in the deep subsurface. The objective of the research project is to determine biodegradation rates for select aromatic and aliphatic compounds that are used during the hydraulic fracturing process in order to better define the degradable or recalcitrant constituents that may pose risk to ecological or human health under natural aquifer conditions. The select chemical classes represent frequently used, potentially toxic compounds that are often undisclosed by chemical manufacturers in hydraulic fracture fluid additives. To realize this objective, the investigators will characterize low and high molecular weight aromatic and aliphatic distillates present in a representative fracturing fluid and identify a subset of risk constituents using high resolution analytical techniques, including gas chromatography (GC) with flame ionization detection, GC mass spectrometry, and multi-dimensional GC. Laboratory experiments employing indigenous microbial populations and select bacterial isolates will be performed to investigate how chemical constituents are biologically degraded across a range of physical and chemical conditions representative of shallow freshwater aquifers, deeper saline bedrock, and shale formation pressures and temperatures. Microbial dynamics will be monitored using high-throughput biotechnology tools, including pyroseqeuncing of the 16S rRNA gene, which allows comparison across a broad range of biological species. Research findings will be used to develop a risk matrix that outlines the presence or absence of potentially toxic organic constituents along a pressure, temperature, and salinity spectrum. Associations between degradable constituents and microorganisms will provide a starting point for understanding the specific microbial metabolic mechanisms responsible for distillate compound biotransformation in fracturing fluids.
The project will significantly improve our understanding of how fracturing fluid distillates are biodegraded by indigenous microorganisms and will identify the key physicochemical factors that may limit or enhance the degradation of higher risk compounds in the environment. Outcomes from this research include better quantification of biodegradation rates and better parameterization of flow and transport models of these systems. It will also provide further insight into the persistence of compounds in order to improve chemical formations in environmentally friendly drilling operations. Research findings will be communicated to students and the broader public through EnergyExplained! lectures, highlighting such issues as scarcity, security, feasibility, and environmental impacts from natural gas and renewable technologies at a variety of local venues (libraries, museum, and/or grade schools). Investigators will also disseminate knowledge on key shale energy issues to non-profits, regulatory agencies, academics, and other stakeholders in the Appalachian region through regular workshops and workgroup meetings led by Ohio State University's Subsurface Energy Resource Center and Extension Office.
