Microbial Aspects of Shale Flowback Fluids and Response to Hydraulic Fracturing Fluids

Recent technological advancements in hydraulic fracturing and horizontal drilling as applied to shale formations have revived interest in Ohio's oil and natural gas reserves.In many cases, short and long-term impacts to the environment from this exploration are not well understood as production in the field outstrips conducted research.The following two studies explore microbial community dynamics in shale well flowback fluids and their response to synthetic fracturing fluid exposure, respectively, and may yield insight into ecological impacts to the surface and subsurface as a result of shale gas development.Microbial diversity in the shale well fluids studied decreased significantly.The microbial ecology of these fluids shifted from one dominated by microbes present in source waters to one consistent with a brine system.In addition, significant enrichment of various hydrocarbon-degrading biomarkers was observed in an aquifer response to frack fluid exposure.Overall, significant dissolved organic carbon attenuation, largely attributed to biodegradation, was observed in both studies.Characterizing microbial community content and dynamics of fluids through hydraulic fracturing, flowback and production periods of shale gas stimulation may aid well operators in maximizing natural gas recovery and practitioners in making informed decisions on wastewater management strategies.In addition, examining how the biogeochemistry of a typical aquifer system responds to fracking fluid exposure can be used as a timely indicator of surface and groundwater pollution by these shale gas-associated fluids.iii Dedication I lovingly dedicate this thesis to my best friend and husband Taylor, whose limitless support never fails to build me up and confirm in me my ability to accomplish so much more than I ever thought possible.