Characterization of Organics in the Marcellus Shale Flowback and Produced Waters

Open Access
Author:
Wolford, Robert Alan
Graduate Program:
Environmental Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 06, 2011
Committee Members:
  • Brian Dempsey, Thesis Advisor
Keywords:
  • chemical oxygen demand
  • produced
  • flowback
  • Marcellus Shale
  • natural organic matter
  • humic
Abstract:
The objective was to accurately characterize organic matter in flowback and produced (> 30 days after fracking) water from Marcellus shale gas development. Flowback and produced waters contain high concentrations of chloride, barium, and bromide. The Gas Technology Institute also reported that average chemical oxygen demand (COD) in flowback waters was 8500 mg/L while the average total organic carbon (TOC) was only 39 mg/L, resulting in an impossibly high COD/TOC ratio of 220. Thus the motivation was to investigate the accuracy of the COD and TOC analyses. We also applied a novel organic fractionation strategy to qualitatively identify organic matter, analyzed for some organics that are added to the fracking solutions, and measured inorganic constituents. A sample that apparently contained 19,000 mg/L COD based on conventional analytical procedures was found to contain only 500 mg/L COD and 80 mg/L TOC, resulting in a more reasonable COD/TOC ratio. Most of the organic matter was organic acids, which are also the dominant constituent in extracts of organic shale that have not been hydrofracked. Analysis of the produced waters by FT-IR also showed the presence of humic material, however further analysis and low SUVA numbers showed that this is probably a minor constituent. Analysis by GC/FID and HPLC showed that the waters contained low amounts of organics that were added to the hydrofracking solution. These results indicate that flowback waters contain some of the fracking constituents while the majority of organics in produced waters are natural compounds from the shale.