Organic and inorganic composition and microbiology of produced waters from Pennsylvania shale gas wells

Applied Geochemistry
By: , and 

Links

Abstract

Hydraulically fractured shales are becoming an increasingly important source of natural gas production in the United States. This process has been known to create up to 420 gallons of produced water (PW) per day, but the volume varies depending on the formation, and the characteristics of individual hydraulic fracture. PW from hydraulic fracturing of shales are comprised of injected fracturing fluids and natural formation waters in proportions that change over time. Across the state of Pennsylvania, shale gas production is booming; therefore, it is important to assess the variability in PW chemistry and microbiology across this geographical span. We quantified the inorganic and organic chemical composition and microbial communities in PW samples from 13 shale gas wells in north central Pennsylvania. Microbial abundance was generally low (66–9400 cells/mL). Non-volatile dissolved organic carbon (NVDOC) was high (7–31 mg/L) relative to typical shallow groundwater, and the presence of organic acid anions (e.g., acetate, formate, and pyruvate) indicated microbial activity. Volatile organic compounds (VOCs) were detected in four samples (∼1 to 11.7 μg/L): benzene and toluene in the Burket sample, toluene in two Marcellus samples, and tetrachloroethylene (PCE) in one Marcellus sample. VOCs can be either naturally occurring or from industrial activity, making the source of VOCs unclear. Despite the addition of biocides during hydraulic fracturing, H2S-producing, fermenting, and methanogenic bacteria were cultured from PW samples. The presence of culturable bacteria was not associated with salinity or location; although organic compound concentrations and time in production were correlated with microbial activity. Interestingly, we found that unlike the inorganic chemistry, PW organic chemistry and microbial viability were highly variable across the 13 wells sampled, which can have important implications for the reuse and handling of these fluids

Study Area

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Organic and inorganic composition and microbiology of produced waters from Pennsylvania shale gas wells
Series title Applied Geochemistry
DOI 10.1016/j.apgeochem.2015.04.011
Volume 60
Year Published 2015
Language English
Publisher Oxford
Publisher location New York, NY
Contributing office(s) National Research Program - Eastern Branch, Toxic Substances Hydrology Program
Description 10 p.
First page 116
Last page 125
Country United States
State Pennsylvania
County Lycoming, Tioga
Online Only (Y/N) N
Additional Online Files (Y/N) N