Organic compounds in hydraulic fracturing fluids and wastewaters: A review

Abstract

High volume hydraulic fracturing (HVHF) of shale to stimulate the release of natural gas produces a large quantity of wastewater in the form of flowback fluids and produced water. These wastewaters are highly variable in their composition and contain a mixture of fracturing fluid additives, geogenic inorganic and organic substances, and transformation products. The qualitative and quantitative analyses of organic compounds identified in HVHF fluids, flowback fluids, and produced waters are reviewed here to communicate knowledge gaps that exist in the composition of HVHF wastewaters. In general, analyses of organic compounds have focused on those amenable to gas chromatography, focusing on volatile and semi-volatile oil and gas compounds. Studies of more polar and non-volatile organic compounds have been limited by a lack of knowledge of what compounds may be present as well as quantitative methods and standards available for analyzing these complex mixtures. Liquid chromatography paired with high-resolution mass spectrometry has been used to investigate a number of additives and will be a key tool to further research on transformation products that are increasingly solubilized through physical, chemical, and biological processes in situ and during environmental contamination events. Diverse treatments have been tested and applied to HVHF wastewaters but limited information has been published on the quantitative removal of individual organic compounds. This review focuses on recently published information on organic compounds identified in flowback fluids and produced waters from HVHF.

Optimization of thin film solid phase microextraction and data deconvolution methods for accurate characterization of organic compounds in produced water

“…Of these hydrocarbons are a number of polycyclic aromatic hydrocarbons (PAHs), the most abundant being phenanthrenes, anthracenes, and naphthalenes that have been previously described in other work [39]. A pesticide, atrazine, was also found in a single sample (PW 3), albeit at low levels that corroborates the idea that pesticides in PW are at ultra‐trace levels and are rarely found in samples [13,40]. Many of these compounds, which given the abundance found in the samples analyzed, pose major environmental concerns due to their toxicity and persistence in the environment, most of which are supported by other works in the literature [14,39,40].…”

“…A pesticide, atrazine, was also found in a single sample (PW 3), albeit at low levels that corroborates the idea that pesticides in PW are at ultra‐trace levels and are rarely found in samples [13,40]. Many of these compounds, which given the abundance found in the samples analyzed, pose major environmental concerns due to their toxicity and persistence in the environment, most of which are supported by other works in the literature [14,39,40]. Most notably is the constituent 1,4‐dioxane, a previously discovered PW component that is associated with human cancer [13,23] and has been shown to be challenging to remove from the waste‐stream [23].…”

A geospatially resolved database of hydraulic fracturing wells for chemical transformation assessment

“…However, to date, only 238 owback and produced samples have been analyzed to identify specic organic compounds in the published literature. 2 This small number of analyses have included inorganic [11][12][13][14][15][16][17] and organic 2,18-25 components of owback water, but the vast well-to-well diversity (spatially and temporally 13,21 ) and comparably complex suites of disclosed additives 26,27 pose massive hurdles for complete characterization at the eld's current pace. In particular, a high degree of uncertainty remains regarding the nature of anthropogenic additives themselves and their capacities to persist or transform in the subsurface.…”

“…Industrial ingredient reports have been disclosed through FracFocus, 36 a publicly available online database, and by the United States Congress. 37 Generally, these chemicals serve a wide array of purposes to optimize hydraulic fracturing operations, 26 from (1) controlling the chemical environment within wells to prevent degradation (e.g., biocides and scaling inhibitors) to (2) altering the uid's physicochemical properties in situ. 26,27 Equipped with an understanding of subsurface conditions, 38 researchers have simulated the shale well parameter space in laboratory systems to interrogate and characterize subsurface reaction pathways, demonstrating conditions or additives that can either mitigate or encourage transformation.…”

Alternative Management of Oil and Gas Produced Water Requires More Research on Its Hazards and Risks

“…Limited characterization studies of produced water have identified nearly 600 chemicals in produced water associated with hydraulic fracturing (USEPA ). More recent studies using high‐resolution mass spectrometry indicate that the number of potentially detectable chemicals may be much greater (Hoelzer et al ; Luek and Gonsior ; Luek et al ; Piotrowski et al ).…”