Repository for Oil and Gas Energy Research (ROGER)

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Ozonation, sorption to granular activated carbon and aerobic degradation were compared as potential treatment methods for removal of dissolved organic carbon (DOC) fractions and selected organic compounds from shale gas flowback water after pre-treatment in dissolved air flotation unit. Flowback water was characterised by high chemical oxygen demand and DOC. Low molecular weight (LMW) acids and neutral compounds were the most abundant organic fractions, corresponding to 47% and 35% of DOC respectively. Ozonation did not change distribution of organic carbon fractions and concentrations of detected individual organic compounds significantly. Sorption to activated carbon targeted removal of individual organic compounds with molecular weight >115 Da, whereas LMW compounds remained largely unaffected. Aerobic degradation was responsible for removal of LMW compounds and partial ammonium removal, whereas formation of intermediates with molecular weight of 200–350 Da was observed. Combination of aerobic degradation for LMW organics removal with adsorption to activated carbon for removal of non-biodegradable organics is proposed to be implemented between pre-treatment (dissolved air floatation) and desalination (thermal or membrane desalination) steps.

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Rapid growth of hydraulic fracturing for shale gas within the USA and the possibility of shale developments within Europe has created public concern about the risks of spills and leaks associated with the industry. Reports from the Texas Railroad Commission (1999 to 2015) and the Colorado Oil and Gas Commission (2009 to 2015) were used to examine spill rates from oil and gas well pads. Pollution incident records for England and road transport incident data for the UK were examined as an analogue for potential offsite spills associated with transport for a developing shale industry. The Texas and Colorado spill data shows that the spill rate on the well pads has increased over the recorded time period. The most common spill cause was equipment failure. Within Colorado 33% of the spills recorded were found during well pad remediation and random site inspections. Based on data from the Texas Railroad Commission, a UK shale industry developing well pads with 10 lateral wells would likely experience a spill for every 16 well pads developed. The same well pad development scenario is estimated to require at least 2856 tanker movements over two years per well pad. Considering this tanker movement estimate with incident and spill frequency data from UK milk tankers, a UK shale industry would likely experience an incident on the road for every 12 well pads developed and a road spill for every 19 well pads developed. Consequently, should a UK shale industry be developed it is important that appropriate mitigation strategies are in place to minimise the risk of spills associated with well pad activities and fluid transportation movements.

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This study investigates the flowback water impacts on the corrosion of mild steel pipelines used to transport the saline wastewater generated during fracturing of the Bakken shale. The uniform corrosion rates were high under acidic conditions compared to those under neutral and alkaline conditions. The pitting attack on the flowback water pipelines was 100-fold and 10-fold higher for acidic and alkaline conditions, respectively, than those for the neutral conditions. The corrosion deposits on the mild steel were characterized by a large specific surface area and high reactivity. These results suggest that the flowback water pipelines become a potential source of contaminants that threaten agricultural land and water resources.

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Water touches most segments of the petroleum industry and thus cost-effective water management is a key part of oil & gas industry operations. The water to be managed is either co-produced with the hydrocarbons, generated as a by-product from oil/gas processing, and/or utilized to support production operations. While a majority of the water usually receives basic treatment, there are multiple recent drivers for advanced treatment that should facilitate beneficial water reuse. Hence, a toolbox of advanced technologies needs to be considered to ensure that fit for purpose treatment is deployed. Membrane processes are key components of the technology toolbox since they include some of the best available technologies. This paper provides an overview of the various case studies from ConocoPhillips global projects portfolio, which covered various operations such as gas fields, oil fields, oil sands & shale plays. In these case studies, a wide spectrum of membrane processes, including membrane bioreactors, reverse osmosis, microfiltration, ultrafiltration, nanofiltration, ceramic membranes, forward osmosis, membrane distillation, pressure retarded osmosis, membrane contactors, and/or new innovative membrane materials were either installed at full scale capacity, evaluated via field/lab testing, or investigated through desktop studies. The information presented demonstrates that reverse osmosis and nanofiltration are widely utilized by the industry for water desalination and desulfating, respectively. In addition, membrane filtration and bioreactors are frequently applied as standalone treatments for inorganics and organics removal, respectively; or as pretreatment to desalination membranes. Novel membrane technologies and materials are also being developed by the industry for niche applications.

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Hydraulic fracturing is the prevailing method for enhancing recovery of hydrocarbon resources from unconventional shale formations, yet little is understood regarding the microbial impact on biogeochemical cycling in natural-gas wells. Although the metabolisms of certain fermentative bacteria and methanogenic archaea that dominate in later produced fluids have been well studied, few details have been reported on microorganisms prevelant during the early flowback period, when oxygen and other surface-derived oxyanions and nutrients become depleted. Here, we report the isolation, genomic and phenotypic characterization of Marinobacter and Arcobacter bacterial species from natural-gas wells in the Utica-Point Pleasant and Marcellus Formations coupled to supporting geochemical and metagenomic analyses of produced fluid samples. These unconventional hydrocarbon system-derived Marinobacter sp. are capable of utilizing a diversity of organic carbon sources including aliphatic and aromatic hydrocarbons, amino acids, and carboxylic acids. Marinobacter and Arcobacter can metabolize organic nitrogen sources and have the capacity for denitrification and dissimilatory nitrate reduction to ammonia (DNRA) respectively; with DNRA and ammonification processes partially explaining high concentrations of ammonia measured in produced fluids. Arcobacter is capable of chemosynthetic sulfur oxidation, which could fuel metabolic processes for other heterotrophic, fermentative, or sulfate-reducing community members. Our analysis revealed mechanisms for growth of these taxa across a broad range of salinities (up to 15% salt), which explains their enrichment during early natural-gas production. These results demonstrate the prevalence of Marinobacter and Arcobacter during a key maturation phase of hydraulically fractured natural-gas wells, and highlight the significant role these genera play in biogeochemical cycling for this economically important energy system.

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Unconventional oil and natural gas (UOG) operations have contributed to a surge in domestic oil and natural gas production in the United States, combining horizontal drilling with hydraulic fracturing to unlock previously inaccessible fossil fuel deposits. >1000 organic chemicals are used in the production process, and wastewater is produced following injection and for the life of the producing well. This wastewater is typically disposed of via injecting into disposal wells for long-term storage, treatment and discharge from wastewater treatment plants, and/or storage in open evaporation pits; however, wastewater spill rates are reported at 2–20% of active well sites across regions, increasing concerns about the environmental impacts of these wastewaters. This study assessed adipogenic activity (both triglyceride accumulation and pre-adipocyte proliferation) for a mixture of 23 commonly used UOG chemicals and a small subset of UOG wastewater-impacted surface water extracts from Colorado and West Virginia, using 3T3-L1 cells and a peroxisome proliferator activated receptor gamma (PPARγ) reporter assay. We report potent and efficacious adipogenic activity induced by both a laboratory-created UOG chemical mixture and UOG-impacted water samples at concentrations below environmental levels. We further report activation of PPARγ at similar concentrations for some samples, suggesting a causative molecular pathway for the observed effects, but not for other adipogenic samples, implicating PPARγ-dependent and independent effects from UOG associated chemicals. Taken together, these results suggest that UOG wastewater has the potential to impact metabolic health at environmentally relevant concentrations.

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Produced water originated from oil and gas production wells was treated by a pilot-scale system including pre-treatment (chemical precipitation), pre-filtration, and post-filtration units. Pre-filtration unit consisted of sand filter, granulated activated carbon (GAC) filter, and ultrafiltration (UF) membrane. Post-filtration unit included reverse osmosis (RO) membrane unit. In this study, two different RO membranes including sea water (SW) and brackish water (BW) membranes were comparatively evaluated in terms of treatment and filtration performance. Besides, a cost analysis was conducted for a real scale RO membrane unit by using the data obtained from the pilot plant study. Average fluxes of 12.7 and 9.4 L/m2 h were obtained by SW and BW membrane units, respectively. Higher COD and conductivity removal efficiencies were obtained by SW membrane in comparison to BW membrane. Total cost of 0.88 €/m3 was estimated for a RO plant treating produced water with a flowrate capacity of 300 m3/d.

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As high-volume hydraulic fracturing (HF) has grown substantially in the United States over the past decade, so has the volume of produced water (PW), i.e., briny water brought to the surface as a byproduct of oil and gas production. According to a recent study (Groundwater Protection Council, 2015), more than 21 billion barrels of PW were generated in 2012. In addition to being high in TDS, PW may contain hydrocarbons, PAH, alkylphenols, naturally occurring radioactive material (NORM), metals, and other organic and inorganic substances. PW from hydraulically fractured wells includes flowback water, i.e., injection fluids containing chemicals and additives used in the fracturing process such as friction reducers, scale inhibitors, and biocides – many of which are known to cause serious health effects. It is hence important to gain a better understanding of the chemical composition of PW and how it is managed. This case study of PW from hydraulically fractured wells in California provides a first aggregate chemical analysis since data collection began in accordance with California's 2013 oil and gas well stimulation law (SB4, Pavley). The results of analyzing one-time wastewater analyses of 630 wells hydraulically stimulated between April 1, 2014 and June 30, 2015 show that 95% of wells contained measurable and in some cases elevated concentrations of BTEX and PAH compounds. PW from nearly 500 wells contained lead, uranium, and/or other metals. The majority of hazardous chemicals known to be used in HF operations, including formaldehyde and acetone, are not reported in the published reports. The prevalent methods for dealing with PW in California – underground injection and open evaporation ponds – are inadequate for this waste stream due to risks from induced seismicity, well integrity failure, well upsets, accidents and spills. Beneficial reuse of PW, such as for crop irrigation, is as of yet insufficiently safety tested for consumers and agricultural workers as well as plant health. Technological advances in onsite direct PW reuse and recycling look promising but need to control energy requirements, productivity and costs. The case study concludes that (i) reporting of PW chemical composition should be expanded in frequency and cover a wider range of chemicals used in hydraulic fracturing fluids, and (ii) PW management practices should be oriented towards safer and more sustainable options such as reuse and recycling, but with adequate controls in place to ensure their safety and reliability.

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Hydraulic fracturing in shale gas formations involves the injection of large volumes of aqueous fluid deep underground. Only a small proportion of the injected water volume is typically recovered, raising concerns that the remaining water may migrate upward and potentially contaminate groundwater aquifers. We implement a numerical model of two-phase water and gas flow in a shale gas formation to test the hypothesis that the remaining water is imbibed into the shale rock by capillary forces and retained there indefinitely. The model includes the essential physics of the system and uses the simplest justifiable geometrical structure. We apply the model to simulate wells from a specific well pad in the :Horn River Basin, British Columbia, where there is sufficient available data to build and test the model. Our simulations match the water and gas production data from the wells remarkably closely and Show that all the injected water can be accounted for within the shale system, with most imbibed into the shale rock matrix and retained there for the long term.

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Hydraulic fracturing fluids are injected into shales" to extend fracture networks that enhance oil and natural gas production from unconventional reservoirs. Here we evaluated the biodegradability of three widely used nonionic polyglycol ether surfactants (alkyl ethoxylates (AEOs), nonylphenol ethoxylates (NPEOs), and polypropylene glycols (PPGs)) that function as weatherizers, emulsifiers, wetting agents, and corrosion inhibitors in injected fluids. Under anaerobic conditions, we observed complete removal of AEOs and NPEOs from solution within 3 weeks regardless of whether surfactants were part of a chemical mixture or amended as individual additives. Microbial enzymatic chain shortening was responsible for a shift in ethoxymer molecular weight distributions and the accumulation of the metabolite acetate. PPGs bioattenuated the slowest, producing sizable concentrations of acetone, an isomer of propionaldehyde. Surfactant chain shortening was coupled to an increased abundance of the diol dehydratase gene cluster (pduCDE) in Firmicutes metagenomes predicted from :the 16S rRNA gene. The pduCDE enzymes are responsible for cleaving ethoxylate chain units into aldehydes before their fermentation into alcohols and carboxylic acids. These data provide new mechanistic insight into the environmental fate of hydraulic fracturing surfactants after accidental release through chain shortening and biotransformation, emphasizing the importance of compound structure disclosure for predicting biodegradation products.

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A thin-film composite, bicontinuous cubic lyotropic liquid crystal polymer (TFC Q(I)) membrane with uniformsize, ionic nanopores was studied for the treatment of hydraulic fracturing flowback water. The TFC QI membrane performance was compared to those of a commercial nanofiltration (NF) membrane (NF270) and a commercial reverse osmosis (RO) membrane (SW30HR) for the filtration of flowback water from the Denver-Julesburg Basin. The permeability, salt rejection, and organic solute rejection for each membrane was evaluated. The results illustrate that the TFC QI membrane maintained its performance to a similar degree as the commercial NF and RO membranes while demonstrating a unique selectivity not observed in the commercial membranes. Specifically, the TFC QI membrane rejected 75% of the salt while recovering 9.6% of the dissolved organic carbon (DOC) and 50% of the water. Of particular interest was the recovery of labile DOC, which was assessed through biodegradation experiments. Analysis following biodegradation of the TFC QI membrane permeate demonstrates the membrane's ability to recover labile DOC in a reduced-saline permeate. Improved recovery of labile DOC (increased to 22%) was demonstrated by reducing the pH of the flowback water. Therefore, the selectivity of the TFC QI membrane provides an opportunity to recover resources from hydraulic fracturing flowback.

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Shale gas development has been heralded as a game changer that has had, and will continue to have, repercussions for energy scenarios around the world, and natural gas has been hailed as the transition fuel to a low carbon future. Shale gas production—made feasible and economical by advances in hydraulic fracturing—offers a solution in the face of increased demand, instability in key producing regions, and societal aversion to the risks of nuclear energy. This “golden future,” however, has come into conflict with increasing concerns over water. This paper examines policy and regulatory frameworks around hydraulic fracturing in Texas and Spain in order to consider the trade-offs—particularly at the expense of water security—that may occur as decision-makers pursue improvements in energy security. We compare regulatory, institutional, and cultural contexts in order to understand and evaluate the robustness of these frameworks to prevent the reduction in water security as a consequence of the pursuit of energy security. Paucity of data is discussed. We also consider questions such as disclosure of information to the public about water use or the chemical composition of frac fluids and public opinion about hydraulic fracturing. Lessons are drawn that may assist policymakers who seek to guarantee water security while pursuing energy security.

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Hydraulic fracturing (HF) has allowed for the utilization of previously unattainable shale oil and gas (O&G) resources. After HF is complete, the waters used to increase the facies' permeability return uphole as wastewaters. When these waters return to the surface, they are characterized by complex organic and inorganic chemistry, and can pose a health risk if not handled correctly. Therefore, these waters must be treated or disposed of properly. However, the variability of these waters' chemical composition over time is poorly understood and likely limits the applicability of their reuse. This study examines the water chemistry of a hydraulically fractured site in the Niobrara formation throughout the flowback period. Samples were collected every other day for the first 18days, then on a regular basis for three months. We identified HF fluid additives, including benzalkonium chlorides (BACs), alkyl ethoxylates (AEOs), and polyethylene glycols (PEGs), as well as geogenic components present in flowback and produced waters, their overall temporal pattern, and variables affecting the reuse of these waters. Observations indicate that alkalinity and iron may limit the reuse of these waters in HF, while chloride and alkalinity may limit the use of these waters for well-casing cement. The presence of numerous surfactant homologs, including biocides, was also observed, with the highest levels at the beginning of the flowback period. Principal component analysis identified three unique groupings in the chemical data that correspond to different stages in the flowback period: (1) the flowback stage (days 1-2); (2) the transition stage (days 6-21); and (3) the produced water stage (days 21-87). Results from this study will be important when designing decision frameworks for assessing water treatment options, particularly if onsite treatment is attempted. Successful reclamation of these waters may alleviate stress on water resources that continues to negatively impact the U. S.

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A long-term field study (405 days) of a hydraulically fractured well from the Niobrara Formation in the Denver-Julesburg Basin was completed. Characterization of organic chemicals used in hydraulic fracturing and their changes through time, from the preinjected fracturing fluid to the produced water, was conducted. The characterization consisted of a mass balance by dissolved organic carbon (DOC), volatile organic analysis by gas chromatography/mass spectrometry, and nonvolatile organic analysis by liquid chromatography/mass spectrometry. DOC decreased from 1500 mg/L in initial flowback to 200 mg/L in the final produced water. Only ∼11% of the injected DOC returned by the end of the study, with this 11% representing a maximum fraction returned since the formation itself contributes DOC. Furthermore, the majority of returning DOC was of the hydrophilic fraction (60–85%). Volatile organic compound analysis revealed substantial concentrations of individual BTEX compounds (0.1–11 mg/L) over the 405-day study. Nonvolatile organic compounds identified were polyethylene glycols (PEGs), polypropylene glycols (PPG), linear alkyl-ethoxylates, and triisopropanolamine (TIPA). The distribution of PEGs, PPGs, and TIPA and their ubiquitous presence in our samples and the literature illustrate their potential as organic tracers for treatment operations or in the event of an environmental spill.

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The rapid expansion of unconventional natural gas production has triggered considerable public concerns, particularly regarding environmental and human health (EHH) risks posed by various chemical additives used in hydraulic fracturing (HF) operations. There is a need to assess the potential EHH hazards of additives used in real-world HF operations. In this study, HF additive and fracturing fluid data was acquired, and EHH hazards were assessed using an indexing approach. The indexing system analyzed chemical toxicological data of different ingredients contained within additives and produced an aggregated EHH safety index for each additive, along with an indicator describing the completeness of the chemical toxicological data. The results show that commonly used additives are generally associated with medium-level EHH hazards. In each additive category, ingredients of high EHH concern were identified, and the high hazard designation was primarily attributed to ingredients' high aquatic toxicity and carcinogenic effects. Among all assessed additive categories, iron control agents were identified as the greatest EHH hazards. Lack of information, such as undisclosed ingredients and chemical toxicological data gaps, has resulted in different levels of assessment uncertainties. In particular, friction reducers show the highest data incompleteness with regards to EHH hazards. This study reveals the potential EHH hazards associated with chemicals used in current HF field operations and can provide decision makers with valuable information to facilitate sustainable and responsible unconventional gas production.

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The widespread use of unconventional drilling involving hydraulic fracturing (“fracking”) has allowed for increased oil-and-gas extraction, produced water generation, and subsequent spills of produced water in Colorado and elsewhere. Produced water contains BTEX (benzene, toluene, ethylbenzene, xylene) and naphthalene, all of which are known to induce varying levels of toxicity upon exposure. When spilled, these contaminants can migrate through the soil and contaminant groundwater. This research modeled the solute transport of BTEX and naphthalene for a range of spill sizes on contrasting soils overlying groundwater at different depths. The results showed that benzene and toluene were expected to reach human health relevant concentration in groundwater because of their high concentrations in produced water, relatively low solid/liquid partition coefficient and low EPA drinking water limits for these contaminants. Peak groundwater concentrations were higher and were reached more rapidly in coarser textured soil. Risk categories of “low,” “medium,” and “high” were established by dividing the EPA drinking water limit for each contaminant into sequential thirds and modeled scenarios were classified into such categories. A quick reference guide was created that allows the user to input specific variables about an area of interest to evaluate that site’s risk of groundwater contamination in the event of a produced water spill. A large fraction of produced water spills occur at hydraulic-fracturing well pads; thus, the results of this research suggest that the surface area selected for a hydraulic-fracturing site should exclude or require extra precaution when considering areas with shallow aquifers and coarsely textured soils.

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Purpose of ReviewIn this study, we compile and curate data from 2012, 2013, and 2014 on flared gas and generated wastewater associated with hydraulic fracturing operations in seven major shale regions of the USA. In the process, we provide an historical perspective of the management practices of flared gas and wastewater prior to the decline in oil prices in 2015. An engineering assessment of the technical potential for repurposing the energy from flared gas for treating hydraulic fracturing wastewater is also considered.Recent FindingsThe seven shale regions were evaluated using mass balances and thermodynamic analysis of the wastewater and flared gas volumes using data compiled from state, federal, and private sources for each region. After curating the publicly available data, we determined that from 2012 through 2014, the Bakken, Marcellus, Utica, and Niobrara flared between 2 and 48 times the amount of natural gas needed to provide energy for treatment of the wastewater produced from the oil and gas industry. The Permian Basin, Eagle Ford, and Haynesville did not have sufficient flared gas to treat the wastewater produced in each respective region and thus would need other energy sources for water and wastewater treatment.SummaryThe findings indicate that novel approaches to managing existing resources and waste streams might have the potential to improve the environmental footprint and economic productivity of select oil and gas sites.

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Approximately 81% of the nation's energy demands are supported by hydrocarbons, largely in part to the relatively recent exploration of oil and gas from unconventional shale energy reserves. The extraction of shale energy requires technological ingenuity, such as hydraulic fracturing and horizontal drilling, and significant freshwater resources to successfully recover the previously sequestered hydrocarbons from low porosity formations. As unconventional oil and gas development continues to expand to meet the growing energy demands, it becomes increasingly more important to understand the potential environmental implications and to practice proper environmental stewardship. For example, concerns over water usage and the related consequences have dramatically increased due to the demand for water used in hydraulic fracturing, the increased volumes of wastewater being produced, and the need to dispose of or reuse the wastewater without compromising the surface and subsurface environments. As such, this chapter will cover the life cycle of water in oil and gas development (conventional and unconventional), including water use and waste production in the drilling, stimulation, and production phases; the current waste management strategies and challenges within the various treatment modalities; and the widespread implications of the varying forms of waste management.

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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.

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One promising water management strategy during hydraulic fracturing is treatment and reuse of flowback/produced water. In particular, the saline flowback water contains many of the chemicals employed for fracking, which need to be removed before possible reuse as “frac water.” This manuscript targets one of the additives; borate-based cross-linkers used to adjust the rheological characteristics of the frac-fluid and turbidity. Alum and ferric chloride were evaluated as coagulants for clarification and boron removal from saline flowback water obtained from a well in the Eagle Ford shale. Extremely high dosages (>9000 mg/L or 333 mM Al and 160 mM Fe) corresponding to Al/B and Fe/B mass ratios of ∼70 and molar ratios of ∼28 and 13 respectively were necessary to remove ∼80% boron. Hence, coagulation does not appear to be feasible for boron removal from high-strength waste streams. X-ray photoelectron spectroscopy revealed BO bonding on surfaces of freshly precipitated Al(OH)3(am) and Fe(OH)3(am) suggesting boron uptake was predominantly via ligand exchange. Attenuated total reflection-Fourier transform infrared spectroscopy provided direct evidence of inner-sphere boron complexation with surface hydroxyl groups on both amorphous aluminum and iron hydroxides. Only trigonal boron was detected on aluminum flocs since possible presence of tetrahedral boron was masked by severe AlO interferences. Both trigonal and tetrahedral conformation of boron complexes were identified on Fe(OH)3 surfaces.

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Hydraulic fracturing to extract oil and natural gas reserves is an increasing practice in many international energy sectors. Hydraulic fracturing flowback and produced water (FPW) is a hyper saline wastewater returned to the surface from a fractured well containing chemical species present in the initial fracturing fluid, geogenic contaminants, and potentially newly synthesized chemicals formed in the fracturing well environment. However, information on FPW toxicological mechanisms of action remain largely unknown. Both cardiotoxic and respirometric responses were explored in zebrafish (Danio rerio) embryos after either an acute sediment-free (FPW-SF) or raw/sediment containing (FPW-S) fraction exposure of 24 and 48 h at 2.5% and 5% dilutions. A 48 h exposure to either FPW fraction in 24–72 h post fertilization zebrafish embryos significantly increased occurrences of pericardial edema, yolk-sac edema, and tail/spine curvature. In contrast, larval heart rates significantly decreased after FPW fraction exposures. FPW-S, but not FPW-SF, at 2.5% doses significantly reduced embryonic respiration/metabolic rates (MO2), while for 5% FPW, both fractions reduced MO2. Expression of select cardiac genes were also significantly altered in each FPW exposure group, implicating a cardiovascular system compromise as the potential cause for reduced embryonic MO2. Collectively, these results support our hypothesis that organics are major contributors to cardiac and respiratory responses to FPW exposure in zebrafish embryos. Our study is the first to investigate cardiac and respiratory sub-lethal effects of FPW exposure, demonstrating that FPW effects extend beyond initial osmotic stressors and verifies the use of respirometry as a potential marker for FPW exposure.

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Rising global energy demands associated to unbalanced allocation of water resources highlight the importance of water management solutions for the gas industry. Advanced drilling, completion and stimulation techniques for gas extraction, allow more economical access to unconventional gas reserves. This stimulated a shale gas revolution, besides tight gas and coalbed methane, also causing escalating water handling challenges in order to avoid a major impact on the environment. Hydraulic fracturing allied to horizontal drilling is gaining higher relevance in the exploration of unconventional gas reserves, but a large amount of wastewater (known as “produced water”) is generated. Its variable chemical composition and flow rates, together with more severe regulations and public concern, have promoted the development of solutions for the treatment and reuse of such produced water. This work intends to provide an overview on the exploration and subsequent environmental implications of unconventional gas sources, as well as the technologies for treatment of produced water, describing the main results and drawbacks, together with some cost estimates. In particular, the growing volumes of produced water from shale gas plays are creating an interesting market opportunity for water technology and service providers. Membrane-based technologies (membrane distillation, forward osmosis, membrane bioreactors and pervaporation) and advanced oxidation processes (ozonation, Fenton, photocatalysis) are claimed to be adequate treatment solutions.

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Hydraulic fracturing, coupled with the advances in horizontal drilling, has been used for recovering oil and natural gas from shale formations and has aided in increasing the production of these energy resources. The large volumes of hydraulic fracturing fluids used in this technology contain chemical additives, which may be toxic organics or produce toxic degradation byproducts. This paper investigated the chemicals introduced into the hydraulic fracturing fluids for completed wells located in Pennsylvania and West Virginia from data provided by the well operators. The results showed a total of 5071 wells, with average water volumes of 5,383,743 ± 2,789,077 gal (mean ± standard deviation). A total of 517 chemicals was introduced into the formulated hydraulic fracturing fluids. Of the 517 chemicals listed by the operators, 96 were inorganic compounds, 358 chemicals were organic species, and the remaining 63 cannot be identified. Many toxic organics were used in the hydraulic fracturing fluids. Some of them are carcinogenic, including formaldehyde, naphthalene, and acrylamide. The degradation of alkylphenol ethoxylates would produce more toxic, persistent, and estrogenic intermediates. Acrylamide monomer as a primary degradation intermediate of polyacrylamides is carcinogenic. Most of the chemicals appearing in the hydraulic fracturing fluids can be removed when adopting the appropriate treatments.

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The extraction of unconventional hydrocarbons, particularly through hydraulic fracturing (‘fracking’), has generated both support and opposition in many countries around the globe. Along with arguments about economic benefits, decarbonisation, transition fuels and groundwater contamination, etc., the rapid expansion of this industry presents a pressing problem as regards the disposal of the resultant waste – including drilling and cutting material, oil and gas residues, various chemicals used in the process, salts and produced water. One putative solution – ‘landfarming’ – is a disposal process that involves spreading oil and gas waste on to land and mixing it with topsoil to allow bioremediation of the hydrocarbons. This paper examines the case of landfarming in New Zealand where the practice has proved controversial due to its association with fracking, fears about the contamination of agricultural land and potential danger to milk supplies. Drawing upon Gieryn’s notion of cultural cartography and boundary work as well as the literature on the politics of scale it analyses the struggles for epistemic authority regarding the safety of landfarming. The paper concludes that scalar practices were central to the production of knowledge (and ignorance) in these credibility struggles, and that the prevailing cultural cartography of knowledge remained the arbiter and basis for policy. The case has wider implications in terms of the management of waste from unconventional hydrocarbons as well as other environmental issues in which the politics of scale figure in contested knowledge claims.

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The Permian Basin is being transformed by the “shale revolution” from a major conventional play to the world’s largest unconventional play, but water management is critical in this semiarid region. Here we explore evolving issues associated with produced water (PW) management and hydraulic fracturing water demands based on detailed well-by-well analyses. Our results show that although conventional wells produce ∼13 times more water than oil (PW to oil ratio, PWOR = 13), this produced water has been mostly injected back into pressure-depleted oil-producing reservoirs for enhanced oil recovery. Unconventional horizontal wells use large volumes of water for hydraulic fracturing that increased by a factor of ∼10–16 per well and ∼7–10 if normalized by lateral well length (2008–2015). Although unconventional wells have a much lower PWOR of 3 versus 13 from conventional wells, this PW cannot be reinjected into the shale reservoirs but is disposed into nonproducing geologic intervals that could result in overpressuring and induced seismicity. The potential for PW reuse from unconventional wells is high because PW volumes can support hydraulic fracturing water demand based on 2014 data. Reuse of PW with minimal treatment (clean brine) can partially mitigate PW injection concerns while reducing water demand for hydraulic fracturing.

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The large volumes and unknown composition of flowback and produced waters cause public concerns about the environmental and social compatibility of hydraulic fracturing and the exploitation of unconventional gas. Flowback and produced waters contain not only residues of fracking additives but also chemical species that are dissolved from the shales. Interactions of different shales with an artificial fracturing fluid were studied in lab experiments under ambient and elevated temperature and pressure conditions. Fluid-rock interactions change the chemical composition of the fracturing fluid and this indicates that geochemistry of the fractured shale needs to be considered to understand flowback water composition.

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Each of the three earthquake sequences in Oklahoma in 2016—Fairview, Pawnee, and Cushing—appears to have been induced by high-volume wastewater disposal within 10 km. The Fairview M5.1 main shock was part of a 2 year sequence of more than 150 events of M3, or greater; the main shock accounted for about half of the total moment. The foreshocks and aftershocks of the M5.8 Pawnee earthquake were too small and too few to contribute significantly to the cumulative moment; instead, nearly all of the moment induced by wastewater injection was focused on the main shock. The M5.0 Cushing event is part of a sequence that includes 48 earthquakes of M3, or greater, that are mostly foreshocks. The cumulative moment for each of the three sequences during 2016, as well as that for the 2011 Prague, Oklahoma, and nine other sequences representing a broad range of injected volume, are all limited by the total volumes of wastewater injected locally.

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In the present study, the K-40, U-238, Ra-226, Pb-210, Ra-228 and Th-228 activity concentrations were measured in 64 samples of wastes generated from shale gas exploration in North-Eastern Poland. The measured samples consist of drill cuttings, solid phase of waste drilling muds, fracking fluids, return fracking fluids and waste proppants. The measured activity concentrations in solid samples vary in a wide range from 116 to around 1100 Bq/kg for K-40, from 14 to 393 Bq/kg for U-238, from 15 to 415 Bq/kg for Ra-226, from 12 to 391 Bq/kg for Pb-210, from a few Bq/kg to 516 Bq/kg for Ra-228 and from a few Bq/kg to 515 Bq/kg for Th-228. Excluding the waste proppants, the measured activity concentrations in solid samples oscillate around their worldwide average values in soil. In the case of the waste proppants, the activity concentrations of radionuclides from uranium and thorium decay series are significantly elevated and equal to several hundreds of Bq/kg but it is connected with the mineralogical composition of proppants. The significant enhancement of Ra-226 and Ra-228 activity concentrations after fracking process was observed in the case of return fracking fluids, but the radium isotopes content in these fluids is comparable with that in waste waters from copper and coal mines in Poland.

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With the economic establishment of the shale gas exploitation, horizontal drilling and hydraulic fracturing have become nowadays common procedures, but not without any controversy. In parallel, the emergent case of deep geothermal energy systems is claimed to not have much to do with the fracking process. Through an intensive review of the available literature and data, we aim to lift the veil on the differences and similarities between shale gas and deep geothermal energy regarding the chemical substances used during the stimulation phase, as far as possible. Such a comparison appears finally not so obvious. In a general way, the effective used quantity of each chemical should not be neglected, even if advertised as being an extremely small percentage of the total stimulation fluids composition. Although some of these substances are considered purely environment/human health friendly, the diversity of potential risks associated with the hazardous chemicals can lead to severe consequences. However, the multitude of possible pathways for these risks tends to show that the main hazards are not especially or exclusively linked to the fluids injection process itself.

Abstract:
Nano-Fe-Co/gamma-Al2O3 catalyst synthesized using the homogeneous precipitation method, and used for heterogeneous Fenton degradation of hydraulic fracturing wastewater in laboratory. The catalysts were characterized by SEM-EDS, XRD, XPS, XRF, BET and FT-IR. The results showed that FeOOH, and CoO are the main catalytically active component. The effects of different reaction parameters such as initial pH, H2O2 dosage and catalyst amount were assessed. Results indicated that maximum removal rate of COD 57.8% occurred at the H2O2 concentration and catalyst dosage were 40 mmolL(-1) 4 gL(-1) and 4 gL(-1), respectively in 90 min. The recycled catalyst was capable of repeating four cycle without a significant decrease in treatment efficiency, and this demonstrated the durability of catalyst. These results indicate the potential of the heterogeneous Fenton system in engineering applications for advanced treatment of fracturing wastewater.

Abstract:
Production of oil from shale and tight reservoirs accounted for almost 50% of 2016 total U.S. production and is projected to continue growing. The objective of our analysis was to quantify the water outlook for future shale oil development using the Eagle Ford Shale as a case study. We developed a water outlook model that projects water use for hydraulic fracturing (HF) and flowback and produced water (FP) volumes based on expected energy prices; historical oil, natural gas, and water-production decline data per well; projected well spacing; and well economics. The number of wells projected to be drilled in the Eagle Ford through 2045 is almost linearly related to oil price, ranging from 20,000 wells at $30/barrel (bbl) oil to 97,000 wells at $100/bbl oil. Projected FP water volumes range from 20% to 40% of HF across the play. Our base reference oil price of $50/bbl would result in 40,000 additional wells and related HF of 265×109 gal and FP of 85×109gal. The presented water outlooks for HF and FP water volumes can be used to assess future water sourcing and wastewater disposal or reuse, and to inform policy discussions.

Abstract:
The use of hydraulic fracturing for shale oil and gas development generates large quantities of flowback and produced (F/P) water as by-products. The current high treatment cost of F/P water inhibits development and profitability of shale oil and gas. The Integrated Precipitative Supercritical (IPSC) process, developed at Ohio University, could remediate F/P water produced from hydraulic fracturing with significantly lower costs than current practices. The objective of this paper is to present results of a techno-economic analysis of the IPSC process using Aspen (R) process software and Microsoft Excel. The Aspen (R) model was used to simulate the IPSC process with its output used as input for the cost analysis. Results indicated an average cost of $6.33 per barrel of F/P water treatment with a possible range from $2.93/bbl to $16.03/bbl determined through sensitivity analyses. The results further indicate that the IPSC process is economically competitive compared to existing practices. (C) 2017 Elsevier Ltd. All rights reserved.

Abstract:
Flowback and produced waters are extremely complex matrices composed of geogenic water and chemical additives. The geogenic fraction is highly saline, with large amounts of total dissolved solids and may contain various hydrocarbons, organic acids, alcohols, radionuclides, and metals. The additives may include surfactants, gels, scale inhibitors, biocides, and friction reducers. Recently, it has been suggested that these produced waters could potentially represent a new water source in areas of water scarcity. Before the use of these waters can be considered for applications outside the oil field, the chemical composition must be better characterized. However, due to the complex nature of these matrices, many methods originally designed for surface and groundwater matrices may not be suitable. In addition, many organic chemicals remain yet unidentified: targeted approaches for organic chemical analysis alone will be insufficient for complete organic chemical characterization. Current trends and emerging technologies in analytical chemistry were reviewed and their applicability to flowback and produced waters was assessed. In addition, we propose under-utilized used approaches that may serve as potential solutions to address the issues created by the complex matrices inherent to flowback and produced waters.

Abstract:
Combining horizontal drilling with high volume hydraulic fracturing has increased extraction of hydrocarbons from low-permeability oil and gas (O accompanied by increased wastewater production. Surface water discharges of O&G wastewater by centralized waste treatment (CWT) plants pose risks to aquatic and human health. We evaluated the impact of surface water disposal of O&G wastewater from CWT plants upstream of the Conemaugh River Lake (dam controlled reservoir) in western Pennsylvania. Regulatory compliance data were collected to calculate annual contaminant loads (Ba, Cl, total dissolved solids (TDS)) to document historical industrial activity. In this study, two CWT plants 10 and 19 km upstream of a reservoir left geochemical signatures in sediments and porewaters corresponding to peak industrial activity that occurred 5 to 10 years earlier. Sediment cores were sectioned for the collection of paired samples of sediment and porewater, and analyzed for analytes to identify unconventional O&G wastewater disposal. Sediment layers corresponding to the years of maximum O&G wastewater disposal contained higher concentrations of salts, alkaline earth metals, and organic chemicals. Isotopic ratios of 226Ra/228Ra and 87Sr/86Sr identified that peak concentrations of Ra and Sr were likely sourced from wastewaters that originated from the Marcellus Shale formation.

Abstract:
Unconventional oil and gas development using hydraulic fracturing has caused conflict and controversy across the globe including the U.S. where some States banned the practice. Nevertheless, North Dakota (ND) has supported the practice because the State perceives the risks to be acceptable and because it has brought growth and opportunities to small communities. However, social acceptance of new technology is based on a number of factors and not contingent on economic benefits. To date, no research has been conducted to understand public risk perception of hazards associated with produced water from hydraulic fracturing in ND. This study focuses on understanding the risk perception of select ND stakeholder groups regarding produced water management and naturally occurring radioactive material. The software Qualtrics was used to create an online survey, collect data, and perform statistical analysis. The most important variables that seem to influence risk perception are the images and thoughts associated with produced water, level of knowledge about produced water handling and content, and knowing how to proceed in case of a spill of produced water. Overall, social risk perception could be in alignment with actual technical risk if availability of objective information is improved.

Abstract:
Direct contact membrane distillation (DCMD) has immense potential in the desalination of highly saline waste-waters where reverse osmosis is not feasible. This study evaluated the potential of DCMD for treatment of produced water generated during extraction of natural gas from unconventional (shale) reservoirs. Exhaust stream from Natural Gas Compressor Station (NG CS), which has been identified as a potential waste heat source, can be used to operate DCMD thereby providing economically viable option to treat high salinity produced water. An ASPEN Plus simulation of DCMD for the desalination of produced/saline water was developed in this study and calibrated using laboratory-scale experiments. This model was used to optimize the design and operation of large scale systems and estimate energy requirements of the DCMD process. The concept of minimum temperature approach used in heat exchanger design was applied to determine the optimum membrane area for large scale DCMD plants. Energy analysis revealed that the waste heat available from NG CS is sufficient to concentrate all the produced water generated in Pennsylvania to 30 wt% regardless of its initial salinity. (C) 2017 Elsevier B.V. All rights reserved.

Abstract:
Most of the shale gas production in northwest China is from continental shale. Identifying hydrogeochemical and isotopic indicators of toxic hydraulic fracturing flowback fluids (HFFF) has great significance in assessing the safety of drinking water from shallow groundwater and stream water. Hydrogeochemical and isotopic data for HFFF from the Dameigou shale formations (Cl/Br ratio (1.81X10(-4)-6.52X10(-4)), Ba/Sr (>0.2), delta B-11 (-10-1) and epsilon(SW)(Sr) (56-65, where epsilon(SW)(Sr) is the deviation of the Sr-87/Sr-86 ratio from that of seawater in parts per 10(4))) were distinct from data for the background saline shallow groundwater and stream water before fracturing. Mixing models indicated that inorganic elemental signatures (Br/Cl, Ba/Sr) and isotopic fingerprints (delta B-11, epsilon(SW)(Sr)) can be used to distinguish between HFFF and conventional oil-field brine in shallow groundwater and stream water. These diagnostic indicators were applied to identify potential releases of HFFF into shallow groundwater and stream water prior to fracturing and flowback. The monitored time series data for shallow groundwater and stream water exhibit no clear trends along mixing curves towards the HFFF end member, indicating that there is no detectable release occurring at present.

Abstract:
Exploration and production of oil and gas (O&G) generates large volumes of wastewater. High salinity and the presence of both dissolved constituents and suspended solids require complex and expensive treatment of O&G produced waters for beneficial reuse (e.g., fracking, irrigation, surface water discharge). Nearly 90% of wastewater produced during the lifetime of O&G wells is currently disposed of due to the high cost of treatment; thus, simple and inexpensive treatment technologies and approaches must be developed to promote water reuse in the O&G industry. In this study we investigated the potential for publicly owned wastewater treatment plants to co-treat produced water and residential waste-water. The removal of organic compounds, nutrients, metals, trace organic compounds, and suspended solids from the combined stream was investigated using a pilot-scale hybrid sequencing batch reactor-membrane bioreactor system. Produced water was initially dosed at 6% by volume, and comparable removal of primary (i.e., chemical oxygen demand, ammonia) and secondary constituents (i.e., trace organic compounds, inorganic contaminants) to control conditions was achieved. When produced water was increased to 20% of the influent by volume, nitrification was lost; however, the dominant biological communities in the bioreactors remained stable, providing evidence of an adaptive system and reliance on non-dominant microorganisms to achieve optimal treatment.

Abstract:
Shale gas drilling flowback fluid (SGDF) generated during shale gas extraction is of great concern due to its high total dissolved solid, radioactive elements and organic matter. To remove the toxic and refractory pollutants in SGDF and improve its biodegradability, a microsacle Fe0/Persulfate/O3 process (mFe0/PS/O3) was developed to pretreat this wastewater obtained from a shale gas well in southwestern China. First, effects of mFe0 dosage, O3 flow rate, PS dosage, pH values on the treatment efficiency of mFe0/PS/O3 process were investigated through single-factor experiments. Afterward, the optimal conditions (i.e., pH = 6.7, mFe0 dosage = 6.74 g/L, PS = 16.89 mmol/L, O3 flow rate = 0.73 L/min) were obtained by using response surface methodology (RSM). Under the optimal conditions, high COD removal (75.3%) and BOD5/COD ratio (0.49) were obtained after 120 min treatment. Moreover, compared with control experiments (i.e., mFe0, O3, PS, mFe0/O3, mFe0/PS, O3/PS), mFe0/PS/O3 system exerted better performance for pollutants removal in SGDF due to strong synergistic effect between mFe0, PS and O3. In addition, the decomposition or transformation of the organic pollutants in SGDF was analyzed by using GC-MS. Finally, the reaction mechanism of the mFe0/PS/O3 process was proposed according to the analysis results of SEM-EDS and XRD. It can be concluded that high-efficient mFe0/PS/O3 process was mainly resulted from the combination effect of direct oxidation by ozone and persulfate, heterogeneous and homogeneous catalytic oxidation, Fenton-like reaction and adsorption. Therefore, mFe0/PS/O3 process was proven to be an effective method for pretreatment of SGDF prior to biological treatment.

Abstract:
High volumes of flowback and produced water are generated everyday as a byproduct of hydraulic fracturing operations and shale gas developments across the United States. Since most shale gas developments are located in semi-arid to arid U.S. regions close to agricultural production, there are many opportunities for reusing these waters as potential alternatives or supplements to fresh water resources for irrigation activities. However, the impacts of high salinity and total organic content of these types of water on crop physiological parameters and plant growth needs to be investigated to determine their utility and feasibility. The aim of the present study was to evaluate the response of switchgrass and rapeseed to treated produced water as an irrigation water source. In this greenhouse study, the influence of produced water at four total organic carbon (TOC) concentrations [1.22, 38.3, 232.2 and 1352.4 mg/l] and three total dissolved solids (TDS) levels [400,3,500, and 21,000 mg/l] on rapeseed (Brassica napus L.) and switchgrass (Panicum virgatum L.), two relatively salt-tolerant, non-food, biofuel crops, was studied. Seedling emergence, biomass yield, plant height, leaf electrolyte leakage, and plant uptake were evaluated. Irrigation water with the highest salinity and TOC concentration resulted in significantly lower growth health and physiological characteristics of both crop species. The organic content of the produced water had a negative impact on biomass yield and physiological parameters of both species. The results of this study could be valuable for regulators and stakeholders in development of treatment standards in which organic matter should be removed to less than 50 mg/l to keep leaf EL (cell damage) to less than 50% and a TOC concentration of less than 5 mg/l required to keep a sustainable biomass production rate.

Abstract:
This paper is the second in a two-part series that assesses and summarizes extant knowledge regarding hydraulic fracturing wastewater management using a comparative, multidisciplinary approach. This study compares the regulatory regimes related to wastewater handling (storage and transport), treatment and disposal practices as they apply to the hydraulic fracturing industry in four unconventional shale plays in North America: the Montney in British Columbia (BC), the Duvernay in Alberta (AB), the Marcellus in the northeastern United States (US) and the Barnett in Texas. In North America, handling, treatment and disposal practices in the regulation of oil and gas wastewater is complex and multifaceted due to shared jurisdiction over many aspects across provincial or state lines, and/or across provincial/state and federal levels. All jurisdictions considered in this assessment have highly specific regulations for many elements of wastewater handling, treatment and disposal. However, much of the guidance for these practices comes from other legislation that makes provisions for environmental or safety performance, or prohibitions against pollution. The research suggests that knowledge gaps exist in the areas of regulatory outcomes, and compliance and best management practices, particularly in how those factors enable and constrain environmentally sustainable practices. BC's area-based-management model and AB's play-based-regulation pilot project are examples of attempted cumulative effects assessment and management noticeably absent from the Marcellus or Barnett plays.

Abstract:
Hydraulic fracturing (HF) has emerged as a major method of unconventional oil and gas recovery. The toxicity of hydraulic fracturing flowback and produced water (HF-FPW) has not been previously reported and is complicated by the combined complexity of organic and inorganic constituents in HF fluids and deep formation water. In this study, we characterized the solids, salts, and organic signatures in an HF-FPW sample from the Duvernay Formation, Alberta, Canada. Untargeted HPLC-Orbitrap revealed numerous unknown dissolved polar organics. Among the most prominent peaks, a substituted tri-phenyl phosphate was identified which is likely an oxidation product of a common polymer antioxidant. Acute toxicity of zebrafish embryo was attributable to high salinity and organic contaminants in HF-FPW with LC50 values ranging from 0.6% to 3.9%, depending on the HF-FPW fractions and embryo developmental stages. Induction of ethoxyresorufin-O-deethylase (EROD) activity was detected, due in part to polycyclic aromatic hydrocarbons (PAHs), and suspended solids might have a synergistic effect on EROD induction. This study demonstrates that toxicological profiling of real HF-FPW sample presents great challenges for assessing the potential risks and impacts posed by HF-FPW spills.

Abstract:
This study examined water quality, naturally-occurring radioactive materials (NORM), major ions, trace metals, and well flow data for water used and produced from start-up to operation of an oil and gas producing hydraulically-fractured well (horizontal) in the Denver-Julesburg (DJ) Basin in northeastern Colorado. Analysis was conducted on the groundwater used to make the fracturing fluid, the fracturing fluid itself, and nine flowback/produced water samples over 220days of operation. The chemical oxygen demand of the wastewater produced during operation decreased from 8200 to 2500mg/L, while the total dissolved solids (TDS) increased in this same period from 14,200 to roughly 19,000mg/L. NORM, trace metals, and major ion levels were generally correlated with TDS, and were lower than other shale basins (e.g. Marcellus and Bakken). Although at lower levels, the salinity and its origin appear to be the result of a similar mechanism to that of other shale basins when comparing Cl/Br, Na/Br, and Mg/Br ratios. Volumes of returned wastewater were low, with only 3% of the volume injected (11millionliters) returning as flowback by day 15 and 30% returning by day 220. Low levels of TDS indicate a potentially treatment-amenable wastewater, but low volumes of flowback could limit onsite reuse in the DJ Basin. These results offer insight into the temporal water quality changes in the days and months following flowback, along with considerations and implications for water reuse in future hydraulic fracturing or for environmental discharge.

Abstract:
The potential hazards and risks associated with well-stimulation in unconventional oil and gas development (hydraulic fracturing, acid fracturing, and matrix acidizing) have been investigated and evaluated and federal and state regulations requiring chemical disclosure for well-stimulation have been implemented as part of an overall risk management strategy for unconventional oil and gas development. Similar evaluations for chemicals used in other routine oil and gas development activities, such as maintenance acidizing, gravel packing, and well drilling, have not been previously conducted, in part due to a lack of reliable information concerning on-field chemical-use. In this study, we compare chemical-use between routine activities and the more closely regulated well-stimulation activities using data collected by the South Coast Air Quality Monitoring District (SCAQMD), which mandates the reporting of both unconventional and routine on-field chemical-use for parts of Southern California. Analysis of this data shows that there is significant overlap in chemical-use between so-called unconventional activities and routine activities conducted for well maintenance, well-completion, or rework. A comparison within the SCAQMD shows a significant overlap between both types and amounts of chemicals used for well-stimulation treatments included under State mandatory-disclosure regulations and routine treatments that are not included under State regulations. A comparison between SCAQMD chemical-use for routine treatments and state-wide chemical-use for hydraulic fracturing also showed close similarity in chemical-use between activities covered under chemical disclosure requirements (e.g. hydraulic fracturing) and many other oil and gas field activities. The results of this study indicate regulations and risk assessments focused exclusively on chemicals used in well-stimulation activities may underestimate potential hazard or risk from overall oil field chemical-use.

Abstract:
Large volumes of water return to the surface following hydraulic fracturing of deep shale formations to retrieve oil and natural gas. Current understanding of the specific organic constituents in these hydraulic fracturing wastewaters is limited to hydrocarbons and a fraction of known chemical additives. In this study, we analyzed hydraulic fracturing wastewater samples using ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) as a non-targeted technique to assign unambiguous molecular formulas to singly charged molecular ions. Halogenated molecular formulas were identified and confirmed using isotopic simulation and MS-MS fragmentation spectra. The abundance of halogenated organic compounds in flowback fluids rather than older wastewaters suggested that the observed molecular ions might have been related to hydraulic fracturing additives and related subsurface reactions, such as through the reaction of shale-extracted chloride, bromide, and iodide with strong oxidant additives (e.g., hypochlorite, persulfate, hydrogen peroxide) and subsequently with diverse dissolved organic matter. Some molecular ions matched the exact masses of known disinfection by-products including diiodoacetic acid, dibromobenzoic acid, and diiodobenzoic acid. The identified halogenated organic compounds, particularly iodinated organic molecules, are absent from inland natural systems and these compounds could therefore play an important role as environmental tracers.

Abstract:
Organic contaminants in shale gas flowback and produced water (FPW) are traditionally expressed as total organic carbon (TOC) or chemical oxygen demand (COD), though these parameters do not provide information on the toxicity and environmental fate of individual components. This review addresses identification of individual organic contaminants in FPW, and stresses the gaps in the knowledge on FPW composition that exist so far. Furthermore, the risk quotient approach was applied to predict the toxicity of the quantified organic compounds for fresh water organisms in recipient surface waters. This resulted in an identification of a number of FPW related organic compounds that are potentially harmful namely those compounds originating from shale formations (e.g. polycyclic aromatic hydrocarbons, phthalates), fracturing fluids (e.g. quaternary ammonium biocides, 2-butoxyethanol) and downhole transformations of organic compounds (e.g. carbon disulphide, halogenated organic compounds). Removal of these compounds by FPW treatment processes is reviewed and potential and efficient abatement strategies are defined.

Abstract:
This paper is the first of a two-part series designed to assess and summarize extant knowledge regarding hydraulic fracturing water and wastewater management practices using a comparative, multidisciplinary approach. To provide context for both papers, the water and wastewater practices are summarized for the four focus plays: Montney, Duvernay, Barnett, and Marcellus. In Alberta and British Columbia, which host the less-studied Duvernay and Montney plays, play-scale unconventional water and wastewater data are extracted and combined from three databases: FracFocus.ca, geoSCOUT, and AccuMap. A reasonable picture of hydraulic fracturing water use and practices in western Canada emerges from the over 4,000 wells studied. From late 2011 to early 2014, the average number of fracturing stages reported increased from 7 to over 14, while reported cumulative water use approached approximately 15 million m3 in 2013, the first year for which full data in all three databases was available. The majority of wells consuming 10,000 to 50,000 m3 of water are slickwater type, located largely in the two target plays; however, several wells using >50,000 m3 of water appear in the Horn River Formation in BC. While it is possible to identify in the databases wastewater treatment facilities and deep wastewater injection wells, it is at present difficult to constrain wastewater disposal practices and chemistry in Alberta and British Columbia. The analysis points to the need for further coordination between academics, industry, and governmental agencies to develop publicly available, searchable databases that carefully document water sourcing, wastewater recycling/reuse/disposal, and chemistry, in order to properly form hydraulic fracturing water management strategies.