Repository for Oil and Gas Energy Research (ROGER)

Abstract:
The return water from hydraulic fracturing operations is characterised by high concentrations of salts and toxic organic compounds. This water is stored on the surface in storage tanks and/or ponds. Wastewater spills caused by inappropriate storage can lead to the contamination of various environmental compartments, thus posing a risk to human health. Such risk can be determined by estimating the concentrations of the substances in the storage system and the behaviour of the same in function of the characteristics of the environment in which they are released. To this end, here we addressed the evolution of the concentrations of pollutants in a tank used to store wastewater from hydraulic fracturing operations. To do this, we estimated both the volume of flowback and the concentrations of the pollutants found in these waters. We then examined the dynamic behaviour of spill-derived compounds in the various environmental compartments in function of the conditions of the medium (humid, semi-arid, and arid). This approach allowed us to rank the hazard posed by the chemical compounds in question, as well as to determine those parameters associated with both the compounds and external natural conditions that contribute to environmental risk. Our results shed greater light on the mechanism by which external environmental variables (especially recharge rate) influence the migration of organic compounds in the vadose zone, and contribute to the prediction of their concentrations. Also, by estimating the time that chemicals remain in contaminated areas, we identify the phases of contamination that pose the greatest risk to human health. In summary, the approach used herein allows the ranking of compounds on the basis of risk to human health and can thus facilitate the design of pollutant management strategies. Of note, our ranked list highlights the relevance of benzene.

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Abstract The seismicity rate in the Delaware Basin, located in western Texas and southeastern New Mexico, has increased by orders of magnitude within the past ~5 years. While no seismicity was reported in the southern Delaware Basin during 1980-2014, 37 earthquakes with M > 3 occurred in this area during 2015-2018. We generated an improved catalog of ~37,000 earthquakes in this region during 2009-2018 by applying multi-station template matching at both regional and local stations using all earthquakes in the ANSS and TexNet catalogs. We found that the vast majority of the seismicity is most likely associated with wastewater disposal, while at least ~5% of the seismicity was induced directly by hydraulic fracturing. We inferred far-field effects of wastewater disposal inducing earthquakes over distances >25 km. The spatial limits of seismicity correlate with geologic structures that include the Central Platform and Grisham Fault, suggesting hydrologic compartmentalization by low-permeability boundaries. Given that the seismicity rate increased throughout the duration of the study, if industry operations continue unaltered it is likely that both the seismicity rate and number of M > 3 earthquakes may continue to increase in the future.

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Assessing the sustainability of energy systems must include attention to the local social and environmental impacts of such energy production, though these do not always easily align with more regional and global concerns. Social science research demonstrates that public perceptions of the social and environmental risks associated with unconventional oil and gas development (glossed by critics as “fracking”) vary both at an individual and community level. This article provides a comparative analysis of three proposed factors that influence risk perceptions: trust in government institutions, socioeconomic profile, and historical experiences with industry. We compare two Colorado communities that each had established a participatory local governance framework to minimize negative environmental impacts from oil and gas developments, but that were characterized by distinct socioeconomic profiles and industrial histories. Our quantitative analysis of citizen comments during public hearings suggests two key findings that were not predicted by the existing literature: neither trust in local government nor historical ties to heavy industry were associated with diminished risk perceptions. These findings suggest new pathways for more constructive engagement among industry, state and local government, and citizens.

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The large increase in unconventional shale gas extraction has raised concerns about potential water contamination from leaks and spills. Shale gas produced water is challenging to detect in areas impacted by legacy contamination, particularly from conventional sources. Previous studies have proposed combinations of Br, SO4, Ba, Cl, and other more specialized stable isotope systems to delineate shale gas produced water from 1) non-impacted waters and 2) other sources of water contamination. In general, the efforts that rely on relatively simple chemistry do not allow differentiation between conventional and unconventional brine chemistry. We examined variations in Ca/Mg and Ca/Sr ratios that seem to arise from variation in temperature with depth, to differentiate among conventional brines, unconventional brines, and non-impacted waters. This approach was applied to four sedimentary basins in the USGS produced water database: Williston, Michigan, Appalachian, and the Green River basin. In addition, the utility of the system was demonstrated with field samples taken during periods of known unconventional brine releases to surface waters. The Ca/Mg and Ca/Sr ratios allow distinction among these three water types in all basins, suggesting a relatively simple and direct way to evaluate water chemistries in landscapes dominated by unconventional shale gas extraction.

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The land-use impacts of the rapid expansion of U.S. oil and gas infrastructure since the early 2000s are a focus of local, state, and federal policymakers. Agriculture is the dominant land use in many areas with active energy development. Prior studies find that energy development displaces agriculture and assume that this effect is both permanent and homogeneous. We take a novel approach, analyzing landowners' capacity to both anticipate displaced production prior to the drilling of oil and gas wells, and reclaim some land once wells are in production. Using North Dakota's Bakken Shale as a case study, we merge agricultural land-use data from 2006 to 2014 with locations and drilling dates of oil and gas wells. We then use panel fixed-effects models to estimate the spatially- and intertemporally-heterogeneous effects of additional wells on agricultural land. We find that drilling is associated with reduced surrounding crop cover and increased fallow acreage. Importantly, the duration of these effects differs across agricultural land covers, and effects are in some cases temporary. Our analysis suggests that overlooking dynamic land use impacts may overestimate the cumulative net impact of oil and gas development on agricultural land uses by up to a factor of two.

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Membrane-based processes are increasingly applied in shale gas flowback and produced water (SGFPW) reuse. However, severe membrane fouling remains a big challenge for maintaining long-term operation. The present paper investigates for the first time the performance of the integrated ozonation-ultrafiltration (UF)-reverse osmosis (RO) process to treat SGFPW for water reuse. Results showed that pre-ozonation could efficiently mitigate membrane fouling. The integrated process removed more than 98% of total dissolved solids (TDS), 96% of dissolved organic carbon (DOC), and 96% of all ionic constituents in SGFPW. Significantly, the effluent could meet the water quality standards of irrigation, livestock water, and surface discharge. Removal of targeted pollutants is negatively influenced by the high concentrations of chloride and bromide because of their high reactivity with ozone and hydroxyl radicals (HO·). Through pre-ozonation, the total fouling index and the hydraulically irreversible fouling index decreased by more than 85% and 47%, respectively. The variation of particle sizes in SGFPW by pre-ozonation manifested the mechanism of UF membrane fouling mitigation, i.e., the pre-ozonation decomposed macromolecular organics into low fractions. The optimal ozone flow rate is 0.4 L/min. Results demonstrated that a sustainable SGFPW reuse could be achieved by the current integrated process.

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Article: Modeling the impact of a potential shale gas industry in Germany and the United Kingdom on ozone with WRF-Chem

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The method of hydraulic fracturing used to exploit unconventional shale gas has raised public concerns over the volumes of freshwater that are extracted for injection operations as well as the volumes of wastewater generated as a by-product of gas production. Using data from the British Columbia Oil and Gas Commission, this paper examines the volumes of produced and injected water from hydraulically fractured gas wells in Northeastern British Columbia. The two major producing shale gas basins in the province are the Montney and the Horn River. In this study, these are divided into several sub-basins based on existing geological and reservoir engineering applications. For each sub-basin the average volumes of wastewater- and injected water per well are calculated and then normalized to cumulative gas production. Ratios of injected water: gas production and wastewater: gas production are then applied to estimated volumes of remaining gas reserves in each sub-basin in order to calculate a total water footprint of future exploitation. These extrapolated water footprints were further elaborated into three scenarios of wastewater recycling rates: 0, 40, and 100% re-use. This study also compares the quality and quantity of wastewater produced from hydraulically fractured wells to their conventional counterparts in the province. Based on these calculations, the total future freshwater withdrawal and wastewater production volumes for all basins range from 1.65 to 3 billion, and 0 to 1.35 billion cubic metres, respectively. Volumes of freshwater withdrawal are relatively modest compared to other industries when considering the size of Northeastern British Columbia and the time-scale of extraction. In general, hydraulically fractured wells in Northeastern British Columbia produce volumes of wastewater that are equal to or lower than those required for injection. Unconventional gas wells often produce far less wastewater than their conventional counterparts.

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Some states and localities restrict siting of new oil and gas (O&G) wells relative to public areas. Colorado includes a 500-foot exception zone for building units, but it is unclear if that sufficiently protects public health from air emissions from O&G operations. To support reviews of setback requirements, this research examines potential health risks from volatile organic compounds (VOCs) released during O&G operations.We used stochastic dispersion modeling with published emissions for 47 VOCs (collected on-site during tracer experiments) to estimate outdoor air concentrations within 2,000 feet of hypothetical individual O&G facilities in Colorado. We estimated distributions of incremental acute, subchronic, and chronic inhalation non-cancer hazard quotients (HQs) and hazard indices (HIs), and inhalation lifetime cancer risks for benzene, by coupling modeled concentrations with microenvironmental penetration factors, human-activity diaries, and health-criteria levels.Estimated exposures to most VOCs were below health criteria at 500–2,000 feet. HQs were < 1 for 43 VOCs at 500 feet from facilities, with lowest values for chronic exposures during O&G production. Hazard estimates were highest for acute exposures during O&G development, with maximum acute HQs and HIs > 1 at most distances from facilities, particularly for exposures to benzene, 2- and 3-ethyltoluene, and toluene, and for hematological, neurotoxicity, and respiratory effects. Maximum acute HQs and HIs were > 10 for highest-exposed individuals 500 feet from eight of nine modeled facilities during O&G development (and 2,000 feet from one facility during O&G flowback); hematologic toxicity associated with benzene exposure was the critical toxic effect. Estimated cancer risks from benzene exposure were < 1.0 × 10−5 at 500 feet and beyond.Implications: Our stochastic use of emissions data from O&G facilities, along with activity-pattern exposure modeling, provides new information on potential public-health impacts due to emissions from O&G operations. The results will help in evaluating the adequacy of O&G setback distances. For an assessment of human-health risks from exposures to air emissions near individual O&G sites, we have utilized a unique dataset of tracer-derived emissions of VOCs detected at such sites in two regions of intense oil-and-gas development in Colorado. We have coupled these emission stochastically with local meteorological data and population and time-activity data to estimate the potential for acute, subchronic, and chronic exposures above health-criteria levels due to air emissions near individual sites. These results, along with other pertinent health and exposure data, can be used to inform setback distances to protect public health.

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Unconventional natural gas (UNG) extraction activities have become important contributors to regional NOx emissions inventories. Currently, there is a knowledge gap in the amount of total N deposition surrounding well pads undergoing UNG extraction despite the fact that some areas with extensive natural gas extraction activity are already in exceedance of nitrogen critical loads. In this study, we measured the magnitude of total dry N deposition from NO2, HNO3, and NH3 attributable to the development of two UNG wells at a Marcellus Shale well pad study site. This study documents concentrations, deposition fluxes, and isotope values of NO2, HNO3, O3, and NH3 up- and down-wind along a 750-m well pad passive sampling transect across a 16-acre well pad containing two unconventional wells during all phases of development and extraction comprising fifteen distinct sampling periods. An access road transect was also utilized to explore reactive N dynamics in a near-road environment on the well pad where NO2 concentration and isotope dynamics were highly correlated with daily traffic count (r2 = 0.78–0.88, p < 0.01). An onsite chemiluminescent NO2 source apportionment model was compared against δ15N–NO2 and δ18O–NO2 source apportionment models (r2 = 0.57 and 0.82 respectively), demonstrating the possible utility of δ18O–NO2 as a source apportionment tool in near-source environments. In addition, the δ15N–NO2 source apportionment method compared well against a background-subtraction method (slope = 0.82, r2 = 0.88, p < 0.001) during non-wintertime conditions and was used to find N loadings directly attributable to well pad activities. In total, the total N deposition across the transect, attributable to well pad activities, utilizing industry's best management practices, ranged from 0.16 to 0.55 kg N ha−1 yr−1. This magnitude of well pad attributable N deposition is high enough to result in exceedances of nitrogen critical loads in areas with high well count densities and high baseline N deposition.

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Research demonstrates that opinions about global warming and induced seismicity, earthquakes caused by human activity, are influenced by political party affiliation and ideology more than by education. Republicans and conservatives typically express less concern about environmental issues. One mechanism for how these factors shape opinion is through elite cues, wherein the prominent cultural, economic, and political voices associated with the major U.S. political parties provide guideposts that laypeople may use to form their opinions, particularly for complex social issues. Using two waves (n = 2586 and n = 2581) from a statewide survey in Oklahoma (USA), we explore the effects of political party affiliation, ideology, and education on residents’ opinions about the causes of and risk associated with these phenomena using Ordinary Least Squares and binary logistic regression equations. We examine whether these factors have a larger impact on opinions about global warming or induced seismicity using seemingly unrelated regression for the OLS equations and seemingly unrelated estimation for the binary logistic equations. These methods allow a global warming model to be estimated simultaneously with an earthquake model using the same independent variables. Consistent with other research, we found strong evidence that Republicans and conservatives perceive less risk from global warming and earthquakes than Democrats and liberals. However, the moderating effect of education on these environmental beliefs was not significant. The effects of political party affiliation and ideology were stronger for the opinions about global warming, which we hypothesize may be explained by the concept of psychological distance. This is an area for further research.

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Potential environmental impacts on shallow groundwater from shale gas development facilitated by horizontal drilling and hydraulic fracturing is a widely debated “hot topic”. In terms of potential aqueous phase contamination (including flowback fluids and produced water), there is a large gap in knowledge of the indicators for routine monitoring and contamination tracing, which should be considered critical and should be prioritized for analysis. Since formation water from shale formations is the main source of flowback fluids and produced water, and there are significant differences in some specific inorganic geochemical and isotopic compositions between shallow groundwater and formation water, this study has provided a framework to determine sensitive monitoring and diagnostic indicators for tracing potential groundwater contamination from produced water using end-member analysis. The results from a case study of the Fuling Gasfield, Sichuan Basin, SW China as the first and largest commercial shale gas development site in China, shows that produced authentic formation water with similar Br/Cl and Na/Cl ratio with seawater and low δ2H and δ18O values compared to the evaporated seawater might originate from evaporated seawater modified by water-rock interactions and be mixed with fresh meteoric water. The inorganic geochemical and isotopic indicators, such as Ba, Li, Na, Cl, Br, 87Sr/86Sr (as εSrsw) and δ11B are sensitive to the detection of contamination of fresh shallow groundwater by produced formation water, even in very small fractions (0.05%). Meanwhile, we present a groundwater contamination case related to shale gas development in the Fuling Gasfield. The robust conservative geochemical (Cl and Br) and isotopic (δ11B and εSrsw) mass balances show that 0.2%–0.9% of formation water entered the shallow groundwater causing contamination. The case has also confirmed the effectiveness of those indicators. Findings from this study may help to improve groundwater monitoring and environmental regulations in countries with shale gas exploration and development.

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Elevated dissolved methane (CH4) concentrations in groundwater are an environmental concern associated with hydraulic fracturing for shale gas. Therefore, determining dissolved CH4 baselines is important for detecting and understanding any potential environmental impacts. Such baselines should change in time and space to reflect ongoing environmental change and should be able to predict the probability that a change in dissolved CH4 concentration has occurred. We considered four dissolved CH4 concentration datasets of English groundwater using a Bayesian approach: two national datasets and two local datasets from shale gas exploration sites. The most sensitive national dataset (the previously published British Geological Survey CH4 baseline) was used as a strong prior for a larger (2153 measurements compared to 439) but less sensitive (detection limit 1000 times higher) Environment Agency dataset. The use of the strong prior over a weak prior improved the precision of the Environment Agency dataset by 75%. The expected mean dissolved CH4 concentration in English groundwater based on the Bayesian approach is 0.24 mg/l, with a 95% credible interval of 0.11 to 0.45 mg/l, and a Weibull distribution of W(0.35±0.01, 0.34±0.16). This indicates the amount of CH4 degassing from English groundwater to the atmosphere equates to between 0.7 to 3.1 kt CH4/year, with an expected value of 1.65 kt CH4/year and a greenhouse gas warming potential of 40.3 kt CO2eq/year. The two local monitoring datasets from shale gas exploration sites, in combination with the national datasets, show that dissolved CH4 concentrations in English groundwater are generally low, but locations with concentrations greater than or equal to the widely used risk action level of 10.0 mg/l do exist. Statistical analyses of groundwater redox conditions at these locations suggest that it may be possible to identify other locations with dissolved CH4 concentrations ≥10.0 mg/l using redox parameters such as Fe concentration.

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Reusing produced water for hydraulic fracturing simultaneously satisfies challenges of fresh water sourcing and the installation/operation of an extensive disposal well infrastructure. Herein, we systematically and rigorously investigate produced water treatment for reuse during hydraulic fracturing. Highly saline and turbid produced water from the Permian Basin was treated by adding chlorine as an oxidant, FeCl3 as the primary coagulant, and an anionic polymer to induce high rate sedimentation to generate “clean brine” by removing suspended solids and iron over a range of environmentally relevant temperatures. Mobile phone video capture, optical microscopy, and digital image/video analysis were employed to characterize floc morphology and measure its size and settling velocity. Conformational changes of the polymeric coagulant between 4 and 44 °C were inferred from viscosity and dynamic light scattering measurements providing clues to its performance characteristics. Floc settling velocities measured over the entire range of polymer dosages and temperatures were empirically modelled incorporating their fractal nature, average size, and the viscosity of the produced water using only a single fitting parameter. Juxtaposing the anionic polymer with the hydrolyzing metal-ion coagulant effectively destabilized the suspension and caused floc growth through a combination of enmeshment, adsorption and charge neutralization and inter-particle bridging as evidenced by Fourier transform infrared spectroscopy and thermogravimetric analysis. Very high turbidity (≥98%) and total iron (≥97%) removals were accomplished even with very short flocculation and sedimentation times of only 6 min each suggesting the feasibility of this approach to reuse produced water for hydraulic fracturing.

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Regulatory monitoring of oil and gas development requires the accurate multi-elemental analysis of wellbore samples on a regular basis. In this study, an unconventional method, comparative neutron activation analysis (comparative NAA), was applied for the multi-elemental characterization of solid and liquid hydraulic fracturing samples at the ppm level. The obtained values from three wastewater samples were compared with the most probable values determined via an inter-laboratory study, which involved 15 different laboratories from the United States, Canada, and Germany. The comparison showed that 15 out of 19 comparative NAA trace element concentration values were considered acceptable, providing a new technique to determine elemental concentrations in high salinity hydraulic fracturing samples.

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Interest in both environmental impact and potential beneficial uses of produced water (PW) has increased with growth in unconventional oil and gas production, especially in semi-arid regions, e.g. the Permian Basin, the most productive tight-oil region in the USA. Characterization of PW compositional variability is needed to evaluate environmental impact, treatment, and reuse potential. Geochemical variability of PW from Guadalupian (Middle Permian) to Ordovician formations was statistically and geostatistically evaluated in the western half of the Permian Basin (Delaware Basin, Central Basin Platform, and Northwest Shelf) using the US Geological Survey’s Produced Waters Geochemical Database and the New Mexico Water and Infrastructure Data System. Mean total dissolved solids (TDS) of PW increased with depth in the Delaware Basin and Central Basin Platform to the Delaware and Wolfcamp formations (Guadalupian age). Mean TDS decreased with further increases in depth. In contrast, the mean salinity of PW was significantly higher within the shallow, younger formations (largest mean TDS in the Artesia Formation); TDS decreased with depth below Guadalupian age formations in the Northwest Shelf. Kriged contour maps of TDS and major ions illustrated spatial variability across the three geo-structural regions as a function of depth. The occurrence of meteoric waters in upper and deeper formations across the three regions was significant, and was attributed to Laramide Orogeny and Basin and Range extension uplifting and tilting effects and recent water flooding. These results quantify PW composition variability, and suggest that upon treatment, PW would support some uses such as onsite reuse and mining.

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Shale gas is one of the most promising unconventional hydrocarbon resources in the 21st century. In recent years, economically recoverable reserves have achieved explosive growth, and drilling techniques have made large breakthroughs. As a clean unconventional energy, shale gas is given substantial consideration by governments. However, the cleanliness of shale gas has been questioned for causing serious air pollution during production. To further measure the air pollution cost during the exploration and transportation of shale gas, this article establishes an economic measurement model of the air pollution cost from the three aspects of human health, social cost and ecological cost by reviewing the relevant literature in the United States and China. This study lays a foundation for further calculating the cost of air pollution around shale gas fields.

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During the 2004–16 shale-gas development in the Appalachian basin, United States, premature mortality from lower air quality and employment followed a boom-and-bust cycle, whereas climate impacts will persist for generations beyond the activity.

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Abstract Aims The anti-fracking movement in Bulgaria, 2011?2013, was a successful grassroots effort to influence national environmental policy. The study draws on social movements and community psychology scholarship to investigate the emergence, development, and implications of activist identities as an important force for the movement's success. Methods Within a qualitative design, data were collected from interviews with activists, observations of organizing events, movement documents, and media publications. Structured and open coding followed by qualitative analyses produced descriptions and explanations of the construction and use of identities in the movement. Results Four major identities emerged in social and discursive interactions among activists and between activists and contextual forces: Victims, Bulgarians, Nature-protectors, and Citizens. The four identities were used interchangeably and afforded differential empowerment and opportunities for participation in policy-making. Conclusion The emerging activist identities were processes and products of the complex relationships between agency and context. The study contributes in illuminating the links between policy context, empowerment, participation, and political action.

Abstract:
Membrane filtration is a technique that can be successfully applied to remove oil from stable oil-in-water emulsions. This is especially interesting for the re-use of produced water (PW), a water stream stemming from the petrochemical industry, which contains dispersed oil, surface-active components and often has a high ionic strength. Due to the complexity of this emulsion, membrane fouling by produced water is more severe and less understood than membrane fouling by more simple oil-in-water emulsions. In this work, we study the relation between surfactant type and the effect of the ionic strength on membrane filtration of an artificial produced water emulsion. As surfactants, we use anionic sodium dodecyl sulphate (SDS), cationic hexadecyltrimethylammonium bromide (CTAB), nonionic Triton TMX-100 (TX) and zwitterionic N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (DDAPS), at various ionic strengths (1, 10, 100 mM NaCl). Filtration experiments on a regenerated cellulose ultrafiltration (UF) membrane showed a pronounced effect of the ionic strength for the charged surfactants SDS and CTAB, although the nature of the effect was quite different. For anionic SDS, an increasing ionic strength leads to less droplet-droplet repulsion, allowing a denser cake layer to form, resulting in a much more pronounced flux decline. CTAB, on the other hand leads to a lower interfacial tension than observed for SDS, and thus more deformable oil droplets. At high ionic strength, increased surfactant adsorption leads to such a low oil-water surface tension that the oil droplets can permeate through the much smaller membrane pores. For the nonionic surfactant TX, no clear effect of the ionic strength was observed, but the flux decline is very high compared to the other surfactants. For the zwitterionic surfactant DDAPS, the flux decline was found to be very low and even decreased with increasing ionic strength, suggesting that membrane fouling decreases with increasing ionic strength. Especially promising is that at lower surfactant concentration (0.1 CMC) and high ionic strength no flux decline was observed, while a high oil retention (85%) was obtained. From our results, it becomes clear that the type of the surfactant used is crucial for a successful application of membrane filtration for PW treatment, especially at high ionic strengths. In addition, they point out that the application of zwitterionic surfactants can be highly beneficial for PW treatment with membranes.

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Flux estimates of volatile organic compounds (VOCs) from oil and gas (O&G) production facilities are fundamental in understanding hazardous air pollutant concentrations and ozone formation. Previous off-site emission estimates derive fluxes by ratioing VOCs measured in canisters to methane fluxes measured in the field. This study uses the Environmental Protection Agency's Other Test Method 33A (OTM 33A) and a fast-response proton transfer reaction mass spectrometer to make direct measurements of VOC emissions from O&G facilities in the Upper Green River Basin, Wyoming. We report the first off-site direct flux estimates of benzene, toluene, ethylbenzene and xylenes from upstream O&G production facilities and find that these estimates can vary significantly from flux estimates derived using both the canister ratio technique and from the emission inventory. The 32 OTM 33A flux estimates had arithmetic mean (and 95% CI) as follows: benzene 17.83 (0.22, 98.05) g/h, toluene 34.43 (1.01, 126.76) g/h, C8 aromatics 37.38 (1.06, 225.34) g/h, and methane 2.3 (1.7, 3.1) kg h-1. 20% of facilities measured account for ~67% of total BTEX emissions. While this heavy tail is less dramatic than previous observations of methane in other basins, it is more prominent than predicted by the emission inventory.

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The Barnett Shale play in North Texas is one of the largest active onshore shale gas regions in the United States. Over the past two decades, unconventional energy production from shale gas in North Texas has grown rapidly. The energy production peaked in 2012 and has declined since. The city of Denton is located at the edge of the Barnett Shale play and is within the Dallas-Fort Worth metropolitan area. In this paper, we describe a long-term trend study of 84 total non-methane organic carbon (TNMOC) species measured at the Denton Airport South monitoring station, an exurban site. The annual mean TNMOC concentrations measured during 2000–2017 increased by +8.03 ± 12.92 ppb-C/year (+12.75%/year). The year-to-year increase in the mean TNMOC concentrations mirrored the energy production volume changes from natural gas wells and liquid condensate facilities within 2-km from the ambient air quality monitoring station. Concentrations of alkanes increased significantly, especially the natural gas species of ethane, propane, n-butane, and isobutane. The annual variations in the ethane concentrations were similar to changes observed in the natural gas and liquid condensate production from nearby wells. High levels of ethane, a dominant natural gas species, were originating from regions with a higher density of gas wells within close proximity of the monitoring site. In contrast, the concentrations of alkene and aromatic species have declined during the study period as a result of decreases from traditional urban emission sources. However, the trend in benzene, a carcinogenic aromatic species found in vehicular and natural gas emissions, and xylene concentrations were similar to the n-alkane trend, suggesting the influence of energy production activities on key ambient aromatic compounds.

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Significantly reducing consumers' electric bills and producing more jobs in USA, the remarkable growth of unconventional oil and gas (UOG) especially shale gas production in the last decade has made an impressive accomplishment. However, threatening the environment caused by UOG spills, UOG has caused enormous concerns about public health risks, there is minimized research examining the UOG spills’ causal mechanism and its spatial and temporal characteristics, which could play pivotal roles in risk control and environmental protection. Using two states Colorado (CO) and New Mexico (NM) in the USA with detailed UOG spill observations from 2005 to 2014, this study designs multi-categorical statistical tests and models to examine the factors that characterize UOG spills including spilled volume, life-year, cause, pathway, and spilled material. The ANOVA of spilled volumes across life-years has a p values 0.517, and hence the differences in spilled volumes among life-years are not significant in both CO or NM, but spilled materials are significantly between life-year 0 and other life-years with a p-value 0.0001. Based on a series of Poisson regression models for the association between pathway and spilled material and the conditional association given causal mechanism, the Chi-squared tests have p-values less than 0.00001, which shows both joint dependence and conditional dependence of pathway and spilled materials by controlling causal factors are significant in both CO and NM. Furthermore, spatiotemporal hot and cold spots of UOG spills are significant in CO, but they are not significant at p-value 0.01 in NM. This study is the first time to analyze and model the multivariate factors of UOG spills, which provides the first-hand insight to the characteristics of spills and to the monitoring and mitigation of potential risks in the lifetime of UOG operations.

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Hydraulic fracturing has transformed how unconventional natural gas and oil resources are extracted across the globe, with much disagreement over its potential environmental impacts, as well as the likelihood of those impacts. Using in-depth interviews, this study examines the views of two stakeholder groups, academic scientists and local governmental representatives, who have been involved in the debate over hydraulic fracturing in Texas’s Dallas-Fort Worth region, fracking’s modern-day birthplace. I explore how individuals within these two groups discuss uncertainty, and how they think their uncertainty framing impacts the public’s perceptions of them. In addition, this study adds to previous research on how expert groups frame uncertainty by integrating Wynne’s (1992) expanded typology of uncertainty, which includes the concepts of risk, uncertainty, ignorance, and indeterminacy.

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Abstract In recent years, numerous small earthquakes have occurred near the town of Pecos in West Texas; however, when this activity began and whether it was caused by increased petroleum industry activity has been uncertain because prior to 2017 there were few permanent seismograph stations in the region. We identify and locate earthquakes using data recorded since 2000 at TXAR, a sensitive 10-station seismic array situated about 240 km south of Pecos. We thus show that in 2007 one earthquake occurred near Pecos, in 2009 several more occurred, and subsequently activity has increased considerably, with more than 2000 events identified in 2017. A time-of-day and year-by-year analysis identifies geographic areas in West Texas where events are likely to be natural earthquakes and quarry blasts. However, for the Pecos events, annual seismicity rates increase along with annual volumes of petroleum production and fluid waste disposal, suggesting a causal link. Analysis of seismograms collected by the EarthScope Transportable Array indicates the 2009 earthquakes had focal depths of 4.0-5.2 km below sea level, within or just below strata where petroleum is produced and/or wastewater is injected. The largest earthquake to date had magnitude ML3.7, but the recent high activity rates suggest that greater magnitudes may be possible. For the years 2000-2017, we provide a catalog of 10,753 epicenters of seismic events recorded at TXAR.

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Baseline mobile surveys of methane sources using vehicle-mounted instruments have been performed in the Fylde and Ryedale regions of Northern England over the 2016-19 period around proposed unconventional (shale) gas extraction sites. The aim was to identify and characterise methane sources ahead of hydraulically fractured shale gas extraction in the area around drilling sites. This allows a potential additional source of emissions to atmosphere to be readily distinguished from adjacent sources, should gas production take place. The surveys have used ethane:methane (C2:C1) ratios to separate combustion, thermogenic gas and biogenic sources. Sample collection of source plumes followed by high precision δ13C analysis of methane, to separate and isotopically characterise sources, adds additional biogenic source distinction between active and closed landfills, and ruminant eructations from manure. The surveys show that both drill sites and adjacent fixed monitoring sites have cow barns and gas network pipeline leaks as sources of methane within a 1 km range. These two sources are readily separated by isotopes (δ13C of -67 to -58 ‰ for barns, compared to -43 to -39 ‰ for gas leaks), and ethane:methane ratios (<0.001 for barns, compared to >0.05 for gas leaks). Under a well-mixed daytime atmospheric boundary layer these sources are generally detectable as above baseline elevations up to 100 m downwind for gas leaks and up to 500 m downwind for populated cow barns. It is considered that careful analysis of these proxies for unconventional production gas, if and when available, will allow any fugitive emissions from operations to be distinguished from surrounding sources.

Abstract:
Baseline mobile surveys of methane sources using vehicle-mounted instruments have been performed in the Fylde and Ryedale regions of Northern England over the 2016-19 period around proposed unconventional (shale) gas extraction sites. The aim was to identify and characterise methane sources ahead of hydraulically fractured shale gas extraction in the area around drilling sites. This allows a potential additional source of emissions to atmosphere to be readily distinguished from adjacent sources, should gas production take place. The surveys have used ethane:methane (C2:C1) ratios to separate combustion, thermogenic gas and biogenic sources. Sample collection of source plumes followed by high precision δ13C analysis of methane, to separate and isotopically characterise sources, adds additional biogenic source distinction between active and closed landfills, and ruminant eructations from manure. The surveys show that both drill sites and adjacent fixed monitoring sites have cow barns and gas network pipeline leaks as sources of methane within a 1 km range. These two sources are readily separated by isotopes (δ13C of -67 to -58 ‰ for barns, compared to -43 to -39 ‰ for gas leaks), and ethane:methane ratios (<0.001 for barns, compared to >0.05 for gas leaks). Under a well-mixed daytime atmospheric boundary layer these sources are generally detectable as above baseline elevations up to 100 m downwind for gas leaks and up to 500 m downwind for populated cow barns. It is considered that careful analysis of these proxies for unconventional production gas, if and when available, will allow any fugitive emissions from operations to be distinguished from surrounding sources.

Abstract:
Unlike conventional resources, unconventional gas (such as shale gas) is trapped in low permeability rock, from which it does not flow naturally. Hence, its extraction is costly and requires sophisticated technologies. Building on my ethnographic work in north-west England and south-east Poland, I explore people’s engagements with shale gas materialities to show how the category of an ‘unconventional resource’ – framed by geological and engineering sciences – has more than merely technological implications. Instead, shale gas produces new sociotechnical relations by trying to remove itself from social entanglements. These attempts fail to contain the unruly forces of the subsurface and local impacts, bringing the alienating dynamics of resource-making into sharp relief. The irregularities of materials and infrastructural limits, integral to the socially dis-embedded ‘unconventionality’ of the developments, inadvertently turn shale gas projects into a site of the political.

Abstract:
Limited understanding of wastewater streams produced from shale oil and gas wells impedes best practices of wastewater treatment and reuse. This study provides a comprehensive and comparative analysis of flowback and produced water from three major and newly developed shale plays (the Bakken shale, North Dakota; the Barnett shale, Texas; and the Denver-Julesburg (DJ) basin, Colorado) in central and western United States. Geochemical features that included more than 10 water quality parameters, dissolved organic matter, as well as microbial community structures were characterized and compared. Results showed that wastewater from Bakken and Barnett shales has extremely high salinity (∼295 g/L total dissolved solids (TDS)) and low organic concentration (80–252 mg/L dissolved organic carbon (DOC)). In contrast, DJ basin showed an opposite trend with low TDS (∼30 g/L) and high organic content (644 mg/L DOC). Excitation-emission matrix (EEM) fluorescence spectra demonstrated that more humic acid and fluvic acid-like organics with higher aromaticity existed in Bakken wastewater than that in Barnett and DJ basin. Microbial communities of Bakken samples were dominated by Fe (III)-reducing bacteria Geobacter, lactic acid bacteria Lactococcus and Enterococcus, and Bradyrhizobium, while DJ basin water showed higher abundance of Rhodococcus, Thermovirga, and sulfate reducing bacteria Thermotoga and Petrotoga. All these bacteria are capable of hydrocarbon degradation. Hydrogenotrophic methanogens dominated the archaeal communities in all samples.

Abstract:
The shale gas flowback and produced water (FPW) from hydraulic fracturing in the Sichuan province of China has relatively low to moderate levels of total dissolved solids (<20 g/L) and organics (<50 mg/L of dissolved organic carbon). As such, a combined ultrafiltration (UF), reverse osmosis (RO) system can be successfully applied to desalinate this feed water with the goal of reuse. However, the concentration of influent organic matter and particulates in the UF and RO stage is high, and the overall ionic and organics composition is highly complex, so that the membrane processes do not perform well, also due to fouling. To ensure the long-term and efficient operation of the UF-RO stages, a combined pretreatment of the FPW with coagulation and adsorption was investigated. The effect of different parameters on the performance on the system was studied in detail. Overall, the coagulation-adsorption pre-treatment greatly reduced fouling of the membrane processes, thanks to the high removal rate of turbidity (98.8%) and dissolved organic carbon (86.3%). The adsorption of organic matter by powdered activated carbon was best described by the Freundlich equilibrium model, with a pseudo second-order model representing the adsorption kinetics. Also, the various ions had competitive removal rates during the adsorption step, a phenomenon reported for the first time for FPW treatment. Also, an optimal dose of activated carbon existed to maximize fouling reduction and effluent quality. The overall treatment system produced a high-quality water streams, suitable for reuse.

Abstract:
Unconventional oil and natural gas (UONG) exploration and production have grown rapidly and are expected to increase further in the U.S. and internationally. Direct measurements of key air pollutant emissions from unconventional oil and gas extraction are limited, especially during drilling and completion (hydraulic fracturing and flowback) of new wells. Knowledge of emission rates (ERs) of air toxics and other air pollutants from these activities is urgently needed to inform public policy. In order to address this key knowledge gap, we use a tracer ratio method to quantify pad-level, activity-specific (drilling, hydraulic fracturing (“fracking”), flowback, and production) ERs of 46 VOCs in the Denver-Julesburg (D-J, a mixed oil and gas play) and Piceance (primarily natural gas) basins in Colorado. Large differences in ERs of individual VOCs were observed across operation types, facilities conducting the same operation type, and over time during a single operation. ERs of benzene and most VOCs were highest in both basins during flowback, when injected fracking fluids and produced water flow to the surface. ERs from production are much lower, an important result given the significant difference in activity duration (days to weeks for flowback vs. decades for production). Fracking ERs of light alkanes and benzene were higher in the Piceance than in the D-J Basin. Findings from this study provide important new information that can be used to evaluate potential health hazards and other air quality impacts of unconventional oil and gas activities in Colorado’s two major oil and gas production basins.

Abstract:
This analysis of in-depth interviews with members of Frack Free Denton and Denton Taxpayers for a Strong Economy explores the dynamic divide caused by hydraulic fracturing in Denton, Texas. The most vocal and persuasive groups involved in the debate have discursive power to influence public opinion, which in turn shapes policies and practices. This analysis shows that pro- and anti-fracking groups conveyed an attachment to and ownership of the local land and engaged in harsh “othering” discourse to describe the opposing group. This study contributes to scholarly understandings of the relationship(s) between public perceptions of hydraulic fracturing, land use, and proximity.

Abstract:
Unintended release of flowback water as a result of above-ground walled storage system (AGWSS) failure was studied using a fuzzy fault tree analysis (FFTA). A fault tree comprising 45 basic events was constructed, and knowledge gathered through expert elicitation was used to estimate the occurrence possibilities of basic events. Fuzzy logic was introduced to reduce the epistemic uncertainties in expert judgments. Consistency analysis and grey pairwise comparison techniques were used to weight the judgments from different experts. The result of a case study shows that the failure probability of AGWSS was estimated to be 5.75E-04, indicating a relatively low level of failure possibility comparing to other systems used for oil and gas production. Importance analysis of basic events indicates that loss of containment integrity, water loading accidents, and external catastrophes are critical causes responsible for AGWSS failure. The developed FFTA methodology can be used by the unconventional gas industry for mitigation of flowback water spill risk.

Abstract:
Although multistage hydraulic fracturing is routinely performed for the extraction of hydrocarbon resources from low permeability reservoirs, the downhole geochemical processes linked to the interaction of fracturing fluids with formation brine and reservoir mineralogy remain poorly understood. We present a geochemical dataset of flowback and produced water samples from a hydraulically fractured reservoir in the Montney Formation, Canada, analyzed for major and trace elements and stable isotopes. The dataset consists in 25 samples of flowback and produced waters from a single well, as well as produced water samples from 16 other different producing wells collected in the same field. Additionally, persulfate breaker samples as well as anhydrite and pyrite from cores were also analyzed. The objectives of this study were to understand the geochemical interactions between formation and fracturing fluids and their consequences in the context of tight gas exploitation. The analysis of this dataset allowed for a comprehensive understanding of the coupled downhole geochemical processes, linked in particular to the action of the oxidative breaker. Flowback fluid chemistries were determined to be the result of mixing of formation brine with the hydraulic fracturing fluids as well as coupled geochemical reactions with the reservoir rock such as dissolution of anhydrite and dolomite; pyrite and organic matter oxidation; and calcite, barite, celestite, iron oxides and possibly calcium sulfate scaling. In particular, excess sulfate in the collected samples was found to be mainly derived from anhydrite dissolution, and not from persulfate breaker or pyrite oxidation. The release of heavy metals from the oxidation activity of the breaker was detectable but concentrations of heavy metals in produced fluids remained below the World Health Organization guidelines for drinking water and are therefore of no concern. This is due in part to the co-precipitation of heavy metals with iron oxides and possibly sulfate minerals.

Abstract:
Abstract An increase in induced seismicity in the central U.S. since 2009 led to establishment of TexNet seismic-monitoring in Texas. Accurate, absolute seismic-event location is critical to TexNet, allowing quantitative evaluation of possible association of seismicity with human activity. For the Delaware Basin, western Texas, relocation using different velocity models and TexNet station subsets shows absolute location error up to 4 ? 5 km. The preferred method to reduce absolute error, ground-truth calibration, is not available in this area. Alternatively, we used industrial well activity as proxy, ground-truth for developing probabilistic, proxy ground-truth (PPGT) station corrections for relocation. Assuming well activity causes seismicity, we defined a distance ? time probability associating events and well activity. We used these associations and other evidence to show some seismicity in the Delaware Basin is more likely due to hydraulic-fracturing than salt-water disposal. We then probabilistically accumulated PPGT station corrections using event hypocenters constrained to associated fracturing-well locations. We applied this procedure within 12 km of TexNet station PB02, optimizing the procedure through comparison of rates of causal and acausal associations. Relative to the initial locations, final PPGT relocations show smaller residuals and shifts in epicenter as much as 3 km, predominantly toward the north and northwest. PPGT residuals are similar to those from relocation with standard station corrections. The initial hypocenters showed an unreasonable deepening with distance from station PB02, whereas PPGT relocations produced an overall flattening of event depths. These results are consistent with PPGT corrections giving real improvement in absolute location accuracy.

Abstract:
This paper explores the impact of shale gas and oil fracking wells on infants’ health at birth across Oklahoma counties. The empirical analysis makes use of the Dumitrescu-Hurlin causality test, as well as the (long-run) Pooled Mean Group method. The results clearly document that there is a unidirectional relationship between fracking activities and three alternative indexes of infants’ health at birth, as well as a significant impact of fracking on infants’ health indicators. In addition, the results illustrate the substantial role of fracking through the drinking water quality channel.

Abstract:
Organohalides are routinely detected in fluid produced from hydraulically fractured oil and natural-gas wells, yet the origin and fate of these compounds remain largely unknown. Because few organohalides are disclosed as fracturing fluid additives, one suspected formation mechanism is the reaction of geogenic halides oxidized by injected additives with natural or anthropogenic organic carbon. However, the potential role of microorganisms in organohalide cycling is currently unknown. Here, we uncover the microorganisms and enzymatic systems that contribute to organohalide transformations during hydraulic fracturing through nontarget organohalide chemical analysis and metagenomics. Twenty organohalide compounds were identified in fluid samples produced from two Marcellus Shale natural-gas wells, comprising five structural classes. Genes encoding halogenation and dehalogenation mechanisms were identified in metagenomes assembled from produced fluids collected from four Appalachian Basin natural-gas wells. Metagenomic results show the presence of non-heme chloroperoxidases, enzymes that generate peracetic acid, which can react with dissolved halides to form highly oxidizing hypohalous acid, a halogenation agent for geogenic or anthropogenic organic matter. Microbial organohalide transformation/mineralization could proceed through hydrolytic dehalogenation, with enzymes inferred to operate on haloacetates, haloacids, and haloalkanes of varying carbon chain lengths, some of which are present in these wells. These results indicate that microorganisms may play an underappreciated role in direct and indirect organohalide transformations in hydraulically fractured oil and gas systems.

Abstract:
While fossil fuel interests have long played a powerful role in shaping American politics and culture, in recent decades, transnational oil and gas companies have formed hundreds of “partnerships” with American colleges and universities to fund energy research and development. Moreover, oil and gas interests have established a foothold in major universities by sponsoring research conferences, scholarships, science centers, and laboratories addressing technological advances in hydraulic fracturing methods, including leasing land for drilling on university-owned property. In this article, I critically assess some of the broad economic linkages between fossil fuel companies and higher education in the United States and the role that corporate philanthropy plays today in expanding the profits and power of the oil and gas industry, as well as the financial base and academic stature of select colleges and universities. Finally, I draw some preliminary conclusions about the growing colonization of university space and other public institutions by energy corporations.

Abstract:
Various chemicals used in hydraulic fracturing have raised environmental and human health (EHH) concerns regarding water resources contamination, leading to the transition towards the use of chemicals with minimum EHH hazards. Chemical hazard screening and indexing approaches have been used to measure the chemical hazard of hydraulic fracturing, and each approach is associated with inherent advantages and limitations. In this study, the two chemical hazard assessment approaches were discussed, and an integrated chemical hazard screening and indexing system was developed to combine the strengths of the two approaches. The integrated system was applied to assess the EHH hazards of representative hydraulic fracturing chemicals used in British Columbia, Canada. The hazard screening results showed that more than half of the ingredients and additives were classified into high hazard groups. Moreover, the integrated system generated more critical hazard assessment results than two hazard indexing systems, revealing that using the individual hazard indexing approach could result in underestimated EHH hazards for chemicals. The integrated system can significantly improve the data confidence levels of hazard assessment results compared to a previously developed indexing system. The integrated system can also help formulate fracturing fluids with low EHH hazards by identifying ingredients of high hazard concerns.

Abstract:
Background Studies have reported associations between unconventional natural gas development (UNGD) and adverse birth outcomes. None have evaluated potential mediating mechanisms. Objectives To evaluate associations between (1) UNGD and antenatal anxiety and depression and (2) antenatal anxiety and depression and preterm birth (<37 weeks gestation) and reduced term birth weight, (3) stochastic direct and indirect effects of UNGD on preterm birth and term birth weight operating through antenatal anxiety and depression, and (4) effect modification by family-level socioeconomic status. Methods This retrospective cohort study included mothers without prevalent anxiety or depression at time of conception, who delivered at Geisinger in Pennsylvania between January 2009–January 2013. We assembled phase-specific UNGD activity data from public sources. Mothers were categorized as exposed (quartile 4) or unexposed (quartiles 1–3) based on average daily inverse distance-squared UNGD activity metric between conception and the week prior to anxiety or depression (cases) or the pregnancy-average daily metric (non-cases). We estimated associations with a doubly robust estimator (targeted minimum loss-based estimation) and adjusted for potential individual- and community-level confounding variables. Results Analyses included 8,371 births to 7,715 mothers, 12.2% of whom had antenatal anxiety or depression. We found 4.3 additional cases of antenatal anxiety or depression per 100 women (95% CI: 1.5, 7.0) under the scenario where all mothers lived in the highest quartile of UNGD activity versus quartiles 1–3. The risk difference appeared larger among mothers receiving Medical Assistance (indicator of low family income) compared to those who did not, 5.6 (95% CI: 0.5, 10.6) versus 2.9 (95% CI: -0.7, 6.5) additional cases of antenatal anxiety or depression per 100 women. We found no relationship between antenatal anxiety or depression and adverse birth outcomes and no mediation effect either overall or when stratifying by Medical Assistance. Conclusion We observed a relationship between UNGD activity and antenatal anxiety and depression, which did not mediate the overall association between UNGD activity and adverse birth outcomes.

Abstract:
Hydraulic fracturing (HF) flowback and produced water (FPW) can be toxic to aquatic life but its chemical content is largely unknown, variable and complex. Seven FPW samples were collected from a HF operation in the Duvernay Formation (Alberta, Canada) over 30 days of flowback and characterized by a nontarget workflow based on high performance liquid chromatography - high resolution mass spectrometry (HRMS). A modified Kendrick mass defect plot and MS/MS spectral interpretation revealed seven series of homologues composed of ethylene oxide (i.e. -CH2CH2O-), among which a series of aldehydes was proposed as degradation products of polyethylene glycols, and two series of alkyl ethoxylate carboxylates could be proprietary HF additives. Many other ions were confidently assigned a formula by accurate mass measurement and were subsequently prioritized for identification by matching to records in ChemSpider and the US EPA's CompTox Chemistry Dashboard. Quaternary ammonium compounds, amine oxides, organophosphorous compounds, phthalate diesters and hydroxyquinoline were identified with high confidence by MS/MS spectra (Level 3), matching to reference spectra in MassBank (Level 2) or to authentic standards (Level 1). Temporal trends showed that most of the compounds declined in abundance over the first nine days of flowback, except for phthalate diesters and hydroxyquinoline that were still observed on Day 30 and had disappearance half-lives of 61 and 91 days, respectively. All the compounds followed first-order disappearance kinetics in flowback, except for polyoxygenated acids which followed second-order kinetics. This analysis and the workflow, based largely on public on-line databases, enabled profiling of complex organic compounds in HF-FPW, and will likely be useful for further understanding the toxicity and chemical fate of HF-FPW.

Abstract:
Hydraulic fracturing (or “fracking”) is one of the most controversial energy production processes in the United States and globally. In democracies, maintaining energy policy on politically salient and controversial issues, such as the use of fracking, depends on popular support at local if not national levels. We therefore study the effectiveness of widely cited arguments about fracking in a representative sample of the United States. Consistent with framing theory, we find that arguments that emphasize the environmental costs of fracking drive down support, while arguments emphasizing job creation and energy security increase it. However, we also show that presenting competing information from pro-fracking and anti-fracking frames together neutralizes individual framing effects, albeit not for every combination of frames and counter-frames. Framing effects become stronger when arguments, particularly about water contamination, are congruent with respondents’ pre-existing beliefs, which may lead to further polarization in the public debate. The exact kinds of arguments and how they are paired with one another do matter—a finding that is relevant for our understanding of public opinion on climate change and renewable energy policy more broadly.

Abstract:
The use of hydraulic fracturing (fracking) to extract oil and gas has generated intense debates in many countries. While the volume of empirical research on fracking attitudes internationally has grown considerably, there remains a need to focus attention on local contexts in which fracking takes place given the high degrees of variability in factors affecting attitude formation at the local scale. The Province of Alberta is a focal point for oil and gas development in Canada, and fracking has been expanding rapidly here, but little research has been conducted on attitudes toward fracking in this province, particularly in communities located in fracking zones. Understanding local perspectives toward fracking is critically important for tailoring energy policies that reflect local interest and concern. We examine perspectives about fracking among residents in three Alberta municipalities, each of which has experienced unique political-economic relationships with the energy industry. Our results suggest that trust, knowledge, and gender (male) are positively associated with fracking support. Notably, in a high energy-dependence community, residents express strong support despite experience with the impacts of fracking, and trust is expressed differently toward government organizations across the three study sites, signalling the importance of local context to fracking attitudes.

Abstract:
Ignorance about baseline conditions can be advantageous to companies that are suspected of causing environmental harm, because it allows them to claim that perhaps the degradation was a pre-existing problem. In the case of Marcellus Shale natural gas extraction in Pennsylvania (USA), gas well operators have created strategic ignorance about and through baselines in at least two ways: (1) drawing attention to weaknesses in the documentation of past environmental states and (2) controlling access to data that was collected in the past. This case further reveals that ordinary individuals and environmental organizations have taken an active interest in producing environmental baselines, separate from any formal regulatory process that might call for them. However, public participation in baselining does not occur on a level playing field, and it is a weak strategy for holding polluters accountable.

Abstract:
We report a 24-month statistical baseline climatology for continuously-measured atmospheric carbon dioxide (CO2) and methane (CH4) mixing ratios linked to surface meteorology as part of a wider environmental baselining project tasked with understanding pre-existing local environmental conditions prior to shale gas exploration in the United Kingdom. The baseline was designed to statistically characterise high-precision measurements of atmospheric composition gathered over two full years (between February 1st 2016 and January 31st 2018) at fixed ground-based measurement stations on, or near to, two UK sites being developed for shale gas exploration involving hydraulic fracturing. The sites, near Blackpool (Lancashire) and Kirby Misperton (North Yorkshire), were the first sites approved in the UK for shale gas exploration since a moratorium was lifted in England. The sites are operated by Cuadrilla Resources Ltd. and Third Energy Ltd., respectively. A statistical climatology of greenhouse gas mixing ratios linked to prevailing local surface meteorology is presented. This study diagnoses and interprets diurnal, day-of-week, and seasonal trends in measured mixing ratios and the contributory role of local, regional and long-range emission sources. The baseline provides a set of contextual statistical quantities against which the incremental impacts of new activities (in this case, future shale gas exploration) can be quantitatively assessed. The dataset may also serve to inform the design of future case studies, as well as direct baseline monitoring design at other potential shale gas and industrial sites. In addition, it provides a quantitative reference for future analyses of the impact, and efficacy, of specific policy interventions or mitigating practices. For example, statistically significant excursions in measured concentrations from this baseline (e.g. >99th percentile) observed during phases of operational extraction may be used to trigger further examination in order to diagnose the source(s) of emission and links to on-site activities at the time, which may be of importance to regulators, site operators and public health stakeholders. A guideline algorithm for identifying these statistically significant excursions, or “baseline deviation events”, from the expected baseline conditions is presented and tested. Gaussian plume modelling is used to further these analyses, by simulating approximate upper-limits of CH4 fluxes which could be expected to give observable enhancements at the monitoring stations under defined meteorological conditions.

Abstract:
Unconventional natural gas extraction by hydraulic fracturing requires millions of gallons of water and generates flowback water, produced water and recycled fluids of varying chemical composition. Ion chromatography (IC) is a relatively low cost and efficient means to determine the anionic composition, however, the wide range in anionic content of these fluids poses a challenge to analytical methods developed for “natural” waters. We report here that the combination of UV and conductivity detectors increased detection sensitivity (e.g., 10–50 ppb) and expanded the number of anions detectable in a single sample run. Samples from four unconventional shale gas wells, two impoundments, nine conventional oil wells, two freshwater streams and mine drainage samples were analyzed in this study. All produced water samples and impoundment samples had high chloride (17,500–103,000 mg L−1, 93,900 to 134,000 mg L−1, 27,700 and 30,700 mg L−1), bromide (178–996 mg L−1, 183–439 mg L−1, 230 and 260 mg L−1) and conductivity (38,500–160,000 μS/cm3, 95,300 to 183,000 μS/cm3, 61,500 and 103,000 μS/cm3), respectively, relative to mine drainage and freshwater stream samples. Molar ratio analysis using Cl−/Br− to Cl− and SO42−/Cl− to Br− revealed significant differences between the samples, providing a simple means for distinguishing water impacted by different sources of contamination.

Abstract:
This paper presents the various tools and data sources in British Columbia (Canada) that can be used by environmental consultants to assess the potential of cross-contamination between shale gas formation fluids and shallow aquifers from hydraulic fracturing and related oil and gas activities. A systematic approach for evaluating the potential of cross-contamination using these data sources is applied to a specific case study at an undisclosed location in the northeastern part of the province. This approach includes defining and then evaluating the basic criteria for assessing the potential of cross-contamination. These criteria are: a leak source; a driving force such as buoyancy or head differential and a leakage pathway. This study has revealed that there is a potential of cross-contamination due to hydraulic fracturing activities and wellbore integrity issues. Wellbore integrity can be compromised by induced seismic events or by unintentional communication with offset hydraulic fractured wells. Induced seismicity is linked to the activity of hydraulic fracturing as well as to the deep disposal of wastewater.

Abstract:
This study proposes a new integrated framework to evaluate groundwater safety by characterizing the short-term spatiotemporal variations of methane migration risk attributed to shale gas development. A set of probabilistic- and conditionally probabilistic-based algorithms is used to represent the temporal and spatial distributions of reliability–resilience–vulnerability (RRV) over the study domain. Using RRV calculation and copula functions, the gas migration index (GMI) is calculated to identify the interrelationships among RRV for identifying the synergetic variation of RRV levels. The framework is demonstrated and discussed through the southwest shale of Bradford County, Pennsylvania. Results show that 1) reliability is quite high (>0.7) over the southern parts while the midland remains high risk of contamination; 2) low-level reliability spreads to the northern and southern areas from the central parts and gradually diffuses through most grids sparsely; reliability implies negative correlations with methane concentrations; 3) the spatiotemporal variation of resilience has high concordance with those of reliability except subtle discrepancies; and 4) the spatial distribution of high-level vulnerability has subtler classifications besides similar outlines to that of low-reliability. Moreover, results from the GMI analysis show that 1) the gas migration risk is consistently low in the south and the north in middle blocks and 2) high-level GMI shows an apparent rampant tendency across the blocks and spreads to the whole north ultimately. Therefore, GMI is better at characterizing groundwater contamination risk than using a single metric. The framework will contribute significantly to improve management practices taken by shale gas operators and regulators in protecting groundwater quality.

Abstract:
Oil and gas (O&G) production in the United States is expected to grow at a substantial rate over the coming decades. Environmental sustainability related to water consumption during O&G extraction can be addressed through treatment and reuse of water returning to the surface after well completion. Water quality is an important factor in reuse applications, and specific treatment technologies must be utilized to remove different contaminants. Among others, biological active filtration can remove dissolved organic matter as a pre-treatment for surface discharge or to facilitate reuse in such applications as hydraulic fracturing, dust suppression, road stabilization, and crop irrigation. Yet, the formation of byproducts during treatment of O&G wastewater remains a concern when evaluating reuse applications. In this study, we investigated the previously unnoticed biotic formation of iodinated organic compounds (IOCs) such as triiodomethane during biological treatment of O&G wastewater for beneficial reuse. Iodide and several IOCs were quantified in O&G produced water before and after treatment in biological active filters filled with different media types over 13 weeks of operation. While iodide and total IOCs were measured at concentrations <53 mg/L and 147 μg/L, respectively, before biological treatment, total IOCs were measured at concentrations close to 4 mg/L after biological treatment. Triiodomethane was the IOC that was predominantly present. IOC formation had a negative strong correlation (r = −0.7 to −0.8, p < 0.05, n = 9) with iodide concentration in the treated O&G wastewater, indicating that iodide introduced to the biological active filter system was utilized in various reactions, including biologically mediated halogenation of organic matter. Additionally, iodide-oxidizing bacteria augmented in the treated produced water pointed towards potential negative environmental implications when releasing biologically treated halide-rich wastewater effluents to the aquatic environment.