Repository for Oil and Gas Energy Research (ROGER)

Abstract:
As oil production in the Permian Basin surges, the impact of shale production on groundwater resources has become a growing concern. Most existing studies focus on the impact of shale production on shallow freshwater aquifers. There is little understanding of the shale development’s impact on other groundwater resources (e.g., deep carbonate aquifers and deep basin meteoric aquifers). The possible natural hydraulic connections between shallow aquifers and formation water suggest such an impact can be consequential. This study explores the relationship between shale production and groundwater using produced water (PW) samples from active unconventional oil wells. Focusing on the most productive portion of the Permian Basin—the four-county region in Southeast New Mexico between 2007 and 2016, a large produced water dataset allows us to analyze the conditional correlations between shale oil production and PW constituents. The results suggest that (1) expanding from primarily conventional wells to unconventional wells during the recent shale boom has led to dramatic increases of the TDS, chloride, sodium, and calcium levels in groundwater (i.e., producing formation). (2) Nearby oil well density positively correlates with the TDS, chloride, and sodium levels in the PW samples.

Abstract:
Despite the growing body of studies on the various fracturing phrases, the research on the differences between subterranean and surface microorganisms at shale gas drilling sites is still limited. Generally, shale gas development and the production process are divided into drilling and fracturing. The distribution of microbial communities in the latter has been paid some attention, but a deficit remains in terms of our understanding of the microbial community in the former, especially for the phase of drilling flowback and drilling flowback surface. In this study, four drilling flowback fluids (DFFs) (H230-flowback drilling cuttings, H23G-flowback drilling mud, H240-flowback drilling sediment, and H21F-flowback drilling water) from the outlet of subterranean pipeline to the inlet of storage tank were successively collected from H2 shale gas field during its initial drilling in Sichuan, China. Natural mountain water (H10W) used as the injection water of H2 was also sampled. Illumina MiSeq 16S rRNA gene sequencing revealed a total of 8 phyla, 17 classes, 35 orders, 61 families, and 98 genera that were recovered from these samples with uneven distribution. The majority of the obtained sequences belonged to the phyla Proteobacteria (75.36%), Bacteroidetes (10.75%), and Firmicutes (5.64%), with significant differences found in DFFs and injection water. The richness of microorganisms gradually increased with the increasing flowback flowing distance (H230< H23G< H240< H21F< H10W), which was employed to reveal a rapid change in microbiota that was evident in samples along the flow path aboveground from a depth of 3548 m. The findings of this study could expand our understanding of the ecological role of microorganisms during the shale gas drilling phase. Furthermore, the study highlights the temporal-spatial trajectory of microbial communities from subterranean environments to the surface in a short period of 30 days.

Abstract:
Hydraulic fracturing of deep shale formations generates large volumes of wastewater that must be managed through treatment, reuse, or disposal. Produced wastewater liberates formation-derived radionuclides and contains previously uncharacterized organohalides thought to be generated within the shale well, both posing unknown toxicity to human and ecological health. Here, we assess the toxicity of 42 input media and produced fluid samples collected from four wells in the Utica formation and Marcellus Shale using two distinct endpoint screening assays. Broad spectrum acute toxicity was assessed using a bioluminescence inhibition assay employing the halotolerant bacterium Aliivibrio fischeri, while predictive mammalian cytotoxicity was evaluated using a N-acetylcysteine (NAC) thiol reactivity assay. The acute toxicity and thiol reactivity of early-stage flowback was higher than later produced fluids, with levels diminishing through time as the natural gas wells matured. Acute toxicity of early stage flowback and drilling muds were on par with the positive control, 3,5-dichlorophenol (6.8 mg L−1). Differences in both acute toxicity and thiol reactivity between paired natural gas well samples were associated with specific chemical additives. Samples from wells containing a larger diversity and concentration of organic additives resulted in higher acute toxicity, while samples from a well applying a higher composition of ammonium persulfate, a strong oxidizer, showed greater thiol reactivity, predictive of higher mammalian toxicity. Both acute toxicity and thiol reactivity are consistently detected in produced waters, in some cases present up to nine months after hydraulic fracturing. These results support that specific chemical additives, the reactions generated by the additives, or the constituents liberated from the formation by the additives contribute to the toxicity of hydraulic fracturing produced waters and reinforces the need for careful consideration of early produced fluid management.

Abstract:
Understanding the behavior and composition of fracturing flowback water (FFW) can provide insight into in situ water–rock interactions, assessment of the success of the fracturing operations. FFW was collected from three wells (Z202-H1, Z203, and Z205) for up to 108 days after fracturing in the same area of western Chongqing, China. The samples were analyzed for the concentrations of various ions (Na+, K+, Ca2+, Mg2+, Ba2+, Sr2+, Cl−, SO42−, Br−, HCO3−, etc.) and for the stable isotope composition (δD and δ18O) of water. With increasing flowback time, the ionic concentration and total salinity increased (e.g., from 315 mg/L to 37117 mg/L after 38 days for well Z203), stable isotopic ratios became heavier (e.g., δD values changed from −23.59‰ to −14.32‰, δ18O values changed from −3.91‰ to −1.92‰). The total salinity of the FFW is shown to be the result of mixing of the highly saline formation water and the low-salinity fracturing water. FFW from Z205 had higher concentrations of Li+ and NO3−, heavier stable isotope compositions, larger Na+/Cl− ratio, smaller (Cl−-Na+)/Mg2+ ratio, and larger SO42− × 100/Cl− ratio compared to the other two wells. All these phenomena revealed that Z205 is more likely to contact with active aquifers which is not conducive to natural gas preservation, because Z205 is close to (less 300 m from) a grade II fault. The RITS and RSIH with flowback time in Z203 were higher than Z202-H1, which shows that FFW from Z203 contained a greater fraction of formation water released from pores or fractures due to complex the network fractures formed by fracturing. Therefore, the fracturing operations of Z203 is better than Z202-H1. This result can reveal the reason for the production difference of adjacent wells, which is difficult to explain by similar total SRV.

Abstract:
Flowback/Produced fluid samples were collected from several wells from two Utica/Point Pleasant (UPP) sites (UPPW and UPPS) in Ohio, and one Marcellus (Marcellus Shale Energy and Environment Laboratory (MSEEL)) site in West Virginia over a period of approximately two years. Although these formations have different ages, depositional environments, diagenetic histories, and geochemical and mineralogical compositions (i.e. the UPP is significantly more carbonate rich than the Marcellus which is more siliceous), analysis of trends in fluid species over time shows that, overall, the TDS and major solubilized elements (Na, Ca, Cl) in the UPP and Marcellus brines are remarkably similar. Total dissolved solutes (TDS) in these brines ranged from approximately 40 to 250 g/L salt, and in general, concentrations increased with time elapsed since natural gas well completion and stimulation. The behavior of Na, Br, and Cl suggests that the produced water signatures from these formations are largely derived from the native formational brines which display evidence of originating from evaporated seawater. There is a strong correlation between Cl and Br, indicating that both species behave conservatively, and the similarity among each of these brines suggests no appreciable contribution of salt from halite dissolution because Br is excluded from the halite structure. Cl/Br ratios in the brines range from ~80 to 120 (mg/L/mg/L). Other elements, such as K, which readily reacts between fluids and ion exchange sites on clays, generally exhibit conservative behavior for an individual site, but show significant variations among each of the different well pads. The concentrations of Sr and Ba vary dramatically among well sites, and increase with respect to Cl− over time, suggesting increasing solubilization, presumably from desorption from clay minerals or dissolution of carbonates or sulfates from the source formation(s). The UPPW well site has very low Ba due to high-sulfate input fluid, which resulted in precipitation of barite/celestite in the brines. In contrast the UPPS well site had elevated Sr (~ 3500 mg/L), presumably due to the use of Sr-rich recycled brine used in hydraulic fracturing. The Marcellus site had the highest Ba concentrations (up to 10 g/L) and highest Ba/Sr ratios in the fluids, due to the high concentration of barium in the Marcellus target (~ 1000 ppm, as compared to ~200 ppm in the UPP). These observations suggest that solutes in the FP fluids are derived from native brines, water-rock interactions that have occurred over geologic time scales, as well as some contribution from contemporaneous reactions in the subsurface. The results also show that the composition of the injected fluid can influence flowback fluid chemistry and possibly production efficiency.

Abstract:
Oil and gas (O&G) extraction generates large volumes of produced water (PW) in regions that are often water-stressed. In Wyoming, generators are permitted under the National Pollutant Discharge Elimination System (NPDES) program to discharge O&G PW for beneficial use. In one Wyoming study region, downstream of the NPDES facilities exist naturally occurring wetlands referred to herein as produced water retention ponds (PWRPs). Previously, it was found that dissolved radium (Ra) and organic contaminants are removed within 30 km of the discharges and higher-resolution sampling was required to understand contaminant attenuation mechanisms. In this study, we sampled three NPDES discharge facilities, five PWRPs, and a reference background wetland not impacted by O&G PW disposal. Water samples, grab sediments, sediment cores and vegetation were collected. No inorganic PW constituents were abated through the PWRP series but Ra was shown to accumulate within PWRP grab sediments, upwards of 2721 Bq kg−1, compared to downstream sites. Ra mineral association with depth in the sediment profile is likely controlled by the S cycle under varying microbial communities and redox conditions. Under anoxic conditions, common in wetlands, Ra was available as an exchangeable ion, similar to Ca, Ba and Sr, and S was mostly water-soluble. 226Ra concentration ratios in vegetation samples, normalizing vegetation Ra to sediment Ra, indicated that ratios were highest in sediments containing less exchangeable 226Ra. Sequential leaching data paired with redox potentials suggest that oxic conditions are necessary to contain Ra in recalcitrant sediment minerals and prevent mobility and bioavailability.

Abstract:
Oilfield flowback and produced water (FPW) is a waste stream that may offer an alternative source of water for multiple beneficial uses. One practice gaining interest in several semi-arid states is the reuse of FPW for agricultural irrigation. However, it is unknown if the reuse of FPW on edible crops could increase health risks from ingestion of exposed food, or impact crop growth. A greenhouse experiment was conducted using wheat (Triticum aestivum) to investigate the uptake potential of select hydraulic fracturing additives known to be associated with health risks. The selected chemicals included acrylamide, didecyldimethylammonium chloride (DDAC), diethanolamine, and tetramethylammonium chloride (TMAC). Mature wheat grain was extracted and analyzed by liquid chromatography-triple quadrupole mass spectrometry (LC-QQQ) to quantify chemical uptake. Plant development observations were also documented to evaluate impacts of the chemicals on crop yield. Analytical results indicated that TMAC and diethanolamine had significantly higher uptake into both wheat grain and stems than control plants which were not exposed to the four chemicals under investigation. Acrylamide was measured in statistically higher concentrations in the stems only, while DDAC was not detected in grain or stems. Growth impacts included lodging in treated wheat plants due to increased stem height and grain weight, potentially resulting from increased nitrogen application. While analytical results show that uptake of select hydraulic fracturing chemicals in wheat grain and stems is measurable, reuse of FPW for irrigation in real world scenarios would likely result in less uptake because water would be subject to natural degradation, and often treatment and dilution practices. Nonetheless, based on the outstanding data gaps associated with this research topic, chemical specific treatment and regulatory safeguards are still recommended.

Abstract:
The large-scale extraction of unconventional resources from shale reservoirs utilizing horizontal hydraulic fracturing has significantly improved economic development in U.S. However, the increased well production has been accompanied by rising concerns about potential impact resulting from excessive freshwater usage and wastewater generation. Currently, water issues have become increasingly challenging with the development of shale reservoirs. In this paper, technical, economic, and environmental challenges encountered during energy production are reviewed with a focus on water issues due to hydraulic fracturing in the U.S. Moreover, the detailed discussion of characteristics and contaminant sources of wastewater indicates the wastewater composition is complicated and varies over time and location. Understanding these factors contributed to high contaminant levels of wastewaters is important to grow awareness of the impacts of hydraulic fracturing on water quality for both operators and the public. Furthermore, pertinent wastewater management strategies for different purposes are highlighted. Although there is no one-size-fits-all solution, understanding the advantages and limitations of different treatment methods is critical for decision-makers to develop appropriate management system. The aim behind this review is to provide a reference for selecting better and practical solutions for current wastewater issues and identifying key issues for future research.

Abstract:
Natural gas, the largest source for electricity generation in the US, is produced via hydraulic fracturing. Fracturing uses water mixed with chemical additives to free natural gas from the shale formation. While downhole, these fluids contact small formation particles produced during well-perforation and remain in contact with the particles until the fluids return to the well surface. We performed experiments to investigate the physical and chemical interactions between Marcellus shale particles and fluid at high temperature (80oC). The treatments in this study include incubating shale particles in solutions containing individual organic and inorganic additives used during fracturing (hydrochloric acid, persulfate, LEB-10X, WGA, FRS, Revert Flow (RF), and BXL). The particles exhibited a measurable influence on flowback fluid chemistry when treated with chemical additives. An optimized methodology was developed for laser-based Particle Size Analysis (PSA) with a wet-dispersion unit that was then used to measure changes in particle size after treatment. The PSA results indicate that mixing speeds >2800 rpm can cause particle breakage and low speeds are required for PSA of shales. We observed no difference in particle size across treatments after incubation, indicating that clay swelling likely occurs during incubation. The influence of contact time was investigated for the inorganic treatments (persulfate and HCl containing treatments) given that these treatments resulted in higher concentrations of element release and precipitation compared to the organics additives tested. The results show that contact time is an essential consideration in shale transformation studies. Our findings link changing water chemistry to specific fracturing additives and provide key information for understanding the fluid-rock interactions.

Abstract:
This research assessed the efficacy of UV and UV advanced oxidation processes (UV/AOPs) to reduce dissolved organic carbon (DOC), total petroleum hydrocarbons (TPH), and microorganisms in hydraulic fracturing produced water. To improve water quality conditions before UV treatment with and without added hydrogen peroxide (UV/H2O2), produced water was treated with coagulation, flocculation, and sedimentation (CFS) and biologically activated carbon filtration (BACF). BACF was more effective than CFS as a pre-UV and UV/AOP treatment strategy and reduced DOC, TPH, and absorbing species by over 70% which, subsequently, resulted in the highest hydroxyl radical steady-state concentrations during UV and UV/H2O2 experiments. UV alone minimally degraded DOC, while UV/H2O2 improved DOC and TPH degradation by 9% to 36%. Interestingly, UV without added H2O2 created an in situ AOP by generating hydroxyl radicals with similar steady-state concentrations to that of UV/H2O2. UV was found to be highly effective for the inactivation of microorganisms that were cultured in produced water by reducing microbial communities dominated by Citrobacter by 4 logs after only 30 mJ/cm2. Together, these results demonstrate UV/AOP as a potential strategy to not only improve the treatment and reuse of produced water but also reduce biocide use in fracturing fluids.

Abstract:
This review focuses on recent developments in electrochemical technology (with special emphasis on electrocoagulation, electro-oxidation, and electro-Fenton) to treat petroleum industry effluents (offshore and hydraulic fracturing extraction, as well as refinery effluents). In addition, an overview is given of what these processes face to position themselves as consolidated technologies.

Abstract:
Carboxymethyl cellulose (CMC) is a polymer used in many different industrial sectors. In the oil and gas industry, CMC is often used during hydraulic fracturing (fracking) operations as a thickening agent for effective proppant delivery. Accumulations of CMC at fracture faces (known as filter cakes) can impede oil and gas recovery. Although chemical oxidizers are added to disrupt these accumulations, there is industrial interest in developing alternative, enzyme-based treatments. Little is known about CMC biodegradation under fracking conditions. Here, we enriched a methanogenic CMC-degrading culture and demonstrated its ability to enzymatically utilize CMC under the conditions that typify oil fields. Using the extracellular enzyme fraction from the culture, significant CMC viscosity reduction was observed between 50 and 80˚C, at salinities up to 20% (w/v) and at pH 5-8 compared to controls. Similar levels of viscosity reduction by extracellular enzymes were observed under oxic and anoxic conditions. This proof-of-concept study demonstrates that enzyme biotechnology holds great promise as a viable approach to treating CMC filter cakes under oilfield conditions.

Abstract:
Hydraulic fracturing of unconventional hydrocarbon resources involves the sequential injection of a high-pressure, particle-laden fluid with varying pH’s to make commercial production viable in low permeability rocks. This process both requires and produces extraordinary volumes of water. The water used for hydraulic fracturing is typically fresh, whereas “flowback” water is typically saline with a variety of additives which complicate safe disposal. As production operations continue to expand, there is an increasing interest in treating and reusing this high-salinity produced water for further fracturing. Here we review the relevant transport and geochemical properties of shales, and critically analyze the impact of water chemistry (including produced water) on these properties. We discuss five major geochemical mechanisms that are prominently involved in the temporal and spatial evolution of fractures during the stimulation and production phase: shale softening, mineral dissolution, mineral precipitation, fines migration, and wettability alteration. A higher salinity fluid creates both benefits and complications in controlling these mechanisms. For example, higher salinity fluid inhibits clay dispersion, but simultaneously requires more additives to achieve appropriate viscosity for proppant emplacement. In total this review highlights the nuances of enhanced hydrogeochemical shale stimulation in relation to the choice of fracturing fluid chemistry.

Abstract:
Surface spills occur frequently during unconventional oil and gas production operations and have the potential to impact groundwater quality. A screening-level analysis using contaminant fate and transport simulations was performed to: (1) evaluate whether hypothetical (yet realistic) spills of aqueous produced fluids pose risks to groundwater quality in the South Platte Aquifer, (2) identify the key hydrologic and transport factors that determine these risks, and (3) develop a screening-level methodology that could be applied for other sites and pollutants. This assessment considered a range of representative hydrologic conditions and transport behavior for benzene, a regulated pollutant in production fluids. Realistic spill volumes and areas were determined using publicly available data collected by Colorado’s regulatory agency. Risk of groundwater pollution was based on predicted benzene concentrations at the groundwater table. Results suggest that the risk of groundwater contamination from benzene in a produced water spill was relatively low in the South Platte Aquifer. Spill size was the dominant factor influencing whether a contaminant reached the water table. Only statistically larger spills (volume per surface area ≥12.0 cm) posed a clear risk. Storm events following a spill were generally required to transport typical (median)-sized spills (0.38 cm volume per surface area) to the water table; typical spills only posed risk if a 500 or 100 year storm (followed by little degradation or sorption) occurred right after the spill. This methodology could be applied to evaluate spills occurring over other aquifers.

Abstract:
The widespread application of directional drilling and hydraulic fracturing technologies expanded oil and gas (OG) development to previously inaccessible resources. A single OG well can generate millions of liters of wastewater, which is a mixture of brine produced from the fractured formations and injected hydraulic fracturing fluids (HFFs). With thousands of wells completed each year, safe management of OG wastewaters has become a major challenge to the industry and regulators. OG wastewaters are commonly disposed of by underground injection, and previous research showed that surface activities at an Underground Injection Control (UIC) facility in West Virginia affected stream biogeochemistry and sediment microbial communities immediately downstream from the facility. Because microbially driven processes can control the fate and transport of organic and inorganic components of OG wastewater, we designed a series of aerobic microcosm experiments to assess the influence of high total dissolved solids (TDS) and two common HFF additives—the biocide 2,2-dibromo-3-nitrilopropionamide (DBNPA) and ethylene glycol (an anti-scaling additive)—on microbial community structure and function. Microcosms were constructed with sediment collected upstream (background) or downstream (impacted) from the UIC facility in West Virginia. Exposure to elevated TDS resulted in a significant decrease in aerobic respiration, and microbial community analysis following incubation indicated that elevated TDS could be linked to the majority of change in community structure. Over the course of the incubation, the sediment layer in the microcosms became anoxic, and addition of DBNPA was observed to inhibit iron reduction. In general, disruptions to microbial community structure and function were more pronounced in upstream and background sediment microcosms than in impacted sediment microcosms. These results suggest that the microbial community in impacted sediments had adapted following exposure to OG wastewater releases from the site. Our findings demonstrate the potential for releases from an OG wastewater disposal facility to alter microbial communities and biogeochemical processes. We anticipate that these studies will aid in the development of useful models for the potential impact of UIC disposal facilities on adjoining surface water and shallow groundwater.

Abstract:
Produced water (PW) generation has been increasing recently due to the expansion of fossil fuel extraction and the aging of oil wells worldwide and especially in the United States (US). The adverse health risks, seismicity, and environmental impacts associated with PW have become a challenging concern. Therefore, there is increased demand for improved PW treatment and reuse management options. There are multiple methods for treating PW; this article focuses on treatment through membrane filtration. Moreover, this mini review aims to summarize statistics on PW abundance, trends in PW generation over time, to briefly call attention to health-related issues, highlight some treatment challenges, and mention potential purposes for reuse with an emphasis on the US, the largest generator of PW worldwide.

Abstract:
Arsenic (As) is a toxic trace element with many sources, including hydrocarbons such as oil, natural gas, oil sands, and oil- and gas-bearing shales. Arsenic from these hydrocarbon sources can be released to the environment through human activities of hydrocarbon production, storage, transportation and use. In addition, accidental release of hydrocarbons to aquifers with naturally occurring (geogenic) As can induce mobilization of As to groundwater through biogeochemical reactions triggered by hydrocarbon biodegradation. In this paper, we review the occurrence of As in different hydrocarbons and the release of As from these sources into the environment. We also examine the occurrence of As in wastes from hydrocarbon production, including produced water and sludge. Last, we discuss the potential for As release related to waste management, including accidental or intentional releases, and recycling and reuse of these wastes.

Abstract:
Hydraulic fracturing has become widely used in recent years to access vast global unconventional sources of oil and gas. This process involves the injection of proprietary mixtures of water and chemicals to fracture shale formations and extract the hydrocarbons trapped within. These injection fluids, along with minerals, hydrocarbons, and saline waters present within the formations being drilled into, return to the surface as flowback and produced water (FPW). FPW is a highly complex mixture, containing metals, salts and clay, as well as many organic chemicals, including polycyclic aromatic hydrocarbons such as phenanthrene. The present study sought to determine the effects of temperature on the accumulation of phenanthrene in rainbow trout (Oncorhynchus mykiss). This model organism resides in rivers overlapping the Montney and Duvernay formations, both highly developed formations for hydraulic fracturing. Rainbow trout acclimated to temperatures of 4, 13 and 17°C were exposed to either 5% or 20% FPW, as well as saline mixtures representing the exact ionic content of FPW to determine the accumulation of radiolabelled 14C phenanthrene within the gill, gut, liver and gallbladder. FPW exposure reduced the overall accumulation of phenanthrene in a manner most often similar to high salinity exposure, indicating that the high ionic strength of FPW is the primary factor affecting accumulation. Accumulation was different at the temperature extremes (4 and 17°C), although no consistent relationship was observed between temperature and accumulation across the observed tissues. These results indicate that several physiological responses occur as a result of FPW exposure and water temperature change which dictate phenanthrene uptake, particularly in the gills. Temperature (and seasonality) alone cannot be used to model the potential accumulation of polycyclic aromatic hydrocarbons after FPW spills.

Abstract:
Oilfield flowback and produced water (FPW) is a waste stream that may offer an alternative source of water for multiple beneficial uses. One practice gaining interest in several semi-arid states is the reuse of FPW for agricultural irrigation. However, it is unknown if the reuse of FPW on edible crops could increase health risks from ingestion of exposed food, or impact crop growth. A greenhouse experiment was conducted using wheat (Triticum aestivum) to investigate the uptake potential of select hydraulic fracturing additives known to be associated with health risks. The selected chemicals included acrylamide, didecyldimethylammonium chloride (DDAC), diethanolamine, and tetramethylammonium chloride (TMAC). Mature wheat grain was extracted and analyzed by liquid chromatography-triple quadrupole mass spectrometry (LC-QQQ) to quantify chemical uptake. Plant development observations were also documented to evaluate impacts of the chemicals on crop yield. Analytical results indicated that TMAC and diethanolamine had significantly higher uptake into both wheat grain and stems than control plants which were not exposed to the four chemicals under investigation. Acrylamide was measured in statistically higher concentrations in the stems only, while DDAC was not detected in grain or stems. Growth impacts included lodging in treated wheat plants due to increased stem height and grain weight, potentially resulting from increased nitrogen application. While analytical results show that uptake of select hydraulic fracturing chemicals in wheat grain and stems is measurable, reuse of FPW for irrigation in real world scenarios would likely result in less uptake because water would be subject to natural degradation, and often treatment and dilution practices. Nonetheless, based on the outstanding data gaps associated with this research topic, chemical specific treatment and regulatory safeguards are still recommended.

Abstract:
The most massive waste stream generated by conventional and unconventional hydrocarbon exploration is the produced water (PW). The costs and environmental issues associated with the management and disposal of PW, which contains high concentrations of inorganic and organic pollutants, is one of the most challenging problems faced by the oil and gas industry. Many of the current strategies for the reuse and recycling of PW are inefficient because of varying water demand and the spatial and temporal variations in the chemical composition of PW. The chemical composition of PW is controlled by a multitude of factors and can vary significantly over time. This study aims to understand different parameters and processes that control the quality of PW generated from hydrocarbon-bearing Formations by analyzing relationships between their major ion concentrations, O, H, and Sr isotopic composition. We selected PW data sets from three conventional (Trenton, Edwards, and Wilcox Formations) and four unconventional (Lance, Marcellus, Bakken, and Mesaverde Formations) oil and gas Formations with varying lithology and depositional environment. Using comparative geochemical data analysis, we determined that the geochemical signature of PW is controlled by a complex interplay of several factors, including the original source of water (connate marine vs. non-marine), migration of the basinal fluids, the nature and degree of water-mineral-hydrocarbon interactions, water recharge, and processes such as evaporation and ultrafiltration processes, and production techniques (conventional vs. unconventional). The design of efficient PW recycle and reuse strategies requires a holistic understanding of the geological and hydrological history of each Formation and an account of temporal and spatial heterogeneities.

Abstract:
Leveraging waste heat has been considered to have significant potential for promoting the economic feasibility of wastewater treatment in unconventional oil and gas (UOG) production. However, its availability near well sites has not been fully understood and other energy sources may be also feasible. In this work, we quantitatively investigate the viability of using waste heat and well-pad natural gas to power on-site wastewater treatment by membrane distillation (MD) for twenty randomly selected wells located in the Denver-Julesburg (DJ) Basin, U.S. Results show that waste heat produced from on-site electrical loads is insufficient for MD treatment of all the wastewater generated during UOG production (2.2–24.3% of thermal energy required for MD treatment). Waste heat from hydraulic fracturing, which persists only for a short timeframe, is able to meet the full or partial energy requirement during the peak period of wastewater production (17–1005% of thermal energy required for MD treatment within the first two months of production), but this scenario varies among wells and is dependent on the energy efficiency of MD. Compared to waste heat, natural gas is a more consistent energy source. The treatment capacity of MD powered by natural gas at the well pad exceeds full wastewater treatment demands for all the twenty wells, with only two wells requiring short-term wastewater storage. Our work indicates that although waste heat has the potential to reduce the electricity consumption and cost of UOG wastewater treatment, it is unlikely to supply sufficient thermal energy required by MD for long-term treatment. Natural gas can serve as an alternative or complementary energy resource. Further investigations, in particular techno-economic analyses, are needed to identify the best suitable energy source or combination for on-site UOG wastewater treatment.

Abstract:
Releases of oil and gas (OG) wastewaters can have complex effects on stream-water quality and downstream organisms, due to sediment-water interactions and groundwater/surface water exchange. Previously, elevated concentrations of sodium (Na), chloride (Cl), barium (Ba), strontium (Sr), and lithium (Li), and trace hydrocarbons were determined to be key markers of OG wastewater releases when combined with Sr and radium (Ra) isotopic compositions. Here, we assessed the persistence of an OG wastewater spill in a creek in North Dakota using a combination of geochemical measurements and modeling, hydrologic analysis, and geophysical investigations. OG wastewater comprised 0.1 to 0.3% of the stream-water compositions at downstream sites in February and June 2015, but could not be quantified in 2016 and 2017. However, OG-wastewater markers persisted in sediments and pore water for 2.5 years after the spill and up to 7.2-km downstream from the spill site. Concentrations of OG wastewater constituents were highly variable depending on the hydrologic conditions. Electromagnetic measurements indicated substantially higher electrical conductivity in groundwater seeps below the streambed 7.2 km downstream from the spill site. Geomorphic investigations revealed mobilization of sediment is an important contaminant transport process. Labile Ba, Ra, Sr, and ammonium (NH4) concentrations extracted from sediments indicated sediments are a long-term reservoir of these constituents, both in the creek and on the floodplain. Using the drivers of ecological effects identified at this intensively studied site we identified 41 watersheds across the North Dakota landscape that may be subject to similar episodic inputs from OG wastewater spills. Effects of contaminants released to the environment during OG waste management activities remain poorly understood; however, analyses of Ra and Sr isotopic compositions, as well trace inorganic and organic compound concentrations at these sites in pore-water provide insights into potentials for animal and human exposures well outside source remediation zones.

Abstract:
Hydraulic fracturing flowback and produced water (FPW) is a highly complex and heterogenous wastewater by-product of hydraulic fracturing practices. To date, no research has examined how FPW exposure to freshwater biota may affect energetic homeostasis following subsequent induction of detoxification processes. Rainbow trout (Oncorhynchus mykiss) were acutely exposed for 48 h to either 2.5% or 7.5% FPW, and hepatic metabolism was assessed either immediately or following a 3-week recovery period. Induction of xenobiotic metabolism was observed with an 8.8-fold increase in ethoxyresorufin-O-deethylase (EROD) activity after 48 h exposure to 7.5% FPW, alongside a 10.3-fold increase in the mRNA abundance of cyp1a, both of which returned to basal level after three weeks. Glucose uptake capacity was elevated by 6.8- and 12.9-fold following 2.5% and 7.5% FPW exposure, respectively, while alanine uptake was variable. Activity measurements and mRNA abundance of key enzymes involved in hepatic metabolism indicated that aerobic metabolism was maintained with exposure, as was glycolysis. Gluconeogenesis, as measured by phosphoenolpyruvate carboxykinase (PEPCK) activity, decreased by ~30% 48 h following 2.5% FPW exposure and ~20% 3 weeks after 7.5% FPW exposure. The abundance of pepck mRNA activity followed similar, yet non-significant, trends. Finally, a delayed increase in amino acid catabolism was observed, as glutamate dehydrogenase (GDH) activity was increased 2-fold in 7.5% FPW exposed fish when compared to saline control fish at the 3-week time point. We provide evidence to suggest that although hepatic metabolism is altered following acute FPW exposure, metabolic homeostasis generally returns 3-weeks post-exposure.

Abstract:
Publicly available toxicological studies on wastewaters associated with unconventional oil and gas (UOG) activities in offshore regions are nonexistent. The current study investigated the impact of hydraulic fracturing-generated flowback water (HF-FW) on whole organism swimming performance/respiration and cardiomyocyte contractility dynamics in mahi-mahi (Coryphaena hippurus—hereafter referred to as “mahi”), an organism which inhabits marine ecosystems where offshore hydraulic fracturing activity is intensifying. Following exposure to 2.75% HF-FW for 24 h, mahi displayed significantly reduced critical swimming speeds (Ucrit) and aerobic scopes (reductions of ∼40 and 61%, respectively) compared to control fish. Additionally, cardiomyocyte exposures to the same HF-FW sample at 2% dilutions reduced a multitude of mahi sarcomere contraction properties at various stimulation frequencies compared to all other treatment groups, including an approximate 40% decrease in sarcomere contraction size and a nearly 50% reduction in sarcomere relaxation velocity compared to controls. An approximate 8-fold change in expression of the cardiac contractile regulatory gene cmlc2 was also seen in ventricles from 2.75% HF-FW-exposed mahi. These results collectively identify cardiac function as a target for HF-FW toxicity and provide some of the first published data on UOG toxicity in a marine species.

Abstract:
The Utica and Marcellus Shale Plays in the Appalachian Basin are the fourth and first largest natural gas producing plays in the United States, respectively. Hydrocarbon production generates large volumes of brine (“produced water”) that must be disposed of, treated, or reused. Though Marcellus brines have been studied extensively, there are few studies from the Utica Shale Play. This study presents new brine chemical analyses from 16 Utica Shale Play wells in Ohio and Pennsylvania. Results from Na–Cl–Br systematics and stable and radiogenic isotopes suggest that the Utica Shale Play brines are likely residual pore water concentrated beyond halite saturation during the formation of the Ordovician Beekmantown evaporative sequence. The narrow range of chemistry for the Utica Shale Play produced waters (e.g., total dissolved solids = 214–283 g/L) over both time and space implies a consistent composition for disposal and reuse planning. The amount of salt produced annually from the Utica Shale Play is equivalent to 3.4% of the annual U.S. halite production. Utica Shale Play brines have radium activities 580 times the EPA maximum contaminant level and are supersaturated with respect to barite, indicating the potential for surface and aqueous radium hazards if not properly disposed of.

Abstract:
Hydraulic fracturing is often criticized due in part to the potential degradation of ground and surface water quality by high-salinity produced water generated during well stimulation and production. This preliminary study evaluated the response of the freshwater mussel, Elliptio complanata, after exposure to produced water. A limited number of adult mussels were grown over an 8-week period in tanks dosed with produced water collected from a hydraulically fractured well. The fatty tissue and carbonate shells were assessed for accumulation of both inorganic and organic pollutants. Ba, Sr, and cyclic hydrocarbons indicated the potential to accumulate in the soft tissue of freshwater mussels following exposure to diluted oil and gas produced water. Exposed mussels showed accumulation of Ba in the soft tissue several hundred times above background water concentrations and increased concentrations of Sr. Cyclic hydrocarbons were detected in dosed mussels and principle component analysis of gas chromatograph time-of-flight mass spectrometer results could be a novel tool to help identify areas where aquatic organisms are impacted by oil and gas produced water, but larger studies with greater replication are necessary to confirm these results.

Abstract:
Key technological breakthroughs, such as hydraulic fracturing (HF) and horizontal drilling, have facilitated the extraction of shale gas. The boost of the shale gas industry has changed global energy markets and led to a decline in natural gas and oil price. Endowed with massive shale gas resources, China is ambitious to develop its shale gas industry, driven by growing energy demand and critical environmental conditions. However, an increasing number of pollution problems coming along with extraction has threatened our environment with atmospheric pollution, water risk, induced seismicity, occupational health, safety, and so on. Because HF needs millions of tons of water and produces a large quantity of effluents, water management becomes one of the most threatened problems. Also, wastewater treatment has become a key factor restricting the development of China’s shale gas industry. In response, international and domestic enterprises have developed a variety of management processes, which are divided into three categories: reinjection, reuse in hydraulic fracturing, and discharge after treatment. In this paper we first summarize Chinese shale gas development, then analyze the production of shale gas wastewater through major extraction techniques. Finally, a review was conducted on current wastewater treatments utilized in China, and advice is offered for future treatment techniques.

Abstract:
Unconventional shale gas production in the United States has been largely improved due to the development of hydraulic fracturing technology and is projected to rapidly grow in the coming years. However, the acquisition of freshwater and management of flowback and produced (FP) water associated with hydraulic fracturing operation are two of the greatest challenges in shale gas development, especially in arid regions. For efficient and sustainable water management, a better understanding of freshwater consumption and FP water production for shale gas wells is necessary to appropriately expand and upgrade the existing water network and shale gas network. To achieve this, we first collected water-use volume and monthly FP water production volume data for shale gas wells drilled in the Eagle Ford and Marcellus shale regions. Next, after integrating the data from multiple database sources, the water recovery ratio was calculated as the ratio of cumulative FP water volume to water-use volume and used as a metric to characterize the wells in these two shale regions. Then, we analyzed the obtained water recovery ratio data according to the location and production history to study the spatiotemporal variations across multiple counties and time periods. It shows that around 30% of the collected wells drilled in the Eagle Ford region have the water recovery ratio greater than 1; however, only 1% of the collected wells drilled in the Marcellus region have the water recovery ratio greater than 1. Besides, the water recovery ratios vary significantly across the counties in each shale region. To demonstrate how different water recovery ratio may affect shale gas development, a shale gas supply chain network (SGSCN) optimization model from the literature was utilized to perform two case studies in the Marcellus region. The optimal results suggest that different configurations of SGSCN are required for economically desirable and practically feasible management of shale gas wells with different water recovery ratios.

Abstract:
Recent advances in horizontal drilling and hydraulic fracturing technologies have allowed producers to extract oil and gas from thin reservoirs that may not be economically viable through vertical drilling. While the new hydraulic fracturing technologies have resulted in substantial economic benefits for the state of Texas, they tend to generate high volumes of truck traffic that diversely affect the transportation system. Many of the affected roads were designed and built several decades ago to meet low traffic demand levels and not heavy repetitive truck loads. The goal of this study is to enhance state agencies’ ability to determine the truck traffic associated with fracking in existing and new wells based on several well characteristics. This paper explores spatio-temporal trends in hydraulic fracturing in Texas and develops a methodology that agencies can use to estimate the amount of water and the number of trucks needed to frack and fully develop a well. The analysis revealed that fracking horizontal wells generates eight times more water and, therefore, truck traffic than vertical wells. The relationship between water volume versus well length is non-linear. The length of laterals has a very strong correlation with frack water (0.818) and sand (0.763), while the vertical well depth has a weak to negligible relationship with fracking materials. The two prediction models presented in the paper produced statistically similar results with average errors of less than 20%. The paper explains how the predicted water volumes can be converted into the number of trucks needed to frack and fully develop a well.

Abstract:
Fertilizer drawn forward osmosis (FDFO) was proposed to extract fresh water from flowback and produced water (FPW) from shale gas extraction for irrigation, with fertilizer types and membrane orientations assessed. Draw solution (DS) with NH4H2PO4 displayed the best performance, while DS with (NH4)2HPO4 resulted in the most severe membrane fouling. DS with KCl and KNO3 led to substantial reverse solute fluxes. FDFO operation where the active layer of the membrane was facing the feed solution outperformed that when the active layer was facing the DS. Diluted DS and diluted FPW samples were used for irrigation of Cherry radish and Chinese cabbage. Compared to deionized water, irrigation with diluted DS (total dissolved solid (TDS) = 350 mg·L-1) promoted plant growth. In contrast, inhibited plant growth was observed when FPW with high salinity (TDS = 5000 mg·L-1) and low salinity (TDS = 1000 mg·L-1) was used for irrigation of long-term (8-week) plant cultures. Finally, upregulated genes were identified to illustrate the difference in plant growing. The results of this study provide a guide for efficient and safe use of FPW after FDFO treatment for agricultural application.

Abstract:
Wastewater discharges from cities and industries, especially megacities, and intensive livestock can be considered as main sources of pollution of our rivers and groundwater. Water pollution, therefore, constitutes a major threat to both aquatic ecosystems and human health. Here we address the influence of chemical pollution in waste- and drinking water, their associated potential toxicological effects, as well as, the available technologies for their removal. This opinion paper provides illustrative selected examples covering a broad range for both drinking water and wastewater treatment processes, for which a battery of toxicity tests is applied for their risk assessment. The examples are classified based on five hot topics: (i) Bioassays for toxicity evaluation, (ii) Toxicity of municipal wastewaters, (iii) Toxicity of pharmaceutical residues and hospital wastewaters, (iv) Toxicity of other non-urban effluent examples, and (v) Drinking water treatment processes and toxicity evaluation. 'Chemical analysis combined with batteries of bioassays covering a broad range of endpoints: cytotoxicity, endocrine disruption, genotoxicity, and other types seem to be good way to assess performance/efficiency of the water treatment processes when removing chemical contaminants.. Altogether, while recognizing that water treatment is a cornerstone for water pollution reduction, providing safe water for both human use and its return back to the aquatic environment will be undoubtedly enhanced with the use of ecotoxicity biomonitoring.

Abstract:
The increased water consumption for hydraulic fracturing and the volume of wastewater generated from shale gas and tight oil exploration are major environmental challenges associated with unconventional energy development. Recycling of the flowback and produced water for hydraulic fracturing is one of the solutions for reducing the water footprint of hydraulic fracturing and removing highly saline oil and gas wastewater. Here we investigated the implications of recycling saline wastewater for hydraulic fracturing by monitoring the natural gas production, flowback water volume, and the water quality of generated flowback water in shale gas wells from Changning gas field in Sichuan Basin, China. A comparison of two sets of shale gas wells, with six wells in each sub-group, from the same location in Changning gas field shows lower (~20%) natural gas production and higher flowback water volume (~18%) in wells that were fracked with recycled saline wastewater relative to wells that were fracked with fresh water after a year of production. Geochemical analysis suggests that hydraulic fracturing with saline wastewater increases the salinity of the wastewater and reduces the magnitude of water-shale rock interactions. In spite of the direct economic consequences in reduction in natural gas production from recycling of wastewater for hydraulic fracturing, in areas where water scarcity could become a limiting factor for future large-scale shale gas development, hydraulic fracturing with recycled flowback water can be more beneficial than utilization of limited freshwater resources, as long as the higher saline flowback water is fully recycled.

Abstract:
A linear programming (LP) model is presented to investigate optimal shale gas wastewater management strategies for Marcellus shale play in Pennsylvania (PA) focusing on membrane distillation (MD) as the treatment technology. The optimization framework established in this study incorporates (1) detailed treatment cost obtained from techno-economic assessment (TEA) of MD, (2) cost of wastewater transportation from shale gas sites to treatment or disposal facilities, and (3) cost of injection into salt water disposal (SWD) wells. The optimization model is applied to four case study areas with significant shale gas extraction: Greene and Washington counties in Southwest PA and Susquehanna and Bradford counties in Northeast PA. The results reveal that onsite treatment in combination with shale gas wastewater treatment at natural gas compressor stations (NG CS) where available waste heat can be utilized for the treatment process are the most economically advantageous management options. The optimal solution could result in over 60% benefit over direct disposal in SWD, which translates to over $16 million/year savings in the counties in Northeast PA. Furthermore, the results of sensitivity analysis indicate that transportation cost is a major contributor to the overall cost of shale gas wastewater management.

Abstract:
Chemical spills in streams can impact ecosystem or human health. Typically, the public learns of spills from reports from industry, media, or government rather than monitoring data. For example, ∼1300 spills (76 ≥ 400 gallons or ∼1500 L) were reported from 2007 to 2014 by the regulator for natural gas wellpads in the Marcellus shale region of Pennsylvania (U.S.), a region of extensive drilling and hydraulic fracturing. Only one such incident of stream contamination in Pennsylvania has been documented with water quality data in peer-reviewed literature. This could indicate that spills (1) were small or contained on wellpads, (2) were diluted, biodegraded, or obscured by other contaminants, (3) were not detected because of sparse monitoring, or (4) were not detected because of the difficulties of inspecting data for complex stream networks. As a first step in addressing the last problem, we developed a geospatial-analysis tool, GeoNet, that analyzes stream networks to detect statistically significant changes between background and potentially impacted sites. GeoNet was used on data in the Water Quality Portal for the Pennsylvania Marcellus region. With the most stringent statistical tests, GeoNet detected 0.2% to 2% of the known contamination incidents (Na ± Cl) in streams. With denser sensor networks, tools like GeoNet could allow real-time detection of polluting events.

Abstract:
Produced water (PW) is a major waste-product of oil and gas production that some consider a viable agricultural irrigation water source. However, the presence of petroleum hydrocarbons, toxic metals and potentially high salinity of PW may be deleterious for soil health. Thus, we irrigated wheat with minimally treated PW to investigate effects on soil health, wheat growth, and the soil microbiome. Irrigation treatments included control irrigation water (IW), 1% and 5% PW dilutions (1% PW, 5% PW), and a saltwater solution with salinity equivalent to the 5% PW dilution (SW). Wheat was irrigated three times a week, for a total of 2.1 L per pot by harvest. During wheat growth, we measured plant physiological parameters, soil electrical conductivity, as well as profiled soil microbial diversity by performing 16S ribosomal ribonucleic acid (rRNA) gene analysis. Soil health parameters were measured after harvest, including chemical, biological, physical, and nutrient properties that were used to calculate an overall soil health index (SQI). SQI analysis revealed that the SW and 5% PW treatments had significantly reduced soil health as compared to the control. Furthermore, the 16S rRNA gene analysis showed that the microbial community membership and structure was significantly different between irrigation treatments, highlighting shifts in the soil microbiome which may impact soil biochemical cycling. Both the SW- and 5% PW-treated wheat had reduced yields as compared to the control. Our results indicate that irrigating wheat with minimally treated PW may result in yield decreases, as well as reducing both overall soil health and soil microbial community diversity. Future large-scale field studies are needed to determine the long-term soil health effects of PW on different soil types and crops.

Abstract:
This study models emissions quantities and neighboring exposure concentrations of six airborne pollutants, including PM10, PM2.5, crystalline silica, arsenic, uranium, and barium, that result from the disposal of Marcellus shale drill cuttings waste during the 2011-to-2017 period. Using these predicted exposures, this study evaluates current setback distances required in Pennsylvania from waste facilities. For potential residents living at the perimeter of the current setback distance, 274 m (900 ft), a waste disposal rate of 612.4 metric tons per day at landfills (the 99th percentile in record) does not result in exceedances of the exposure limits for any of the six investigated pollutants. However, the current setback distance can result in exceedance with respect to the 24-hr daily concentration standards for PM10 and PM2.5 established in the National Air Ambient Quality Standards (NAAQS), if daily waste disposal rate surpasses 900 metric tons per day. Dry depositions of barium-containing and uranium-containing particulate matter should not be a danger to public health based on these results. To investigate the air quality impacts of waste transportation and the potential for reductions, this paper describes an optimization of landfill locations in Pennsylvania indicating the potential benefits in reduced environmental health hazard level possible by decreasing the distance traveled by waste disposal trucks. This strategy could reduce annual emissions of PM10 and PM2.5 by a mean of 64% and reduce the expected number of annual fatal accidents by nearly half and should be considered a potential risk management goal in the long run. Therefore, policy to limit or encourage reduction of distances traveled by waste removal trucks and manage setback distances as a function of delivered waste quantities is merited. Implications This study shows the necessity of reviewing current setback distance required in Pennsylvania, which might not ensure 24-hr mean PM10 and PM2.5 levels below the values stated in National Ambient Air Quality Standards for the residents living at the perimeter. Furthermore, this study also reveals potential tremendous benefits from optimizing location of landfills accepting drill cuttings within Pennsylvania, with PM10 and PM2.5 emission, total distance traveled shrinking, and number of fatal accidents shrinking by nearly half.

Abstract:
As global exploration of shale gas reserves increases, there is a need for accurate and efficient approach to proper water management, which is one of the vital problems related to shale gas production. This study looks at the effect of using multiple or hybrid treatment technologies in maximizing hydraulic fracturing wastewater reuse, whilst ensuring sustainability of the process in terms of energy and associated cost. The study considers ultrafiltration and membrane distillation processes as possible pre-treatment and desalination technologies for flowback water management. It also considers the possibility of supplying the electrical and thermal energy requirements of these regenerators using flared gas. Two different scenarios are considered based on flowback water composition in hydraulic fracturing in terms of salinity. Application of the proposed model to a case study leads to 24.13 % reduction in the quantity of water needed for fracturing. In terms of energy requirements, the approach yields 31.6 % reduction in the required thermal energy in membrane distillation and 8.62 % in energy requirement for ultrafiltration. For flowback water with moderate total dissolved solids concentration, 93.6 % of wastewater reuse comes from pre-treated water by ultrafiltration and 6.4 % from membrane distillation. However, as the flowback water salinity becomes higher, the percentage of pre-treated reusable water reduces to 81.1 % and the percentage supply through membrane distillation increases to 18.9 %. In all cases, the results indicate that the decision to allow the pre-treated water to pass through desalination technology strictly depends on the quantity of water required by a wellpad and the salinity of the wastewater.

Abstract:
Formulated products used in hydraulic fracturing are designed to address specific subsurface challenges during oil and gas well completion and are intended for the treatment of a myriad of issues in a wellbore; however, there are public concerns regarding the use of certain chemical ingredients in hydraulic fracturing. Public perception of hydraulic fracturing and concerns regarding water and chemical usage provide the industry with a unique opportunity to review current chemistries and water management practices with the aim being to identify more environmentally acceptable alternatives or replacements. Herein we describe what the industry considers to be the greatest challenges, what is currently being done, and potential opportunities to provide alternatives that lead to a more sustainable industry.

Abstract:
Hydraulic fracturing (HF) technology is increasingly utilized for oil and gas extraction operations. The widespread use of HF has led to concerns of negative impacts on both the environment and human health. Indeed, the potential endocrine disrupting impacts of HF chemicals is one such knowledge gap. Herein, we used structure-based molecular docking to assess the binding affinities of 60 HF chemicals to the human androgen receptor (AR). Five HF chemicals had relatively high predicted AR binding affinity, suggesting the potential for endocrine disruption. We next assessed androgenic and antiandrogenic activities of these chemicals in vitro. Of the five candidate AR ligands, only Genapol®X–100 significantly modified AR transactivation. To better understand the structural effect of Genapol®X–100 on the potency of AR inhibition, we compared the antiandrogenic activity of Genapol®X–100 with that of its structurally similar chemical, Genapol®X–080. Interestingly, both Genapol®X–100 and Genapol®X–080 elicited an antagonistic effect at AR with 20% relative inhibitory concentrations of 0.43 and 0.89 μM, respectively. Furthermore, we investigated the mechanism of AR inhibition of these two chemicals in vitro, and found that both Genapol®X–100 and Genapol®X–080 inhibited AR through a noncompetitive mechanism. The effect of these two chemicals on the expression of AR responsive genes, e.g. PSA, KLK2, and AR, was also investigated. Genapol®X–100 and Genapol®X–080 altered the expression of these genes. Our findings heighten awareness of endocrine disruption by HF chemicals and provide evidence that noncompetitive antiandrogenic Genapol®X–100 could cause adverse endocrine health effects.

Abstract:
Uranium and other radionuclides are prominent in many unconventional oil/gas shales and is a potential contaminant in flowback/produced waters due to the large volumes/types of chemicals injected into the subsurface during stimulation. To understand the stability of U before and after stimulation, a geochemical study of U speciation was carried out on three shales (Marcellus, Green River, and Barnett). Two types of samples for each shale were subjected to sequential chemical extractions: unreacted and shale reacted with synthetic hydraulic fracture fluid. A significant proportion of the total U (20-57%) was released from these three shales after reaction with fracture fluid, indicating that U is readily leachable. The total U released exceeds labile water soluble and exchangeable fractions in unreacted samples, indicating that fluids leach more recalcitrant phases in the shale. Radiographic analysis of unreacted Marcellus shale thin sections shows U associated with detrital quartz and the clay matrix in the shale. Detrital zircon and TiO2 identified by electron microprobe could account for the hotspots. This study shows that significant proportions of U in three shales are mobile upon stimulation. In addition, the extent of mobilization of U depends on the U species in these rocks.

Abstract:
Large amounts of fracturing flowback and wastewater with complex compositions are produced during hydraulic fracturing. Characterization of hydraulic fracturing flowback and produced water (HF-FPW) is an important initial step in efforts to determine a suitable treatment method for this type of wastewater. In the present study, fracturing flowback and produced water samples were obtained from well CN-F and well CN-E in the prophase and anaphase stages of the Changning shale gas mining area. Chemical characterization of inorganic and organic substances was then conducted. Metal contents were determined by inductively coupled plasma optical emission spectroscopy (ICP-OES), and all inorganic anions involved were determined by ion chromatography. The organic pollutant components were analyzed in detail by combining Fourier transform infrared spectrometer (FTIR) and gas chromatography-mass spectrometer (GC-MS). Results showed that samples contained salt (TDS = 30,000–50,000 mg/L), metals (e.g., 650 ± 50 mg/L calcium), and total organic carbon (TOC = 32–178 mg/L). The organic substances detected in all samples could be divided into six categories, alkanes, aromatics, halogenated hydrocarbons, alcohols, esters, and ketones. C6–C21 straight-chain alkanes and C7–C13 naphthenes had the highest amount of organic matter, reaching more than 48%. The organic matter contained fracturing fluid additives, such as surfactants (e.g., ethylene glycol), and nitrotrichloromethane, which is a chlorinated product of some additives. These results provide information on the chemical composition of HF-FPW in Sichuan, China, as well as a basis for subsequent processing.

Abstract:
Background Hydraulic fracturing often involves the injection of millions of gallons of fracturing fluids into underground shales to extract oil and natural gas, raising health concerns over potential water contamination. Many state and federal governmental agencies rely on the third-party FracFocus online registry for disclosure of chemical ingredients in fracturing fluids, but withholding chemicals as trade secrets is common. In 2016, a new format, known as the systems approach was widely encouraged as a method of reducing withholding by decoupling disclosed chemicals from their functions, protecting against reverse-engineering of fracture fluid formulas by competitors. In this study, we assess the extent to which elevated use of the systems approach in FracFocus version 3.0 translated into greater chemical disclosure. Methods We analysed 108 137 disclosure forms submitted to FracFocus between Jan 1, 2011, and Dec 31, 2018, to estimate the effect of expanded use of the systems approach on chemical withholding. We compared the proportion of forms withholding at least one chemical ingredient across time, between approaches, and by state and drilling operator. Findings Since the 2016 expansion of the systems approach, 15 677 (82%) of systems approach forms have withheld an ingredient. 13 462 (89%) of 15 062 traditional FracFocus version 3.0 forms withheld an ingredient. In the quarter following the transition (July, to September, 2016), 1211 (93%) of 1304 traditional forms withheld an ingredient, compared with only 958 (76%) of 1262 systems approach forms. However, withholding rates increased throughout 2017 and, by 2018, 6949 (87%) of 8016 systems approach forms were withholding ingredients. At the end of our analysis period in the fourth quarter of 2018, systems approach forms had even greater withholding (903 [88%] of 1025 forms) than did traditional forms (855 [85%] of 1004 forms). We did not find that states or operators that submitted more systems approach forms had lower withholding. Interpretation The systems approach has not reduced FracFocus chemical withholding, which continues to occur in around 87% of well fracture disclosures. FracFocus might not be an appropriate substitute for regulatory action, and measures are urgently needed for environmental and public safety. Funding University of Chicago Argonne National Laboratory Seed Grant.

Abstract:
Managing produced water from oil and gas wells constitutes a significant portion of the costs of operating a well. In this work, we have designed two different centralized water treatment facilities capable of managing produced water from oil and gas wells in Texas and Louisiana, both of which convert the produced water into the following valuable resources: ten-pound brine and fresh water. The two main designs each use commercially available technology with varying levels of establishment in treating produced water. Both treatment processes remove oil and grease and suspended solids, reduce the divalent ion concentrations, and concentrate the brines to a near-saturation state. The baseline design uses chemical precipitation to remove the divalent ions to meet the reuse specifications, whereas the advanced design uses nanofiltration (NF) membranes to separate divalent ions and uses reserve osmosis (RO) membranes to partially concentrate the brine. Both models use mechanical vapor recompression to concentrate the brine up to NaCl saturation. The baseline process is shown to be cost-effective for low-hardness brines. In the case of high hardness, the chemical precipitation step is cost-prohibitive. We find that NF membranes are a promising alternative to chemical precipitation as a means of separating monovalent and divalent ions.

Abstract:
Produced water is the largest waste stream associated with oil and gas operations. This complex fluid contains petroleum hydrocarbons, heavy metals, salts, naturally occurring radioactive materials and any remaining chemical additives. In the United States, west of the 98th meridian, the federal National Pollutant Discharge Elimination System (NPDES) exemption allows release of produced water for agricultural beneficial reuse. The goal of this study was to quantify mutagenicity of a produced water NPDES release and discharge stream. We used four mutation assays in budding yeast cells that provide rate estimates for copy number variation (CNV) duplications and deletions, as well as forward and reversion point mutations. Higher mutation rates were observed at the discharge and decreased with distance downstream, which correlated with the concentrations of known carcinogens detected in the stream (e.g., benzene, radium), described in a companion study. Mutation rate increases were most prominent for CNV duplications and were higher than mutations observed in mixtures of known toxic compounds. Additionally, the samples were evaluated for acute toxicity in Daphnia magna and developmental toxicity in zebrafish. Acute toxicity was minimal, and no developmental toxicity was observed. This study illustrates that chemical analysis alone (McLaughlin et al., 2020) is insufficient for characterizing the risk of produced water NPDES releases and that a thorough evaluation of chronic toxicity is necessary to fully assess produced water for beneficial reuse.

Abstract:
While development of the Utica/Point Pleasant Shale (UPP) is extensive in Ohio (U.S.) and increasing in Pennsylvania and West Virginia, few studies report the chemistry of produced waters from UPP wells. These data have important implications for developing best management practices for handling and waste disposal, or identifying the fluid in the event of accidental spill events. Here, we evaluated the elemental and isotope chemistry of UPP produced waters from 26 wells throughout Ohio, Pennsylvania, and West Virginia to determine any unique fluid chemistries that could be used for forensic studies. Compared to the Marcellus, UPP produced waters contain higher activities of total radium (226Ra + 228Ra) and higher 228Ra/226Ra ratios. As with the Marcellus Shale, elemental ratios (Sr/Ca) and isotope ratios (87Sr/86Sr) can distinguish UPP produced waters from many conventional oil and gas formations. Sr/Ca and 87Sr/86Sr ratios can fingerprint small fractions (∼0.1%) of UPP produced water in freshwater. However, because Marcellus and UPP produced waters display similar major elemental chemistry (i.e., Na, Ca, and Cl) and overlapping ratios of Sr/Ca and 87Sr/86Sr, 228Ra/226Ra ratios may be the best tracer to distinguish these waters.

Abstract:
Unconventional methods of oil and natural gas extraction have been a growing part of North America's energy sector for the past 20-30 years. Technologies such as horizontal hydraulic fracturing have facilitated the exploitation of geologic reserves that were previously resistant to standard drilling approaches. However, the environmental risks associated with hydraulic fracturing are relatively understudied. One such hazard is the wastewater by-product of hydraulic fracturing processes: flowback and produced water (FPW). During FPW production, transport, and storage, there are many potential pathways for environmental exposure. In the current review, toxicological hazards associated with FPW surface water contamination events and potential effects on freshwater biota are assessed. This review contains an extensive survey of chemicals commonly associated with FPW samples from shale formations across North America and median 50% lethal concentration values (LC50) of corresponding chemicals for many freshwater organisms. We identify the characteristics of FPW which may have the greatest potential to be drivers of toxicity to freshwater organisms. Notably, components associated with salinity, the organic fraction, and metal species are reviewed. Additionally, we examine the current state of FPW production in North America and identify the most significant obstacles impeding proper risk assessment development when environmental contamination events of this wastewater occur. Findings within this study will serve to catalyze further work on areas currently lacking in FPW research, including expanded whole effluent testing, repeated and chronic FPW exposure studies, and toxicity identification evaluations.

Abstract:

Abstract:
Mixing of acid mine drainage (AMD) and hydraulic fracturing flowback fluids (HFFF) could represent an efficient management practice to simultaneously manage two complex energy wastewater streams while reducing freshwater resource consumption. AMD discharges offer generally high sulfate concentrations, especially from the bituminous coal region of Pennsylvania; unconventional Marcellus shale gas wells generally yield HFFF enriched in alkaline earth metals such as Sr and Ba, known to cause scaling issues in oil and gas (O&G) production. Mixing the two waters can precipitate HFFF-Ba and -Sr with AMD-SO4, therefore removing them from solution. Four AMD discharges and HFFF from two unconventional Marcellus shale gas wells were characterized and mixed in batch reactors for 14 days. Ba could be completely removed from solution within 1 day of mixing in the form BaxSr1–xSO4 and no further significant precipitation occurred after 2 days. Total removal efficiencies of Ba + Sr + SO4 and the proportion of Ba and Sr in BaxSr1–xSO4 depended upon the Ba/Sr ratio in the initial HFFF. A geochemical model was calibrated from batch reactor data and used to identify optimum AMD–HFFF mixing ratios that maximize total removal efficiencies (Ba + Sr + SO4) for reuse in O&G development. Increasing Ba/Sr ratios can enhance total removal efficiency but decrease the efficiency of Ra removal. Thus, treatment objectives and intended beneficial reuse need to be identified prior to optimizing the treatment of HFFF with AMD.

Abstract:
Hydraulic fracturing of horizontal wells is a cost effective means for extracting oil and gas from low permeability formations. Hydraulic fracturing often produces considerable volumes of flowback and produced water (FPW). FPW associated with hydraulic fracturing has been shown to be a complex, often brackish mixture containing a variety of anthropogenic and geogenic compounds. In the present study, the risk of FPW releases to aquatic systems was studied using the model benthic invertebrate, Lumbriculus variegatus and field-collected FPW from a fractured well in Alberta. Acute, chronic, and pulse toxicity were evaluated to better understand the implications of accidental FPW releases to aquatic environments. Although L. variegatus is thought to have a high tolerance to many stressors, acute toxicity was significant at low concentrations (i.e. high dilutions) of FPW (48 h LC50: 4–5%). Chronic toxicity (28 d)of FPW in this species was even more pronounced with LC50s (survival/reproduction) and EC50s (total mass) at dilutions as low as 0.22% FPW. Investigations evaluating pulse toxicity (6 h and 48 h exposure) showed a significant amount of latent mortality occurring when compared to the acute results. Additionally, causality in acute and chronic bioassays differed as acute toxicity appeared to be primarily driven by salinity, which was not the case for chronic toxicity, as other stressors appear to be important as well. The findings of this study show the importance of evaluating multiple exposure regimes, the complexity of FPW, and also shows the potential aquatic risk posed by FPW releases.

Abstract:
Shale gas extraction processes generate a large amount of hypersaline wastewater, whose spills or discharges may significantly increase the bromide levels in downstream water supplies and result in the formation of brominated disinfection byproducts (DBPs) upon chlorination. Although a few studies have investigated selective bromide removal from produced water, the low removal efficiencies and complex system setups are not desirable. In this study, we examined a simple cost-effective approach for selective bromide removal from produced water relying on the oxidation by un-activated peroxymonosulfate (PMS). More than 95% of bromide was removed as Br2(g) in less than 10 min under weakly acidic conditions without significant formation of Cl2(g) even when the chloride concentration was more than two orders of magnitude higher. A kinetic model considering the involved reactions was then developed to describe the process well under various reaction conditions. The organic compounds in produced water neither noticeably lowered bromide removal efficiency nor reacted with the halogen species to form halogenated byproducts. The tests in batch and continuously-stirred tank reactor systems suggested that it was feasible to achieve both high bromide removal and neutral effluent pH such that further pH adjustment was not necessary before discharge. After the treatment, the effect of the produced water on DBP formation was largely eliminated.