Repository for Oil and Gas Energy Research (ROGER)

Abstract:
Hydraulic fracturing technology has made unconventional oil and gas development economically viable; however, it can lead to potential environmental issues such as groundwater pollution. Strontium isotope (87Sr/86Sr) is considered as a sensitive tracer to indicate potential groundwater contamination. In this study, strontium (Sr) and 87Sr/86Sr sources of hydraulic fracturing flowback fluid are identified with 87 flowback fluid samples and 5 borehole core samples. High Sr concentrations and 87Sr/86Sr values were found in fracturing flowback fluid. The hydrogeochemistry evidence shows high Sr and 87Sr/86Sr in fracturing flowback fluid mainly comes from formation water with high ion concentrations, while Sr and 87Sr/86Sr of formation water develop in diagenesis and long term water-rock interaction (e.g., feldspar dissolution and clay mineral transformations) under the high temperature and pressure. A complete evaluation system was executed to assess the sensitivity of 87Sr/86Sr indicating potential pollution on groundwater. The mixing curves which 87Sr/86Sr combined with Sr and Cl were also established by mixing models to indicate groundwater pollution. The modeling results show mineral dissolution/precipitation and cation exchange have little impact on 87Sr/86Sr in the mixing process between fracturing flowback fluid and groundwater, which 87Sr/86Sr can identify contamination when only 0.89% of fracturing flowback fluid mixes with groundwater. Finally, the potential contamination pathways are discussed. It is highly unlikely fracturing flowback fluid contaminates groundwater and soil through upward migration, whereas leakage is a more prevalent pollution pathway.

Abstract:
Spills of hydraulic fracturing (HF) fluids and of produced water during unconventional gas extraction operations may cause soil contamination. We studied the degradation and microbial toxicity of selected HF chemical components including two biocides (methylisothiozolinone- MIT, chloromethylisothiozolinone- CMIT), a gel-breaker aid (triethanolamine -TEA), and three geogenic chemicals (phenol, m-cresol and p-cresol) in ultrapure water, HF fluid and produced water in five different soil types (surface and subsurface soils). The degradation of the two biocides (in soils treated with HF fluid or ultrapure water) and of the three geogenic chemicals (in soils treated with produced water) was rapid (in all cases DT50 values < 2 days in surface soils). In contrast, the loss of TEA was much slower in soils, especially in those treated with HF fluid (DT50 > 30 days). Sorption coefficients (Koc in L/Kg) in these soils ranged from 71 to 733 for TEA, 64–408 for MIT and 11–72 for CMIT. In terms of soil microbial toxicity, exposure to HF fluid and produced water reduced microbial respiration, albeit temporarily. The overall microbial activities in surface soils contaminated with produced water had fully recovered in most soils. In contrast, the HF fluid addition to soils completely inhibited the nitrification in all soils, with little recovery over the 60 day experimental period. In the case of produced water exposure, three out of five surface soils showed complete recovery in nitrification during the study period. The functional genes for nitrogen fixation (nifH) and carbon cycling (GA1) and microbial community composition (16 S rRNA) were significantly affected by HF fluid in some soils. Overall, the study shows that the HF fluid can have significant detrimental impact on soil microbial functions, especially on nitrogen cycling. More work is needed to identify the exact cause of microbial toxicity in soils contaminated with HF fluid.

Abstract:
Production of high volumes of flowback and produced water (FPW) from hydraulic fracturing (HF) is among the environmental concerns associated with hydrocarbon recovery from unconventional low-permeability formations. FPW management costs are a key factor for oil and gas companies in deciding the fate of FPW (treatment, disposal, recycling, and reuse). In this study, a comprehensive library of more than 20,000 oil and gas wells in the Montney Formation, Canada, is created to compare the FPW management costs from conventional and hydraulically fractured wells. The results indicate that for oil wells, both conventional and HF wells have similar volumetric oil–water ratios during the first two years of production. Since HF wells in the study region produce higher volumes of oil, on average, than conventional wells, the gross revenue from a typical HF oil well is higher than a typical conventional oil well. However, over the course of two years of production, conventional gas wells have higher volumetric gas–water ratios than HF gas wells. Estimation of the gross revenue for gas wells is sensitive to the average natural gas price and FPW management costs as HF wells typically generate more natural gas and FPW than conventional wells. Due to the fluctuating nature of oil and gas prices, we have created master curves for revenue (i.e., produced hydrocarbon value) and FPW management costs. The master curves cover oil and gas price ranges of $10–100/bbl and $0.5–5/MMBtu, respectively. Furthermore, since the FPW management costs may vary depending on the implemented technology or local labor costs, the master curves encompass a FPW management cost range of $5–100/m3. The provided master curves introduce a basis for the rapid analysis of FPW management costs of oil and gas wells, and can be incorporated with other well operational costs (such as drilling and completions, water withdraw permit, and well maintenance) for detailed evaluation of the profitability of hydrocarbon recovery processes.

Abstract:
Oil and gas production necessitates substantial use of water. Inspired by the water footprint theory, in this study, we proposed a novel factor to measure unconventional water use in various processing and production activities. The proposed factor was used to establish a method for evaluating the water footprint in oil and gas production. Through analyzing water use characteristics in oil and gas exploration, construction, production, and operation in China, it was found that the direct blue and grey water footprints of oil and gas production in 2018 were 3.08 and 6.64 m3/toe, respectively. Technological innovation and increased use of unconventional water reduced the blue water footprint. The unconventional water use factor was 4.61 m3/toe in 2018. Because of the growth of natural gas, especially unconventional production, China is predicted to require 1.42 billion m3 of water for oil and gas production in 2030, marking a 43% increase.

Abstract:
Substantial quantities of produced water generated during the extraction of oil and gas from unconventional reservoirs present significant environmental concern and increase the operating cost for this industry. Membrane Distillation (MD) can serve as a potential solution for beneficial reuse of produced water by generating high-quality permeate and reducing the volume of produced water requiring disposal. This study investigated treatment of produced water from Permian Basin in both laboratory and pilot-scale studies. Laboratory tests revealed the potential to successfully recover 50% of produced water although some increase in permeate conductivity was observed due to the passage of ammonia from the feed side. Initial pilot-scale test with filtration of raw produced water as the only pre-treatment step led to precipitation of SrSO4, NaCl, and Fe in the system once the solubility limits for these salts were exceeded. However, chemical pretreatment that included pH adjustment, aeration, and barite precipitation, allowed successful steady-state operation of the AGMD pilot system for 5 days where the produced water was concentrated from 127 g/L to 255 g/L (~50% water recovery) while recovering high quality permeate. Overall, greater than 99.7 % salt rejection was achieved with the average permeate flux of 1.86 LMH. Mass balance analysis suggested potential Ba and Ca precipitation in the system but there was no impact on AGMD performance and permeate quality during 5 days of continuous operation in the field.

Abstract:
Unconventional natural gas development (fracking) has been a rapidly expanding technique used for the extraction of natural gas from the Marcellus Shale formation in Pennsylvania. There remains a knowledge gap regarding the ecological impacts of fracking, especially regarding the long-term health of native Brook trout (Salvelinus fontinalis) populations. During the summer of 2015, Brook trout were sampled from twelve streams located in forested, northwestern Pennsylvania in order to evaluate the impacts of fracking on Brook trout. Four stream sites were undisturbed (no fracking activity), three had a developed well pad without fracking activity, and five had active fracking with natural gas production. Liver tissue was isolated from two to five fish per stream and underwent RNA-Seq analysis to identify differentially expressed genes between ecosystems with differing fracking status. Data were analyzed individually and with samples pooled within-stream to account for hierarchical data structure and variation in sample coverage within streams. Differentially expressed and differentially alternatively spliced genes had functions related to lipid and steroid metabolism, mRNA processing, RNA polymerase and protein regulation. Unique to our study, genes related to xenobiotic and stress responses were found as well as potential markers for endocrine disruption and saline adaptation that were identified in watersheds with active fracking activity. These results support the utility of RNA-Seq to assess trout health and suggest detrimental impacts of fracking on sensitive trout populations.

Abstract:
The data in this report are associated with “Characterization of Produced Water and Surrounding Surface Water in the Permian Basin, the United States” (Jiang et al. 2022) and include raw data on produced water (PW) quality and Pecos River water quality in the Permian Basin, which is one of the major oil and gas producing areas in the U.S. The data include 46 samples for PW and 10 samples for Pecos River water. The data include wet chemistry, mineral salts, metals, oil and grease, volatile and semi-volatile organic compounds, radionuclides, ammonia, hydraulic fracturing additives, and per- and polyfluoroalkyl substances. The PW samples were collected from five different locations in the Permian Basin. Twenty-four of the PW samples and the ten Pecos River samples were analyzed by the authors. The information for the rest of PW samples (22 samples) was provided by industrial collaborators in the Permian Basin. Statistical analyses were performed on the combined data to obtain Mean, Max, Min, 25th percentile, 50th percentile, and 75th percentile of each analyte.

Abstract:
Unconventional oil and gas development (UOGD) sometimes impacts water resources, including incidents of methane (CH4) migration from compromised wells and spills that degrade water with salts, organics, and metals. We hypothesized that contamination may be more common where UOGD overlaps with legacy coal, oil, and gas extraction. We tested this hypothesis on ∼7000 groundwater analyses from the largest U.S. shale gas play (Marcellus), using data mining techniques to explore UOGD contamination frequency. Corroborating the hypothesis, we discovered small, statistically significant regional correlations between groundwater chloride concentrations ([Cl]) and UOGD proximity and density where legacy extraction was extremely dense (southwestern Pennsylvania (SWPA)) but no such correlations where it was minimal (northeastern Pennsylvania). On the other hand, legacy extraction of shallow gas in SWPA may have lessened today’s gas leakage, as no regional correlation was detected for [CH4] in SWPA. We identify hotspots where [Cl] and [CH4] increase by 3.6 and 3.0 mg/L, respectively, per UOG well drilled in SWPA. If the [Cl] correlations document contamination via brines leaked from wellbores, impoundments, or spills, we calculate that thallium concentrations could exceed EPA limits in the most densely developed hotspots, thus posing a potential human health risk.

Abstract:
Shale gas wastewater (SGW) has great potential for the recovery of valuable elements, but it also poses risks in terms of environmental pollution, with heavy metals and naturally occurring radioactive materials (NORM) being of major concerns. However, many of these species have not been fully determined. For the first time, we identify the elements present in SGW from the Sichuan Basin and consequently draw a comprehensive periodic table, including 71 elements in 15 IUPAC groups. Based on it, we analyze the elements possessing recycling opportunities or with risk potentials. Most of the metal elements in SGW exist at very low concentrations (< 0.2 mg/L), including rare earth elements, revealing poor economic feasibility for recovery. However, salts, strontium (Sr), lithium (Li), and gallium (Ga) are in higher concentrations and have impressive market demands, hence great potential to be recovered. As for environmental burdens related to raw SGW management, salinity, F, Cl, Br, NO3−, Ba, B, and Fe, Cu, As, Mn, V, and Mo pose relatively higher threats in view of the concentrations and toxicity. The radioactivity is also much higher than the safety range, with the gross α activity and gross β activity in SGW ranging from 3.71–83.4 Bq/L, and 1.62–18.7 Bq/L, respectively and radium-226 as the main component. The advanced combined process “pretreatment-disk tube reverse osmosis (DTRO)” with pilot-scale is evaluated for the safe reuse of SGW. This process has high efficiency in the removal of metals and total radioactivity. However, the gross α activity of the effluent (1.3 Bq/L) is slightly higher than the standard for discharge (1 Bq/L), which is thus associated with potential long-term environmental hazards.

Abstract:
Unconventional energy extraction has been accompanied by a faster increase in aggregate wastewater generation compared with conventional practice. Understanding the extent to which it is due to technologies, energy production, or geological characteristics has implications for reducing the associated environmental risks. We analyze how wastewater generation patterns differ between unconventional wells and conventional wells, accounting for differences in well configurations and local geology. Using the 2008–2016 monthly production data from 50,039 wells, we show that unconventional wells generated more wastewater in the first 12 months of production but less cumulative discharge than conventional wells. Unconventional oil wells had a lower wastewater-to-energy ratio throughout their lifetime than their conventional counterparts, whereas no efficiency gap existed among gas wells. We find both an increasing initial discharge gap and growing efficiency gains between unconventional wells and conventional wells starting production in more recent years, likely due to increased penetration and persistent improvements of unconventional technologies over time. Our findings call for targeted strategies to balance the short-term disposal burden and the long-term efficiency gains of unconventional energy extraction.

Abstract:
This study focuses on rock-fluid interaction during hydraulic fracturing in shale gas reservoir. Hydraulic fracturing is a well stimulation technique used to create fracture network in reservoirs by connecting the main planar hydraulic fracture with the pre-existing natural fracture. Hydraulic fracturing fluid additives such as surfactants are added into the hydraulic fracturing fluid system to enhance oil and gas productivity by assisting fluid recovery after fracturing. The main objective of this study is to evaluate the effectiveness and formation damage parameters of the proposed novel green surfactant as hydraulic fracturing fluid additive where commercial-chemical based surfactant was studied for comparison purpose. The green surfactant used was D-limonene whereas Sodium Alpha Olefin Sulfonate (AOS) was used as commercial-chemical based surfactant. Thermogravimetric analysis (TGA) was done to ensure the D-limonene can withstand the high reservoir temperature in which the D-limonene had inflection point and onset temperature of 410 °C and 380 °C respectively. Soaking test was then conducted where the shale samples were soaked in hydraulic fracturing fluid for seven days. The outcome of the soaking test was then studied in Scanning Electron Microscopy (SEM) and wettability analysis. The SEM test showed that the average pore size of the soaked shale samples were similar to the original shale sample which indicated minimal to no formation damage caused by the hydraulic fracturing fluid. Besides that, the contact angle test resulted in the distilled water and D-limonene forming a contact angle of 90° and 0° respectively on the shale samples. The AOS formed contact angles between 65° and 75° for the tested concentrations. From the results, the shale sample was found to be oil wet and showed a high affinity towards the D-limonene followed by AOS and distilled water. Higher affinity of the surfactants promoted the desorption of the hydraulic fracturing fluid from the shale surface.

Abstract:
Environmental concerns with unconventional oil and gas development are frequently centered on elevated water usage and the induction of seismic events during waste disposal. Reuse of produced water for subsequent production well stimulation can effectively address these concerns, but the variability among such samples must be well understood. Twenty-four samples of wastewater from unconventional oil and gas development were collected from south and west Texas to assess their variability and feasibility for direct reuse. Bulk metrics were collected, including total organic carbon, total nitrogen, as well as total dissolved and suspended solids. The profiles of pertinent inorganic constituents were also evaluated. Variations were not only seen between regions but also among samples collected from the same region. For example, the average total organic carbon for Eagle Ford samples collected was 700 ± 500 mg/L, while samples collected from the Per-mian Basin featured an average total organic carbon concentration of 600 ± 900 mg/L. The Permian Basin total organic carbon ranged from 38 to 2600 mg/L. The total dissolved solids levels had the same variability between regions, with an average value for Eagle Ford of 20,000 ± 10,000 mg/L and a Permian Basin value of 150,000 ± 40,000 mg/L. However, samples were more reproducible within a given region. Collectively, the data indicate that the direct reuse of raw produced water for subsequent production well development without treatment is not feasible based on the reported reuse thresholds. Unconventional development wastewater samples from the Permian Basin were also compared to produced water values from conventional oil and gas wells in the same region, as reported by the United States Geological Survey. Samples collected in the Permian Basin consistently demonstrated lower ionic strength compared to conventional produced water data.

Abstract:
Although shale gas has shown promising potential to alleviate energy crisis as a clean energy resource, more attention has been paid to the harmful environmental impacts during exploitation. It is a critical issue for the management of shale gas wastewater (SGW), especially the organic compounds. This review focuses on analytical methods and corresponding treatment technologies targeting organic matters in SGW. Firstly, detailed information about specific shale-derived organics and related organic compounds in SGW were overviewed. Secondly, the state-of-the art analytical methods for detecting organics in SGW were summarized. The gas chromatography paired with mass spectrometry was the most commonly used technique. Thirdly, relevant treatment technologies for SGW organic matters were systematically explored. Forward osmosis and membrane distillation ranked the top two most frequently used treatment processes. Moreover, quantitative analyses on the removal of general and single organic compounds by treatment technologies were conducted. Finally, challenges for the analytical methods and treatment technologies of organic matters in SGW were addressed. The lack of effective trace organic detection techniques and high cost of treatment technologies are the urgent problems to be solved. Advances in the extraction, detection, identification and disposal of trace organic matters are critical to address the issues.

Abstract:
Ground-level ozone adversely affects human health and ecosystems. The effectiveness of control programs depends on which precursor(s) are controlled, by how much, and where and when emission reductions occur. We use the adjoint of the Community Multiscale Air Quality model to investigate odd oxygen (Ox ≡ O3 + NO2) sensitivities in California’s San Joaquin Valley (SJV) to precursor emissions from local and upwind sources. Sensitivities are mapped and disaggregated by hour and day. Taken together, impacts of precursor emissions in the San Francisco Bay area and Sacramento Valley are similar in magnitude to impacts of local SJV emissions. Same-day emission sensitivities are mostly attributable to local sources, with the most influential anthropogenic emissions of VOCs (volatile organic compounds) and NOx (nitrogen oxides) occurring in the morning (9–11 am) and early afternoon hours (1–3 pm), respectively. For the northernmost SJV receptor, the influence from Sacramento Valley emissions peaks 5–6 h later than Bay area emissions; this difference diminishes for SJV receptors located further downwind. Results show a shift toward more NOx-sensitive conditions in the afternoon with all but the southernmost receptor shifting from VOC- to NOx-sensitive conditions. We also evaluate opportunities to control pollution through shifts in precursor emission location and timing.

Abstract:
Water, water, everywhere, Nor any drop to drink!—The Rime of the Ancient Mariner, Samuel Taylor ColeridgeThis study shows that Wolfcamp-produced waters in the Permian Delaware Basin are predominantly in situ Wolfcamp shale formation water with δ18O ∼6.5 ± 0.5‰ (standard mean ocean water) and a salinity as low as 20,000 ppm, consistent with illite-water equilibrium at peak burial conditions.Produced waters in the Delaware Basin have highly radiogenic 87/86Sr ratios of ∼0.7085–0.7095 believed to be sourced from evaporative brines in the Salado salts and overlying shallow Ochoan evaporites. Despite Wolfcamp-produced waters in the Midland Basin routinely having total dissolved solids of up to ∼250,000 ppm, which is double that in the Delaware Basin, chloride-bromide systematics of produced waters show that only minimal halite dissolution was involved in both basins.High-salinity produced waters in the Bone Spring Formation and the upper Wolfcamp formation from the Delaware Basin (∼50,000–125,000 ppm) are mixtures of Wolfcamp formation water and Ochoan evaporative brines that have mixed with local meteoric water. These brines infiltrated deep into the Delaware Basin during uplift of the western edge of the Delaware Basin via permeable Guadalupian and Leonardian sandstone and siltstones.Due to the high illite content in the Wolfcamp shale, the shale-siltstone interface likely behaved as a clay membrane. Salinity differences of up to approximately 100,000 ppm across this interface created potential gradients in ion and water activity (aw), producing an osmotic pressure gradient.Ion diffusion into the shales results in the flow of water out of the shales (high aw) into high-salinity siltstones (low aw). The coupled osmosis–diffusion model predicts high absolute osmotic pressures of up to ∼1680 psi and cocurrent flow of oil and water out of the shale. However, the flow of water out of the shale into adjacent siltstone faces an opposing osmotic pressure. This may explain the high fluid pressures encountered in the Wolfcamp shale and why oil production in the Delaware Basin produces so much water.

Abstract:
Wastewater generated during petroleum extraction (produced water) may contain high concentrations of dissolved organics due to their intimate association with organic-rich source rocks, expelled petroleum, and organic additives to fluids used for hydraulic fracturing of unconventional (e.g., shale) reservoirs. Dissolved organic matter (DOM) within produced water represents a challenge for treatment prior to beneficial reuse. High salinities characteristic of produced water, often 10× greater than seawater, coupled to the complex DOM ensemble create analytical obstacles with typical methods. Excitation-emission matrix spectroscopy (EEMS) can rapidly characterize the fluorescent component of DOM with little impact from matrix effects. We applied EEMS to evaluate DOM composition in 18 produced water samples from six North American unconventional petroleum plays. Represented reservoirs include the Eagle Ford Shale (Gulf Coast Basin), Wolfcamp/Cline Shales (Permian Basin), Marcellus Shale and Utica/Point Pleasant (Appalachian Basin), Niobrara Chalk (Denver-Julesburg Basin), and the Bakken Formation (Williston Basin). Results indicate that the relative chromophoric DOM composition in unconventional produced water may distinguish different lithologies, thermal maturity of resource types (e.g., heavy oil vs. dry gas), and fracturing fluid compositions, but is generally insensitive to salinity and DOM concentration. These results are discussed with perspective toward DOM influence on geochemical processes and the potential for targeted organic compound treatment for the reuse of produced water.

Abstract:
The expansion of oil and gas extraction from unconventional reservoirs has led to an increase in the amount of produced water that has to be managed by this industry. Direct contact membrane distillation (DCMD) is a promising technology for treatment of produced water to enable water recovery and reduce the environmental footprint of this industry. The feasibility of DCMD for the treatment of highly saline produced water from the Permian Basin in TX with commercially available polyethylene and polytetrafluoroethylene membranes was evaluated in this study. An increase in water recovery by a DCMD system operated in the batch (concentrating) mode led to an increase in permeate conductivity. Partial removal of organic compounds from the produced water by biodegradation, chemical oxidation, and/or activated carbon adsorption could not resolve deterioration in permeate quality, and none of the organics observed in the permeate contributed to its conductivity. The observed increase in permeate conductivity was attributed to the passage of ammonia vapor from the feed side followed by protonation on the permeate side. This study revealed that permeate conductivity may not always be a reliable indicator of membrane wetting and underscores the importance of understanding the interactions between specific solutes and membrane materials.

Abstract:
Demographers have applied various sociological and economic theories of fertility in attempts to clarify the dynamics of adolescent fertility, particularly its sharp decline in the United States over the last 20 years. Using the restricted detailed natality file from the National Center for Health Statistics, I analyze the impact of the oil and gas hydraulic fracturing boom in North Dakota and Montana on adolescent female fertility rates, testing pro-cyclical, mating market, and adult formation theories of adolescent fertility. Restricted difference-in-differences models demonstrate a positive and significant association between the oil boom and increased births in adolescent women aged 15–19, but more fully specified models demonstrate changing economic and social conditions appear to be driving the effect. Leveraging the exogenous shock of a bust in oil prices, a comparative interrupted time-series regression demonstrates a sizeable year-over-year decrease in adolescent female fertility for the shale region. Fertility rate changes in this age group do not appear attributable to changing racial or ethnic composition of oil-producing counties. Instead, increases in adolescent female fertility are largely driven by increasing births among white teens. The proximate mechanism driving this effect is the increasing employed share of young men aged 14–24, lending support to a substrand of adult formation and mating market explanations of adolescent female fertility.

Abstract:
A thorough understanding of produced water (PW) quality is critical to advance the knowledge and tools for effective PW management, treatment, risk assessment, and feasibility for beneficial reuse outside the oil and gas industry. This study provides the first step to better understand PW quality to develop beneficial reuse programs that are protective of human health and the environment. In total, 46 PW samples from unconventional operations in the Permian Basin and ten surface water samples from the Pecos River in New Mexico were collected for quantitative target analyses of more than 300 constituents. Water quality analyses of Pecos River samples could provide context and baseline information for the potential discharge and reuse of treated PW in this area. Temporal PW and river water quality changes were monitored for eight months in 2020. PW samples had total dissolved solids (TDS) concentrations ranging from 100,800–201,500 mg/L. Various mineral salts, metals, oil and grease, volatile and semi-volatile organic compounds, radionuclides, ammonia, hydraulic fracturing additives, and per- and polyfluoroalkyl substances were detected at different concentrations. Chemical characterization of organic compounds found in Pecos River water showed no evidence of PW origin. Isometric log-ratio Na-Cl-Br analysis showed the salinity in the Pecos River samples appeared to be linked to an increase in natural shallow brine inputs. This study outlines baseline analytical information to advance PW research by describing PW and surrounding surface water quality in the Permian Basin that will assist in determining management strategies, treatment methods, potential beneficial reuse applications, and potential environmental impacts specific to intended beneficial use of treated PW.

Abstract:
Uncertainty is an undeniable aspect of underground operations, such as wellbore stimulation treatments, where combined rock and fluid interaction add a layer of complexity to the uncertainty. There are social and environmental concerns about the probable outcome of operations like hydraulic fracturing. Hydraulic fracturing treatments may affect the integrity of sub-surface geological strata or might initiate unexpected potential risks to the environment when the created fracture extends beyond its engineered design. Therefore, it is necessary to investigate a range of possible scenarios by which the fracture may experience a deviation from its planned behaviour. In this study, we model the uncertainty associated with hydraulic fracturing using fracture growth simulation. The uncertainty of a range of treatment parameters, such as pumping flow rate, injection duration and mechanical properties of the underground geological layer, is investigated. Monte Carlo simulation is used to examine different probable fracturing scenarios and numerous fracturing simulations with numerical and analytical models. The probability analysis is performed in a case study to identify the cumulative distribution functions (CDFs) of fracture growth. The emerging least, median and most likely situations of fracture growth are analysed to evaluate the fracturing uncertainty. Our results indicate that the numerical modelling approach may predict a more extensive fracture growth in the vertical plane. The numerical model may suggest a more conservative way to address environmental concerns. The resulting cumulative distribution of probabilities suggests the CDFs of the analytical model as the lower band for fracture length, whereas the numerical CDFs presents the upper band.

Abstract:
Epidemiologic studies have observed elevated health risks in populations living near unconventional oil and gas development (UOGD). In this narrative review, we discuss strengths and limitations of UOG exposure assessment approaches used in or available for epidemiologic studies, emphasizing studies of children’s health outcomes.

Abstract:
Recent studies confirm that the distribution of injection‐induced earthquakes (IIE) can be related to both natural (e.g., tectonic, geological, and hydrological) settings and operational details. However, the relative importance of operational factors with respect to the natural ones has not been fully understood for the western Canada sedimentary basin. In this study, we train the eXtreme Gradient Boosting (XGBoost) machine‐learning algorithm to comprehensively evaluate six geological and seven industrial operational factors suspected to be correlated with the distribution of IIE in the northern Montney play (NMP), British Columbia. We then derive the Shapley Additive Explanations values to quantitatively interpret the outputs from XGBoost. Our results reveal that operational and geological factors have comparable contributions to the IIE distribution. The top four features that contribute most to the seismicity pattern are horizontal distance to the Cordilleran deformation front, cumulative injected volume, shut‐in pressure and vertical distance to the Debolt formation (with respect to the hydraulic fracturing [HF] depth). Features with secondary influence are the thickness of the Montney formation, breakdown pressure, cumulative fault length per unit area, and vertical distance to the basement (with respect to the HF depth). Other remaining features (e.g., the average treating pressure and injection rate) appear the least related. Our results provide critical information to establishing a comprehensive susceptibility model that includes key geological and operational factors affecting the IIE distribution in the NMP area.

Abstract:
Belmont County, Ohio is heavily dominated by unconventional oil and gas development that results in high levels of ambient air pollution. Residents here chose to work with a national volunteer network to develop a method of participatory science to answer questions about the association between impact on the health of their community and pollution exposure from the many industrial point sources in the county and surrounding area and river valley. After first directing their questions to the government agencies responsible for permitting and protecting public health, residents noted the lack of detailed data and understanding of the impact of these industries. These residents and environmental advocates are using the resulting science to open a dialogue with the EPA in hopes to ultimately collaboratively develop air quality standards that better protect public health. Results from comparing measurements from a citizen-led participatory low-cost, high-density air pollution sensor network of 35 particulate matter and 25 volatile organic compound sensors against regulatory monitors show low correlations (consistently R2 < 0.55). This network analysis combined with complementary models of emission plumes are revealing the inadequacy of the sparse regulatory air pollution monitoring network in the area, and opening many avenues for public health officials to further verify people’s experiences and act in the interest of residents’ health with enforcement and informed permitting practices. Further, the collaborative best practices developed by this study serve as a launchpad for other community science efforts looking to monitor local air quality in response to industrial growth.

Abstract:
Eighty percent of US oil and natural gas (O&G) production sites are low production well sites, with average site-level production ≤15 barrels of oil equivalent per day and producing only 6% of the nation’s O&G output in 2019. Here, we integrate national site-level O&G production data and previously reported site-level CH4 measurement data (n = 240) and find that low production well sites are a disproportionately large source of US O&G well site CH4 emissions, emitting more than 4 (95% confidence interval: 3—6) teragrams, 50% more than the total CH4 emissions from the Permian Basin, one of the world’s largest O&G producing regions. We estimate low production well sites represent roughly half (37—75%) of all O&G well site CH4 emissions, and a production-normalized CH4 loss rate of more than 10%—a factor of 6—12 times higher than the mean CH4 loss rate of 1.5% for all O&G well sites in the US. Our work suggests that achieving significant reductions in O&G CH4 emissions will require mitigation of emissions from low production well sites.

Abstract:
We sampled headwater streams to characterize impacts of unconventional shale gas development (SGD) on aquatic ecosystems. The study area was relatively un-impacted by confounding activities. Intensity of SGD over the study decreased then increased again but not to levels seen the first year. Shale gas development was associated with increased, but non-impaired, water pH and specific conductance during the latter part of the study. Metrics summarizing macroinvertebrate assemblages were better on average in un-impacted reaches. A genus-level multimetric index of biotic integrity was statistically lower downstream of impacts compared to upstream, but only in the year when SGD activity was most intense. Multivariate analyses indicated that assemblages diverged in similarity downstream compared to upstream of impacts in the first and last years of the study when SGD activity was elevated. Assemblage divergence was related to variation in water quality. Indicator species analysis linked a few key taxa to un-impacted conditions in the first year of the study; tolerant taxa were indicators for impacted conditions later in the study. Our study links SGD to weak negative changes in water quality and benthic macroinvertebrates, which may have negative consequences to food quality for wildlife that rely on aquatic prey within forested systems.

Abstract:
The presence of active or inactive (i.e., postproduction) oil and gas wells in neighborhoods may contribute to ongoing pollution. Racially discriminatory neighborhood security maps developed by the Home-Owners Loan Corporation (HOLC) in the 1930s may contribute to environmental exposure disparities.

Abstract:
The COVID-19 epidemic had unprecedented impacts on oil and gas markets. Vanishing energy demand in this sector led to significant drop of oil and gas prices over a short period of time. Some operators choose to curtail their production at particular wells, while others did not. In this paper, we look at two examples one from an unconventional gas play and the other from an unconventional oil play in the United States. Through public productions data, we tried to decipher the decision process of operators in these areas and compare the differences in shut-in choices.

Abstract:
Understanding emissions of methane from legacy and ongoing shale gas development requires both regional studies that assess the frequency of emissions and case studies that assess causation. We present the first direct measurements of emissions in a case study of a putatively leaking gas well in the largest shale gas play in the United States. We quantify atmospheric methane emissions in farmland >2 km from the nearest shale gas well cited for casing and cementing issues. We find that emissions are highly heterogeneous as they travel long distances in the subsurface. Emissions were measured near observed patches of dead vegetation and methane bubbling from a stream. An eddy covariance flux tower, chamber flux measurements, and a survey of enhancements of the near-surface methane mole fraction were used to quantify emissions and evaluate the spatial and temporal variability. We combined eddy covariance measurements with the survey of the methane mole fraction to estimate total emissions over the study area (2,800 m2). Estimated at ∼6 kg CH4 day–1, emissions were spatially heterogeneous but showed no temporal trends over 6 months. The isotopic signature of the atmospheric CH4 source (δ13CH4) was equal to −29‰, consistent with methane of thermogenic origin and similar to the isotopic signature of the gas reported from the nearest shale gas well. While the magnitude of emissions from the potential leak is modest compared to large emitters identified among shale gas production sites, it is large compared to estimates of emissions from single abandoned wells. Since other areas of emissions have been identified close to this putatively leaking well, our estimate of emissions likely represents only a portion of total emissions from this event. More comprehensive quantification will require more extensive spatial and temporal sampling of the locations of gas migration to the surface as well as an investigation into the mechanisms of subsurface gas migration. This work highlights an example of atmospheric methane emissions from potential stray gas migration at a location far from a well pad, and further research should explore the frequency and mechanisms behind these types of events to inform careful and strategic natural gas development.

Abstract:
The association between hydraulic fracturing and human development is not well understood. Several studies have identified significant associations between unconventional natural gas development and adverse birth outcomes; however, geology and legislation vary between regions.To examine the overall association between residential proximity to hydraulic fracturing sites and adverse birth outcomes, and investigate whether well density influenced this association.This population-based retrospective cohort study of pregnant individuals in rural Alberta, Canada, took place from 2013 to 2018. Participants included reproductive-aged individuals (18-50 years) who had a pregnancy from January 1, 2013, to December 31, 2018, and lived in rural areas. Individuals were excluded if they lived in an urban setting, were outside of the age range, or were missing data on infant sex, postal code, or area-level socioeconomic status.Oil and gas wells that underwent hydraulic fracturing between 2013 to 2018 were identified through the Alberta Energy Regulator (n = 4871). Individuals were considered exposed if their postal delivery point was located within 10 km of 1 or more wells that was hydraulically fractured during 1 year preconception or during pregnancy.Outcomes investigated were spontaneous and indicated preterm birth, small for gestational age, major congenital anomalies, and severe neonatal morbidity or mortality.After exclusions, the sample included 26 193 individuals with 34 873 unique pregnancies, and a mean (SD) parental age of 28.2 (5.2) years. Small for gestational age and major congenital anomalies were significantly higher for individuals who lived within 10 km of at least 1 hydraulically fractured well after adjusting for parental age at delivery, multiple births, fetal sex, obstetric comorbidities, and area-level socioeconomic status. Risk of spontaneous preterm birth and small for gestational age were significantly increased in those with 100 or more wells within 10 km.Results suggest that individuals who were exposed to hydraulic fracturing within pregnancy may be at higher risk of several adverse birth outcomes. These results may be relevant to health policy regarding legislation of unconventional oil and gas development in Canada and internationally.

Abstract:
Natural gas production from the Appalachian region has reached record levels, primarily due to the rapid increase in development of unconventional oil and gas (UOG) resources. In 2020, over 65,000 conventional wells reported natural gas production; however, this only represented 5% of the total natural gas produced. The remaining 95% of natural gas production can be attributed to 3,901 UOG wells. There has been a wide body of research on disturbance trends related to unconventional development in the region; however, there is limited characterization of disturbance related to production of conventional oil and gas (COG) or research that details energy production in relation to land disturbance. This study compares land disturbance from COG and UOG development as well as energy production. Land disturbance related to COG and UOG development was assessed for wells drilled during 2009–2012. Production data were summarized for the same wells during the period of 2009–2020. The average area disturbed for COG pads was 0.82 ha while UOG pads disturbed 4.02 ha. Results from this study showed that COG wells disturbed significantly less land area during construction; however, UOG wells produced almost 28 times more energy per hectare of land disturbed. This energy production imbalance as well as the over 65,000 COG wells reporting production in 2020, indicates that the retirement and restoration of COG infrastructure could be done without significantly impacting total energy production. Continued research that includes ecosystem services and carbon sequestration opportunities in relation to production losses from retiring existing infrastructure should be considered.

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Upstream oil and gas systems are negatively impacted by microbial activities that produce hydrogen sulfide gas, enhance corrosion rates of metals, and cause costly damage to infrastructure through biofouling. Although alternatives to biocides such as sulfate removal membranes and corrosion resistant coatings and materials have been developed, biocides and inhibitors still provide the main defense against microbial activity. However, the environmental and economic challenges of employing biocides necessitate oil and gas industries devise better strategies for their use and application. Since oil and gas environments represent physically controlled environments with highly stressed microbial communities experiencing episodes of intermittent slow growth and dormancy, one such strategy can take advantage of environmental stressors (e.g., salinity, starvation, oxygen) to enhance biocide efficacy. Although it is generally thought environmental stressors recruit determinants of resistance in bacteria, there are instances where stress decreases the energy or metabolic state of a cell increasing its susceptibility to some biocides. This review examines stressors in oil and gas environments and provides examples where stress can both increase and decrease biocidal susceptibility. By describing how these stressors and biocides impact metabolic activity as well as affect regulation of genes involved in energy production and conversion, this knowledge can be used to develop new strategies that take advantage of vulnerabilities in bacteria to improve biocide efficacy and reduce environmental threats and operator costs.

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The demand for natural gas has led to the development of techniques used to access unconventional oil and natural gas (UOG) resources, due to the novelty of UOG, the potential impacts to freshwater ecosystems are not fully understood. We used a dual pronged approach to study the effects of UOG development on microbial biodiversity and function via a laboratory microcosm experiment and a survey study of streams with and without UOG development within their watersheds. The microcosm experiment simulated stream contamination with produced water, a byproduct of UOG operations, using sediment collected from one high water-quality stream and two low water-quality streams. For the survey study, biofilm and sediment samples were collected from streams experiencing varying levels of UOG development. In the microcosm experiment, produced water decreased microbial aerobic and anaerobic CO2 production in the high water-quality stream sediment but had a positive effect on this microbial activity in the lower water-quality stream sediments, suggesting habitat degradation alters the response of microbes to contaminants. Results from the stream survey indicate UOG development alters stream water temperature, chemistry, sediment aerobic and anaerobic CO2 production, and microbial community biodiversity in both sediments and biofilms. Correlations among UOG associated land use, environmental, and microbial variables suggest increases in light availability and sediment delivery to streams, due to deforestation and land disturbance, impact stream microbial communities and their function. Consistent changes in the relative abundance of bacterial taxa suggest microorganisms may be good indicators of the environmental changes associated with UOG development. The observed impacts of UOG development on microbial community composition and carbon cycling could have cascading effects on stream health and broader ecosystem function.

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Since the early 2000s, unconventional natural gas development (UNGD) has rapidly grown throughout Pennsylvania. UNGD extracts natural gas using a relatively new method known as hydraulic fracturing (HF). Here we addressed the association of HF with asthma Hospitalization Admission Rates (HAR) using publicly available data. Using public county-level data from the Pennsylvania Department of Health (PA-DOH) and the Pennsylvania Department of Environmental Protection for the years 2001–2014, we constructed regression models to study the previously observed association between asthma exacerbation and HF. After considering multicollinearity, county-level demographics and area-level covariables were included to account for known asthma risk factors. We found a significant positive association between the asthma HAR and annual well density for all the counties in the state (3% increase in HAR attributable to HF, p<0.001). For a sensitivity analysis, we excluded urban counties (urban counties have higher asthma exacerbations) and focused on rural counties for the years 2005–2014 and found a significant association (3.31% increase in HAR attributable to HF in rural counties, p<0.001). An even stronger association was found between asthma hospitalization admission rates (HAR) and PM2.5 levels (7.52% increase in HAR attributable to PM2.5, p<0.001). As expected, asthma HAR was significantly higher in urban compared to rural counties and showed a significant racial disparity. We conclude that publicly available data at the county-level supports an association between an increase in asthma HAR and UNGD in rural counties in Pennsylvania.

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With growing evidence of widespread health and environmental impacts from oil and gas activity, localities and states are beginning to develop protective measures. Interdisciplinary approaches that integrate across human, wildlife, domesticated animal, and land health are likely to provide more just and comprehensive solutions than would be possible with siloed approaches. However, this is not common practice, and there is little guidance on how to apply such a strategy. In the present article, we summarize the state of knowledge on the impacts of terrestrial unconventional oil and gas development from the fields of ecology and public health. We then discuss synergies and trade-offs regarding impacts and mitigation strategies emerging from these two literatures. Finally, we provide recommendations for research and practice to fill knowledge gaps and better inform integrated decision-making to achieve multiple benefits and minimize impacts on human, wildlife, domesticated animals, and land health from energy development.

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Hydraulic fracturing (HF) of shale and other permeable rock formations to extract gas and oil is a water-intensive process that returns a significant amount of flowback and produced water (FPW). Due to the complex chemical composition of HF fluids and FPW, this process has led to public concern on the impacts of FPW disposal, spillage and spreading to regional freshwater resources, in particular to shallow groundwater aquifers. To address this, a better understanding of the chemical composition of HF fluid and FPW is needed, as well as the environmental fate properties of the chemical constituents, such as their persistence, mobility and toxicity (PMT) properties. Such research would support risk-based management strategies for the protection of regional water quality, including both the phase-out of problematic chemicals and better hydraulic safeguards against FPW contamination. This article presents recent strategies to advance the assessment and analysis of HF and FPW associated organic chemicals.

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Due to the growing hydraulic fracturing (HF) practices in China, the environmental risks of pollutants in flowback and produced waters (FPW) and sludge in impoundments for FPW reserves have drawn increasing attention. In this context, we first characterized the comparative geochemical characteristics of the FPW and the sludge in impoundments that collected FPW from 75 shale gas wells, and then the risks associated with the pollutants were assessed. The results demonstrated that four organic compounds detected in the FPW, naphthalene, acenaphthene, dibutyl phthalate, and bis(2-ethylhexyl)phthalate, were potential threats to surface waters. The concentrations of trace metals (copper, cadmium, manganese, chromium, nickel, zinc, arsenic, and lead) in the FPW and sludge were low; however, those of iron, barium, and strontium were high. The accumulation of chromium, nickel, zinc, and lead in the sludge became more evident as the depth increased. The environmental risks from heavy metals in the one-year precipitated sludge were comparable to those reported in the environment. However, the radium equivalent activities were 10–41 times higher than the recommended value for human health safety, indicating potential radiation risks. Although hydrophobic organic compounds, such as high-molecular-weight polycyclic aromatic hydrocarbons (PAHs), phthalate esters (PAEs), benzene, ethylbenzene, toluene, and xylene (BTEX), tended to accumulate in the sludge, their environmental risks were within tolerable ranges after proper treatment. Multiple antibiotic resistance genes (ARGs), such as those for macrolide, lincosamide, streptogramin (MLS), tetracycline, and multidrug resistances, were detected in the shale gas wastewaters and sludge. Therefore, the environmental risks of these emerging pollutants upon being discharged or leaked into surface waters require further attention.

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Water scarcity has emerged as one of the most important global challenges of the twenty-first century. With rising demand for energy, and water being a critical input in energy production, the availability of water resources has put energy sustainable production under growing strain. While unconventional natural gas (especially shale gas) is seen as an important bridge for promoting the transition of energy system from high to low carbon, water availability is a significant constraint on the development of energy resources owing to the massive quantity of water used by the hydraulic fracturing. Against this background, our study aims to optimize the allocation of regionally scarce water resources for fostering integrated economic, social, and environmental growth in shale gas development plays. In light of the uncertainty inherent in the water supply management system for shale gas development, this work employed the Interval Two-stage Stochastic Programming (ITSP) to establish an optimal allocation model for water resources between wells jointly dispatched by surface water, underground water and reused water. The model predicted water scarcity, optimal water allocation, and the total benefit of the shale gas development water supply system under various scenarios. Furthermore, when compared to the Two-stage Stochastic Programming (TSP) model results, it was found that the ITSP model's interval value may present decision makers with more ideas and options than the TSP model. In addition, since the ITSP model is oblivious to the system risk issue, it incorporated robust optimization into the original ITSP model to build the Interval Two-stage Robust Stochastic Programming (ITRSP) model. Our findings were expressed as intervals that more accurately represent the actual optimal allocation of water resources, which also provided a broader decision-making space for decision makers in managing shale gas development water supply management schemes.

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To potentially mitigate further climate change, the US needs to move away from fossil fuels and towards carbon-free sources of energy. The issue of climate change is highly polarized, which has led to beliefs about climate change becoming entangled with political beliefs. Yet, public support for decreasing the use of fossil fuels and increasing renewable sources is high. In this paper, we use an original survey of about 1300 respondents to examine the potential for the entanglement of political beliefs, climate change beliefs, and energy preferences. We find that the majority of respondents support a decreased use of fossil fuels, a slight increase of nuclear energy, and a large increase of renewable sources; however, conservative Republicans prefer smaller decreases of fossil fuels and smaller increases in renewables. Additionally, we find that as respondents increasingly accept the scientific consensus on climate change, they support larger decreases in fossil fuels and larger increases in renewable energy. Finally, using mediation analysis we find that climate beliefs mediate the relationship between political beliefs and energy preferences for conservative Republicans and liberal Democrats, but not those with more moderate political beliefs. These findings point to the potential for energy preferences to become entangled in climate change as a result of elite discourse.

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Here, we report the draft genome sequence of three glutaraldehyde-resistant isolates from produced water from hydraulic fracturing operations. The three strains were identified as Marinobacter sp. strain G11, Halomonas sp. strain G15, and Bacillus sp. ...

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Brazil has the 10th largest shale gas reservoir, and the Paraná sedimentary basin has a potential area for shale gas production in the western portion of the São Paulo state. Despite that, the knowledge about the impacts of fracking on the local water resources is still limited. This study presents a novel reproducible method to compute the risk of water scarcity in areas with restricted or no shale gas development. Using geospatial numerical simulations under five scenarios from 500 to 2500 wells, we find that the fracking-related risk of water scarcity in the São Paulo state is low. For the 2013–2019 period, the long-term average seasonal water availability is between 0.05 and 1 Gm³ per water resources management unit, whereas fracking water demand would hardly overcome 6 Mm³ y−1. For instance, with 2500 wells, the fracking demand in Pontal do Paranapanema, the most prospective region for shale gas, would not overcome 3% of the yearly local water demand. The riskier areas are in Aguapeí and Baixo do Tietê water resources management units, during winter and autumn, and the most water-stressed area is São José dos Dourados. In regions and periods of low water availability, fracking operators can use adaptative strategies for shale gas production. In the context of imminent droughts, this research debates national energy security and casts doubt on the water efficiency and sustainability of the state's energy generation. At last, this research provides early insights to support shale gas and water policy, and future studies to further investigate relevant aspects to the Brazilian Water-Energy nexus.

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We investigate the interplay between energy prices and drilling activities in the United States and how this relationship has evolved due to the shale revolution. We hypothesize (1) there exists significant information spillover between drilling activities and energy prices; (2) the amount of information transmitted between drilling activities and energy prices has increased since the shale boom; (3) natural gas market is increasingly important information transmitter since the rise of unconventional oil and gas production. Using connectedness indexes constructed based on vector autoregressive models and data from 1997 to 2019, we find support for all three hypotheses. In particular, the linkage between drilling activities, measured by active rotary rigs in operation, and oil and gas prices in the US has strengthened since 2012. Oil and gas drilling activities have become more responsive to price variations during the shale revolution. However, the information transmitted from oil prices to rig count declined when oil prices fluctuated in a relatively stable range toward the end of the sample period. In contrast, the information transmitted from gas prices to gas rig counts has increased during the same time frame.

Abstract:
For tectonic earthquakes, slip rate spans a continuum from creep to supershear earthquakes, where slow slip events (SSEs) are important in releasing stress without radiating damaging seismic energy. Industrial-scale subsurface fluid injection has caused induced earthquakes, but the role of SSEs in fault activation is currently unclear. Ground-deformation observations, measured by satellite radar, show that SSEs up to magnitude 5.0 occurred during hydraulic fracturing (HF) operations in northwestern Canada, corroborated by reported deformation of the steel well casing. Although the magnitude 5.0 SSE exceeded the magnitude of the largest induced earthquake in this region (magnitude 4.55), it was undetected by seismograph networks. The observed SSEs occurred within a buried thrust belt and their magnitude and duration are consistent with scaling behavior of SSEs in unbounded natural systems, e.g. slab interfaces in subduction zones.

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Unconventional oil and gas (UOG) production requires a vast quantity of freshwater while generating substantial volumes of wastewater. Although numerous studies have focused on technology development, other aspects beyond treatment technology, including regulations, economics, system logistics, and public perception, play equally or more important roles collectively in the selection and deployment of UOG wastewater management practices. In this article, we begin with a critical analysis of the motivations that drive UOG wastewater management towards treatment and reuse. Then we examine four main barriers against such a paradigm shift, pertaining to treatment technology, regulatory compliance, economic feasibility, and social acceptance. Despite the need of further improving technology efficiency for UOG wastewater treatment, the lack of established regulatory framework, the uncertainties of economic viability, as well as public resistance, hinder practical implementation of treatment technologies. We highlight the importance of knowledge and collaborative efforts from engineers, regulators, policy makers, economists, and social scientists to address those barriers, and emphasize that future research efforts should be directed at domains well beyond treatment technology. A systems approach and broader collaboration across multiple disciplines is needed to translate technology innovation into solutions that truly improve water sustainability in the context of rising UOG production.

Abstract:
Canadian freshwater ecosystems are vulnerable to oil spills from pipelines, which contain mostly diluted bitumen. This study aimed to compare the toxicity of a dilbit and a conventional oil on developing rainbow trout. A total of five exposure scenarios were performed, from 10 to 43 days, using water-accommodated fraction (WAF) with an initial loading of 1:9 oil to water ratio (w/v) in a range of dilutions from 0.32 to 32% WAF, respectively, with TPAH and VOC concentrations from 2.41 to 17.5 μg/L and 7.94–660.99 μg/L, and with or without a recovery period. Following the five exposures, several endpoints were examined, including survivorship, morphometrics, gene expression, and enzymatic activity. Significant mortality rates were measured for the highest WAF concentration of the dilbit in all five exposures (60–100% mortality at 32% WAF). In comparison, the highest WAF concentration of the conventional oil induced significant mortality in three out of the five exposure (from 35 to 100% mortality at 32% WAF). Hatching delays were noted in embryos exposed to both oils. Developmental delays were observed in dilbit-exposed embryos and are suspected to be an indicator of reduced survivorship after hatching. The induced expression of cyp1a remained a reliable biomarker of exposure and of fish malformations, though it did not always predict mortality. Using CYP1A activity in combination with cyp1a may bring more insights in studies of oil risk assessment. This study demonstrates that dilbits are more toxic to early life stages compared to conventional oils and highlights the need to consider the most sensitive stage of development when performing risk assessment studies on oils.

Abstract:
Over the last decade, there has been a rapid growth in the use of hydraulic fracturing (fracking) to recover unconventional oil and gas in the Permian Basin of southeastern New Mexico (NM) and western Texas. Fracking generates enormous quantities of wastes that contain technologically enhanced naturally occurring radioactive materials (TENORM), which poses risks to human health and the environment because of the relatively high doses of radioactivity. However, very little is known about the chemical composition and radioactivity levels of Permian Basin fracking wastes. Here, we report chemical as well as radiochemical compositions of hydraulic fracking wastes from the Permian Basin. Radium, the major TENORM of interest in unconventional drilling wastes, varied from 19.1 ± 1.2 to 35.9 ± 3.2 Bq/L for 226Ra, 10.3 ± 0.5 to 21.5 ± 1.2 Bq/L for 228Ra, and 2.0 ± 0.05 to 3.7 ± 0.07 Bq/L for 224Ra. In addition to elevated concentrations of radium, these wastewaters also contain elevated concentrations of dissolved salts and divalent cations such as Na+ (31,856–43,000 mg/L), Ca2+ (668–4123 mg/L), Mg2+ (202–2430 mg/L), K+ (148–780 mg/L), Sr2+ (101–260 mg/L), Cl− (5160–66,700 mg/L), SO42− (291–1980 mg/L), Br− (315–596 mg/L), SiO2 (20–32 mg/L), and high total dissolved solid (TDS) of 5000–173,000 mg/L compared to background waters. These elevated levels are of radiological significance and represent a major source of Ra in the environment. The recent discovery of large deposits of recoverable oil and gas in the Permian Basin will lead to more fracking, TENORM generation, and radium releases to the environment. This paper evaluates the potential radiation risks associated with TENORM wastes generated by the oil and gas recovery industry in the Permian Basin.

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Little is known about whether exposure to unconventional oil and gas development is associated with higher mortality risks in the elderly and whether related air pollutants are exposure pathways. We studied a cohort of 15,198,496 Medicare beneficiaries (136,215,059 person-years) in all major US unconventional exploration regions from 2001 to 2015. We gathered data from records of more than 2.5 million oil and gas wells. For each beneficiary’s ZIP code of residence and year in the cohort, we calculated a proximity-based and a downwind-based pollutant exposure. We analysed the data using two methods: a Cox proportional hazards model and a difference-in-differences design. We found evidence of a statistically significant higher mortality risk associated with living in proximity to and downwind of unconventional oil and gas wells. Our results suggest that primary air pollutants sourced from unconventional oil and gas exploration can be a major exposure pathway with adverse health effects in the elderly.

Abstract:
Unconventional oil and gas (UOG) extraction can augment energy supplies in countries with viable gas resources, but it risks damaging water resources. Water supply problems for fracking can also limit UOG extraction, especially in water-stressed regions. Regulations are one of the main tools used to minimize UOG extraction impacts on water resources. Many states in the US and Canada have extensive regulations to protect water resources during UOG extraction but they are often ineffective, either because they were poorly drafted or because they are not properly enforced. South Africa is a water-scarce, groundwater-dependent country that is considering UOG extraction in the future. South African groundwater experts were surveyed on what regulations are needed to protect groundwater resources and how to enforce them. This study recommends specific UOG extraction regulations to protect groundwater resources, which are not only relevant to South Africa, but also to other countries that extract UOG resources.

Abstract:
This paper presents a mathematical programming approach for the strategic planning of managing wastewater generated by hydraulic fracturing operations in shale gas production. The proposed approach aims to achieve optimal selection of treatment, storage, and reuse activities. The approach also accounts for the variability of wastewater characteristics including the short-term flowback and transition water as well as the longer-term produced water. Because of the different compositions of the pollutants in the various types of wastewater, stream segregation is considered as an option. Furthermore, the model accounts for seasonal variabilities in freshwater availability. Economic and environmental objectives are considered. The economic objective function aims to determine the minimum total cost, which is composed of freshwater, treatment, storage, and transport costs. Credit is given for reused water. The environmental objective focuses on the reduction of freshwater requirements needed for the fracturing step. The proposed model determines trade-offs between cost and water consumption. A case study is presented, and the results show that it is possible to reduce up to 32.43% of freshwater consumed and to reuse up to 12.26% of the total wastewater from wells for fracturing needs.