Repository for Oil and Gas Energy Research (ROGER)

Abstract:
A survey was conducted on West Virginia land owners with completed shale gas wells located on their property. The research objective was to determine how the separation of mineral from surface rights impacted reported problems and satisfaction with natural gas drilling. Empirical results of theoretical models showed that split estate owners had a statistically greater number of reported problems with drilling. Surface owner dissatisfaction with drilling outcomes was explained primarily by the number of reported problems and nonmonetary compensation. Our results provide motivation for policies to strengthen surface owner rights. (JEL K11, Q48)

Abstract:
Exploration and extraction of oil and natural gas have increased in recent years and are expected to expand in the future. Reduction in water quality from energy extraction may negatively affect water supply for agriculture and urban use within catchments as well as down river. We used non-invasive genetic techniques and capture–recapture modeling to estimate the abundance and density of North American river otters (Lontra canadensis), a sentinel species of aquatic ecosystems, in Southwestern Wyoming. While densities in two of three river reaches were similar to those reported in other freshwater systems in the western US (1.45–2.39 km per otter), otters appeared to avoid areas near energy development. We found no strong difference in habitat variables, such as overstory cover, at the site or reach level. Also, fish abundance was similar among the three river reaches. Otter activity in our study area could have been affected by elevated levels of disturbance surrounding the industrial gas fields, and by potential surface water contamination as indicated by patterns in water conductivity. Continued monitoring of surface water quality in Southwestern Wyoming with the aid of continuously recording devices and sentinel species is warranted.

Abstract:
The rapid growth of hydraulic fracturing for oil and gas extraction in the U.S. has led to 135 active "frac" sand mines, processing plants, and rail transfer stations in Wisconsin. Potential environmental health risks include increased truck traffic, noise, ecosystem loss, and groundwater, light, and air pollution. Emitted air contaminants include fine particulate matter (PM2.5) and respirable crystalline silica. Inhalation of fine dust particles causes increased mortality, cardiovascular disease, lung disease, and lung cancer. In the authors' pilot study, use of a filter-based ambient particulate monitor found PM2.5 levels of 5.82-50.8 mu g/m(3) in six 24-hour samples around frac sand mines and processing sites. Enforcement of the existing U.S. Environmental Protection Agency annual PM2.5 standard of 12 mu g/m(3) is likely to protect the public from silica exposure risks as well. PM2.5 monitoring around frac sand sites is needed to ensure regulatory compliance, inform nearby communities, and protect public health.

Abstract:
Detailed research on the content of heavy metals in ground and surface waters in the upper Sanna River catchment was initiated in 2013. The investigations were conducted in one of the most promising areas of potential shale gas extraction, in which the Frampol 1 test wellbore was drilled in 2012 (SE Poland, Roztocze Region). In the area of the wellbore, hydrochemical analyses of the waters of the river drainage zone were performed. Water was sampled from six objects representing soil water, porous groundwater, fissure-layer groundwater, and river water. The hydrological regime of groundwater and surface water was analysed based on data obtained from automatic recorders of water levels and results of periodic measurements of water flow. In 2013, water was sampled on a monthly basis for determination of the levels of Ba, Sr, Al, Fe, Mn, Zn, Cu, Cd, Co, Cr, Ni, As, V, Rb, Pb, Th, and U. The analysis results showed that the concentration of Sr was usually in the range of 100-400 A mu g/L, Fe 10-100 A mu g/L, Ba 10-40 A mu g/L, and Mn, Al, and Zn 1-10 A mu g/L. The concentration of the other metals generally did not exceed 1 A mu g/L. The concentrations of the elements analysed in the zone of drinking water intake were within the range specified by Polish and WHO standards. Significant differences were found in the metal content in the analysed waters; they were related to the water intake site, form of land management, and hydrometeorological conditions. The highest metal content was recorded in soil and river waters and the lowest in the spring waters of the main water-bearing horizon. At the current stage of the research, no impact of the Frampol 1 shale gas exploration wellbore on the metal content in the upper Sanna River catchment was found.

Abstract:
One of the critical environmental questions about hydraulic fracturing in shales is the potential for contamination of ground and surface water. There are two specific concerns arising from hydraulic treatments: 1) whether hydraulic fractures extend upward through overlying strata to reach overlying aquifers containing drinking water, and 2) whether injected fluids push native fluids upward into these overlying aquifers. In this work, the extent of likely fracture growth through overlying layers during hydraulic treatment of the Marcellus shale was estimated using a hydraulic fracture model. A wide range of material and fluid flow properties in a multi-layered geologic model was considered. The model was based on conditions and characteristics applicable to the Marcellus shale in that part of the Appalachian basin within southwestern Pennsylvania. Predictions of vertical termination frequencies for hydraulic fractures were used in a multi-layer model of the strata and natural fractures for studying brine migration through the natural and induced fracture network. NFFLOW, the software for explicitly modeling flow within networks of fractures, was utilized to compute transient flow rates according to the schedule of injected fluid during hydraulic fracturing. To aid our analysis, the modeled sequence of geologic strata was capped with a fictitious unfractured, but moderately-permeable layer, which serves as a monitoring zone. The analysis assumes one well lateral was placed in the middle of the Marcellus shale with hydraulic fractures penetrating layers in the model. The newly-developed geomechanical module within NFFLOW was used to represent stress-sensitivity of the fractures. This allows the opening and closing of fracture apertures with changes in fluid pressures within fracture segments. Pressure increases in the formations overlying the Tully limestone, indicating fluid flow, was observed due to the hydraulic stimulation; and the impact of these increased pressures on brine migration towards the surface was considered.

Abstract:
The air quality in the outflow from Fort Worth, TX was studied in June 2011 at a location surrounded by oil and gas development in the Barnett Shale. The objectives of this study were to understand the major sources of volatile organic compounds (VOCs) and organic aerosols and explore the potential influence each VOC source had on ozone and secondary organic aerosol formation. Measurements of VOCs were apportioned between six factors using Positive Matrix Factorization (PMF): Natural Gas (25 ± 2%; ±99% CL); Fugitive Emissions (15 ± 2%); Internal Combustion Engines (15 ± 2%); Biogenic Emissions (7 ± 1%); Industrial Emissions/Oxidation 1(8 ± 1%); and Oxidation 2 (18 ± 2%). Reactivity calculations suggest the Biogenic and Oxidation 2 factors were the most likely VOC sources to influence local ozone. However, enough OH reactivity was calculated for factors related to the oil and gas development that they could incrementally increase O3. Three organic aerosol (OA) types were identified with PMF applied to high-resolution time-of-flight aerosol mass spectrometry measurements: hydrocarbon-like OA (HOA; 11% of mass) and two classes of oxidized OA (semi- and less-volatile OOA, SV and LV; 45% and 44%, respectively). The HOA correlated with the Internal Combustion Engine VOC factor indicating that a large fraction of the HOA was emitted by gasoline and diesel motors. The SV-OOA correlated with the oxidized VOC factors during most of the study, whereas a correlation between LV-OOA and the oxidized VOC factors was only observed during part of the study. It is hypothesized that SV-OOA and the oxidized VOC factors correlated reasonably well because these factors likely were separated by at most only a few oxidation generations on the oxidation pathway of organic compounds.

Abstract:
Diffusive sampler monitoring techniques were employed during wintertime studies from 2009 to 2012 to assess the spatial distribution of air pollutants associated with the Pinedale Anticline and Jonah Field oil and natural gas (O&NG) developments in the Upper Green River Basin, Wyoming. Diffusive sampling identified both the extent of wintertime ozone (O3) episodes and the distributions of oxides of nitrogen (NOx), and a suite of 13 C5+ volatile organic compounds (VOC), including BTEX (benzene, toluene, ethylbenzene and xylene isomers), allowing the influence of different O&NG emission sources to be determined. Concentration isopleth mapping of both diffusive sampler and continuous O3 measurements show the importance of localized production and advective transport. As for O3, BTEX and NOx mixing ratios within O&NG development areas were elevated compared to background levels, with localized hotspots also evident. One BTEX hotspot was related to an area with intensive production activities, while a second was located in an area influenced by emissions from a water treatment and recycling facility. Contrastingly, NOx hotspots were at major road intersections with relatively high traffic flows, indicating influence from vehicular emissions. Comparisons of observed selected VOC species ratios at a roadside site in the town of Pinedale with those measured in O&NG development areas show that traffic emissions contribute minimally to VOCs in these latter areas. The spatial distributions of pollutant concentrations identified by diffusive sampling techniques have potential utility for validation of emission inventories that are combined with air quality modeling.

Abstract:
Shale gas involves a technology which is a controversial method of energy production mainly because there are uncertainties about the possible environmental and human health impacts. The article aims to identify the level of knowledge in relation to the impact of environmental risks attached to shale gas exploitation in the academic and scientifi c community. It does so by employing the expert elicitation approach which has the benefi t of quantifying the judgment of individual experts. We have revealed a consistency among researchers in assessing the level of uncertainty of the main environmental risks and a preferred policy option in dealing with uncertainty, a vow for improved transparency, openness and ease of access to information. Shale gas policy-making in Europe needs a science- based approach as science informs policy by delivering objective and reliable knowledge. The article concludes that developing a comprehensive approach based on scientifi c data and an appropriate regulatory framework will provide a path forward for the future development of contested policies like shale gas.

Abstract:
Growth of the unconventional gas industry is predicted to continue to be an important component of the global energy landscape. The rapid expansion of shale and tight gas development has raised many environmental and human health concerns, particularly in regards to ground and surface water contamination. The unconventional gas industry has begun to transition toward the use of hydraulic fracturing chemicals that pose minimal environmental and human health hazards in order to mitigate the risks associated with possible chemical containment failure. Integrated chemical hazard evaluation has been facilitated by an adapted index-based approach to combine noncommensurate multiparameter chemical hazard data into a single score value. Comparative analysis of existing chemical hazard index scoring systems as well as the formulation of a novel hydraulic fracturing fluid greenness assessment system revealed several important considerations for index development and application. Index scores calculated using the investigated index systems highlighted the need for informed, optimized hazard class selection as input for score determination, the maintenance of hazard category intensity during parameter transformation, as well as representative hazard class and chemical component mathematical weightings, and robust aggregation techniques for final score calculation. Continued research should work to model the combined hazard posed by individual chemicals while considering the effect of dilution as well as incorporate additional index metrics beyond hazard intensity. Fully disclosed index systems, applied with complete knowledge of their strengths and weaknesses, provide useful monitoring and communication tools to promote environmental-best practices in the unconventional gas industry.

Abstract:
During hydraulic fracturing millions of gallons of water are typically injected at high pressure into deep shale formations. This water can be housed in fractures, within the shale matrix, and can potentially migrate beyond the shale formation via fractures and/or faults raising environmental concerns. We describe a generic framework for producing estimates of the volume available in fractures and undamaged shale matrix where water injected into a representative shale site could reside during hydraulic fracturing, and apply it to a representative site that incorporates available field data. The amount of water that can be stored in the fractures is estimated by calculating the volume of all the fractures associated with a discrete fracture network (DFN) based on real data and using probability theory to estimate the volume of smaller fractures that are below the lower cutoff for the fracture radius in the DFN. The amount of water stored in the matrix is estimated utilizing two distinct methods-one using a two-phase model at the pore-scale and the other using a single-phase model at the continuum scale. Based on these calculations, it appears that most of the water resides in the matrix with a lesser amount in the fractures.

Abstract:
Oil and natural gas operations have been shown to contaminate surface and ground water with endocrine-disrupting chemicals. In the current study, we fill several gaps in our understanding of the potential environmental impacts related to this process. We measured the endocrine-disrupting activities of 24 chemicals used and/or produced by oil and gas operations for five nuclear receptors using a reporter gene assay in human endometrial cancer cells. We also quantified the concentration of 16 of these chemicals in oil and gas wastewater samples. Finally, we assessed reproductive and developmental outcomes in male C57BL/6J mice after the prenatal exposure to a mixture of these chemicals. We found that 23 commonly used oil and natural gas operation chemicals can activate or inhibit the estrogen, androgen, glucocorticoid, progesterone, and/or thyroid receptors, and mixtures of these chemicals can behave synergistically, additively, or antagonistically in vitro. Prenatal exposure to a mixture of 23 oil and gas operation chemicals at 3, 30, and 300 μ g/kg · d caused decreased sperm counts and increased testes, body, heart, and thymus weights and increased serum T in male mice, suggesting multiple organ system impacts. Our results suggest possible adverse developmental and reproductive health outcomes in humans and animals exposed to potential environmentally relevant levels of oil and gas operation chemicals.

Abstract:
Hundreds of organic chemicals are used during natural gas extraction via high-volume hydraulic fracturing (HVHF). However, it is unclear whether these chemicals, injected into deep shale horizons, reach shallow groundwater aquifers and affect local water quality, either from those deep HVHF injection sites or from the surface or shallow subsurface. Here, we report detectable levels of organic compounds in shallow groundwater samples from private residential wells overlying the Marcellus Shale in northeastern Pennsylvania. Analyses of purgeable and extractable organic compounds from 64 groundwater samples revealed trace levels of volatile organic compounds, well below the Environmental Protection Agency’s maximum contaminant levels, and low levels of both gasoline range (0–8 ppb) and diesel range organic compounds (DRO; 0–157 ppb). A compound-specific analysis revealed the presence of bis(2-ethylhexyl) phthalate, which is a disclosed HVHF additive, that was notably absent in a representative geogenic water sample and field blanks. Pairing these analyses with (i) inorganic chemical fingerprinting of deep saline groundwater, (ii) characteristic noble gas isotopes, and (iii) spatial relationships between active shale gas extraction wells and wells with disclosed environmental health and safety violations, we differentiate between a chemical signature associated with naturally occurring saline groundwater and one associated with alternative anthropogenic routes from the surface (e.g., accidental spills or leaks). The data support a transport mechanism of DRO to groundwater via accidental release of fracturing fluid chemicals derived from the surface rather than subsurface flow of these fluids from the underlying shale formation.

Abstract:
While scientists are paying increasing attention to the seismicity potentially induced by hydrocarbon exploitation, so far, little is known about the reverse problem, i.e. the impact of active faulting and earthquakes on hydrocarbon reservoirs. The 20 and 29 May 2012 earthquakes in Emilia, northern Italy (Mw 6.1 and 6.0), raised concerns among the public for being possibly human-induced, but also shed light on the possible use of gas wells as a marker of the seismogenic potential of an active fold and thrust belt. We compared the location, depth and production history of 455 gas wells drilled along the Ferrara-Romagna arc, a large hydrocarbon reserve in the southeastern Po Plain (northern Italy), with the location of the inferred surface projection of the causative faults of the 2012 Emilia earthquakes and of two pre-instrumental damaging earthquakes. We found that these earthquake sources fall within a cluster of sterile wells, surrounded by productive wells at a few kilometres' distance. Since the geology of the productive and sterile areas is quite similar, we suggest that past earthquakes caused the loss of all natural gas from the potential reservoirs lying above their causative faults. To validate our hypothesis we performed two different statistical tests (binomial and Monte Carlo) on the relative distribution of productive and sterile wells, with respect to seismogenic faults. Our findings have important practical implications: (1) they may allow major seismogenic sources to be singled out within large active thrust systems; (2) they suggest that reservoirs hosted in smaller anticlines are more likely to be intact; and (3) they also suggest that in order to minimize the hazard of triggering significant earthquakes, all new gas storage facilities should use exploited reservoirs rather than sterile hydrocarbon traps or aquifers.

Abstract:
Summary If unconventional gas development (UGD) continues to expand in Australia, the potential health and environmental impacts should be adequately addressed and preventive public health measures should be implemented. The United States has embraced UGD and has decades of experience that could be beneficial to Australia as stakeholders debate the potential benefits and harms of the technique. Additional research on the health impacts of UGD is necessary. Baseline and trend morbidity and mortality data need to be collected to assess changes in population health over time. To date, few health or epidemiological studies have been conducted, so it remains difficult to assess actual health outcomes. In the absence of scientific consensus, there are two possible risks: failing to develop unconventional natural gas when the harms are manageable; or developing it when the harms are substantial. Many government bodies around the world have chosen to minimise the risk of the latter until the impacts of UGD are better understood. Policies should be informed by empirical evidence based on actual experience rather than assurance of best practices. There is a strong rationale for precautionary measures based on the health and environmental risks identified in the scientific literature.

Abstract:
Construction of unconventional natural gas (UNG) infrastructure (e.g., well pads, pipelines) is an increasingly common anthropogenic stressor that increases potential sediment erosion. Increased sediment inputs into nearby streams may decrease autotrophic processes through burial and scour, or sediment bound nutrients could have a positive effect through alleviating potential nutrient limitations. Ten streams with varying catchment UNG well densities (0–3.6 wells/km2) were sampled during winter and spring of 2010 and 2011 to examine relationships between landscape scale disturbances associated with UNG activity and stream periphyton [chlorophyll a (Chl a)] and gross primary production (GPP). Local scale variables including light availability and water column physicochemical variables were measured for each study site. Correlation analyses examined the relationships of autotrophic processes and local scale variables with the landscape scale variables percent pasture land use and UNG metrics (well density and well pad inverse flow path length). Both GPP and Chl a were primarily positively associated with the UNG activity metrics during most sample periods; however, neither landscape variables nor response variables correlated well with local scale factors. These positive correlations do not confirm causation, but they do suggest that it is possible that UNG development can alleviate one or more limiting factors on autotrophic production within these streams. A secondary manipulative study was used to examine the link between nutrient limitation and algal growth across a gradient of streams impacted by natural gas activity. Nitrogen limitation was common among minimally impacted stream reaches and was alleviated in streams with high UNG activity. These data provide evidence that UNG may stimulate the primary production of Fayetteville shale streams via alleviation of N-limitation. Restricting UNG activities from the riparian zone along with better enforcement of best management practices should help reduce these possible impacts of UNG activities on stream autotrophic processes.

Abstract:
Oil and gas extraction and coal-fired electrical power generating stations produce wastewaters that are treated and discharged to rivers in Western Pennsylvania with public drinking water system (PDWS) intakes. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to quantify inorganic species in wastewater and river samples using a method based on EPA Method 200.7 rev4.4. A total of 53 emission lines from 30 elements (Al, As, B, Ba, Ca, Cd, Ce, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Ti, Tl, V, and Zn) were investigated. Samples were prepared by microwave-assisted acid digestion using a mixture of 2% HNO3 and 0.5% HCl. Lower interferences and better detection characteristics resulted in selection of alternative wavelengths for Al, As, Sb, Mg, Mo, and Na. Radial view measurements offered accurate determinations of Al, Ba, K, Li, Na, and Sr in high-brine samples. Spike recovery studies and analyses of reference materials showed 80–105% recoveries for most analytes. This method was used to quantify species in samples with high to low brine concentrations with method detection limits a factor of 2 below the maximum contaminant limit concentrations of national drinking water standards. Elements B, Ca, K, Li, Mg, Na, and Sr were identified as potential tracers for the sources impacting PDWS intakes. Usability of the ICP-OES derived data for factor analytic model applications was also demonstrated.

Abstract:
Unconventional gas development (UGD) is growing rapidly in the United States. Drawing on insights from risk perception and risk governance theories and recent public opinion surveys, we find that UGD is an emerging technology that is likely to be perceived as risky, even though objective risk assessments suggest that risks are low and controllable through best risk management practices. Perceived risk varies significantly depending on the state and locality but perceptions of risk appear to be increasing as the technology is used more widely in the United States and as organized opponents of the technology intensify their efforts. Risk perceptions are attenuated somewhat because of the perceived benefits of UGD and compensation schemes for individuals and communities. The types of triggering events necessary for large-scale social amplification and stigmatization have not yet occurred but awareness of UGD is growing and organized opposition has been sufficient to cause prohibitions of UGD in some U.S. states and localities. Additional directions for social science research on public reactions to UGD are recommended.

Abstract:
The probability that new hydraulically fractured wells drilled within the area of New York underlain by the Marcellus Shale will intersect an existing wellbore is calculated using a statistical model, which incorporates: the depth of a new fracturing well, the vertical growth of induced fractures, and the depths and locations of existing nearby wells. The model first calculates the probability of encountering an existing well in plan view and combines this with the probability of an existing well-being at sufficient depth to intersect the fractured region. Average probability estimates for the entire region of New York underlain by the Marcellus Shale range from 0.00% to 3.45% based upon the input parameters used. The largest contributing parameter on the probability value calculated is the nearby density of wells meaning that due diligence by oil and gas companies during construction in identifying all nearby wells will have the greatest effect in reducing the probability of interwellbore communication.

Abstract:
The rapid development of high-volume horizontal hydraulic fracturing for mining natural gas from shale has posed potential impacts on human health and biodiversity. The produced flow back waters after hydraulic stimulation are known to carry high levels of saline and total dissolved solids. To understand the toxicity and potential carcinogenic effects of these wastewaters, flow back waters from five Marcellus hydraulic fracturing oil and gas wells were analyzed. The physicochemical nature of these samples was analyzed by inductively coupled plasma mass spectrometry and scanning electron microscopy/energy dispersive X-ray spectroscopy. A cytotoxicity study using colony formation as the endpoint was carried out to define the LC50 values of test samples using human bronchial epithelial cells (BEAS-2B). The BEAS-2B cell transformation assay was employed to assess the carcinogenic potential of the samples. Barium and strontium were among the most abundant metals in these samples and the same metals were found to be elevated in BEAS-2B cells after long-term treatment. BEAS-2B cells treated for 6 weeks with flow back waters produced colony formation in soft agar that was concentration dependent. In addition, flow back water-transformed BEAS-2B cells show better migration capability when compared to control cells. This study provides information needed to assess the potential health impact of post-hydraulic fracturing flow back waters from Marcellus Shale natural gas mining.

Abstract:
Enhanced geothermal systems, shale gas, and geological carbon sequestration all require underground fluid injection in high-pressure conditions. Fluid injection creates fractures, induces seismicity, and has the potential to reactivate nearby faults that can generate a large magnitude earthquake. Mechanisms of fluid injection-induced seismicity and fault reactivation should be better understood to be able to mitigate larger events triggered by fluid injection. This study investigates fluid injection, induced seismicity, and triggering of fault rupture using hydromechanical-coupled discrete element models. Results show that a small amount of fluid pressure perturbation can trigger fault ruptures that are critically oriented and stressed. Induced seismicity by rock failure shows in general higher b-values (slope of magnitude-frequency relation) compared to seismicity triggered by the fault fracture slip. Numerical results closely resemble observations from geothermal and shale-gas fields and demonstrate that discrete element modeling has the potential to be applied in the field as a tool for predicting induced seismicity prior to in situ injection.

Abstract:
We evaluated the overall water footprint of hydraulic fracturing of unconventional shale gas and oil throughout the United States based on integrated data from multiple database sources. We show that between 2005 and 2014, unconventional shale gas and oil extraction used 708 billion liters and 232 billion liters of water, respectively. From 2012 to 2014, the annual water use rates were 116 billion liters per year for shale gas and 66 billion liters per year for unconventional oil. Integrated data from 6 to 10 years of operation yielded 803 billion liters of combined flowback and produced water from unconventional shale gas and oil formations. While the hydraulic fracturing revolution has increased water use and wastewater production in the United States, its water use and produced water intensity is lower than other energy extraction methods and represents only a fraction of total industrial water use nationwide.

Abstract:
Liquefied petroleum gases (LPGs) together with other natural gas liquids (NGLs) have played an important role in the current U.S. shale gas boom. Depressed gas prices in recent years have made pure natural gas operations less profitable. The result is that liquids components in gas production have become increasingly important in ensuring the profitability of shale gas operations. In this paper we investigate whether the shale gas expansion, which has led to an increase in associated LPG production, has also affected the historically strong relationship between LPG and oil prices. Revealing the strength and stability of the LPG/oil relationship is relevant when it comes to the future profitability and development of the U.S. natural gas sector. Our results suggest that the LPG/oil relationship has weakened in recent years with a move towards cheaper liquids relative to oil. This is consistent with developments in the natural gas sector with increased liquids production. A consequence is that U.S. natural gas operations cannot automatically rely on high liquids prices to ensure profitability.

Abstract:
This paper describes a fully independent public participation and review process on the environmental, economic, health, community and social risks and benefits of hydraulic fracturing for the development of unconventional gas and oil resources. We describe the approach taken to maximise public engagement in the process and how that participation informed the work of an independent panel charged with examining the scientific evidence and related legal issues. The major findings from the review are presented, including a risk matrix which summarises the frequency, severity and mitigation measures for 16 potential hazards associated with hydraulic fracturing, as they may pertain to the province of Nova Scotia in Canada. We discuss the complexity of managing public perceptions of novel risks such as hydraulic fracturing and conclude with brief observations on the contribution of the review to public policy.

Abstract:
Because of its resource potential and clean burning advantages, the development of shale gas can significantly increase the supply of cleaner energy while offering the associated benefits. To foster shale gas development, many policy incentives have been introduced in China. However, the current incentives have not been sufficiently aggressive, and the shale gas industry has been slow to develop. Existing policies thus need to be further improved. To provide effective support for decision makers in China, a technical and economic evaluation is performed in this study to explore the profitability of shale gas production in pilot zones. The results show that shale gas production is subeconomic under the current technical and economic conditions. Based on this evaluation, a policy analysis is conducted to investigate the profitability improvement offered by the major policies available in China to elucidate a path toward improving incentive policies. The results indicate that policy instruments related to gas prices, financial subsidies, corporate income taxes or combinations thereof could be used as priority options to improve policy incentives. Based on these results, recommendations are presented to improve the current incentive polices aimed at accelerating shale gas development.

Abstract:
The oil crisis and the successful commercial exploitation of shale gas in America have made shale gas become the focus of global energy industry. Shale gas industry will be developed mainly in the future. Sichuan has natural geographical advantages and becomes the main battlefield of shale gas in China. So it is necessary and urgent to analyze the current situation of Sichuan shale gas. This paper introduces the status quo of shale gas in Sichuan, and systematically analyzes the industrial environment for developing Sichuan shale gas from four aspects of policy, economy, society, technology. Then the issues facing Sichuan are discussed. Finally, the paper puts forward some corresponding recommendations to provide certain references to the development of shale gas industry in Sichuan.

Abstract:
Managing the wastewater discharged from oil and shale gas fields is a big challenge, because this kind of wastewater is normally polluted by high contents of both oils and salts. Conventional pressure-driven membranes experience little success for treating this wastewater because of either severe membrane fouling or incapability of desalination. In this study, we designed a new nanocomposite forward osmosis (FO) membrane for accomplishing simultaneous oil/water separation and desalination. This nanocomposite FO membrane is composed of an oil-repelling and salt-rejecting hydrogel selective layer on top of a graphene oxide (GO) nanosheets infused polymeric support layer. The hydrogel selective layer demonstrates strong underwater oleophobicity that leads to superior anti-fouling capability under various oil/water emulsions, and the infused GO in support layer can significantly mitigate internal concentration polarization (ICP) through reducing FO membrane structural parameter by as much as 20%. Compared with commercial FO membrane, this new FO membrane demonstrates more than three times higher water flux, higher removals for oil and salts (>99.9% for oil and >99.7% for multivalent ions) and significantly lower fouling tendency when investigated with simulated shale gas wastewater. These combined merits will endorse this new FO membrane with wide applications in treating highly saline and oily wastewaters.

Abstract:
Development of unconventional shale gas resources involves intensive capital investment accompanying large commercial production uncertainties. Economic appraisal, bringing together multidisciplinary project data and information and providing likely economic outcomes for various development scenarios, forms the core of business decision-making. This paper uses a discounted cash flow (DCF) model to evaluate the economic outcome of shale gas development in the Horn River Basin, northeastern British Columbia, Canada. Through numerical examples, this study demonstrates that the use of a single average decline curve for the whole shale gas play is the equivalent of the results from a random drilling process. Business decision based on a DCF model using a single decline curve could be vulnerable to drastic changes of shale gas productivity across the play region. A random drilling model takes those drastic changes in well estimated ultimate recovery (EUR) and decline rates into account in the economic appraisal, providing more information useful for business decisions. Assuming a natural gas well-head price of $4/MCF and using a 10 % discount rate, the results from this study suggest that a random drilling strategy (e.g., one that does not regard well EURs), could lead to a negative net present value (NPV); whereas a drilling sequence that gives priority to developing those wells with larger EURs earlier in the drilling history could result in a positive NPV with various payback time and internal rate of return (IRR). Under a random drilling assumption, the breakeven price is $4.2/MCF with more than 10 years of payout time. In contrast, if the drilling order is strictly proportional to well EURs, the result is a much better economic outcome with a breakeven price below the assumed well-head price accompanied by a higher IRR.

Abstract:
Multiple stressors threaten stream physical and biological quality, including elevated nutrients and other contaminants, riparian and in-stream habitat degradation and altered natural flow regime. Unconventional oil and gas (UOG) development is one emerging stressor that spans the U.S. UOG development could alter stream sedimentation, riparian extent and composition, in-stream flow, and water quality. We developed indices to describe the watershed sensitivity and exposure to natural and anthropogenic disturbances and computed a vulnerability index from these two scores across stream catchments in six productive shale plays. We predicted that catchment vulnerability scores would vary across plays due to climatic, geologic and anthropogenic differences. Across-shale averages supported this prediction revealing differences in catchment sensitivity, exposure, and vulnerability scores that resulted from different natural and anthropogenic environmental conditions. For example, semi-arid Western shale play catchments (Mowry, Hilliard, and Bakken) tended to be more sensitive to stressors due to low annual average precipitation and extensive grassland. Catchments in the Barnett and Marcellus-Utica were naturally sensitive from more erosive soils and steeper catchment slopes, but these catchments also experienced areas with greater UOG densities and urbanization. Our analysis suggested Fayetteville and Barnett catchments were vulnerable due to existing anthropogenic exposure. However, all shale plays had catchments that spanned a wide vulnerability gradient. Our results identify vulnerable catchments that can help prioritize stream protection and monitoring efforts. Resource managers can also use these findings to guide local development activities to help reduce possible environmental effects.

Abstract:
From production through distribution, oil and gas infrastructure provides the largest source of anthropogenic methane in the United States and the second largest globally. Using a Picarro G2132i Cavity Ring-Down spectrometer, we mapped natural gas leaks across the streets of three United States cities?Durham, NC, Cincinnati, OH, and Manhattan, NY?at different stages of pipeline replacement of cast iron and other older materials. We identified 132, 351, and 1050 leaks in Durham, Cincinnati, and Manhattan, respectively, across 595, 750, and 247 road miles driven. Leak densities were an order of magnitude lower for Durham and Cincinnati (0.22 and 0.47 leaks/mi, respectively) than for Manhattan (4.25 leaks/mi) and two previously mapped cities, Boston (4.28 leaks/mi) and Washington, DC (3.93 leaks/mi). Cities with successful pipeline replacement programs have 90% fewer leaks per mile than cities without such programs. Similar programs around the world should provide additional environmental, economic, and consumer safety benefits.

Abstract:
The prospect of ‘fracking’ for shale gas in South Africa's Karoo has generated heated exchanges in public forums and in the media. This article seeks to understand why common ground in the debate has proved to be so elusive. The article divides the parties to the impasse into three camps and examines the ethical positions which seem to inform each faction's standpoint. The article finds that the tensions between the main protagonists’ positions are due to two related ethical ‘faultlines’. The first revolves around the inherent incompatibility of consequentialism with moral absolutism. The second relates to tensions between nature as an instrumental good, and an ethic that treats nature as an intrinsic good. The discussion considers the merits of cost–benefit analysis and whether, at the very least, exploration for shale gas should be permitted. The article concludes by weighing up the preconditions for a rapprochement being reached between the contending factions.

Abstract:
Emissions of volatile organic compounds (VOCs) and hazardous air pollutants (HAPs) from oil and natural gas production were investigated using direct measurements of component-level emissions on pads in the Denver-Julesburg (DJ) Basin and remote measurements of production pad-level emissions in the Barnett, DJ, and Pinedale basins. Results from the 2011 DJ on-site study indicate that emissions from condensate storage tanks are highly variable and can be an important source of VOCs and HAPs, even when control measures are present. Comparison of the measured condensate tank emissions with potentially emitted concentrations modeled using E&P TANKS (American Petroleum Institute [API] Publication 4697) suggested that some of the tanks were likely effectively controlled (emissions less than 95% of potential), whereas others were not. Results also indicate that the use of a commercial high-volume sampler (HVS) without corresponding canister measurements may result in severe underestimates of emissions from condensate tanks. Instantaneous VOC and HAP emissions measured on-site on controlled systems in the DJ Basin were significantly higher than VOC and HAP emission results from the study conducted by Eastern Research Group (ERG) for the City of Fort Worth (2011) using the same method in the Barnett on pads with low or no condensate production. The measured VOC emissions were either lower or not significantly different from the results of studies of uncontrolled emissions from condensate tanks measured by routing all emissions through a single port monitored by a flow measurement device for 24 hr. VOC and HAP concentrations measured remotely using the U.S. Environmental Protection Agency (EPA) Other Test Method (OTM) 33A in the DJ Basin were not significantly different from the on-site measurements, although significant differences between basins were observed.Implications: VOC and HAP emissions from upstream production operations are important due to their potential impact on regional ozone levels and proximate populations. This study provides information on the sources and variability of VOC and HAP emissions from production pads as well as a comparison between different measurement techniques and laboratory analysis protocols. On-site and remote measurements of VOC and HAP emissions from oil and gas production pads indicate that measurable emissions can occur despite the presence of control measures, often as a result of leaking thief hatch seals on condensate tanks. Furthermore, results from the remote measurement method OTM 33A indicate that it can be used effectively as an inspection technique for identifying oil and gas well pads with large fugitive emissions.

Abstract:
Atmospheric mercury emissions in the Barnett Shale area were studied by employing both stationary measurements and mobile laboratory surveys. Stationary measurements near the Engle Mountain Lake showed that the median mixing ratio of total gaseous mercury (THg) was 138 ppqv (140 ± 29 ppqv for mean ± S.D.) during the June 2011 study period. A distinct diurnal variation pattern was observed in which the highest THg levels appeared near midnight, followed by a monotonic decrease until midafternoon. The influence of oil and gas (ONG) emissions was substantial in this area, as inferred from the i-pentane/n-pentane ratio (1.17). However, few THg plumes were captured by our mobile laboratory during a ?3700 km survey with detailed downwind measurements from 50 ONG facilities. One compressor station and one natural gas condensate processing facility were found to have significant THg emissions, with maximum THg levels of 963 and 392 ppqv, respectively, and the emissions rates were estimated to be 7.9 kg/yr and 0.3 kg/yr, respectively. Our results suggest that the majority of ONG facilities in this area are not significant sources of THg; however, it is highly likely that a small number of these facilities contribute a relatively large amount of emissions in the ONG sector.

Abstract:
It has been suggested by some that methane contamination of water wells is the main negative consequence of the development of natural gas resources. Concurrently, speculation in academic white papers and in the press that methane may be toxic has resulted in public concern. In northern Pennsylvania, methane being released from groundwater and entering homes (so-called stray gas) has become a focus of this concern. This phenomenon was widespread decades before shale gas development was initiated. This paper reviews the available literature on the safety and health hazards associated with natural gas. It concludes that the risks to homeowners are highest from flash fires occurring in methane oxygen gas clouds at relatively low methane concentrations collecting in poorly ventilated, confined areas of houses such as basements. Such risks can be mitigated effectively and in most cases at minimal cost. Methane can result in death from hypoxia (lack of oxygen) but only at methane levels in the air of more than 60%, which are unlikely to develop except under exceptional circumstances. There is no evidence that low to moderate levels of exposure to methane in air have any toxic effect on humans, and evidence for such effects at very high levels (already fatal because of hypoxia) is equivocal. It seems likely that methane at concentrations at least as high as 2.5% may well have positive health benefits for some diseases.

Abstract:
The rapid expansion of shale gas exploration worldwide is a significant source of environmental controversy. Successful shale gas policy-making is dependent upon a clear understanding of the dynamics of competing stakeholder perspectives on these issues, and so methods are needed to delineate the areas of agreement and conflict that emerge. This empirical study, based in the United Kingdom, examines emergent perspectives on a range of environmental, health and socio-economic impacts associated with shale gas fracking using Q-methodology: a combined qualitative–quantitative approach. The analysis reveals three typologies of perspectives amongst key industry, civil society and non-affiliated citizen stakeholders; subsequently contextualised in relation to Dryzek's typology of environmental discourses. These are labelled (A) ‘Don't trust the fossil fuels industry: campaign for renewables’ (mediating between sustainable development and democratic pragmatism discourses), (B) ‘Shale gas is a bridge fuel: economic growth and environmental scepticism’ (mediating between economic rationalism and ecological modernisation discourses) and (C) ‘Take place protective action and legislate in the public interest’ (reflecting a discourse of administrative rationalism). The implications of these competing discourses for nascent shale gas policy in the UK are discussed in light of recent government public consultation on changes to national planning policy.

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New technologies and rising energy prices have resulted in many energy companies investing significant amounts of capital in rural America. Much of the recent focus of energy companies has been on the development of shale oil and natural gas. We examine the differences in levels of support and opposition to shale oil and gas development, building on the literatures of the growth-machine coalition, polluter-industrial complex, and environmental justice. Specifically, we examine different frames of shale development held by government leaders and the public who reside above the New Albany shale play in Southern Illinois and Northwest Kentucky. Using a combination of interview, survey, and participant observation data, we find that government officials emphasize economic growth and many support shale development. While most government leaders claimed that there was not a major division in their communities about shale development, we found the public to be split, with a large countercoalition to shale development in existence.

Abstract:
Understanding the transport of hydraulic fracturing (HF) fluid that is injected into the deep subsurface for shale gas extraction is important to ensure that shallow drinking water aquifers are not contaminated. Topographically driven flow, overpressured shale reservoirs, permeable pathways such as faults or leaky wellbores, the increased formation pressure due to HF fluid injection, and the density contrast of the HF fluid to the surrounding brine can encourage upward HF fluid migration. In contrast, the very low shale permeability and capillary imbibition of water into partially saturated shale may sequester much of the HF fluid, and well production will remove HF fluid from the subsurface. We review the literature on important aspects of HF fluid migration. Single-phase flow and transport simulations are performed to quantify how much HF fluid is removed via the wellbore with flowback and produced water, how much reaches overlying aquifers, and how much is permanently sequestered by capillary imbibition, which is treated as a sink term based on a semianalytical, one-dimensional solution for two-phase flow. These simulations include all of the important aspects of HF fluid migration identified in the literature review and are performed in five stages to faithfully represent the typical operation of a hydraulically fractured well. No fracturing fluid reaches the aquifer without a permeable pathway. In the presence of a permeable pathway, 10 times more fracturing fluid reaches the aquifer if well production and capillary imbibition are not included in the model.

Abstract:
BACKGROUND: Unconventional natural gas development has expanded rapidly. In Pennsylvania, the number of producing wells increased from 0 in 2005 to 3,689 in 2013. Few publications have focused on unconventional natural gas development and birth outcomes. METHODS: We performed a retrospective cohort study using electronic health record data on 9,384 mothers linked to 10,946 neonates in the Geisinger Health System from January 2009 to January 2013. We estimated cumulative exposure to unconventional natural gas development activity with an inverse-distance squared model that incorporated distance to the mother's home; dates and durations of well pad development, drilling, and hydraulic fracturing; and production volume during the pregnancy. We used multilevel linear and logistic regression models to examine associations between activity index quartile and term birth weight, preterm birth, low 5-minute Apgar score and small size for gestational age birth, while controlling for potential confounding variables. RESULTS: In adjusted models, there was an association between unconventional natural gas development activity and preterm birth that increased across quartiles, with a fourth quartile odds ratio of 1.4 (95% confidence interval = 1.0, 1.9). There were no associations of activity with Apgar score, small for gestational age birth, or term birth weight (after adjustment for year). In a posthoc analysis, there was an association with physician-recorded high-risk pregnancy identified from the problem list (fourth vs. first quartile, 1.3 [95% confidence interval = 1.1, 1.7]). CONCLUSION: Prenatal residential exposure to unconventional natural gas development activity was associated with two pregnancy outcomes, adding to evidence that unconventional natural gas development may impact health.

Abstract:
There is a nationwide trend to develop shale formations due to advances in horizontal drilling and hydraulic fracturing technology. The Barnett Shale in north Texas is one of the largest onshore natural gas fields in the US, and has experienced exponential growth since the 1990’s. This immense amount of well development and gas production has occurred near heavily populated, urban areas, leading to increased public concern regarding the impacts of these activities on human health and welfare. The Texas Commission on Environmental Quality (TCEQ) is charged with regulating sources of air emissions from natural gas operations (NGOs) and is in a unique position to evaluate any associated risks. The goal of this manuscript is to describe the problem formulation process used by the TCEQ to characterize risks associated with air emissions from NGOs, and the subsequent risk management strategies implemented. Details on how potential sources of risk to human health were identified and quantified are provided. Initial assessments identified volatile organic compounds (VOCs) as chemicals of concern. Over 4.7 million data points for VOCs were used in this assessment on both a short-term and long-term basis. Only one short-term sample measured VOCs levels above short-term health concern. Several short-term samples measured VOCs above odor-based values. None of the VOCs were measured above levels of long-term health concern. We describe efforts to engage stakeholders early in the risk assessment process and outreach programs used. Finally, details on new rules and regulations that are being used to more efficiently manage risks are provided. Given the resources and experience TCEQ possesses to evaluate environmental impacts that may be caused by shale gas development and production, it is our hope that this manuscript may serve as a resource to others to identify and manage risks associated with oil and gas activities in their area.

Abstract:
Flowback fluids associated with hydraulic fracturing shale gas extraction are a potential source of contamination for shallow aquifers. In the Marcellus Shale region of northeastern Pennsylvania, certified water tests have been used to establish baseline water chemistry of private drinking water wells. This study investigates whether a single, certified multiparameter water test is sufficient for establishing baseline water chemistry from which possible future contamination by flowback waters could be reliably recognized. We analyzed the water chemistry (major and minor inorganic elements and stable isotopic composition) of multiple samples collected from lake, spring, and well water from 35 houses around Fiddle Lake, Susquehanna County, PA that were collected over approximately a two-year period. Statistical models estimated variance of results within and between households and tested for significant differences between means of our repeated measurements and prior certified water tests. Overall, groundwater chemistry varies more spatially due to heterogeneity of minerals within the bedrock aquifer and due to varying inputs of road salt runoff from paved roads than it does temporally at a single location. For wells located within road salt-runoff zones, Na+ and Cl− concentrations, although elevated, are generally consistent through repeated measurements. High acid neutralizing capacity (ANC) and base cation concentrations in well water sourced from mineral weathering reactions, and a uniform stable isotopic composition for well water, suggests long flowpaths for groundwater that dampen seasonal variability of most elements. Exceptions occur for two wells within road salt runoff zones that show the greatest range of concentrations for Na+ and Cl−, suggesting that these wells have a faster pathway to surficial recharge. Additionally, sampling protocols can induce variability for Fe, Mn, and Pb, making other elements identified in flowback fluids (Ba, Br, Ca, Cl, Mg, Na, Sr) more dependable indicators of contamination. Although there is general concordance between our repeated measurements and the certified test results, characterizing baseline chemistry is strengthened when results from multiple households are combined to establish regional upper baseline limits that will have a low probability of being exceeded by future samples unless conditions have changed.

Abstract:
Hydraulically fractured shales are becoming an increasingly important source of natural gas production in the United States. This process has been known to create up to 420 gallons of produced water (PW) per day, but the volume varies depending on the formation, and the characteristics of individual hydraulic fracture. PW from hydraulic fracturing of shales are comprised of injected fracturing fluids and natural formation waters in proportions that change over time. Across the state of Pennsylvania, shale gas production is booming; therefore, it is important to assess the variability in PW chemistry and microbiology across this geographical span. We quantified the inorganic and organic chemical composition and microbial communities in PW samples from 13 shale gas wells in north central Pennsylvania. Microbial abundance was generally low (66–9400 cells/mL). Non-volatile dissolved organic carbon (NVDOC) was high (7–31 mg/L) relative to typical shallow groundwater, and the presence of organic acid anions (e.g., acetate, formate, and pyruvate) indicated microbial activity. Volatile organic compounds (VOCs) were detected in four samples (∼1 to 11.7 μg/L): benzene and toluene in the Burket sample, toluene in two Marcellus samples, and tetrachloroethylene (PCE) in one Marcellus sample. VOCs can be either naturally occurring or from industrial activity, making the source of VOCs unclear. Despite the addition of biocides during hydraulic fracturing, H2S-producing, fermenting, and methanogenic bacteria were cultured from PW samples. The presence of culturable bacteria was not associated with salinity or location; although organic compound concentrations and time in production were correlated with microbial activity. Interestingly, we found that unlike the inorganic chemistry, PW organic chemistry and microbial viability were highly variable across the 13 wells sampled, which can have important implications for the reuse and handling of these fluids.

Abstract:

Abstract:
This study investigated the utility of multistation waveform cross correlation to help discern induced seismicity. Template matching was applied to all Ohio earthquakes cataloged since the arrival of nearby EarthScope TA stations in late 2010. Earthquakes that were within 5km of fluid injection activities in regions that lacked previously documented seismicity were found to be swarmy. Moreover, the larger number of events produced by template matching for these swarmy sequences made it easier to establish more detailed temporal and spatial relationships between the seismicity and fluid injection activities, which is typically required for an earthquake to be considered induced. Study results detected three previously documented induced sequences (Youngstown, Poland Township, and Harrison County) and provided evidence that suggests two additional cases of induced seismicity (Belmont/Guernsey County and Washington County). Evidence for these cases suggested that unusual swarm-like behaviors in regions that lack previously documented seismicity can be used to help distinguish induced seismicity, complementing the traditional identification of an anthropogenic source spatially and temporally correlated with the seismicity. In support of this finding, we identified 17 additional cataloged earthquakes in regions of previously documented seismicity and away from disposal wells or hydraulic fracturing that returned very few template matches. The lack of swarminess helps to indicate that these events are most likely naturally occurring.

Abstract:
The risk of contamination of surface waters from hydraulic fracturing activities (i.e., fracking) to extract gas from underground shale formations has been viewed primarily in the context of localized point-source events such as spills with no evidence of contaminants entering food chains. We showed that in watersheds where hydraulic fracturing occurs, an obligate riparian songbird and top predator in headwater systems, the Louisiana Waterthrush (Parkesia motacilla), accumulated metals associated with the fracking process. In both the Marcellus and Fayetteville shale regions, barium and strontium were found at significantly higher levels in feathers of birds in sites with fracking activity than at sites without fracking. The question of what pathway these metals followed from the shale layers to enter the food chain was not resolved by this study, but our data suggested a recent origin for these metals in the riparian systems we studied because levels of barium and strontium in feather samples from reference sites in the Marcellus Region without fracking activity did not differ from historical samples of waterthrush feathers gathered prior to any fracking in the region. Our finding of similarly elevated levels of metals associated with fracking in two geographically distant shale formations suggests hydraulic fracturing may be contaminating surface waters and underscores the need for additional monitoring and study to further assess ecological and human health risks posed by the increasingly widespread development of unconventional sources of natural gas around the world.

Abstract:
Public and regulatory agencies are concerned over the potential for drinking water contamination related to high-volume hydraulic fracturing (hydrofracking) of the Marcellus shale in Pennsylvania and in New York State (NYS), where exploitation of Marcellus gas has not yet begun. Unique natural tracers are helpful for distinguishing the influence of formation water and/or flow-back water. Here we use halogen concentrations, particularly bromine and iodine, to characterize natural variability of baseline water chemistry in the southern tier of NYS. Majority of streams and drinking water wells have Br and I concentrations below 1 and 0.1 μM, respectively, a range typical for relatively pristine surface water and shallow groundwater. Wells that have higher Br and I concentrations are likely affected by formation waters. Br/I ratios indicate two different sources of formation waters in these wells, possibly controlled by geologic settings. Our results suggest that iodine, combined with other halogens, may be a novel and sensitive tool for fingerprinting trace levels of formation water signal in drinking water sources.

Abstract:
The ecologically sensitive Susquehanna River Basin (SRB) is an important recharge area and drinking water source for a large population in the northeastern United States. Seasonal road salt application, the presence of regional brines at shallow depths, and produced waters associated with active and legacy conventional Upper Devonian oil and gas wells could increase total dissolved solids (TDS) in groundwater and streams. This study focused on SRB watersheds along the New York/Pennsylvania border, in order to assess current water quality and to establish baseline geochemistry for ground and surface water in a region with potential for increased development of the Marcellus Shale and other unconventional shale gas units. Geochemical composition was determined for 300 stream samples collected from ten sites in four watersheds over variable seasonal flow conditions, and for groundwater from over 500 drinking water wells in this region. Results indicate that many streams and groundwater wells in the study area have elevated TDS levels that indicate pre-existing contributions from saline sources. Dilution of these inputs with fresh water, and the lack of low-level trace element concentrations and isotopic composition in many water quality analyses, highlight the need for alternate robust and sensitive chemical signatures. Comparison with Cl/Br anion ratios and 87Sr/86Sr isotope ratios indicate that the (Ba + Sr)/Mg ratio can be used to discriminate between road salt and regional brine in these cases, and mixing models show that even small additions (0.1–0.01%) of these contaminants can be detected with this cation ratio. The (Ba + Sr)/Mg ratio may be even more sensitive (by an order of magnitude) to incursions of Marcellus Shale produced water, depending on the composition of Marcellus produced waters in this region. This study highlights the need for baseline sampling of freshwater reservoirs and the characterization of potential high TDS sources at a local and regional scale.

Abstract:
Drill cuttings generated during unconventional natural gas extraction from the Marcellus Shale, Appalachian Basin, U.S.A., generally contain a very large component of organic-rich black shale because of extensive lateral drilling into this target unit. In this study, element concentrations and Pb isotope ratios obtained from leached drill cuttings spanning 600 m of stratigraphic section were used to assess the potential for short and long term environmental impacts from Marcellus Shale waste materials, in comparison with material from surrounding formations. Leachates of the units above, below and within the Marcellus Shale yielded Cl/Br ratios of 100–150, similar to produced water values. Leachates from oxidized and unoxidized drill cuttings from the Marcellus Shale contain distinct suites of elevated trace metal concentrations, including Cd, Cu, Mo, Ni, Sb, U, V and Zn. The most elevated Mo, Ni, Sb, U, and V concentrations are found in leachates from the lower portion of the Marcellus Shale, the section typically exploited for natural gas production. In addition, lower 207Pb/206Pb ratios within the lower Marcellus Shale (0.661–0.733) provide a distinctive fingerprint from formations above (0.822–0.846) and below (0.796–0.810), reflecting 206Pb produced as a result of in situ 238U decay within this organic rich black shale. Trace metal concentrations from the Marcellus Shale leachates are similar to total metal concentrations from other black shales. These metal concentrations can exceed screening levels recommended by the EPA, and thus have the potential to impact soil and water quality depending on cuttings disposal methods.

Abstract:
Fluids co-produced with methane from hydraulically fractured organic-rich shales of the Marcellus Formation (USA) are characterized by high total dissolved solids (TDS), including elevated levels of Ba, Sr and Br. To investigate the source and geologic history of these high-TDS fluids and their dissolved constituents, we carried out a series of sequential extraction experiments on dry-drilled cuttings extracted within, below and above the Marcellus Shale from a well in Tioga County, New York State. The experiments were designed to extract (1) water soluble components, (2) exchangeable cations, (3) carbonate minerals, and (4) hydrochloric acid-soluble constituents. The geochemistry of the resultant leachates highlights the different geochemical reservoirs for extractable elements within the shale; notably, Na and Br were largely water-soluble, while Ba was extracted primarily from exchangeable sites, and Ca and Sr were found both in exchangeable sites and carbonate. Strontium isotope ratios measured on the leachates indicate that each of the element reservoirs has a distinct value. Measured 87Sr/86Sr ratios in the water soluble component are similar to those of Marcellus produced water, while the ion exchange reservoir yields lower ratios, and carbonate Sr is lower still, approaching Devonian-Silurian seawater values. Despite the isotopic similarity of water leachates and produced water, the total water chemistry argues against generation of produced water by interaction of hydraulic fracturing fluid with “dry” shale. The high-TDS produced water is most likely trapped formation water (within and/or adjacent to the shale) that is released by hydraulic fracturing. The formation water was affected by multiple processes, possibly including basin scale, tectonically-driven fluid flow. Significant chemical and isotopic differences between Marcellus Shale produced water and overlying Upper Devonian/Lower Mississippian produced waters suggests a hydrologic barrier has been maintained in parts of the Appalachian Basin since the late Paleozoic.

Abstract:
Development of unconventional shale gas wells can generate significant quantities of drilling waste, including trace metal-rich black shale from the lateral portion of the drillhole. We carried out sequential extractions on 15 samples of dry-drilled cuttings and core material from the gas-producing Middle Devonian Marcellus Shale and surrounding units to identify the host phases and evaluate the mobility of selected trace elements during cuttings disposal. Maximum whole rock concentrations of uranium (U), arsenic (As), and barium (Ba) were 47, 90, and 3333 mg kg−1, respectively. Sequential chemical extractions suggest that although silicate minerals are the primary host for U, as much as 20% can be present in carbonate minerals. Up to 74% of the Ba in shale was extracted from exchangeable sites in the shale, while As is primarily associated with organic matter and sulfide minerals that could be mobilized by oxidation. For comparison, U and As concentrations were also measured in 43 produced water samples returned from Marcellus Shale gas wells. Low U concentrations in produced water (<0.084–3.26 μg L−1) are consistent with low-oxygen conditions in the wellbore, in which U would be in its reduced, immobile form. Arsenic was below detection in all produced water samples, which is also consistent with reducing conditions in the wellbore minimizing oxidation of As-bearing sulfide minerals. Geochemical modeling to determine mobility under surface storage and disposal conditions indicates that oxidation and/or dissolution of U-bearing minerals in drill cuttings would likely be followed by immobilization of U in secondary minerals such as schoepite, uranophane, and soddyite, or uraninite as conditions become more reducing. Oxidative dissolution of arsenic containing sulfides could release soluble As in arsenate form under oxic acidic conditions. The degree to which the As is subsequently immobilized depends on the redox conditions along the landfill flow path. The results suggest that proper management of drill cuttings can minimize mobilization of these metals by monitoring and controlling Eh, pH and dissolved constituents in landfill leachates.

Abstract:
The Middle Devonian age Marcellus Shale contains one of the largest shale gas plays in North America. Hydrocarbon production in the eastern part of the play is mostly “dry gas,” consisting of essentially pure methane. Production of natural gas liquids (condensate) increases toward the west, which is the area currently, being targeted by developers. Two Marcellus Shale cores from West Virginia were analyzed to compare the isotopic and geochemical characteristics of a liquids-prone well (WV-7) in Wetzel County with a gas-prone well (WV-6) in Monongalia County. The contrasts between the cores indicate that the conditions of the Marcellus Shale deposition were different between the two sites. The dominant organic matter preserved in each core is isotopically different; δ13Corg values are lighter on average in WV-6 compared with WV-7. A possible explanation is that a larger fraction of terrestrial organic matter was preserved in the WV-6 core, whereas WV-7 may contain a greater percentage of marine organic matter. Clastic-influx proxies (e.g. Ti/Al, Ca/Al and Mg/Al) also suggest that the WV-6 core site received a higher siliciclastic input compared to WV-7, consistent with a more proximal location to dry land and the delivery of greater amounts of terrestrial organic matter. Depleted δ13Ccarb values, low concentrations of redox sensitive elements (e.g. V, Cr, Ni and U), and high variability δ15N values in the WV-6 core all suggest the presence of higher dissolved oxygen concentration and short term shifts in an oxic/anoxic boundary near the sediment–water interface during deposition. These lines of evidence indicate that the depositional conditions were favorable for the accumulation of predominantly gas-prone Type III kerogen in the Marcellus Shale at the WV-6 site. In contrast, the Marcellus Shale at the WV-7 site was deposited in a more distal area that received a low terrestrial sediment supply, organic matter primarily derived from marine algae, and bottom water conditions that were dominantly anoxic. Such conditions were favorable for the accumulation of Type II kerogen that has a greater capacity to generate liquid hydrocarbons. Differences between the liquids-prone and gas-prone parts of the Marcellus Shale play have been largely ascribed to depth-of-burial and thermal maturation history; this study indicates that depositional environment and sedimentary facies may have played significant roles as well.

Abstract:
Unconventional natural gas development via horizontal drilling and hydraulic fracturing has greatly increased the supply of natural gas in the United States. However, the practice presents concerns about the possibility for impacts on shallow groundwater aquifers. The Deep River Triassic Basin in central North Carolina is likely to contain natural gas that could be extracted via hydraulic fracturing in the future. Unlike other states where hydraulic fracturing has been employed, North Carolina has no history of commercial oil and gas extraction. In this study, we measured water chemistry, dissolved gases, and volatile organic compounds in 51 private drinking water well samples over the Deep River Triassic Basin. Our data document the background water quality of shallow aquifers in the Deep River Basin, which could provide an important baseline dataset if hydraulic fracturing occurs here in the future. We found only two of the 51 water wells sampled had dissolved CH4 concentrations >0.1 mg/L, and no well had a methane concentration >0.5 mg/L. The δ 13C–CH4 of the two highest CH4 concentration water wells (−69.5‰ and −61‰) suggest a biogenic CH4 source and are distinct from the δ 13C–CH4 of two test gas wells drilled in the area (−54.41‰ and −45.11‰). Unlike other basins overlying shale gas formations in the US, we find no evidence for CH4 migration into shallow groundwater in the Triassic basin. In addition, we found only seven VOCs in five water samples, with all levels below the US EPA’s maximum contaminant levels. Ion and trace metal concentrations in most samples were also below US EPA primary drinking water standards, with the exception of two samples that exceed the standards for As. We modeled the depth of the upper surface of the Cumnock Shale formation in the Deep River Basin using a kriging algorithm and found that its depth below the surface is shallow (0–∼1500 m) relative to other shale formations that have been drilled commercially in the US, including the Marcellus in Pennsylvania and the Fayetteville in Arkansas. The relatively shallow shale, combined with the presence of multiple faults and diabase intrusions that characterize the geology of the area, may make the Deep River Triassic Basin more vulnerable to deep fluid connectivity to shallow aquifers.