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Berlin Brandenburg

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  • 1
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 19 May 2015, Vol.112(20), pp.6325-30
    Description: High-volume hydraulic fracturing (HVHF) has revolutionized the oil and gas industry worldwide but has been accompanied by highly controversial incidents of reported water contamination. For example, groundwater contamination by stray natural gas and spillage of brine and other gas drilling-related fluids is known to occur. However, contamination of shallow potable aquifers by HVHF at depth has never been fully documented. We investigated a case where Marcellus Shale gas wells in Pennsylvania caused inundation of natural gas and foam in initially potable groundwater used by several households. With comprehensive 2D gas chromatography coupled to time-of-flight mass spectrometry (GCxGC-TOFMS), an unresolved complex mixture of organic compounds was identified in the aquifer. Similar signatures were also observed in flowback from Marcellus Shale gas wells. A compound identified in flowback, 2-n-Butoxyethanol, was also positively identified in one of the foaming drinking water wells at nanogram-per-liter concentrations. The most likely explanation of the incident is that stray natural gas and drilling or HF compounds were driven ∼ 1-3 km along shallow to intermediate depth fractures to the aquifer used as a potable water source. Part of the problem may have been wastewaters from a pit leak reported at the nearest gas well pad-the only nearby pad where wells were hydraulically fractured before the contamination incident. If samples of drilling, pit, and HVHF fluids had been available, GCxGC-TOFMS might have fingerprinted the contamination source. Such evaluations would contribute significantly to better management practices as the shale gas industry expands worldwide.
    Keywords: Marcellus Shale ; High-Volume Hydraulic Fracturing ; Natural Gas ; Shale Gas ; Water Quality ; Water Movements ; Extraction and Processing Industry -- Methods ; Groundwater -- Chemistry ; Natural Gas -- Adverse Effects ; Water Pollutants, Chemical -- Analysis ; Water Supply -- Analysis
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 2
    Language: English
    In: Hydrogeology Journal, 8/2014, Vol.22(5), pp.1055-1066
    Description: Multiple geographic information system (GIS) datasets, including joint orientations from nine bedrock outcrops, inferred faults, topographic lineaments, geophysical data (e.g. regional gravity, magnetic and stress field), 290 pre-gas-drilling groundwater samples (Cl–Br data) and Appalachian Basin brine (ABB) Cl–Br data, have been integrated to assess pre-gas-drilling salinization sources throughout Susquehanna County, Pennsylvania (USA), a focus area of Marcellus Shale gas development. ABB has migrated naturally and preferentially to shallow aquifers along an inferred normal fault and certain topographic lineaments generally trending NNE–SSW, sub-parallel with the maximum regional horizontal compressive stress field (orientated NE–SW). Gravity and magnetic data provide supporting evidence for the inferred faults and for structural control of the topographic lineaments with dominant ABB shallow groundwater signatures. Significant permeability at depth, imparted by the geologic structures and their orientation to the regional stress field, likely facilitates vertical migration of ABB fluids from depth. ABB is known to currently exist within Ordovician through Devonian stratigraphic units, but likely originates from Upper Silurian strata, suggesting significant migration through geologic time, both vertically and laterally. The natural presence of ABB-impacted shallow groundwater has important implications for differentiating gas-drilling-derived brine contamination, in addition to exposing potential vertical migration pathways for gas-drilling impacts.De nombreux jeux de données de systèmes d’information géographique (SIG), comprenant l’ orientation des joints de neuf affleurements de roche, des failles supposées, des linéaments topographiques, des données géophysiques (par exemple gravité régionale, champs magnétique et de contrainte), 290 échantillons d’eau souterraine (Cl–Br) et de données Cl–Br provenant de saumures du bassin appalachien (Appalachian Basin brine, ABB), ont été intégrés pour évaluer des sources de salinisation antérieurement à la foration de forage de gaz, dans la province de Susquehanna en Pennsylvanie (Etats-Unis), une zone d’intérêt particulier pour le développement du gaz des schistes de Marcellus. Les ABB ont migré naturellement et préférentiellement vers les couches aquifères peu profondes le long d'une faille normale supposée et de certains linéaments topographiques de direction générale NNE–SSW, subparallèles au champ de contrainte régional de compression horizontale maximale (orienté NE–SW). Les données de gravité et de magnétisme apportent des éléments de confirmation des failles supposées et du contrôle structural des linéaments topographiques avec les signatures des ABB dominantes dans les eaux souterraines des aquifères peu profonds. Une perméabilité significative en profondeur, liée aux structures géologiques et à leur orientation selon les champs de contrainte régional, facilite probablement la migration verticale des fluides de l’ABB depuis la profondeur. On sait que des ABB existent actuellement dans les unités stratigraphiques de l’Ordovicien au Dévonien, mais elles proviennent probablement de couches du Silurien supérieur, ce qui suggère une migration significative à travers les temps géologiques, à la fois verticalement et transversalement. La présence naturelle d’eau souterraine de faible profondeur impactée par les ABB a des implications importantes pour différentier une contamination par des saumures provenant des forages de gaz, en plus d’exposer des voies verticales potentielles de migration pour des impacts de forage.Múltiples conjuntos de datos de un sistema de información geográfica (GIS), incluyendo orientaciones de diaclasas de nueve afloramientos de basamento, fallas inferidas, lineamientos topográficos, datos geofísicos (por ejemplo gravedad regional, campos magnéticos y de tensiones), 290 muestras de agua subterránea de perforaciones previas de gas (datos de Cl–Br) y datos de Cl–Br de la salmuera de la cuenca Appalachian (ABB), fueron integrados para evaluar las fuentes de salinización en perforaciones previas de gas a través de Susquehanna County, Pennsylvania (EEUU), una zona focal del desarrollo de gas de Marcellus Shale. ABB ha migrado naturalmente y preferencialmente hacia los acuíferos someros a lo largo de una falla normal inferida y ciertos lineamientos topográficos de tendencia generalmente NNE–SSW, sub-paralelo con el máximo campo regional horizontal compresivo de tensiones (orientado NE–SW). Los datos de gravedad y magnéticos proveen evidencias de apoyo para las fallas inferidas y para el control estructural de los lineamientos topográficos con marcas de ABB dominantes en el agua subterránea somera. La permeabilidad significativa en profundidad, determinada por las estructuras geológicas y su orientación hacia el campo regional de tensiones, muy probablemente facilita la migración de fluidos ABB desde profundidad. Se conoce que el ABB existe comúnmente dentro de unidades estratigráficas del Ordovícico y a través de unidades Devónicas, pero probablemente se origina desde estrato del Silúrico superior, lo que sugiere una migración significativa a través del tiempo geológico, tanto verticalmente como lateralmente. La presencia natural en el agua subterránea somera impactada por ABB tiene importantes implicancias para diferenciar la contaminación por salmuera derivada de las perforaciones de gas, además de exponer las trayectorias de una potencial migración vertical para los impactos en las perforaciones de gas.结合多重地理信息系统数据集,包括九个基岩出露点的节理走向、推断的断层、地形轮廓、地球物理数据(如区域重力、地磁及应力场)、290个气体钻探前的水样(Cl–Br数据)及阿巴拉契亚流域卤水Cl–Br数据评价了(美国)宾西法尼亚州整个萨斯奎哈纳县气体钻探前盐化之源,这个地区是玛西拉页岩气开发的重点区域。阿巴拉契亚流域卤水自然而优先地运移到沿推断的正断层的浅层含水层,某些地形轮廓通常走向为NNE–SSW,近似平行于最大的区域横向抗压应力场(走向NE–SW)。重力和地磁数据为推断的断层和主要为阿巴拉契亚流域卤水浅层含水层特征的地形轮廓构造控制提供支持证据。地质构造及其到区域应力场的走向造成的深部显著的透水性可能促进深部的阿巴拉契亚流域卤水液体的垂直运移。已知阿巴拉契亚流域卤水目前存在于奥陶纪到泥盆纪的地层单元内,但是可能来源于晚志留纪地层,表明在漫长的地质年代中,垂直和侧向上都有很大的运移。自然存在的受到阿巴拉契亚流域卤水影响的浅层地下水除了可以暴露出气体钻探影响的潜在垂直运移通道外,还可以区分气体钻探导致的卤水污染。Múltiplas bases de dados de sistemas de informação geográfica (SIG), incluindo orientações de fraturas de nove afloramentos do soco, falhas inferidas, lineamentos topográficos, dados geofísicos (e.g. campo gravítico, campo magnético e campo de tensões regionais), 290 amostras de água subterrânea anteriores às perfurações para produção de gás (dados de Cl–Br) e dados de Cl–Br da salmoura da Bacia dos Apalaches (ABB), foram integrados para avaliar fontes de salinização anteriores às perfurações destinadas à produção de gás em todo o Condado de Susquehanna, na Pensilvânia (EUA), uma área em foco no desenvolvimento do gás dos Xistos Marcellus. A ABB migrou natural e preferencialmente para os aquíferos pouco profundos ao longo de uma falha normal inferida e de certos lineamentos topográficos geralmente com orientação NNE–SSW, subparalelos à tensão compressiva horizontal regional máxima (orientada NE–SW). Dados gravimétricos e magnéticos fornecem elementos comprovativos da existência das falhas inferidas e do controlo estrutural dos lineamentos topográficos com água subterrânea a pequena profundidade com assinatura dominante da ABB. A permeabilidade significativa em profundidade, transmitida pelas estruturas geológicas e pela sua orientação em relação ao campo de tensões regional, facilita provavelmente a migração vertical de fluidos de ABB de profundidade. Sabe-se atualmente que a ABB ocorre nas unidades estratigráficas do Ordovícico até ao Devónico, mas que tem origem provável nos estratos do Silúrico Superior, sugerindo uma migração significativa ao longo do tempo geológico, tanto vertical como lateralmente. A presença natural de águas subterrâneas pouco profundas com influência da ABB tem implicações importantes na diferenciação da contaminação por salmoura derivada das perfurações para gás, para além de expor vias de migração vertical potenciais para impactes das perfurações de gás.
    Keywords: Earth Sciences ; Hydrogeology ; Hydrology/Water Resources ; Geology ; Waste Water Technology / Water Pollution Control / Water Management / Aquatic Pollution ; Marcellus Shale ; Fractured Rocks ; Lineaments ; Salinization ; USA ; Geography ; Geology;
    ISSN: 1431-2174
    E-ISSN: 1435-0157
    Source: Springer (via CrossRef)
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  • 3
    Language: English
    In: International Journal of Coal Geology, 01 June 2014, Vol.126, pp.140-156
    Description: Improvements in horizontal drilling and hydrofracturing have revolutionized the energy landscape by allowing the development of so-called “unconventional” gas resources. The Marcellus play in the northeastern U.S.A. documents how fast this technology developed: the number of unconventional Marcellus wells in Pennsylvania (PA) increased from 8 in 2005 to ~ 7234 today. Publicly available databases in PA show only rare evidence of contamination of surface and groundwaters. This could document that incidents that impact PA waters have been relatively rare and that contaminants were quickly diluted. However, firm conclusions are hampered by i) the lack of information about location and timing of incidents; ii) the tendency to not release water quality data related to specific incidents due to liability or confidentiality agreements; iii) the sparseness of sample and sensor data for the analytes of interest; iv) the presence of pre-existing water impairments that make it difficult to determine potential impacts from shale-gas activity; and v) the fact that sensors can malfunction or drift. Although the monitoring data available to assess contamination events in PA are limited, the state manages an online database of violations. Overall, one fifth of gas wells drilled were given at least one non-administrative notice of violation (NOV) from the PA regulator. Through March 2013, 3.4% of gas wells were issued NOVs for well construction issues and 0.24% of gas wells received NOVs related to methane migration into groundwater. Between 2008 and 2012, 161 of the ~ 1000 complaints received by the state described contamination that implicated oil or gas activity: natural gas was reported for 56% and brine salt components for 14% of the properties. Six percent of the properties were impacted by sediments, turbidity, and/or drill cuttings. Most of the sites of groundwater contamination with methane and/or salt components were in previously glaciated northern PA where fracture flow sometimes allows long distance fluid transport. No cases of subsurface transport of fracking or flowback fluids into water supplies were documented. If Marcellus-related flowback/production waters did enter surface or groundwaters, the most likely contaminants to be detected would be Na, Ca, and Cl, but those elements are already common in natural waters. The most Marcellus-specific “fingerprint” elements are Sr, Ba, and Br. For example, variable Br concentrations measured in southwestern PA streams were attributed to permitted release of wastewaters from unconventional shale gas wells into PA streams through municipal or industrial wastewater treatment plants before 2011. Discharge has now been discontinued except for brines from a few plants still permitted to discharge conventional oil/gas brines after treatment. Overall, drinking water supply problems determined by the regulator to implicate oil/gas activities peaked in frequency in 2010 while spill rates increased through 2012. Although many minor violations and temporary problems have been reported, the picture that emerges from PA is that the fast shale-gas start may have led to relatively few environmental incidents of significant impact compared to wells drilled; however, the impacts remain difficult to assess due to the lack of transparent and accessible data.
    Keywords: Unconventional Shale Gas ; Environmental Impact ; Hydraulic Fracturing ; Hydrofracturing ; Water Quality ; Marcellus Shale ; Engineering
    ISSN: 0166-5162
    E-ISSN: 1872-7840
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