Conventional Oil—The Forgotten Part of the Water-Energy Nexus

The impacts of unconventional oil and gas production via high-volume hydraulic fracturing (HVHF) on water resources, such as water use, groundwater and surface water contamination, and disposal of produced waters, have received a great deal of attention over the past decade. Conventional oil and gas production (e.g., enhanced oil recovery [EOR]), which has been occurring for more than a century in some areas of North America, shares the same environmental concerns, but has received comparatively little attention. Here, we compare the amount of produced water versus saltwater disposal (SWD) and injection for EOR in several prolific hydrocarbon producing regions in the United States and Canada. The total volume of saline and fresh to brackish water injected into depleted oil fields and nonproductive formations is greater than the total volume of produced waters in most regions. The addition of fresh to brackish “makeup” water for EOR may account for the net gain of subsurface water. The total amount of water injected and produced for conventional oil and gas production is greater than that associated with HVHF and unconventional oil and gas production by well over a factor of 10. Reservoir pressure increases from EOR and SWD wells are low compared to injection of fluids for HVHF, however, the longer duration of injections could allow for greater solute transport distances and potential for contamination. Attention should be refocused from the subsurface environmental impacts of HVHF to the oil and gas industry as a whole.     

Site-dependent models of earthquake ground motion

Random vibration analyses of structural systems subjected to seismic loading are dependent upon the characterization of earthquake ground motion as a stochastic process. The response of structural systems to earthquakes is dependent strongly on the local geological conditions, which should be incorporated into seismological models of ground motion. In the study presented herein, three previously developed ground-motion models are adapted to incorporate site-dependent characteristics. Records obtained from two recording stations in California are used as a basis for the ground-motion models. Single-degree-of-freedom (SDOF) oscillators are subjected to ensembles of accelerograms generated from these models, and both elastic and inelastic response are considered. Response statistics are compared to those generated by the analysis of structural response to ensembles of recorded motion from the two sites. The important features of the ground motion for effective reproduction of response statistics are identified, and observations are made on the sensitivity of specific response parameters to site-dependent characteristics of the ground motion.     

The relationships between tropical Atlantic sea level variability and major climate indices

Relationships were examined between variability in tropical Atlantic sea level and major climate indices with the use of TOPEX/POSEIDON altimeter and island tide gauge data with the aim of learning more about the external influences on the variability of the tropical Atlantic ocean. Possible important connections were found between indices related to the El Niño–Southern Oscillation (ENSO) and the sea levels in all three tropical regions (north, equatorial, and south), although the existence of only one major ENSO event within the decade of available altimetry means that a more complete investigation of the ENSO-dependence of Atlantic sea level changes has to await for the compilation of longer data sets. An additional link was found with the Indian Ocean Dipole (IOD) in the equatorial region, this perhaps surprising observation is probably an artifact of the similarity between IOD and ENSO time series in the 1990s. No evidence was obtained for significant correlations between tropical Atlantic sea level and North Atlantic Oscillation or Antarctic Oscillation Index. The most intriguing relationship observed was between the Quasi-Biennial Oscillation and sea level in a band centered approximately on 10°S. A plausible explanation for the relationship is lacking, but possibilities for further research are suggested.     

Strong variation in weathering of layered rock maintains hillslope‐scale strength under high precipitation

The evolution of volcanic landscapes and their landslide potential are both dependent upon the weathering of layered volcanic rock sequences. We characterize critical zone structure using shallow seismic V_p and V_s profiles and vertical exposures of rock across a basaltic climosequence on Kohala peninsula, Hawai’i, and exploit the dramatic gradient in mean annual precipitation (MAP) across the peninsula as a proxy for weathering intensity. Seismic velocity increases rapidly with depth and the velocity–depth gradient is uniform across three sites with 500–600 mm/yr MAP, where the transition to unaltered bedrock occurs at a depth of 4 to 10 m. In contrast, velocity increases with depth less rapidly at wetter sites, but this gradient remains constant across increasing MAP from 1000 to 3000 mm/yr and the transition to unaltered bedrock is near the maximum depth of investigation (15–25 m). In detail, the profiles of seismic velocity and of weathering at wet sites are nowhere monotonic functions of depth. The uniform average velocity gradient and the greater depths of low velocities may be explained by the averaging of velocities over intercalated highly weathered sites with less weathered layers at sites where MAP > 1000 mm/yr. Hence, the main effect of climate is not the progressive deepening of a near‐surface altered layer, but rather the rapid weathering of high permeability zones within rock subjected to precipitation greater than ~1000 mm/yr. Although weathering suggests mechanical weakening, the nearly horizontal orientation of alternating weathered and unweathered horizons with respect to topography also plays a role in the slope stability of these heterogeneous rock masses. We speculate that where steep, rapidly evolving hillslopes exist, the sub‐horizontal orientation of weak/strong horizons allows such sites to remain nearly as strong as their less weathered counterparts at drier sites, as is exemplified by the 50°–60° slopes maintained in the amphitheater canyons on the northwest flank of the island. Copyright © 2017 John Wiley & Sons, Ltd.     

Extracting drainage networks and their connectivity using LiDAR data

Policies, measures, and models geared towards flood prevention and managing surface waters benefit from high quality data on the presence and characteristics of drainage ditches. As a cost and labour effective alternative for acquiring such data through field surveys, we propose a method (a) to extract vector data representing ditch drainage networks based on local morphologic features derived from high resolution digital elevation models (DEM) and (b) to identify possible connections in the ditch network by calculating a probability of the connectivity using a logistic regression where the predictor variables are characteristics of the ditch centre lines or derived from the DEM. Using Light Detection and Ranging (LiDAR) derived DEMs with a 1 m resolution, the method was developed and tested for a mixed agricultural residential area in north‐eastern Belgium. The derived ditch segments had an error of omission of 8% and an error of commission of 5%. The original positional accuracy of the centre lines of the extracted ditches was 0.6 m and could be improved to 0.4 m by shifting each vertex to the position of the lowest LiDAR point located within a radius equal to the spatial resolution of the used DEM. About 69% of the false disconnections in the network were identified and corrected leading to a reduction of the unconnected parts of the ditch network by 71%. The extracted and connected network approximated the reference ditch network fairly well.     

Indicators of sediment and biotic mercury contamination in a southern New England estuary

Total mercury (Hg) and methylmercury (MeHg) were analyzed in near surface sediments (0-2 cm) and biota (zooplankton, macro-invertebrates, finfish) collected from Narragansett Bay (Rhode Island/Massachusetts, USA) and adjacent embayments and tidal rivers. Spatial patterns in sediment contamination were governed by the high affinity of Hg for total organic carbon (TOC). Sediment MeHg and percent MeHg were also inversely related to summer bottom water dissolved oxygen (DO) concentrations, presumably due to the increased activity of methylating bacteria. For biota, Hg accumulation was influenced by inter-specific habitat preferences and trophic structure, and sediments with high TOC and percent silt-clay composition limited mercury bioavailability. Moreover, hypoxic bottom water limited Hg bioaccumulation, which is possibly mediated by a reduction in biotic foraging, and thus, dietary uptake of mercury. Finally, most biota demonstrated a significant positive relationship between tissue and TOC-normalized sediment Hg, but relationships were much weaker or absent for sediment MeHg. These results have important implications for the utility of estuarine biota as subjects for mercury monitoring programs.     

Eddy covariance imaging of diffuse volcanic CO<Subscript>2</Subscript> emissions at Mammoth Mountain,CA, USA

Use of eddy covariance (EC) techniques to map the spatial distribution of diffuse volcanic CO₂ fluxes and quantify CO₂ emission rate was tested at the Horseshoe Lake tree-kill area on Mammoth Mountain, California, USA. EC measurements of CO₂ flux were made during September–October 2010 and ranged from 85 to 1,766 g m⁻² day⁻¹. Comparative maps of soil CO₂ flux were simulated and CO₂ emission rates estimated from three accumulation chamber (AC) CO₂ flux surveys. Least-squares inversion of measured eddy covariance CO₂ fluxes and corresponding modeled source weight functions recovered 58–77% of the CO₂ emission rates estimated based on simulated AC soil CO₂ fluxes. Spatial distributions of modeled surface CO₂ fluxes based on EC and AC observations showed moderate to good correspondence (R ² = 0.36 to 0.70). Results provide a framework for automated monitoring of volcanic CO₂ emissions over relatively large areas.     

Collapse structures in the Permian of the Saar-Nahe area,Southwest Germany

Volcanic breccias near an intrusive rhyolite dome in the Permian Saar-Nahe trough of southwest Germany have been identified as complex pipe-like subsidence-structures occupying the site and immediate neighbourhood of explosive volcanoes.At the Rödern, at first fine-grained, well-bedded and later coarser-grained and poorly bedded pyroclastic materials were deposited on top of a lava flow that formed the regional surface. Collapse along a ringfault with differential subsidence of 500 to 700 m produced a saucer-shaped structure in which steeply dipping pyroclastic beds still overlie the lava flow on which they were originally deposited. In the actual feeder, large blocks of country-rock subsided individually prior to wholesale subsidence of the entire feeder-content. Intrusion of a high alumina quartz tholeiite into the pyroclastic beds terminated the activity.The Hirschberg structure has essentially the same history, but is more fragmented. Subsidences vary between 150 and 260 m. Intrusion of petrographically and chemically similar basalt took place mainly near the margin of the ringfault.Three smaller structures also contain bedded pyroclastic deposits that subsided approximately 600, 1100, and 1400 m. The surface expressions of these five collapse structures are assumed to have been small collapse-calderas with diameters of several 100 m. to 1.5 km.

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Zusammenfassung Vulkanische Brekzien im Rotliegenden der Umgebung des Donnersberges in der Saar-Nahe-Senke/Pfalz liegen in Einbruchsstrukturen vor, die den ursprünglichen Schlot und seine unmittelbare Umgebung einnehmen.Am Rödern wurden ehemals auf einer Olivin-Basalt-Lava feinkörnige und spÄter grobkörnige Pyroclastica abgelagert. Einbruch an einem Ringbruch und differentielle Absenkung zwischen 500 und 700 m führte zur Anlage der trichterförmigen Struktur der geschichteten Pyroclastica. Trotz der Absenkung liegen sie immer noch mit ungestörtem Kontakt, jedoch nun steil einfallend, dem mitabgesenkten Olivin-Basalt auf.Am ursprünglichen Schlot ist Absenkung einzelner gro\er Nebengesteinsschollen und nachfolgend des gesamten Schlotinhaltes festzustellen. Die vulkanische AktivitÄt wurde durch Intrusion eines high-alumina Quarz-Tholeiites abgeschlossen.Der Hirschberg weist im wesentlichen die gleiche Struktur und Entwicklungsgeschichte auf, ist jedoch in mehrere Schollen untergliedert. Die BetrÄge der differentiellen Absenkung liegen zwischen 150 und 260 m. Infolge der Zerblockung innerhalb des Ringbruches intrudierte Basalt vorwiegend im Bereich der Verwerfungen, also am Ringbruch und zwischen einzelnen Schollen.Drei kleinere Strukturen enthalten ebenfalls geschichtete Pyroclastica und weisen maximale AbsenkungsbetrÄge von 600, 1100 und 1400 m auf.Im Bereich der ursprünglichen ErdoberflÄche müssen infolge der Einbrüche tiefe Krater vorgelegen haben, die als kleine Einbruchscalderen bezeichnet werden können.

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Résumé Aux alentours du «Donnersberg» dans la «Saar-Nahe-Senke» (Palatinat, Sudouest de l'Allemagne) des brèches volcaniques du Permien inférieur sont conservées à l'intérieur de structures d'effondrement. Celles-ci se trouvent au lieu mÊme de la cheminée originale et à ses alentours immédiats.Une de ces structures, le «Rödern», est caractérisée par des dépÔts pyroclastiques — fins à la base et plus grenus vers le sommet — couvrant des laves basaltiques à olivine. L'effondrement à l'intérieur d'une faille annulaire et une subsidence différentielle de 500 à 700 m ont eu comme résultat une structure rappelant un entonnoir. Les dépÔts pyroclastiques stratifiés reposent, quoiqu'avec un pendage fort, toujours en superposition normale et non faillés sur les basaltes à olivine qui eux aussi ont été affectés par la subsidence.A la cheminée mÊme on constate l'affaissement de grands panneaux de roches encaissantes suivi de l'effondrement de tout le remplissage de cheminée. L'activité s'achève par des venues d'une «high-alumina Quarz-Tholeiite».Le «Hirschberg», dont la structure et l'évolution ressemblent à celles du «Rödern», est caractérisé par une fragmentation du bloc effondré. L'affaissement de différents panneaux varie entre 150 et 260 m. Suite à la fragmentation de nouvelles venues basaltiques prennent place, soit le long de la faille annulaire, soit le long des failles entre les differents panneaux.Des dépÔts pyroclastiques stratifiés sont conservés encore dans trois autres structures plus petites. L'affaissement à l'intérieur de ces structures est de 600, 1100 et 1400 m au maximumQuant à la morphologie de la région après l'effondrement, on peut supposer qu'elle était caractérisée par l'existence de cratères profonds (caldères d'effondrement).

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, Donnersberg ( -, ) , . - Rödern - , . - 500–700 , . , .- , . . - Hirschberg, , , . 150–260 . , . . . - ; 600, 1100 1400 . - , , , , .

     

Time series analysis of CO concentrations from an Eastern Kentucky coal fire

Coal fires in natural outcrops, in abandoned and active coal mines, and in coal and coal-refuse piles are responsible for the uncontrolled emissions of gases, including CO, CO₂, H₂S, hydrocarbons, and volatile aromatics. Typically, measurements of gases at a mine vent are made over a short time interval, perhaps no more than 10 min, including the time for replicate measurements. Such timing provides little information on longer-term variations in emissions, although comparisons of seasonal measurements suggest such changes do occur. To address this problem, we placed temperature and CO data loggers in coal fire vents to collect time series measurements for a period of up to three weeks. For one experiment, 11 days of data at one-minute intervals indicated that the CO emissions were generally in the 400–550 ppmv range. However near daily depressions in CO concentrations occurred and in some cases fell below 50 ppmv; followed by an increase to ~ 700–800 ppmv; in turn followed by a return to the ambient conditions. Data for a separate 21-day collection period in a different vent of the same fire exhibited similar trends, albeit at a higher CO concentration. The drop in CO concentration may be associated with a meteorologically-driven inhalation cycle of the fire, whereby air diluted the combustion generated CO. We propose this was followed by an increase in the intensity of the fire due to increased O₂ from the inhaled air, producing increased CO concentrations, before settling back to the ambient conditions.     

Origin and crystallization history of Permian tholeiites from the Saar-Nahe trough,SW Germany

The Hirschberg and Rödern diatremes, within the Permian Saar-Nahe trough, SW Germany, are composed chiefly of basaltic tuffs, with associated small intrusions of K-rich tholeiites. Several tholeiite bodies carry 2–20 mm crystals of magnesian clinopyroxene and orthopyroxene, the latter containing up to 5.5% Al₂O₃ and often extensively resorbed and rimmed by fine-grained olivine and clinopyroxene. Experimental duplication of these pyroxenes has been achieved under conditions of Pload=6–10 kb, T=1280–1080° C and 2–4 wt.-% H₂O, confirming that they represent a rare occurence of high pressure phenocrysts in tholeiitic basalts.These conditions of pyroxene crystallization also place constraints on processes of magma generation, indicating that the tholeiites originated by partial melting of unusually hydrous peridotite mantle (0.4–0.8% H₂O) beneath a relatively thin continental crust (maximum thickness approximately 30 km). Water present in the mantle at the site of magma generation may have been derived from the dehydration of oceanic lithosphere prior to the formation of the Saar-Nahe trough. This lithosphere probably underwent subduction at the margin of the Palaeozoic European continent during the Hercynian cycle of sedimentation, andesitic volcanism and folding. The termination of this cycle was followed by a period of basin-range type tensional faulting, leading to the formation of the Permian basins of present-day Central Europe, and widespread bimodal basalt/rhyolite volcanism.