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211.
Effective stresses and shear failure pressure from in situ Biot's coefficient,Hejre Field,North Sea
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J.B. Regel K.A. Andreassen N.C. Høegh van Gilse I.L. Fabricius 《Geophysical Prospecting》2017,65(3):808-822
We propose a combination of Biot's equations for effective stress and the expression for shear failure in a rock to obtain an expression for minimum pore pressure in a stable vertical well bore. We show that a Biot's coefficient calculated from logging data in the Hejre Field, North Sea, is significantly different from 1. The log‐derived Biot's coefficient is above 0.8 in the Shetland Chalk Group and in the Tyne Group, and 0.6–0.8 in the Heno Sandstone Formation. We show that the effective vertical and horizontal stresses obtained using the log‐derived Biot's coefficient result in a drilling window for a vertical well larger than if approximating Biot's coefficient by 1. The estimation of the Biot's coefficient is straightforward in formations with a stiff frame, whereas in formations such as shales, caution has to be taken. We discuss the consequence of assumptions made on the mineral composition of shales as unphysical results could be obtained when choosing inappropriate mineral moduli. 相似文献
212.
Samson Afewerki Asbjørn Karlsen Danny MacKinnon 《Norsk geografisk tidsskrift. Norwegian journal of geography》2019,73(1):4-15
ABSTRACTThe authors employ the global production network (GPN) approach to analyse the development of the renewable energy sector. Through a case study of the development of a Hywind floating offshore wind project (Hywind) across two oil and gas economies, namely Norway and Scotland, the paper sheds light on the key drivers and role of core GPN actors. Methodologically, the authors investigate the process from both ‘inside-out’ and ‘outside-in’ perspectives, referring to the efforts of firms expanding into overseas markets and the efforts of host countries to attract investment from outside their territories. The analysis shows how the configuration of extractive production networks is shaped by the interactions between the network development practices of firms and the market development strategies of host states. The authors conclude that the distinct materiality of floating wind power technology shapes the territorial configuration of the production network by enabling its spatial extension across a range of locations. By contrast, existing research on other extractive sectors has emphasized the spatially constraining effects of materiality (Bridge 2008). 相似文献
213.
Peter Rasmussen George Pantopoulos Jørn B. Jensen Jesper Olsen Hans Røy Ole Bennike 《Boreas: An International Journal of Quaternary Research》2020,49(1):108-128
Holocene sedimentation patterns and environmental development in Aarhus Bay, Denmark, were reconstructed based on proxy analyses of two sediment cores (M1 and M5). Together, the two cores offer an opportunity to examine the history of the area during the past c. 10 000 years. The investigation consisted of acoustic mapping and multi-proxy analyses of the sediment cores including macrofossils, sediment physical properties, sediment accumulation rates, grain size, and X-ray fluorescence elemental counts. Radiocarbon dating of the two sediment successions revealed that they cover the periods c. 10 000–3700 cal. a BP (M1) and c. 4400 cal. a BP to the present (M5). The data from the M1 site indicate the presence of a near-shore lake environment between c. 10 000 and 9000 cal. a BP. The first intrusion of marine water into the area is dated to c. 9000 cal. a BP. In the following c. 1300 years, brackish-water conditions prevailed in the area characterized by a mixture of taxa from marine, limnic and terrestrial habitats, reflecting a shallow estuarine environment. Around 7700 cal. a BP full marine conditions were established, accompanied by a marked increase in sedimentation rates. The changes to full marine conditions and higher sedimentation rates are probably due to a significant sea-level rise leading to flooding of former land areas and intensified erosion. A subsequent distinct decrease in sedimentation rates around 6350 cal. a BP is presumably linked to a previously documented sea-level drop about this time. Continuous sedimentation ceased around 3700 cal. a BP in the central part of the bay, most probably due to a major sea-level lowering involving widespread erosion. In the eastern and deeper part of the bay, sedimentation continued until today. Fully marine conditions prevailed there for at least the last 4400 years. 相似文献
214.
Following the first International Conference on Gas in Marine Sediments in Edinburgh, UK (1990), another eight successful conferences have provided a continuous forum for scientists from a variety of disciplines, organisations and countries. The 9th meeting of the Shallow Gas Group was held in September 2008 in Bremen, a hanseatic city more than 1,200 years old in northern Germany. The Shallow Gas Group was joined for this conference by participants of the HERMES EU-funded project and by members of an industry-funded project. Volume 30 (3/4) of Geo-Marine Letters is a double issue containing 25 selected papers from the 9th conference in Bremen, guest edited by G. Bohrmann and B.B. Jørgensen. The papers represent the broad spectrum of oral and poster contributions from the conference, covering a wide range of aspects of gas in marine sediments from many parts of the world. The next conference of the Shallow Gas Group is planned to be held in Listvyanka at Lake Baikal, Russia, in September 2010. 相似文献
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Dissolved organic matter (DOM) export to a temperate estuary: seasonal variations and implications of land use 总被引:1,自引:0,他引:1
Colin A. Stedmon Stiig Markager Morten Søndergaard Torben Vang Anker Laubel Niels Henrik Borch Anders Windelin 《Estuaries and Coasts》2006,29(3):388-400
Inputs of dissolved carbon, nitrogen, and phosphorus were assessed for an estuary and its catchment (Horsens, Denmark). Seasonal
patterns in the concentrations of DOM in the freshwater supply to the estuary differed depending on the soil and drainage
characteristics of the area. In streams draining more natural areas the, patterns observed were largely driven by seasonal
temperature fluctuations. The material exported from agricultural areas was more variable and largely controlled by precipitation
events. Positive exponential relationships were found between the nitrogen and phosphorus loading, and the percentage of catchment
area used for agriculture. Colored DOM (CDOM) loading measurements were found to be a good predictor of dissolved organic
carbon (DOC) loading across the different subcatchments, offering a rapid and inexpensive alternative of operationally monitoring
DOC export. For all the dissolved nutrient inputs to the estuary, dissolved inorganic nitrogen (DIN) and dissolved organic
phosphorus dominated the loadings. Although 81% of the nitrogen annually supplied to the estuary was DIN, 83% of the nitrogen
exported from the estuary was dissolved organic nitrogen (DON). Results show that increasing the area of the catchment covered
by forest and natural pastures would have a positive effect on the trophic status of the estuary, leading to a considerable
decrease in the phosphorus loading and a shift in the nitrogen loading from DIN to DON. Such a change in land use would also
increase the export of DOC and CDOM to the estuary having the potential to increase oxygen consumption and reduce the photic
depth. 相似文献
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Stable remanent directions encountered in three oriented lake-sediment cores, covering 6 m of gyttja deposits, reveal declination swings with amplitudes of the order of ± 50°. Anomalously low inclinations, scattered around the horizontal in the upper 2 m of core, is attributed to compressional disturbances of the alignment of magnetic grains during the coring procedure. Four 14C dates obtained (1250, 1940, 4600 and 6330 y B.P.) have enabled a correlation with features ‘c’–‘g’ of the British Geomagnetic Master Curve). For the older part of the curve, features ‘h’ and ‘i’, the correlation is questionable. Magneto-mineralogical parameters and qualitative chemical analysis of individual grains by secondary X-ray emission analysis reveal the presence of pure magnetite grains. Scanning electron micrographs show a dominant proportion of concoidal slightly elongated grains (10–80 μm). A few almost-perfect octahedral magnetite crystals can be related to outcrops of augen gneisses in the vicinity confirming a detrital origin of these grains. 相似文献