Quartz Cement in Middle Jurassic Reservoir Sandstones in North Sea A Review. Part II： Duration and Silica Sources     

Shao nan Zhang Knut Bj Φ rlykke 《沉积学报》2000,18(1):119-126

The timing and duration of quartz cementation in sandstones have been mainly inferred from diagenetic texture, relationship between pore filling minerals, fluid inclusions and isotopic data. Fluid inclusion temperatures from North Sea reservoir sandstones indicate that most of the quartz cement forms at temperature exceeding 90℃ and is continually proceeding after oil emplacement, based on the fluid inclusion temperatures in quartz overgrowth which is approaching the bottom-hole temperatures. The duration of quartz cement after oil emplacement depends upon the saturation of porewater and the distribution of pore water film and the property of water-wet or oil-wet of the reactants. The leaching of K-feldspar by meteoric water requires pore water flow to move the released potassium and sodium and silica out the solution, which suggests the mechanism does not appear to be a major source of silica for quartz cementation. The quartz cementation coincidence with the compaction and pressure solution suggests the major source of silica. The alteration of feldspar by illitization of kaolinite may serve as another important source of silica at deep burial depth. External sources are not need to call on for illustrating the quartz cementation, because there is no evidences for large scale convection of pore water flow occurred in the burial history of reservoir sandstones of middle Jurassic in the North Sea.  相似文献   

A New method for identifying possible causal relationships between CO2, total solar irradiance and global temperature change   总被引：1，自引：0，他引：1  

Seip  Knut L.  Grøn  Øyvind 《Theoretical and Applied Climatology》2017,129(3-4):923-938

The study compares two formulas for calculating the daily evapotranspiration ET₀ for a reference crop. The first formula was proposed by Allen et al. (AL), while the second one was proposed by Katerji and Perrier with the addition of the carbon dioxide (CO₂) effect on evapotranspiration (KP). The study analyses the impact of the calculation by the two formulas on the irrigation requirement (IR). Both formulas are based on the Penman-Monteith equation but adopt different approaches for parameterising the canopy resistance r _c . In the AL formula, r _c is assumed constant and not sensitive to climate change, whereas in the KP formula, r _c is first parameterised as a function of climatic variables, then ET₀ is corrected for the air CO₂ concentration. The two formulas were compared in two periods. The first period involves data from two sites in the Mediterranean region within a measured climate change period (1981–2006) when all the input climatic variables were measured. The second period (2070–2100) involves data from a future climate change period at one site when the input climatic variables were forecasted for two future climate scenarios (A2 and B2). The annual cumulated values of ET₀ calculated by the AL formula are systematically lower than those determined by the KP formula. The differences between the ET₀ estimation with the AL and KP formulas have a strong impact on the determination of the IR for the reference crop. In fact, for the two periods, the annual values of IR when ET₀ is calculated by the AL formula are systematically lower than those calculated by the KP formula. For the actual measured climate change period, this reduction varied from 26 to 28 %, while for the future climate change period, it varied based on the scenario from 16 % (A2) to 20 % (B2).  相似文献   

Resource management regimes and innovation in peripheral nature-based tourism: The case of North Cape tourism and sea-fishing tourism     

Heidi Holmgren  Knut Bjørn Lindkvist 《Norsk geografisk tidsskrift. Norwegian journal of geography》2016,70(4):203-215

The study objective was to analyse how capitalized and non-capitalized resource rents act as mechanisms of innovation in nature-based tourism within a centre–periphery context dominated by distance, instability, and dependency. The authors studied 55 out of 64 businesses engaged in tourism in Nordkapp Municipality in Norway in the period 2002–2012. Data were collected from a survey, interviews, and empirical observations, and then analysed using both deductive and inductive methodological approaches. The main findings were that tourism in the Nordkapp Municipality had suffered from a lack of local innovation initiatives caused by the capitalized resource rent of tourism to North Cape and its leakage. Nevertheless, local tourism had increased partly because of the inclusion of new and more attractive products, due to the open-access, non-capitalized resource management in fishing tourism that operated simultaneously with the closed and capitalized context of North Cape tourism. The authors conclude that this open-access regime of fishing tourism stimulated innovation and further development of coastal tourism, and even affected traditional North Cape tourism. Non-capitalized resource rent had not leaked out because it had not been collected by external companies and because it had acted as an innovation mechanism on the periphery.  相似文献   

Limits to transparency exploring conceptual and operational aspects of the ICES framework for providing precautionary fisheries management advice     

Hauge  Kjellrun Hiis; Nielsen  Kare Nolde; Korsbrekke  Knut 《ICES Journal of Marine Science》2007,64(4):738-743

  相似文献   

Growth, reproductive cycle, and movement of berried European lobsters (Homarus gammarus) in a local stock off southwestern Norway     

Agnalt  Ann-Lisbeth; Kristiansen  Tore S.; Jorstad  Knut E. 《ICES Journal of Marine Science》2007,64(2):288-297

  相似文献   

The ocean/continent transition along a profile through the Lofoten basin,Northern Norway     

Andreas Goldschmidt-Rokita  Knut J. F. Hansch  Hans B. Hirschleber  Takaya Iwasaki  Toshihiko Kanazawa  Hideki Shimamura  Markvard A. Sellevoll 《Marine Geophysical Researches》1994,16(3):201-224

The Cenozoic margins of the Norwegian-Greenland Sea offer ideal conditions for passive margin studies. A series of structural elements, first observed on these margins, led to the concept of volcanic passive margins. Questions still remain about the development of such features and the location of the boundary between oceanic and continental crust. Despite the thin sediment cover of the margins, seismic reflection data are not able to image the deeper structures due to the occurrence of igneous rocks at shallow depth.This paper presents a 320-km long profile perpendicular to the strike of the main structural units of the Lofoten Margin in Northern Norway. A geological model is proposed, based on observations made with ocean bottom seismographs, which recorded seismic refraction data and wide angle reflections, along with a seismic reflection profile covering the same area. Ray-tracing was used to calculate a geophysical model from the shelf area into the Lofoten basin. The structures typical of a volcanic passive margin were found, showing that the Lofoten Margin was influenced by increased volcanic activity during its evolution. The ocean/continent transition is located in a 30-km wide zone landwards of the Vøring Plateau escarpment.The whole margin is underlain by a possibly underplated, high velocity layer. Evidence for a pre-rift sediment basin landwards of the escarpment, overlain by basalt flows, was seen. These structural features, related to extensive volcanism on the Lofoten Margin, are not as distinct as further south along the Norwegian Margin. Viewed in the light of the hot-spot theory of White and McKenzie (1989) the Lofoten Margin can be interpreted as a transitional type between volcanic and non-volcanic passive margin.  相似文献   

A precision kite or balloon-borne mini-sonde for wind and turbulence measurements     

Ann-Sofi Smedman  Knut Lundin  Hans Bergström  Ulf Högström 《Boundary-Layer Meteorology》1991,56(3):295-307

A highly mobile system for accurate measurements of wind speed and horizontal turbulence in the lowest few hundred meters of the atmosphere is presented. It consists of a light-weight sonde (only 50 g, including batteries that permit 12 h of continuous operation) which can be easily lifted by a small kite in winds below 5 m/s and up to at least 25 m/s. In winds below 5 m/s, a small kytoon may be used instead. The signals from the sonde are received by a standard FM-radio equipped with a frequency converter, and data are recorded on ordinary cassette tapes. Field tests against towermounted precision instruments were performed at two sites during neutral and unstable conditions with the sonde suspended 25 m below a small kite, the measuring heights being 11 and 18 m respectively during the two test series. Mean wind speeds are found to be accurate to within ±0.2 m/s. Wind speed spectra obtained with the flying sonde can be evaluated up to 0.5 Hz and are found to agree closely with the spectra of the longitudinal component recorded simultaneously by the tower-mounted instrument at the same height. After correction for high frequency loss, which amounted to 5% at this low height (it is expected to decrease rapidly with height), the standard deviation of the wind recorded by the sonde agreed to within 2% with that obtained by the reference instrument. A notable result of the field tests is that there was no sign of degradation of the performance of the sonde in strong turbulence conditions.  相似文献   

Holocene aeolian dynamics in the European sand‐belt as indicated by geochronological data     

Johann Friedrich Tolksdorf  Knut Kaiser 《Boreas: An International Journal of Quaternary Research》2012,41(3):408-421

Aeolian sands are widespread in the European sand‐belt. While there is a consensus about the timing of increased aeolian activity and, in contrast, of surface stabilization during the Lateglacial, knowledge about Holocene aeolian dynamics is still very sparse. It is generally assumed that aeolian processes have been closely connected to human activities since at least the Neolithic period. A compilation of 189 luminescence dates from aeolian sands of Holocene age and 301 ¹⁴C‐dates from palaeo‐surfaces, comprising palaeosols, buried peats and archaeological features from the whole sand‐belt, is plotted as histograms and kernel density plots and divided into sub‐phases by cluster analysis. This is also done separately for the dates from the areas west and east of the river Elbe. Our results show that aeolian activity did not cease with the end of the Younger Dryas but continued in the whole European sand‐belt until the Mid‐Atlantic (c. 6500 a BP), presenting evidence of vegetation‐free areas at least at the local scale. During the subsequent time period evidence of aeolian sedimentation is sparse, and surface stabilization is indicated by a cluster of palaeo‐surfaces ascribed to the early Subboreal (c. 5000 cal. a BP). The agglomeration of luminescence ages around 4000 years is probably connected with intensified land use during the Late Neolithic. Younger phases of aeolian sedimentation are indicated by clusters of luminescence ages around 1800 years, a group of luminescence ages from the Netherlands and NW Germany around 900 years, and a group of ages around 680 years in Germany. Among the dates from palaeo‐surfaces, clusters were identified around 2700, 1300 and 900 cal. a BP as well as around 690 cal. a BP in the western part and 610 cal. a BP in the eastern part of the sand‐belt. The clusters within the luminescence ages and the ¹⁴C‐dates coincide with phases where increased human impact can be deduced from archaeological and historical sources as well as from environmental history.  相似文献   

Microfabric and rock properties of experimentally compressed silt-clay mixtures     

Manzar Fawad  Nazmul Haque MondolJens Jahren  Knut Bjørlykke 《Marine and Petroleum Geology》2010

Oedometric mechanical compaction tests were performed on brine-saturated synthetic samples consisting of silt-clay mixtures to study changes in microfabric and rock properties as a function of effective stress. The silt consisted of crushed quartz (∼100%) with grain size range between 4 and 40 μm, whereas the clay consisted of 81% kaolinite, 14% mica/illite and 5% microcline of grain size between 0.4 and 30 μm. Five sample pairs ranging in composition from pure silt to pure clay were compacted to 5 and 50 MPa effective stress respectively. SEM studies were carried out to investigate microfabric changes in the mechanically compacted silt-clay mixtures. The degree of alignment of the different minerals present (quartz, mica/illite and kaolinite) were computed by using an image analysis software. Experimental compaction have measured the changes in the rock properties such as porosity and velocity as a function of effective stress for different mixtures of clay and silt. Clay-rich samples showed a higher degree of mineral orientation and lower porosity compared to silt-dominated samples as a function of effective stress. Pure clay sample had 11% porosity at 50 MPa effective stress whereas the pure silt sample retained about 29% porosity at the same effective stress. The experiments showed that low porosity down to 11% is possible by mechanical compaction only. A systematic increase in strain was observed in the silt-clay mixtures with increasing clay content but the porosity values found for the 50:50 silt-clay mixture were lower than that of 25:75 silt-clay mixture. No preferential mineral orientation is expected before compaction owing to the high initial porosity suggesting that the final fabric is a direct result of the effective stress. Both P- and S-wave velocities increased in all silt-clay mixtures with increasing effective stress. The maximum P- and S-wave velocities were observed in the 25:75 silt-clay mixture whereas the minimum Vp and Vs were recorded in the pure silt mixture. At 50 MPa effective stress P- wave velocities as high as 3 km/s resulted from experimental mechanical compaction alone. The results show that fine-grained sediment porosity and velocity are dependent on microfabric, which in turn is a function of grain size distribution, particle shape, sediment composition and stress. At 5 MPa effective stress, quartz orientation increased as a function of the amount of clay indicating that clay facilitate rotation of angular quartz grains. Adding clay from 25% to 75% in the silt-clay mixtures at 50 MPa effective stress decreased the quartz alignment. The clay mineral orientation increased by increasing both the amount of clay and the effective stress, the mica/illite fabric alignment being systematically higher than that of kaolinite. Even small amount of silt (25%) added to pure clay reduced the degree of clay alignment significantly. This study demonstrates that experimental compaction of well characterized synthetic mudstones can be a useful tool to understand microfabric and rock properties of shallow natural mudstones where mechanical compaction is the dominant process.  相似文献   

Engineering characterisation of Norwegian glaciomarine silt     

Michael Long  Gisli Gudjonsson  Shane Donohue  Knut Hagberg 《Engineering Geology》2010,110(3-4):51-65

Guidance is provided for geotechnical engineers designing civil engineering works in silty soils based on a detailed characterisation of a glaciomarine silt from Os in western Norway. It was found that these soils are susceptible to disturbance by good quality fixed piston tube sampling and care needs to be taken when using laboratory derived design parameters, particularly for consolidation and shear strength properties. A technique for assessing sample disturbance using shear wave velocity and suction measurements proved promising. Conventional techniques for determining soil strength from triaxial tests in silt are inappropriate due to the dilational nature of the material and more reliable and logical strength estimates can be made from a limiting strain criterion. Field vane data should be used with caution as measured strength, particularly remoulded values, may be high and it seems more reliable parameters can be derived from CPTU tests. One dimensional consolidation and creep of these silts can be modelled successfully by the well-known Janbu formulation. The behaviour of the Os silts does not fit easily into classical soil mechanics and published frameworks for soft soils. It seems the material is of “transitional” type and this work adds to the database of such soils which includes other natural silts and gap graded soils. For future work it is recommended that larger sample tubes (say 75 mm) with a very sharp cutting edge should be used in parallel with in situ CPTU testing.  相似文献