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1.
Erling K. Stenevik Webjrn Melle Eilif Gaard Astthor Gislason Cecilie T.. Broms Irina Prokopchuk Bjrnar Ellertsen 《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2672
Egg production of Calanus finmarchicus was studied during joint basin-scale surveys in April–June 2003 in the Norwegian Sea. Surveys covered the whole Norwegian Sea and were conducted from Norwegian, Icelandic and Faroese research vessels. Stations were classified as being in pre-bloom, bloom or post-bloom phase according to levels of chlorophyll a and nitrate. Individual egg production rates and population egg production rates were calculated and compared between areas. Both individual egg production rates (eggs female−1 day−1) and population egg production rates (eggs m−2 day−1) were significantly higher in bloom areas compared with pre-bloom and post-bloom areas. However, when integrated over an estimated duration of the three phases, the time-integrated egg production (eggs m−2) in most years was highest in the pre-bloom phase, and this was explained by the longer duration of this phase compared with the two other phases. 相似文献
2.
With multiscale permeability estimation one does not select parameterization prior to the estimation. Instead, one performs a hierarchical search for the right parameterization while solving a sequence of estimation problems with an increasing parameterization dimension. In some previous works on the subject, the same refinement is applied all over the porous medium. This may lead to over-parameterization, and subsequently, to unrealistic permeability estimates and excessive computational work. With adaptive multiscale permeability estimation, the new parameterization at an arbitrary stage in the estimation sequence is such that new degrees of freedom are not necessarily introduced all over the porous medium. The aim is to introduce new degrees of freedom only where it is warranted by the data. In this paper, we introduce a novel adaptive multiscale estimation. The approach is used to estimate absolute permeability from two-phase pressure data in several numerical examples. 相似文献
3.
Hege Fonneland-Jorgensen Harald Furnes Karlis Muehlenbachs Yildirim Dilek 《Island Arc》2005,14(4):517-541
Abstract The Solund‐Stavfjord ophiolite complex (SSOC) in western Norway represents a remnant of the Late Ordovician oceanic lithosphere, which developed in an intermediate‐ to fast‐spreading Caledonian back‐arc basin. The internal architecture and magmatic features of its crustal component suggest that the SSOC has a complex, multistage sea floor spreading history in a supra‐subduction zone environment. The youngest crustal section associated with the propagating rift tectonics consists of a relatively complete ophiolite pseudostratigraphy, including basaltic volcanic rocks, a transition zone between the sheeted dyke complex and the extrusive sequence, sheeted dykes, and high‐level isotropic gabbros. Large‐scale variations in major and trace element distributions indicate significant remobilization far beyond that which would result from magmatic processes, as a result of the hydrothermal alteration of crustal rocks. Whereas K2O is strongly enriched in volcanic rocks of the extrusive sequence, Cu and Zn show the largest enrichment in the dyke complex near the dyke–volcanic transition zone or within this transition zone. The δ18O values of the whole‐rock samples show a general depletion structurally downwards in the ophiolite, with the largest and smallest variations observed in volcanic rocks and the transition zone, respectively. δ18O values of epidote–quartz mineral pairs indicate 260–290°C for volcanic rocks, 420°C for the transition zone, 280–345°C for the sheeted dyke complex and 290–475°C for the gabbros. The 87Sr/86Sr isotope ratios show the widest range and highest values in the extrusive rocks (0.70316–0.70495), and generally the lowest values and the narrowest range in the sheeted dyke complex (0.70338–0.70377). The minimum water/rock ratios calculated show the largest variations in volcanic rocks and gabbros (approximately 0–14), and generally the lowest values and range in the sheeted dyke complex (approximately 1–3). The δD values of epidote (?1 to ?12‰), together with the δ18O calculated for Ordovician seawater, are similar to those of present‐day seawater. Volcanic rocks experienced both cold and warm water circulation, resulting in the observed K2O‐enrichment and the largest scatter in the δ18O values. As a result of metal leaching in the hot reaction zone above a magma chamber, Zn is strongly depleted in the gabbros but enriched in the sheeted dyke complex because of precipitation from upwelling of discharged hydrothermal fluids. The present study demonstrates that the near intact effect of ocean floor hydrothermal activity is preserved in the upper part of the SSOC crust, despite the influence of regional lower greenschist facies metamorphism. 相似文献
4.
Seal capacity estimation from subsurface pore pressures 总被引：1，自引：0，他引：1
A cap rock's capacity to seal hydrocarbons depends on its wettability and the sizes of the pore throats within the interconnected pore system that the leaking hydrocarbons must penetrate. These critical pore throat sizes are often poorly constrained in hydrocarbon exploration, partly because measurements of pore throat sizes have not been performed, and partly because pore throat measurements on a few individual samples in the cap rock may not be representative for the seal capacity of the top seal as a whole. To the contrary, the presence of formation overpressure can normally be estimated in drilled exploration targets. The presence of overpressure in reservoirs testifies to small pore throats in the cap rocks, as large pore throats will result in sufficiently high cap rock permeability to bleed off the overpressure. We suggest a stepwise procedure that enables quantification of top seal capacities of overpressured traps, based on subsurface pressure information. This procedure starts with the estimation of cap rock permeabilities, which are consistent with observed overpressure gradients across the top seals. Knowledge of burial histories is essential for these estimations. Relationships between pore throat size and permeability from laboratory experiments are then applied to estimate critical pore throat diameters in cap rocks. These critical pore throat diameters, combined with information of the physical properties of the pore fluids, are then used to calculate membrane seal capacity of cap rocks. Estimates of top seal capacity based on this procedure are rather sensitive to the vertical fluid velocity, but they are also to some extent sensitive to inaccuracies of the pore throat/permeability relationship, overpressure gradient, interfacial tensions between pore fluids, hydrocarbon density and water viscosity values. Despite these uncertainties, applications of the above‐mentioned procedure demonstrated that the mere presence of reservoir overpressures testifies to sufficient membrane seal capacity of cap rocks for most geological histories. Exempt from this statement are basins with rapid and substantial sediment compaction in the recent past. 相似文献
5.
E.K. Hege E.N. Hubbard J.D. Drummond P.A. Strittmatter S.P. Worden T. Lauer 《Icarus》1982,50(1):72-81
We report speckle interferometric observations of Pluto and its moon (1978 P1) Charon obtained on 5 June 1980 with a single 1.8-m mirror of the Multiple Mirror Telescope. Our observations yield a separation of 0″.31 (±0″.05) between Pluto and Charon at position angle 285° (±7°) for JD 2444395.75. This result and other direct observations indicate an adjustment of +4.0 hr to the orbital epoch of R. S. Harrington and J. W. Christy [Astron.J.86, 442–443 (1981)]. Our observation, which represents the first resolution of the system near minimum separation, also suggests that the inclination of the orbit to the plane of the sky should be increased by 3°; this will delay the onset of the predicted eclipsee season by one apparition to 1984 or 1985. Our data are consistent with Pluto diameter 0″.14 (±0″.02) = 3000 (±400) km and Charon diameter 0″..05 (±0″.03) = 1100 (±600) km. 相似文献
6.
?yvind Breivik Tor Christian Bekkvik Cecilie Wettre Atle Ommundsen 《Ocean Dynamics》2012,62(2):239-252
The task of determining the origin of a drifting object after it has been located is highly complex due to the uncertainties
in drift properties and environmental forcing (wind, waves, and surface currents). Usually, the origin is inferred by running
a trajectory model (stochastic or deterministic) in reverse. However, this approach has some severe drawbacks, most notably
the fact that many drifting objects go through nonlinear state changes underway (e.g., evaporating oil or a capsizing lifeboat).
This makes it difficult to naively construct a reverse-time trajectory model which realistically predicts the earliest possible
time the object may have started drifting. We propose instead a different approach where the original (forward) trajectory
model is kept unaltered while an iterative seeding and selection process allows us to retain only those particles that end
up within a certain time–space radius of the observation. An iterative refinement process named BAKTRAK is employed where
those trajectories that do not make it to the goal are rejected, and new trajectories are spawned from successful trajectories.
This allows the model to be run in the forward direction to determine the point of origin of a drifting object. The method
is demonstrated using the leeway stochastic trajectory model for drifting objects due to its relative simplicity and the practical
importance of being able to identify the origin of drifting objects. However, the methodology is general and even more applicable
to oil drift trajectories, drifting ships, and hazardous material that exhibit nonlinear state changes such as evaporation,
chemical weathering, capsizing, or swamping. The backtracking method is tested against the drift trajectory of a life raft
and is shown to predict closely the initial release position of the raft and its subsequent trajectory. 相似文献
7.
A field experiment was conducted to investigate how water-based drill cuttings and sediment type influence colonization of soft bottom communities. Bottom frames with trays containing defaunated sediments were placed at the seabed for 6 months to study colonization of macrofauna. Two different sediments (coarse and fine) were used, and 6 or 24 mm layer of water-based drill cuttings were added on top of these sediments. Some of the sediments were controls with no additions. In the end of the experiment, the oxygen availability in sediment porewater and macrofaunal abundance were reduced in treatments with 24 mm drill cuttings compared to controls. Tube-building annelids were particularly sensitive to drill cuttings. However, these responses were only minor, and notably, the drill cuttings initiated a weaker faunal response than sediment type and site of the bottom frame. Sediments capped with water-based drill cuttings thus showed a rapid colonization of macrofaunal communities. 相似文献
8.
Kerstin Drost Richard Wirth Jan Košler Hege Fonneland Jørgensen Theodoros Ntaflos 《Contributions to Mineralogy and Petrology》2013,165(4):737-756
Xenotime overgrowths on detrital zircon in siliciclastic sediments have been reported in numerous studies. However, in natural samples, solid solution of zircon and xenotime is limited to near-end-member compositions. In order to characterize the interface region between both minerals and to draw inferences on the growth mechanisms of authigenic xenotime, we studied xenotime overgrowths on detrital zircon grains from two Phanerozoic sandstone samples with contrasting post-depositional histories. In one sample, the small (≤10 μm), pyramidal xenotime overgrowths are of diagenetic origin and grew without major discontinuity on the detrital zircon grain. The second sample shows up to >50-μm-wide, porous and inclusion-rich, hydrothermal xenotime overgrowths on detrital zircon, whereas the transition zone between both minerals is accompanied by large pore volume. Chemical compositions of the xenotime precipitates from the two samples differ particularly in Y, REE, Th and Sc concentrations, whereas high MREE availability in the diagenetic sample and the presence of Sc in the hydrothermal sample, respectively, appear to have promoted xenotime growth. Transmission electron microscopy on electron-transparent foils cut from the interface region shows that both the diagenetic xenotime and the hydrothermal xenotime are crystalline and grew in optical and crystallographic continuity to their detrital zircon substrata. Only a narrow transition zone (≤90 nm—diagenetic sample, 200–300 nm—hydrothermal sample) between zircon and xenotime is in part made up of nanometre-scale crystalline domains that are slightly distorted and may have formed from dissolution–re-precipitation processes at the zircon rim along with precipitation from the respective fluid. 相似文献
9.
Dag Myrhaug Muk Chen Ong Henrik Føien Cecilie Gjengedal Bernt J. Leira 《Ocean Engineering》2009,36(8):605-616
This paper provides a method by which the scour depth below pipelines and around single vertical piles for combined random waves plus current including effects of second-order wave asymmetry can be derived. Here the empirical formulas proposed by Sumer and Fredsøe [1996. Scour below pipelines in combined waves and current. In: Proceedings of the 15th OMAE Conference, Florence, Italy. Vol. 5, ASME, New York, pp. 595–602] for pipelines, and by Sumer and Fredsøe [2002. The mechanics of scour in the marine environment. World Scientific, Singapore] for vertical piles are used together with Stokes second-order wave theory by assuming the basic harmonic wave motion to be a stationary Gaussian narrow-band random process. Comparisons are made with the Sumer and Fredsøe [1996. Scour below pipelines in combined waves and current. In: Proceedings of the 15th OMAE Conference, Florence, Italy. Vol. 5, ASME, New York, pp. 595–602; 2001. Scour around pile in combined waves and current. Journal of Hydraulic Engineering, 127(5), 403–411] data for linear random waves plus current. An example of calculation is also presented. 相似文献
10.