Geomechanical modelling to assess fault integrity at the CO2CRC Otway Project,Australia     

C. M. Aruffo  A. Rodriguez-herrera  E. Tenthorey  F. Krzikalla  J. Minton  A. Henk 《Australian Journal of Earth Sciences》2013,60(7):987-1001

This paper presents the first published 3D geomechanical modelling study of the CO2CRC Otway Project, located in the state of Victoria, Australia. The results of this work contribute to one of the main objectives of the CO2CRC, which is to demonstrate the feasibility of CO₂ storage in a depleted gas reservoir. With this aim in mind, a one-way coupled flow and geomechanics model is presented, with the capability of predicting changes to the in situ stress field caused by changes in reservoir pressure owing to CO₂ production and injection. A parametric study investigating the pore pressures required to reactivate key, reservoir-bounding faults has been conducted, and the results from the numerical simulation and analytical analysis are compared. The numerical simulation indicates that the critical pore fluid pressure to cause fault reactivation is 1.15 times the original pressure as opposed to 1.5 times for the comparable analytical model. Possible reasons for the differences between the numerical and analytical models can be ascribed to the higher degree of complexity incorporated in the numerical model. Heterogeneity in terms of lateral variations of hydrological and mechanical parameters, effect of topography, presence of faults and interaction between cells are considered to be the main sources for the different estimation of critical pore pressure. The numerical model, which incorporates this greater complexity, is able then to better describe the state of stress that acts in the subsurface compared with a simple 1D analytical model. Moreover, the reactivation pressures depend mainly on the state of stress described; therefore we suggest that numerical models be performed when possible.  相似文献   

On the mathematical stability of stratified flow models with local turbulence closure schemes     

Eric Deleersnijder  Emmanuel Hanert  Hans Burchard  Henk A. Dijkstra 《Ocean Dynamics》2008,58(3-4):237-246

Occasionally, numerical simulations using local turbulence closure schemes to estimate vertical turbulent fluxes exhibit small-scale oscillations in space, causing the eddy coefficients to vary over several orders of magnitude on short distances. Theoretical developments suggest that these spurious oscillations are essentially due to the way the eddy coefficients depend on the vertical gradient of the model’s variables. An instability criterion is derived based on the assumptions that the artefacts under study are due to the development of small-amplitude, small time- and space-scale perturbations of a smooth solution. The relevance of this criterion is demonstrated by applying it to a series a closure schemes, ranging from the Pacanowski–Philander formulas to the Mellor–Yamada level 2.5 model.  相似文献   

Harmonizing North Sea policy in the Netherlands     

Henk van Hoorn  Gerard Peet  Koos Wieriks 《Marine Policy》1985,9(1):53-61

  相似文献   

Tectonics and global change - inferences from Late Cenozoic subsidence and uplift patterns in the Atlantic/ Mediterranean region     

Sierd Cloetingh  Henk Kooi 《地学学报》1992,4(3):340-350

Quantitative subsidence analysis for a number of rifted basins in the northern Atlantic/Mediterranean region provides evidence for rapid phases of PlioQuaternary subsidence. The observed acceleration in tectonic subsidence occurs after a phase of general quiescence in subsidence in these basins and deviates from predictions of stretching models. The latter indicate a decay of subsidence with time after Mesozoic-Tertiary basin formatioh and a slow tectonic subsidence in Plio-Quaternary times. A possible explanation for the observed patterns of anomalous subsidence could be an increase in the level of intraplate compression in the northern Atlantic region. Intraplate stress changes in the Plio-Quaternary are related to the dynamics of African/ Eurasian collision processes and a reorganization of spreading directions in the AtlAntic, possibly reflecting a plate reorganization of global nature.
It seems that the Plio-Quaternary record reflects a period of increased levels of neotectonic activity, interplaying with periods of (de)glaciation. Stress-induced topography in the onshore parts of continental margins, coupled with the stress-induced subsidence in the offshore deeper parts of the basins, could have contributed to recent phases of uplift in Fennoscandia, augmenting the uplift induced by glacial unloading. Estimates of ice thicknesses are directly inferred from the observed uplift ignoring other driving mechanisms whereas topography plays a crucial role in the dynamics of glaciation. It is, therefore, important to quantdy the interplay of rapid tectonic uplift and subsidence phases with climatic effects during the Plio-Quaternary.  相似文献   

Beggiatoa in microbial mats at hydrocarbon vents in the Gulf of Mexico and Warm Mineral Springs,Florida     

John Larkin  Margaret C. Henk  Paul Aharon 《Geo-Marine Letters》1994,14(2-3):97-103

Microbial mats were collected from a variety of sites near hydrocarbon vents along the slope in the northern Gulf of Mexico and, for comparison, from Warm Mineral Springs, Florida, USA. A predominant microorganism in each of the mats was the giant bacterium,Beggiatoa. Diameters of the bacterial filaments ranged from about 6 µm to approximately 200 µm. The latter organisms are the largest prokaryotic organisms yet found. All filaments over about 10 µm in diameter contained a large central vacuole, producing a cell with the cytoplasm as a cylindrical tube underlying the cytoplasmic membrane. Sulfur globules were confined to this peripheral layer. Push cores often contained pyrite tubules whose appearance is suggestive of aBeggiatoa origin. Determinations of ¹³C inBeggiatoa mats from vents along the Louisiana slope yielded values in the range of –26.6 to –27.9 (PDB), suggesting an unusually high degree of isotope fractionation (–24.9) relative to the carbon source in the ambient seawater, which is typical of sulfur-oxidizing chemoautotrophs. The presence of S^O (elemental sulfur) within cells ofBeggiatoa resulting from oxidation of H₂S supports the importance of bacterial sulfate reduction processes in the underlying vents for the sustenance of theBeggiatoa mats.  相似文献   

The 1999 Flatfish Symposium: where to go from now?     

Henk W. van der Veer  Richard D. M. Nash 《Journal of Sea Research》2001,45(3-4)

A summary report of the 1999 Flatfish Symposium is presented. The Symposium was built on the themes of the previous Symposia, whereby the link is through processes related to recruitment. As in the previous Symposia, the papers presented have a strong focus on temperate species and basic information on (sub)tropical species is still lacking. The lack of insight into (sub)stock structure is still a problem and more insight is necessary into the methodologies for determining and describing stock structure. Another important unresolved issue concerns the quantitative understanding of the physical processes that affect the cross-shelf transport and exchange of eggs and larvae. Finally, there is a need for bioenergetic approaches to habitat quality and quantity both at the individual and population level to assess the qualitative and quantitative use of habitats in space and time. Applying global information systems (GIS) might be promising in this respect. With respect to management issues two items are of utmost importance: the collapse and recovery of stocks and the problems relating to re-stocking.  相似文献   

A comparison of management planning and implementation in three Indonesian marine protected areas     

Jackie Alder  N. A. Sloan  Henk Uktolseya 《Ocean & Coastal Management》1994,24(3)

A comparison of three marine protected areas in Indonesia illustrates many of the problems in management planning and implementation. Major factors influencing management are proximity to urban areas, the protected area's economic potential, current uses and the resolution of jurisdictional disputes. Isolation does not prevent resource depletion. Improving the economic conditions of local residents and gaining their commitment to environmentally sustainable commercial and subsistence resource uses within and near protected areas are vital to implementing area management.  相似文献   

Cenozoic alongslope processes and sedimentation on the NW European Atlantic margin     

Jan Sverre Laberg  Martyn S. Stoker  K.I. Torbjrn Dahlgren  Henk de Haas  Haflidi Haflidason  Berit O. Hjelstuen  Tove Nielsen  Pat M. Shannon  Tore O. Vorren  Tjeerd C.E. van Weering  Silvia Ceramicola 《Marine and Petroleum Geology》2005,22(9-10):1069

Based on studies of sediment accumulations deposited from-and erode by-alongslope flowing ocean currents on the European continental margin from Porcupine (Ireland) to Lofoten (Norway), the evolution of the Cenozoic paleocirculation was reconstructed as part of the STRATAGEM project. There is evidence of ocean current-controlled erosion and deposition in the Rockall Trough, in the Faeroe-Shetland Channel and on the Vøring Plateau since the late Eocene, although the circulation pattern remains ambiguous. The late Palaeogene flow in the Rockall Trough was almost probably driven by southerly-derived Tethyan Outflow Water. The extent and strength of any northerly-derived flow is uncertain. From the early Neogene (early-mid-Miocene), there was a massive regional expansion of contourite drift development both in the North Atlantic and in the Norwegian-Greenland Sea. This was most probably related to the development of the Faroe Conduit, the opening of the Fram Strait and the general subsidence of the Greenland-Scotland Ridge. These may have combined to cause a considerable acceleration in the exchange and overflow of deep waters between the Arctic and Atlantic Oceans. An early late Neogene (late early Pliocene) regional erosional event has been ascribed to a vigorous pulse of bottom-current activity, most probably the result of a global reorganisation of ocean currents associated with the closure of the Central American Seaway. During the late Neogene, contourites and sediment drifts developed in deep-water basins, between units of glacigenic sediments as well as infill of several paleo-slide scars. These sediments were derived from areas of bottom-current erosion as well as from the development of Plio-Pleistocene prograding sediment wedges, incorporating the extensive sediment supply derived from shelf-wide ice sheets. Presently a profound winnowing prevails along the shelf and upper slope due to the inflowing currents of Atlantic water. Depocentres of sediments derived from the winnowing are located (locally) in lower slope embayments and in slide scars.  相似文献   

Oblique sand ridges in confined tidal channels due to Coriolis and frictional torques     

Hepkema  Tjebbe M.  de Swart  Huib E.  Nnafie  Abdel  Schramkowski  George P.  Schuttelaars  Henk M. 《Ocean Dynamics》2020,70(12):1505-1513

Ocean Dynamics - The role of the Coriolis effect in the initial formation of bottom patterns in a tidal channel is studied by means of a linear stability analysis. The key finding is that the...  相似文献   

Tungsten isotopes as tracers of core-mantle interactions: The influence of subducted sediments   总被引：1，自引：0，他引：1  

O. Nebel  P.Z. Vroon  F.E. Jenner  J.A. Mavrogenes 《Geochimica et cosmochimica acta》2010,74(2):751-2136

The postulated difference in W isotopic composition of the Earth’s core of ∼2 ε_W units, compared to the bulk silicate earth (BSE) has previously been used to search for evidence of core-mantle interaction (CMI) in ocean island basalts (OIB). The absence of W isotope anomalies has thus been taken as evidence that CMI does not occur. However, the addition of subducted sediment with high W to the sources of OIB could obscure a core signature. This possibility brings into question the utility of W isotopes as tracers for CMI. To accurately consider the effects of sediment addition to mantle sources of OIB with respect to W requires improved constraints on the abundances of W in subducting sediment. Here, we present high-precision W abundance data (and other HFSE) for a suite of sediments from the Banda subduction regime in East Indonesia. Subducting East Indonesian sediments have trace element concentrations that resemble those of average upper continental crust (UCC), making these sediments valuable to consider as typical of subducted sediments. Average W abundances of 2.1 ppm, corrected for carbon content coupled with current models of 0.5% core addition and 1% sediment addition to EM1 or HIMU plume, suggest that a model hybrid source should exhibit values of ε_W = −0.24 with ∼25 ppb W. Prior studies have not reported such low W isotopic compositions or high estimated W concentrations present in the sources of either Hawaiian or French Polynesian lavas, so such large additions of core material to these plume sources seems unlikely. Given these constraints, core contributions to these source, if present, can be no more than ∼0.1%.  相似文献