scholarly journals Hydrogeological characterisation of a glacially affected barrier island – the North Frisian Island of Föhr

2012 ◽  
Vol 9 (4) ◽  
pp. 5085-5119 ◽  
Author(s):  
T. Burschil ◽  
W. Scheer ◽  
R. Kirsch ◽  
H. Wiederhold
Keyword(s):  
North Sea ◽  
Underground Structure ◽  
Empirical Relation ◽  
Geophysical Methods ◽  
Strong Impact ◽  
Hydrogeological Model ◽  
Borehole Data ◽  
The North ◽  
The North Sea ◽  
D Model

Abstract. We present the application of geophysical investigations to characterise and improve the geological/hydrogeological model through the estimation of petrophysical parameters for groundwater modelling. Seismic reflection and airborne electromagnetic surveys in combination with borehole information enhance the 3-D geological model and allow a petrophysical interpretation of the subsurface. The North Sea Island of Föhr has a very complex underground structure what was already known from boreholes. The local waterworks use a freshwater body embedded in saline groundwater. Several glaciations disordered the Youngest Tertiary and Quaternary sediments by glaciotectonic thrust-faulting as well as incision and refill of glacial valleys. Both underground structures have a strong impact on the distribution of freshwater bearing aquifers. An initial hydrogeological model of Föhr was built from borehole data alone and was restricted to the southern part of the island where in the sandy areas of the Geest a large freshwater body was formed. We improved the geological/hydrogeological model by adding data from different geophysical methods, e.g. airborne electromagnetics (EM) for mapping the resistivity of the entire island, seismic reflections for detailed cross sections in the groundwater catchment area, and geophysical borehole logging for calibration of these measurements. An integrated evaluation of the results from the different geophysical methods yields reliable data. To determinate petrophysical parameter about 18 borehole logs, more than 75 m deep, and nearby airborne EM inversion models were analyzed concerning resistivity. We establish an empirical relation between measured resistivity and hydraulic conductivity for the specific area – the North Sea island of Föhr. Five boreholes concerning seismic interval velocities discriminate sand and till. The interpretation of these data was the basis for building the geological/hydrogeological 3-D model. We fitted the relevant model layers to all geophysical and geological data and created a consistent 3-D model. This model is the fundament for groundwater simulations considering forecasted changes in precipitation and sea level rise due to climate change.

scholarly journals Compiling geophysical and geological information into a 3-D model of the glacially-affected island of Föhr

2012 ◽  
Vol 16 (10) ◽  
pp. 3485-3498 ◽  
Author(s):  
T. Burschil ◽  
W. Scheer ◽  
R. Kirsch ◽  
H. Wiederhold
Keyword(s):  
Climate Change ◽  
Water Resources ◽  
Geophysical Methods ◽  
Groundwater Modelling ◽  
Strong Impact ◽  
Subsurface Structure ◽  
Hydrogeological Model ◽  
Borehole Data ◽  
Geophysical Investigation ◽  
D Model

Abstract. Within the scope of climatic change and associated sea level rise, coastal aquifers are endangered and are becoming more a focus of research to ensure the future water supply in coastal areas. For groundwater modelling a good understanding of the geological/hydrogeological situation and the aquifer behavior is necessary. In preparation of groundwater modelling and assessment of climate change impacts on coastal water resources, we setup a geological/hydrogeological model for the North Sea Island of Föhr. Data from different geophysical methods applied from the air, the surface and in boreholes contribute to the 3-D model, e.g. airborne electromagnetics (SkyTEM) for spatial mapping the resistivity of the entire island, seismic reflections for detailed cross-sections in the groundwater catchment area, and geophysical borehole logging for calibration of these measurements. An iterative and integrated evaluation of the results from the different geophysical methods contributes to reliable data as input for the 3-D model covering the whole island and not just the well fields. The complex subsurface structure of the island is revealed. The local waterworks use a freshwater body embedded in saline groundwater. Several glaciations reordered the youngest Tertiary and Quaternary sediments by glaciotectonic thrust faulting, as well as incision and refill of glacial valleys. Both subsurface structures have a strong impact on the distribution of freshwater-bearing aquifers. A digital geological 3-D model reproduces the hydrogeological structure of the island as a base for a groundwater model. In the course of the data interpretation, we deliver a basis for rock identification. We demonstrate that geophysical investigation provide petrophysical parameters and improve the understanding of the subsurface and the groundwater system. The main benefit of our work is that the successful combination of electromagnetic, seismic and borehole data reveals the complex geology of a glacially-affected island. A sound understanding of the subsurface structure and the compilation of a 3-D model is imperative and the basis for a groundwater flow model to predict climate change effects on future water resources.

Impact of Climate Change on the North Sea Offshore Energy Sector

2018 ◽  
Author(s):  
Nicolas Fournier ◽  
Galina Guentchev ◽  
Justin Krijnen ◽  
Andy Saulter ◽  
Caroline Acton ◽  
...  
Keyword(s):  
Climate Change ◽  
Sea Level ◽  
North Sea ◽  
Wave Climate ◽  
Energy Industry ◽  
Strong Impact ◽  
Impact Of Climate Change ◽  
The North ◽  
Climate Indicators ◽  
The North Sea

The complex nature of the energy industry across extraction, transportation, processing, delivery and decommissioning creates significant challenges to how the sector responds, adapts and mitigates against risks posed by the changing future climate. Any disruption in this interconnected system will affect both industry and society. For example, in the summer of 2005 Hurricane Katrina and a month later Hurricane Rita had wide reaching impacts on the US offshore Oil and Gas industry which resulted in an increase in global oil prices due to loss of production and refinery shutdowns in the Gulf of Mexico. Preparing, mitigating and adapting to these climate changes is dependent upon identifying appropriate climate indicators as well as the associated critical operational thresholds and design criteria of the identified vulnerable assets. The characterization and understanding of the likely changes in these climate indicators will form the basis for adaptation plans and mitigating actions. The Met Office in collaboration with energy industry partners, under the Copernicus Clim4energy European project, has developed a Climate Change Risk Assessment tool, which allows the visualization and extraction of the most recent sea level and wave climate information to evaluate their future changes. This study illustrates the application of this tool for evaluation of the potential vulnerability of an offshore infrastructure in the North Sea. The analysis shows that for this asset there is a small increase in sea level of 0.20–0.30 m at the location of interest by 2050. However, there is a small decrease or no consistent changes projected in the future wave climate. This wave signal is small compared to the uncertainty of the wave projections and the associated inter-annual variability. Therefore, for the 2050s time horizon, at the location of interest, there is no strong impact of climate change at the annual scale on the significant wave height, the sea level and thus the associated climate change driven extreme water level. However, further analysis are required at the seasonal and monthly scales.

scholarly journals Hydraulic properties at the North Sea island of Borkum derived from joint inversion of magnetic resonance and electrical resistivity soundings

2012 ◽  
Vol 16 (9) ◽  
pp. 3279-3291 ◽  
Author(s):  
T. Günther ◽  
M. Müller-Petke
Keyword(s):  
Magnetic Resonance ◽  
Water Content ◽  
North Sea ◽  
Climate Changes ◽  
Joint Inversion ◽  
Geophysical Methods ◽  
Joint Analysis ◽  
The North ◽  
The North Sea ◽  
The Impact

Abstract. For reliably predicting the impact of climate changes on salt/freshwater systems below barrier islands, a long-term hydraulic modelling is inevitable. As input we need the parameters porosity, salinity and hydraulic conductivity at the catchment scale, preferably non-invasively acquired with geophysical methods. We present a methodology to retrieve the searched parameters and a lithological interpretation by the joint analysis of magnetic resonance soundings (MRS) and vertical electric soundings (VES). Both data sets are jointly inverted for resistivity, water content and decay time using a joint inversion scheme. Coupling is accomplished by common layer thicknesses. We show the results of three soundings measured on the eastern part of the North Sea island of Borkum. Pumping test data is used to calibrate the petrophysical relationship for the local conditions in order to estimate permeability from nuclear magnetic resonance (NMR) data. Salinity is retrieved from water content and resistivity using a modified Archie equation calibrated by local samples. As a result we are able to predict porosity, salinity and hydraulic conductivities of the aquifers, including their uncertainties. The joint inversion significantly improves the reliability of the results. Verification is given by comparison with a borehole. A sounding in the flooding area demonstrates that only the combined inversion provides a correct subsurface model. Thanks to the joint application, we are able to distinguish fluid conductivity from lithology and provide reliable hydraulic parameters as shown by uncertainty analysis. These findings can finally be used to build groundwater flow models for simulating climate changes. This includes the improved geometry and lithological attribution, and also the parameters and their uncertainties.

Crystal stresses in the north sea from breakouts and other borehole data

1993 ◽  
Vol 30 (7) ◽  
pp. 1111-1114 ◽  
Author(s):  
S.M. Cowgill ◽  
P.G. Meredith ◽  
S.A.F. Murrell ◽  
N.R. Brereton
Keyword(s):  
North Sea ◽  
Borehole Data ◽  
The North ◽  
The North Sea

3-D Model and Field Studies of Silt Transport in the Dutch Coastal Zone of the North Sea with Emphasis on Dump Sites

1991 ◽  
Vol 24 (10) ◽  
pp. 39-43 ◽  
Author(s):  
R. Spanhoff ◽  
J. M. de Kok
Keyword(s):  
Numerical Modelling ◽  
North Sea ◽  
Suspended Sediments ◽  
Field Studies ◽  
River Rhine ◽  
Coastal Zones ◽  
The North ◽  
The North Sea ◽  
Outflow Region ◽  
D Model

A proper management of coastal zones and adjacent estuaries with respect to man-made contaminants requires tools to describe and predict transports of suspended sediments. In a complicated area such as the outflow region of the river Rhine a coherent program of combined field studies and numerical modelling is required to arrive at such tools. Elements of an on-going program are described.

An evaluation of seismic and borehole data available from onshore and offshore site investigations of relict glaciated areas

1991 ◽  
Vol 7 (1) ◽  
pp. 573-578 ◽  
Author(s):  
F. S. Stewart
Keyword(s):  
North Sea ◽  
Structural Information ◽  
Late Quaternary ◽  
Seismic Survey ◽  
Borehole Data ◽  
The North ◽  
Site Investigations ◽  
The North Sea ◽  
Engineering Projects ◽  
Sedimentation Processes

AbstractUsing late Quaternary ice marginal sites from the North Sea and Iceland a comparison of the sedimentary information available from subaerial and submarine site investigations was made. This was with regard to palaeo-environmental reconstructions of ice marginal Sedimentation processes. A detailed high resolution seismic survey in-the North Sea was compared to a similar subaerial site in Iceland. Submarine cores were compared with logged sections available from cliffs. These comparisons highlighted the differences in resolution of the structural information available and also the problems of applying existing modeis of glacimarine Sedimentation to offshore sites. This has raised questions concerning the accuracy of reconstructing palaeo-environments and processes in offshore sites presently under investigation. The implications of this for engineering projects in offshore areas requiring very precise site information about relict glaciated areas are significant.

scholarly journals Models of overpressure build-up in shallow sediments by glacial deposition and glacial loading with respect to chimney formation

2021 ◽  
Author(s):  
Magnus Wangen
Keyword(s):  
Soil Properties ◽  
North Sea ◽  
Glacial Sediments ◽  
The North ◽  
Last Glaciation ◽  
Order Of Magnitude ◽  
Horizontal Compressive Stress ◽  
The North Sea ◽  
Poroelastic Model ◽  
D Model

AbstractChimneys and pipe structures have been observed in the caprock above the Utsira Aquifer in the North Sea. The caprock is of Pleistocene age and the chimneys appear to have been formed by natural hydraulic fracturing towards the end of the last glaciation. We study six different models for the pressure build-up in the Utsira Aquifer with respect to chimney formation. The first two models produce overpressure by a rapid deposition of glacial sediments. Using these two models, we show that the caprock permeability must be as low as 100 nD for sufficiently strong overpressure to develop. This value seems to be one order of magnitude lower than the measured permeabilities of the caprock. The four remaining models produce overpressure by a glacial loading of the caprock and the aquifer. This study shows that a 1-D model of a caprock with soil properties cannot produce conditions for chimney formation unless the least horizontal compressive stress is much less than the overburden. Furthermore, a 1-D poroelastic model of glacial loading of an aquifer and a caprock cannot produce conditions for chimney formation based on available geomechanical data. However, we demonstrate that a 2-D poroelastic model can produce conditions for chimney formation with glacial loads that partially cover the surface.

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