Geophysical investigations of buried Quaternary valleys in Denmark: an integrated application of transient electromagnetic soundings, reflection seismic surveys and exploratory drillings

Jørgensen, Flemming; Lykke‐Andersen, Holger; Sandersen, Peter B.E.; Auken, Esben; Nørmark, Egon

doi:10.1016/j.jappgeo.2003.08.017

Cited by 99 publications

(75 citation statements)

References 15 publications

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“…Prior to the import of the seismic data to the geological interpretation software, the elevation values are adjusted, based on an assumed constant seismic velocity of 1800 m s −1 (Kristensen et al, 2015), a common velocity for Miocene and Quaternary deposits in Denmark (Høyer et al, 2011;Jørgensen et al, 2003). Elevation corrections are important because of the considerable effect of the topography that, even if mildly varying, can significantly affect the quality of the final results along the extended profile.…”

Section: High-resolution Seismic Datamentioning

confidence: 99%

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Multiple-point statistical simulation for hydrogeological models: 3-D training image development and conditioning strategies

Høyer

Vignoli

Hansen

et al. 2017

Hydrol. Earth Syst. Sci.

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Abstract. Most studies on the application of geostatistical simulations based on multiple-point statistics (MPS) to hydrogeological modelling focus on relatively fine-scale models and concentrate on the estimation of facies-level structural uncertainty. Much less attention is paid to the use of input data and optimal construction of training images. For instance, even though the training image should capture a set of spatial geological characteristics to guide the simulations, the majority of the research still relies on 2-D or quasi-3-D training images. In the present study, we demonstrate a novel strategy for 3-D MPS modelling characterized by (i) realistic 3-D training images and (ii) an effective workflow for incorporating a diverse group of geological and geophysical data sets. The study covers an area of 2810 km 2 in the southern part of Denmark. MPS simulations are performed on a subset of the geological succession (the lower to middle Miocene sediments) which is characterized by relatively uniform structures and dominated by sand and clay. The simulated domain is large and each of the geostatistical realizations contains approximately 45 million voxels with size 100 m × 100 m × 5 m. Data used for the modelling include water well logs, high-resolution seismic data, and a previously published 3-D geological model. We apply a series of different strategies for the simulations based on data quality, and develop a novel method to effectively create observed spatial trends. The training image is constructed as a relatively small 3-D voxel model covering an area of 90 km 2 . We use an iterative training image development strategy and find that even slight modifications in the training image create significant changes in simulations. Thus, this study shows how to include both the geological environment and the type and quality of input information in order to achieve optimal results from MPS modelling. We present a practical workflow to build the training image and effectively handle different types of input information to perform large-scale geostatistical modelling.

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Section: High-resolution Seismic Datamentioning

confidence: 99%

“…The TIs are built in Geoscene3D using the voxel modelling tools described in Jørgensen et al (2013). In practice, each sand and clay layer is defined by so-called "interpretation" points.…”

Section: Training Imagementioning

confidence: 99%

Multiple-point statistical simulation for hydrogeological models: 3-D training image development and conditioning strategies

Høyer

Vignoli

Hansen

et al. 2017

Hydrol. Earth Syst. Sci.

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“…The SkyTEM method has been extensively used for subsurface mapping in Denmark (Jorgensen et al, 2003a(Jorgensen et al, , 2005, where it has proven to be a successful tool for hydrogeological investigations. SkyTEM data have the advantage of a high spatial resolution in the top 20 to 30 m and large spatial coverage.…”

Section: Geophysical Datamentioning

confidence: 99%

Challenges in conditioning a stochastic geological model of a heterogeneous glacial aquifer to a comprehensive soft data set

Koch

Jensen

et al. 2014

Hydrol. Earth Syst. Sci.

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Abstract. In traditional hydrogeological investigations, one geological model is often used based on subjective interpretations and sparse data availability. This deterministic approach usually does not account for any uncertainties. Stochastic simulation methods address this problem and can capture the geological structure uncertainty. In this study the geostatistical software TProGS is utilized to simulate an ensemble of realizations for a binary (sand/clay) hydrofacies model in the Norsminde catchment, Denmark. TProGS can incorporate soft data, which represent the associated level of uncertainty. High-density (20 m × 20 m × 2 m) airborne geophysical data (SkyTEM) and categorized borehole data are utilized to define the model of spatial variability in horizontal and vertical direction, respectively, and both are used for soft conditioning of the TProGS simulations. The category probabilities for the SkyTEM data set are derived from a histogram probability matching method, where resistivity is paired with the corresponding lithology from the categorized borehole data. This study integrates two distinct data sources into the stochastic modeling process that represent two extremes of the conditioning density spectrum: sparse borehole data and abundant SkyTEM data. In the latter the data have a strong spatial correlation caused by its high data density, which triggers the problem of overconditioning. This problem is addressed by a work-around utilizing a sampling/decimation of the data set, with the aim to reduce the spatial correlation of the conditioning data set. In the case of abundant conditioning data, it is shown that TProGS is capable of reproducing non-stationary trends. The stochastic realizations are validated by five performance criteria: (1) sand proportion, (2) mean length, (3) geobody connectivity, (4) facies probability distribution and (5) facies probability-resistivity bias.In conclusion, a stochastically generated set of realizations soft-conditioned to 200 m moving sampling of geophysical data performs most satisfactorily when balancing the five performance criteria. The ensemble can be used in subsequent hydrogeological flow modeling to address the predictive uncertainty originating from the geological structure uncertainty.

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“…Studies utilizing multiple geophysical methods combined with geologic and hydrogeologic data are particularly effective for 3D mapping of hydrostratigraphic units (e.g., Gabriel et al 2003;Jørgensen et al 2003aJørgensen et al , 2003bSteuer et al 2009; Stumpf and Ismail 2013;Cassidy et al 2014;Sapia et al 2014). In Ontario, shallow seismic reflection, gravity, and electromagnetic surveys have been used at mostly regional scales to delineate the nature of the infilled sediment and bedrock valley geometry (e.g., Greenhouse and Monier-Williams 1986;Greenhouse and Karrow 1994;Zweirs et al 2008;Burt 2011;Bajc et al 2012;Pugin et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Geophysical, geological, and hydrogeological characterization of a tributary buried bedrock valley in southern Ontario

et al. 2018

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Buried bedrock valleys infilled with Quaternary-aged sediment have the potential to become productive aquifers owing to prevalent sand and gravel deposits often associated with these topographic lows. In areas where groundwater is drawn from the underlying bedrock aquifer, buried bedrock channels may significantly affect the spatial distribution of recharge and localized contaminant pathways. Therefore, understanding the form, distribution, and the nature of Quaternary infill sediments within these buried bedrock river valleys, and their relationship to hydraulically transmissive bedrock features is an important aspect of groundwater resource management. Here, we evaluate the effectiveness of electrical resistivity and seismic refraction collected over a partially urbanized 150 ha area with variable vegetation, roads, and structures, to map the spatial distribution of sediments and delineation of a channel segment associated with a regional bedrock valley. Electrical resistivity and seismic refraction was performed along 13 (covering ϳ11.6 km) and seven transects (covering ϳ0.9 km), respectively, to map and characterize the bedrock surface morphology beneath a variable thickness of unconsolidated deposits. Three continuously cored holes and downhole geophysical logs, supplemented with four nearby water well records captured the in-channel as well as adjacent Quaternary stratigraphy (ϳ15-40 m). Cores recorded multiple glacial till deposits and ice-marginal processes associated with ice advances and retreats. Hydraulic transmissivity of the bedrock around the valley feature was evaluated using a FLUTe hydraulic transmissivity profiling technique. This study demonstrates the potential of combining several surface geophysical methods with sedimentological analysis of continuous cores and hydraulic data for characterizing tributary bedrock channel morphology and Quaternary infill at a scale relevant to localized studies of municipal production well recharge zones and contaminant transport and fate.Résumé : Les vallées ensevelies taillées dans le roc remplies de sédiments d'âge quaternaire ont le potentiel de devenir des aquifères productifs en raison des importants dépôts de sable et de gravier souvent associés à ces dépressions topographiques. Dans les régions où l'eau souterraine est tirée de l'aquifère rocheux sous-jacent, les chenaux ensevelis taillés dans le roc pourraient avoir une importante incidence sur la répartition spatiale de la recharge et des voies de propagation des contaminants. La compréhension de la forme, de la répartition et de la nature des sédiments quaternaires qui remplissent ces vallées fluviales ensevelies et leur lien avec des caractéristiques du substrat rocheux transmissif est un aspect important de la gestion des ressources d'eau souterraine. Nous évaluons l'efficacité des méthodes de résistivité électrique et de sismique réfraction utilisées dans une zone partiellement urbanisée de 150 ha présentant une répartition variable de la végétation, des routes et des ouvrages, pour c...

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Geophysical investigations of buried Quaternary valleys in Denmark: an integrated application of transient electromagnetic soundings, reflection seismic surveys and exploratory drillings

Cited by 99 publications

References 15 publications

Multiple-point statistical simulation for hydrogeological models: 3-D training image development and conditioning strategies

Multiple-point statistical simulation for hydrogeological models: 3-D training image development and conditioning strategies

Challenges in conditioning a stochastic geological model of a heterogeneous glacial aquifer to a comprehensive soft data set

Geophysical, geological, and hydrogeological characterization of a tributary buried bedrock valley in southern Ontario

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