About
161
Publications
53,816
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
4,111
Citations
Current institution
Publications
Publications (161)
Ziel dieses Beitrags ist die Evaluierung KI-basierter Methoden zur Detektion
von Massenbewegungen in geologischen Karten. Moderne KI-Architekturen wie CNNs und YOLO ermöglichen hier effiziente Bilderkennung und Musteridentifikation. Durch Datenaugmentation wird die Generalisierungsfähigkeit verbessert. Diese neuartige Anwendung verspricht eine effi...
Identifying rock properties at the pore scale plays a crucial role in understanding larger-scale properties. For this purpose, the digital rock physics technique is used to model rock images at the pore scale. Achieving high-resolution (HR) images with a large field of view (FoV) is essential for pore-scale modeling of heterogeneous rock samples, w...
Digital Rock Physics can significantly enhance our understanding of rock behavior. However, modeling heterogeneous rocks remains challenging because of the trade-off between resolution and field of view. To address this, researchers have developed multi-scale pore network models (PNMs), which integrate networks from different scales to create unifi...
Multi-scale modelling techniques are commonly used to characterize heterogeneous rock samples. However, open challenges limit the efficiency of these models. A significant issue is the tradeoff between resolution and field of view (FoV) during imaging. Capturing an image of a heterogeneous rock sample that includes pores of different scales with a...
The anticipation of fluid transport behavior within porous media holds significant importance in a diverse array of applications, encompassing subsurface hydrology (Hu and Pfingsten 2023); petroleum industry (Moslemipour and Sadeghnejad 2021), geothermal energy utilization (Meller et al. 2017), and secure subsurface storage of hydrogen or CO2 (Esfa...
Understanding the properties of rocks is crucial in various porous media, especially in heterogeneous carbonate and tight sandstone rocks. Digital Rock Physics (DRP) has emerged as a valuable tool, which is grounded in imaging and computation. Techniques like industrial X-ray CT and FIB-SEM are usually used for image acquisition in DRP. However, th...
In frozen cylinders composed of deuterium ice (T m + 3.8 • C) and 10 % water ice (T m 0 • C), it is possible to track melt pathways produced by increasing the temperature during deformation. Raising the temperature to +2 • C produces water (H 2 O) which combines with the D 2 O ice to form mixtures of HDO. As a consequence of deformation, HDO and H...
In frozen cylinders composed of deuterium ice (Tm+3.8 ∘C) and 10 % water ice (Tm0 ∘C), it is possible to track melt pathways produced by increasing the temperature during deformation. Raising the temperature to +2 ∘C produces water (H2O) which combines with the D2O ice to form mixtures of HDO. As a consequence of deformation, HDO and H2O meltwater...
Recent predictive analytics and soft computing methods enhanced the exploration of new hydrocarbon reserves. Machine learning (ML) has showed a promising role in oil and gas explorations in recent years. Among the applications, determining a proper location for injection and production wells along with their optimum operating conditions is a comple...
In the workflow of digital rock physics, obtaining high-resolution rock images is crucial for accurately predicting rock parameters. The image resolution is dictated by the imaging technique, which often leads to a trade-off between image resolution and field of view. To address this challenge, super-resolution convolutional neural networks (SRCNNs...
Particle transport and deposition in porous media play a crucial role in subsurface contaminant transport, underground gas storage, and enhanced oil recovery. Accurate prediction of permeability alterations using numerical methods is of the utmost importance. Recent advancements in imaging technology and digital rock physics, have facilitated the e...
This study introduces a novel approach for generating realistic 3D unstructured multi-scale binary images of heterogeneous rock samples. The integration of pores at different scales into a unified image poses a significant challenge in multi-scale modeling. To address this, the proposed method utilizes a distinct reconstruction strategy that separa...
This work aims to analyse the mechanisms and factors contributing to shallow soil landslides in river valleys entrenched in lowlands on the example of the Central Radunia Valley. The combination of susceptibility analysis using geographic-information-system-based statistical models, field surveys, analysis of archival materials, and numerical model...
Pore-scale properties can be obtained by building a reliable digital twin of porous media through the digital rock physics (DRP) workflow. The two prerequisites of DRP are reliable imaging and computing power. Determining a proper image resolution that can reveal the actual pore-scale properties is challenging as there is a trade-off between the re...
Die Flutkatastrophe im Ahrtal zeigt nachhaltig, dass Extremwetterereignisse in deutschen Mittelgebirgen neben Überschwemmungen auch gravitative Massenbewegungen auslösen können, die große Schäden an Infrastruktur verursachen und eine Gefahr für Bevölkerung und Einsatzkräfte darstellen. Vor dem Hintergrund einer Aufarbeitung und eines Verstehens der...
More than half of the world's oil is reserved in heterogeneous carbonate and tight sandstone rocks. A comprehensive understanding of rock properties is essential for efficient production from these reservoirs. Digital rock physics (DRP) is an approach that has been used in recent years to evaluate rock properties on the pore scale. Image acquisitio...
Subsurface transport of colloids is of critical importance in various engineering and scientific applications, such as groundwater transport, underground H2 or CO2 storage, oil and gas reservoirs, and geothermal energy [1]. Migration and deposition of such particles can significantly alter the physical properties of porous media [2,3]. In recent ye...
The necessity to scale energy storage capacities in Europe is vital for expanding renewable energy production and avoiding shortcomings in energy supply. In decarbonizing energy systems, hydrogen, in its diverse colors, will play a crucial role as an energy carrier. Storing hydrogen in the subsurface comes with various uncertainties. Independent in...
Resampling is an interpolation technique that is used to increase (upsampling) or decrease (downsampling) the resolution of images by the desired ratio. Upsampling or downsampling and changing the resolution of images to fuse them with different resolutions is one of the most important applications of resampling methods in the digital rock physics...
Excessive water production is one of the main problems of mature reservoirs, which reduces hydrocarbon production and economic reservoir lifetime, and may pose severe environmental issues. Injection of pH-sensitive microgel is one of the most recently developed methods that can be used for both water shut-off and deep conformance control purposes....
In frozen cylinders composed of deuterium ice (Tm+3.8 ºC) and 10 % water ice (Tm 0 ºC) it is possible to track melt pathways produced by increasing the temperature during deformation. Raising the temperature to +2 ºC produces water (H2O) which combines with the D2O ice to form mixtures of HDO. As a consequence of deformation, HDO and H2O meltwater...
The evolution of pore structure caused by particle retention is a function of heterogeneity and non-linear coupling of particle transport and fluid flow. Pore-scale modelling enable us to elucidate the role of various mechanisms controlling particle transport and deposition. This study incorporated the Eulerian-Lagrangian approach to investigate th...
Osuwiska należą do naturalnych procesów geologicznych. W przypadku ich występowania na terenach zagospodarowanych przez człowieka konsekwencje ruchów masowych mogą mieć katastrofalny charakter. Połączenie sprzyjających osuwiskom uwarunkowań geośrodowiskowych i duże nagromadzenie elementów podlegających ryzyku sprawiają, że skala i skutki zagrożeń r...
The investigation of mass movements is of major interest in mountain regions as these events represent a significant hazard for people and cause severe damage to crucial infrastructure. The torrential rainfall event that mainly occurred on the 14 July 2021 in western Central Europe not only led to severe flooding catastrophes (e.g., Meuse, Ahr and...
Calcite is a highly abundant mineral in the Earth's crust and occurs as a cement phase in numerous siliciclastic sediments, where it often represents the most reactive component when a fluid percolates through the rock. Hence, the objective of this study is to derive calcite dissolution rates on different scales in a reservoir sandstone using miner...
This work aims to analyse the mechanisms and factors contributing to shallow soil (earth) landslides in river valleys of lowland areas on the example of the mass movement in Rutki, where various research methods were used. The study used mainly primary data, i.e. field observation, piezometers and inclinometers. We collected and reinterpreted secon...
Solute transport containing particles is essential in various applications, including filtration industry, subsurface contaminant transport in hydrology or environmental engineering, formation damage in the petroleum industry, and subsurface biocolloids or microorganism transport [1-4]. The evolution of pore-scale structure because of particle rete...
The two paradigms of digital rock physics, chemistry, and biology are imaging and computation (Sadeghnejad et al. 2021). An unbiased characterization of rocks not only requires a sample with a sufficient volume (i.e., representative elementary volume, REV) to account for sample heterogeneity but also requires a high-resolution image with enough por...
Diagenetic illite growth in porous sandstones leads to significant modifications of the initial pore system which result in tight reservoirs. Understanding and quantifying these changes provides insight into the porosity-permeability history of the reservoir and improves predictions on petrophysical behavior. To characterize the various stages of d...
Image segmentation remains the most critical step in Digital Rock Physics (DRP) workflows, affecting the analysis of physical rock properties. Conventional segmentation techniques struggle with numerous image artifacts and user bias, which lead to considerable uncertainty. This study evaluates the advantages of using the random forest (RF) algorith...
Kurzfassung: Das Mittelrhein-und das Moseltal sind in den letzten Jahren häufig von Steinschlägen und Felsstürzen betroffen gewesen. Durch die geomorphologische Grundsituation sowie die dichte Verkehrsinfrastruktur innerhalb der Täler kommt es in diesem Gebiet immer wieder zu erheblichen Schadensfällen. Diese haben weitreichende wirtschaftliche und...
Microbial activities are in the focus of interest in many subsurface studies, including contaminant hydrogeology, microbial enhance oil recovery, geo-methanation processes (e.g., in situ conversion of CO2/H2 to methane), and deep geothermal systems. Microbial growth and biomass/biofilm deposition in the subsurface influence the hydrodynamic propert...
Für die Beurteilung der Rutschungsanfälligkeit von Hängen ist die Auswahl der beeinflussenden Faktoren entscheidend. Ein bekannter Faktor, der Rutschungen kontrolliert, sind die Lagerungsverhältnisse von Gesteinsformationen. Die Arbeitsgruppe MABEIS hat eine GIS-gestützte halbautomatische Methode entwickelt, um quantitative Informationen über die O...
Obszar badań znajduje się na Nizinie Polskiej, w obrębie stożka sandrowego rozciętego głęboką doliną rzeki Raduni. Obejmuje on zbocza doliny środkowej Raduni o długości około 4,5 km pomiędzy Babim Dołem a Borkowem. Odcinek ten charakteryzują znaczne nachylenia (25°-40°) i energia rzeźby (25-35 m) oraz najwyższe spadki rzeki dochodzące do 6,8 ‰. Cel...
Accumulation of microbial biomass and its influence on porous media flow were investigated under saturated flow conditions. Microfluidic experiments were performed with model organisms, and their accumulation was observed in the pore space and on the sub-pore scale. Time-lapse optical imaging revealed different modes of biomass accumulation through...
Conventional and unconventional hydrocarbon rocks have complicated pore structures with heterogeneities distributed over various length scales (from nanometre to centimetre or even larger scales). Effective characterization of the properties of such rocks based on their digital twins is a challenging task. Digital rock physics (DRP) can be used to...
Conventional and unconventional hydrocarbon rocks have complicated pore structures with heterogeneities distributed over various length scales (from nanometre to centimetre or even larger scales). Effective characterization of the properties of such rocks based on their digital twins is a challenging task. Digital rock physics (DRP) can be used to...
Core flooding experiments to determine multiphase flow in properties of rock such as relative permeability can show significant fluctuations in terms of pressure, saturation, and electrical conductivity. That is typically not considered in the Darcy scale interpretation but treated as noise. However, in recent years, flow regimes that exhibit spati...
Nowadays, digital rock physics (DRP) has enabled us to obtain comprehensive and accurate information from porous media and a better understanding of physics at the pore scale. Advances in the micro-computed tomography technology (µCT) have led to high-quality, high-resolution images from rock samples. However, this increase in image quality or reso...
This paper presents radon flux profiles from four regions in Schleswig–Holstein (Northern Germany). Three of these regions are located over deep-rooted tectonic faults or salt diapirs and one is in an area without any tectonic or halokinetic activity, but with steep topography. Contrary to recently published studies on spatial patterns of soil rado...
Background
The prevalence of hard tissue formations in the dental pulp varies considerably. Beside ageing processes and irritations of the dental pulp, etiological associations with cardiovascular disease and dietary habits have been discussed, which are of particular research interest. The aim of this pilot study is to provide new insights on stru...
Computer X-ray microtomography (µXCT) represents a powerful tool for investigating the physical properties of porous rocks. While calculated porosities determined by this method typically match experimental measurements, computed permeabilities are often overestimated by more than 1 order of magnitude. This effect increases towards smaller pore siz...
In recent years, the Upper Middle Rhine Valley has been affected by several debris flow events as a result of heavy rainfall. As a result, several train accidents with far reaching damage occurred. Therefore there is a need for a precautionary hazard analysis in order to prevent further property damage and possibly personal injury. The here present...
Computer microtomography (µXCT) represents a powerful tool for investigating the physical properties of porous rocks. While calculated porosities determined by this method typically match experimental measurements, computed permeabilities are often overestimated by more than one order of magnitude. This effect increases towards smaller pore sizes,...
Violence seems deeply rooted in human nature and an endemic potential for such is today frequently associated with differing ethnic, religious or socio-economic backgrounds. Ethnic nepotism is believed to be one of the main causes of inter-group violence in multi-ethnic societies. At the site of Els Trocs in the Spanish Pyrenees, rivalling groups o...
We present a new statistical variance approach for characterizing heterogeneities related to pore spaces in reservoir rocks. Laboratory-based computer microtomography data for reservoir sandstone samples were acquired and processed using advanced image segmentation techniques. The samples were processed using a method based on the digital rock phys...
Long-term evolution of permeability and tortuosity due to porosity changes evoked by reactivity of aqueous solutions is of paramount importance for predicting water-rock interaction. This challenge is best tackled by introducing reactive transport modelling on the pore-scale, where the modeling domain is a high-resolution tomographic image of the p...
Heterogeneity of geological materials poses various problems when evaluating reservoir quality and storage potential. We analysed samples of different sedimentary facies of a Rotliegend sandstone from the Flechtingen High (Northern Germany) to determine the influence of depositional environment and diagenetic history on mineralogical composition an...
This presentation is about variance in 3D porous media. It is directly linked to the paper "Analysis of variance porosity and heterogeneity of permeability at the pore scale" (Jacob et al. 2019, TIPM)
Despite the availability of both commercial and open source software, an ideal tool for digital rock physics analysis for accurate automatic image analysis at ambient computational performance is difficult to pin point. More often image segmentation is driven manually where the performance remains limited to two phases. Discrepancies due to artefac...
Mine water hydraulics and geothermal potential of a deep shaft of the flooded Wolf mine in the Siegerland ore district of the Rhenish Massif in Germany were investigated. The electrical conductivity (EC), temperature, pH, and Eh were logged to 580 m below water table using multi-parameter borehole tools in 2009 and 2015. Some variations were detect...
The impact of fracture geometry and aperture distribution on fluid movement and on non-reactive solute transport was investigated experimentally and numerically in single fractures. For this purpose a hydrothermally altered and an unaltered granite drill core with axial fractures were investigated. Using three injection and three extraction locatio...
Fluctuating energy production by renewables is one of the main issues in transition times of energy production from conventional power plants to an energy production by renewables. Using excess produced electricity (windy/sunny periods) to convert water to oxygen and hydrogen and storing the hydrogen in depleted oil-, gas fields or sedimentary aqui...
Full text (read-only): https://rdcu.be/1OcE . Animal resources have been part of hominin diets since around 2.5 million years ago, with sharp-edged stone tools facilitating access to carcasses. How exactly hominins acquired animal prey and how hunting strategies varied through time and space is far from clear. The oldest possible hunting weapons kn...
Zusammenfassung
Das vorliegende Fallbeispiel führt unterschiedliche Feld- und Labormethoden zusammen und zeigt, wie für einen Standort in einem Kluftgrundwasserleiter die Kombination unterschiedlicher Untersuchungsverfahren zu einem plausiblen geologischen und hydrogeologischen Bild führt. Anlass für die Untersuchungskampagne ist eine große Grundwa...
In this study, we introduce CobWeb 1.0 which is a graphical user interface tailored explicitly for accurate image segmentation and representative elementary volume analysis of digital rock images derived from high resolution tomography. The CobWeb code is a work package deployed as a series of windows executable binaries which use image processing...
In this study, we introduce CobWeb 1.0 which is a graphical user interface tailored explicitly for accurate image segmentation and representative elementary volume analysis of digital rock images derived from high resolution tomography. The CobWeb code is a work package deployed as a series of windows executable binaries which use image processing...
Randall’s plaques (RP) are preferred sites for the formation of calcium oxalate monohydrate (COM) kidney stones. However, although processes of interstitial calcium phosphate (CaP) plaque formation are not well understood, the potential of plaque microstructures as indicators of CaP precipitation conditions received only limited attention. We inves...
Mineral precipitations are a common feature and limitation of initially open, permeable rock fractures by forming sealing structures or secondary roughness in open voids. Hence, the objective of this numerical study is the evaluation of hydraulic properties of fractures sealed by hydrothermally induced needle and compact quartz growth. Phase-field...
Many studies indicate the recovery of crude oil by waterflooding can be improved by lowering the salinity
of injected water. This so-called low-salinity effect is often associated with the change of the wetting state of
rock towards more water-wet. However, it is not very well understood how wettability alteration at the pore level could lead to an...
Accurate mapping of gas hydrate-bearing sediments is of great importance due to two main reasons i) its potential as an energy resource [e.g. Collett and Ladd, 2000] and ii) its potential as a driver for geohazards, namely as a contributing factor for global climate change [e.g. Kvenvolden, 1993] and large submarine landslides [e.g. Nixon and Grozi...
Authigenic carbonate build-ups develop at seafloor methane-seeps, where microbially mediated sulphate-dependent anaerobic oxidation of methane facilitates carbonate precipitation. Despite being valuable recorders of past methane seepage events, their role as archives of atmospheric processes has not been examined. Here we show that cyclic sedimenta...
To date, very little is known about the distribution of natural gas hydrates in sedimentary matrices and its influence on the seismic properties of the host rock, in particular at low hydrate concentration. Digital rock physics offers a unique approach to this issue yet requires good quality, high-resolution 3-D representations for the accurate mod...
Many studies indicate that the recovery of crude oil by waterflooding can be improved in both sandstone and carbonate rocks by lowering the salinity of injected water. This so-called low salinity effect is thought to be associated with the change of the wetting state of rock towards more water wet. However, it is not very well understood how wettab...
The goal of this study is to better understand the
porosity and permeability in shales to improve modelling fluid and gas flow
related to shale diagenesis. Two samples (WIC and HAD) were investigated,
both mid-Jurassic organic-rich Posidonia shales from Hils area, central
Germany of different maturity (WIC R0 0.53 % and HAD R0
1.45 %). The method f...
Various geoscientific applications require a fast
prediction of fracture permeability for an optimal workflow. Hence, the
objective of the current study is to introduce and validate a practical
method to characterize and approximate single flow in fractures under
different stress conditions by using a core-flooding apparatus, in situ
X-ray computed...
An essential part of the collaborative research project
H2STORE (hydrogen to store), which is funded by the German government,
was a comparison of various analytical methods for characterizing reservoir
sandstones from different stratigraphic units. In this context Permian,
Triassic and Tertiary reservoir sandstones were analysed. Rock core
materia...
Image processing of X-ray-computed polychromatic cone-beam micro-tomography
(μXCT) data of geological samples mainly involves artefact reduction
and phase segmentation. For the former, the main beam-hardening (BH)
artefact is removed by applying a best-fit quadratic surface algorithm to a
given image data set (reconstructed slice), which minimizes...
To date, very little is known about the distribution of gas hydrates in sedimentary matrices and the resulting matrix-pore network affecting the seismic properties at low hydrate concentration. Digital rock physics offers a unique solution to this issue yet requires good quality, high resolution 3D representations for the accurate modelling of petr...
The goal of this study is to better understand the porosity and permeability in shales to improve modelling fluid and gas flow related to shale diagenesis. Two samples (WIC and HAD) were investigated, both Mid Jurassic Posidonia organic rich shales from central Germany of different maturity (WIC R0 0.53 % and HAD R0 1.45 %). The method for image co...
The objective of the current study is to investigate and validate stress-dependent single fluid flow in a fractured core sample using in situ X-ray computed tomography (CT) scans and a finite-volume method solving the Navier-Stokes-Brinkman equations. The permeability of the fractured sandstone sample was measured stepwise during a loading-unloadin...
An essential part of the collaborative research project H2STORE ("hydrogen to store"), which is founded by the German government, was a comparison of various analytical methods to characterize reservoir sandstones from different stratigraphic units. In this context Permian, Triassic and Tertiary reservoir sandstones were analysed. Rock core materia...
Pore-scale images obtained from a synchrotron-based X-ray computed micro-tomography (CT) imbibition experiment in sandstone rock were used to conduct Navier-Stokes flow simulations on the connected pathways of water and oil phases. The resulting relative permeability was compared with steady-state Darcy-scale imbibition experiments on 5 cm large t...
In X-ray computed microtomography (μXCT) image processing is the most important operation prior to image analysis. Such processing mainly involves artefact reduction and image segmentation. We propose a new two-stage post-reconstruction procedure of an image of a geological rock core obtained by polychromatic cone-beam μXCT technology. In the first...
Summary In this study we present the results from the first direct observation of gas hydrate nucleation and growth in a sedimentary matrix on the sub-µm resolution applying time-resolved synchrotron-based tomography (SXCT). The aim is a subsequent use of the resulting three-dimensional (3D) data as a direct model input to obtain effective elastic...
In geochemically perturbed systems where porewater and mineral assemblages are unequilibrated the processes of mineral precipitation and dissolution may change important transport properties such as porosity and pore diffusion coefficients. These reactions might alter the sealing capabilities of the rock by complete pore-scale precipitation (cement...
Fractional flow has been studied at the pore scale under dynamic flow conditions by
using fast synchrotron-based X-ray computed micro-tomography. The pore-scale flow
regimes have been mapped in a “phase diagram” where the regimes of connected
pathway flow and ganglion dynamics are characterized by fractional flow and capillary
number. The regimes a...
In this study, a new numerical solver based on a coupling of the Navier-Stokes and Brinkman equations is presented. The solver can model 3D horizontal steady-state flow conditions with interactions between the aquifer, gravel-pack, well screen, and open borehole at the interface between the borehole and the surrounding porous filter and aquifer, th...
The characterization of the quality and storage capacity of geological underground reservoirs is one of the most important and challenging tasks for the realization of carbon capture and storage (CCS) projects. One approach for such an evaluation is the upscaling of data sets achieved by laboratory CO2 batch experiments to field scale. (Sub)-micros...
During imbibition, initially connected oil is displaced until it is trapped as immobile clusters. While initial and final states have been well described before, here we image the dynamic transient process in a sandstone rock using fast synchrotron-based X-ray computed microtomography. Wetting film swelling and subsequent snap off, at unusually hig...
The formation process of gas hydrates in sedimentary matrices is of crucial importance for the physical and transport properties of the resulting aggregates. This process has never been observed in situ at submicron resolution. Here we report on synchrotron-based microtomographic studies by which the nucleation and growth processes of gas hydrate w...
The formation process of gas hydrates in sedimentary matrices is of crucial importance for the physical and transport properties of the resulting aggregates. This process has never been observed in-situ with sub-micron resolution. Here, we report on synchrotron-based micro-tomographic studies by which the nucleation and growth processes of gas hydr...
