Jens Hornung | Technische Universität Darmstadt (original) (raw)
Papers by Jens Hornung
Solid Earth Discussions, 2013
Permeability is one of the most important petrophysical parameters to describe the reservoir prop... more Permeability is one of the most important petrophysical parameters to describe the reservoir properties of sedimentary rocks, pertaining to problems in hydrology, geothermics, and hydrocarbon reservoir analysis. Outcrop analogue studies, well core measurements, and individual sample analysis take advantage of a variety of commercially available devices for permeability measurements. Very often, permeability data derived from different devices need to be merged within one study (e.g. outcrop minipermeametry and lab-based core plug measurements). To enhance accuracy of different gas-driven permeability measurements, devicespecific aberrations need to be taken into account. The application of simple one-to-one correlations may draw the wrong picture of permeability trends. For this purpose, transform equations need to be established.
Palaeobiodiversity and Palaeoenvironments, 2010
This review paper summarizes the sedimentary and palaeoenvironmental evolution of the Junggar Bas... more This review paper summarizes the sedimentary and palaeoenvironmental evolution of the Junggar Basin in Northwest China largely based on hardly accessible Chinese language papers, and complemented by own field observations and a critical survey of key sediment cores from petroleum wells. We have combined this information and updated existing lithofacies and isopach maps for characteristic time slices of basin evolution and palaeoenvironmental change. The Junggar Basin was initiated during the late stage of collisional tectonics in the southern Central Asian Orogenic Belt (Altaids) since the Early Permian. According to studies in surrounding mountain chains and geophysical surveys, the basement consists of a collage of oceanic basins, intraoceanic island arcs, and microcontinents of Precambrian to Palaeozoic age. The basin fill is subdivided into three tectonically controlled stratigraphic sequences which are separated by two regional angular unconformities. The first cycle in the Permian and Triassic is characterized by an Early Permian extensional strike-slip and a Late Permian to Triassic compressional foreland setting. After an Early Permian marine regression, persistent nonmarine fluvio-lacustrine conditions were established containing probably the thickest organic-rich mudstone interval in the world, which act as major source rocks of the basin. Starting with four depocenters, the basin was unified during the Triassic. The preserved total maximum thickness of this cycle is about 8,500 m in the southern depocenter. During the second intracontinental depression cycle, subsidence slowed down and the depocenter migrated towards the basin center reaching a maximum thickness of 6,000 m. The palaeoenvironment was dominated by a large oscillating freshwater lake receiving changing quantities of clastic sediments from the surrounding mountain ranges and forming alluvial fans, braid plains, and deltas partly containing coal seams of economic interest. Sedimentary facies, pollen, and palaeobotanical plant fossils show an overall aridization trend and a shrinking lake cover. During the Neogene cycle, the depocenter migrated back to the south and the former asymmetric foreland basin was reactivated due to thrusting and rapid uplift of the Tian Shan. The maximum thickness of these molasse-type deposits exceeds 5,000 m. Despite its strong potential, there is still a lack of high resolution bio-and cyclostratigraphy, sequence stratigraphy, and palaeoclimate studies in the Junggar Basin to elucidate local versus regional palaeoenvironmental patterns and to better constrain fardistance tectonic forcing.
Zeitschrift der Deutschen Gesellschaft für Geowissenschaften, 2014
ABSTRACT Filtering and storage of precipitation, runoff, and subsequent groundwater recharge is g... more ABSTRACT Filtering and storage of precipitation, runoff, and subsequent groundwater recharge is governed by the structure and properties of the shallow subsurface and the soils formed therein. Hence, detailed knowledge about the three-dimensional structure, thickness and composition of the shallow subsurface is essential to quantify these processes; special benefit can be derived in connection with the hydraulic and material-specific properties. Geobodies can be mapped by complementary, non-invasive, geophysical methods. Associated with lithofacies, geophysical and other properties these "geobothes" can be fingerprinted. A 3D model containing e.g. porosity, field capacity, permeability, grain size and soil chemistry can be build. Geoelectrical resistance tomography and three-dimensional (3D) ground-penetrating radar surveys have been carried out in the catchment of the "Seebach" (Forbach, Bunter, Black Forest, Southern Germany). A test field was established and investigated with respect to the sedimentological and pedological architecture of the shallow subsurface, going along with lithofacies mapping, granulometry, and permeability investigations. The synthesis of all data resulted in a three-dimensional quantitative subsurface model of the shallow subsurface architecture. Together with the associated hydrological characteristics, this can serve as input parameters for water budget and sorption models.
Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen
Spatial relationships of rock and petrophysical properties on a grid block scale (decimeter) are ... more Spatial relationships of rock and petrophysical properties on a grid block scale (decimeter) are poorly known. These however are input to effective property models and near well-bore heterogeneities in geocellular models. To investigate and visualize such relationships slabs of typical clastic and carbonate reservoir rocks were analyzed. To this end rock properties such as grain size, sorting, pore types as well as petrophysical properties like porosity, permeability, ultrasonic speed and resistivity were systematically described. Results are displayed as property maps.
Fluviatile und Schwemmfächerabfolgen, zudem in Kombination mit tektonischer Aktivität, produziere... more Fluviatile und Schwemmfächerabfolgen, zudem in Kombination mit tektonischer Aktivität, produzieren eine extrem heterogene und komplexe Untergrundarchitektur. Um die Qualität von Grundwassermodellen zu verbessern und ingenieurgeologische Fragestellungen mit ausreichender Sicherheit nach Stand von Wissenschaft und Technik beantworten zu können, sind deshalb an den Ablagerungsprozessen orientierte, detaillierte Untergrundmodelle essentiell. Engständige Bohrungsraster können in den meisten Fällen nicht korrekt korreliert werden und kleinräumige Problemzonen erhöhen das gutachterliehe Risiko. Multimethodische Ansätze können dagegen komplexe, mit klassischen Verfahren nicht prognostizierbare Ablagerungsprozesse und Untergrundstrukturen quantifizieren.
In the frame of aquifer studies in Saudi Arabia, we measured porosity and permeability of sandsto... more In the frame of aquifer studies in Saudi Arabia, we measured porosity and permeability of sandstones of the Palaeozoic Wajid Sandstone in order to get a database for a regional groundwater model. The Wajid sandstone is subdivided into five formations, which differ in their dominant depositional environment. From the base to the top these are: (i) Dibsiyah Formation representing a shallow-marine clastic shelf, (ii) Sanamah Formation containing glacial to proglacial sediments most of them deposited in tunnel valleys, (iii) Qusaibah Formation characterized by highstand shales, (iv) Khusayyayn Formation showing large-scale tabular cross-bedded tidal sands, and the (v) Juwayl Formation again containing glacial to proglacial sediments mostly deposited in tunnel valleys and overlain by shallow-marine tidal beds.
Alluvial fans represent sediment sinks directly at the outlet of the source area in mountain land... more Alluvial fans represent sediment sinks directly at the outlet of the source area in mountain landscapes. They contain multiple information on short-term as well as on long-term changes of sediment supply and of environmental parameters like climate and vegetation. However, most studies on alluvial fans are restricted to selective surface analysis and almost no studies exist which aim to clear the subsurface geometry of an alluvial fan in total. Our study is embedded in the SedyMONT research program within the TOPO-EUROPE framework and aims to clarify the subsurface structure of an alluvial fan by a time-controlled 3D architectural model. The Illgraben fan is located in the Central Alps of Switzerland within the Rhone valley and covers an area of about 6.5 km2. Currently construction works for a highway cuts through the fan exposing its deposits (mainly gravel and diamicton) up to 15 m depth and therefore offers the unique opportunity to link ground penetrating radar (GPR) investigat...
Dielectric permittivity is an important parameter for all investigations based on electromagnetic... more Dielectric permittivity is an important parameter for all investigations based on electromagnetic waves (e.g. GPR and TDR measurements). In combination with the electric conductivity, it is crucial for the determination of the propagation velocity, the reflection coefficient and the decay of the electromagnetic wave. The dielectric permittivity depends on several factors like water content, mineralogy, grain size, and bulk density of the material. Our laboratory measurements of dielectric permittivity show quantitative relations between these parameters and that commonly used general algorithms for moisture detection bear significant inaccuracies (up to 200% error for clay substrates). Therefore, it is crucial to determine the permittivity for every specific application. This paper provides new algorithms for some most important substrate types, which can be used to recalibrate TDR-tools for specific applications. However, measurements of the dielectric permittivity are also frequen...
International Journal of Earth Sciences, 2010
This study presents an almost complete Middle Miocene to Pleistocene sequence of synrift sediment... more This study presents an almost complete Middle Miocene to Pleistocene sequence of synrift sediments in the western branch of the East African Rift. The studied succession is exposed in several patches on an eastward tilted block between the northern tip of the Rwenzori Block and the eastern shoulder of the Albert Rift. In this position, it reaches a maximum thickness of 600 m of which 350 m have been logged systematically by analysing lithofacies and sediment architecture. Stratigraphic subdivision of the succession relies on published biostratigraphic data of endemic mollusc associations and their correlation across East Africa. The synrift sediments encountered are siliciclastics ranging from clay to coarse gravel with gypsum and ferrugineous interlayers or impregnations. Lithofacies and architectural analysis indicate alluvial plain, delta plain, nearshore, delta front, or lacustrine depositional environments. Based on the vertical stacking pattern, prograding and retrograding trends of the depositional environments, and climatic indicators (e.g. conservation of feldspar, gypsum, and/or iron hydroxide precipitation), four evolutionary phases can be distinguished: (i) a first phase between ca. 14.5 and 10.0 Ma is characterised by bedload-dominated fluvial environment with massive sandy to gravelly bedforms, feldspar-rich sands, rare iron impregnations and relatively low accommodation space. This phase is interpreted as pre-and early synrift sedimentation under a semiarid climate. (ii) From ca. 10.0 to 4.5 Ma predominantly fine-grained siliciclastics were deposited in a distal fluvial plain to lacustrine setting characterised by limited accommodation space. Fluctuation of thin beds, dominance of clay and frequent iron impregnations point to a more humid climate with seasonality and weak tectonic activity. (iii) During the third phase between 4.5 and 2.0 Ma delta plain and nearshore deposits with frequent ferrugineous impregnations and rich mollusc associations occurred, indicating a humid period with lake-level highstands and accelerated subsidence. (iv) During the final sedimentary interval between 2.0 and 1.5 Ma gravel units reoccurred with less iron-but more carbonate and gypsum impregnations, and arkosic sandstones. This phase recorded a general aridisation trend most probably caused by the upcoming rain barrier of the Rwenzori Mountains together with accelerated rift-flank uplift and strong subsidence of the rift floor. The results of this study are of particular importance for delineating key controls on sedimentation in the Albert Rift.
Solid Earth Discussions, 2013
Permeability is one of the most important petrophysical parameters to describe the reservoir prop... more Permeability is one of the most important petrophysical parameters to describe the reservoir properties of sedimentary rocks, pertaining to problems in hydrology, geothermics, and hydrocarbon reservoir analysis. Outcrop analogue studies, well core measurements, and individual sample analysis take advantage of a variety of commercially available devices for permeability measurements. Very often, permeability data derived from different devices need to be merged within one study (e.g. outcrop minipermeametry and lab-based core plug measurements). To enhance accuracy of different gas-driven permeability measurements, devicespecific aberrations need to be taken into account. The application of simple one-to-one correlations may draw the wrong picture of permeability trends. For this purpose, transform equations need to be established.
Palaeobiodiversity and Palaeoenvironments, 2010
This review paper summarizes the sedimentary and palaeoenvironmental evolution of the Junggar Bas... more This review paper summarizes the sedimentary and palaeoenvironmental evolution of the Junggar Basin in Northwest China largely based on hardly accessible Chinese language papers, and complemented by own field observations and a critical survey of key sediment cores from petroleum wells. We have combined this information and updated existing lithofacies and isopach maps for characteristic time slices of basin evolution and palaeoenvironmental change. The Junggar Basin was initiated during the late stage of collisional tectonics in the southern Central Asian Orogenic Belt (Altaids) since the Early Permian. According to studies in surrounding mountain chains and geophysical surveys, the basement consists of a collage of oceanic basins, intraoceanic island arcs, and microcontinents of Precambrian to Palaeozoic age. The basin fill is subdivided into three tectonically controlled stratigraphic sequences which are separated by two regional angular unconformities. The first cycle in the Permian and Triassic is characterized by an Early Permian extensional strike-slip and a Late Permian to Triassic compressional foreland setting. After an Early Permian marine regression, persistent nonmarine fluvio-lacustrine conditions were established containing probably the thickest organic-rich mudstone interval in the world, which act as major source rocks of the basin. Starting with four depocenters, the basin was unified during the Triassic. The preserved total maximum thickness of this cycle is about 8,500 m in the southern depocenter. During the second intracontinental depression cycle, subsidence slowed down and the depocenter migrated towards the basin center reaching a maximum thickness of 6,000 m. The palaeoenvironment was dominated by a large oscillating freshwater lake receiving changing quantities of clastic sediments from the surrounding mountain ranges and forming alluvial fans, braid plains, and deltas partly containing coal seams of economic interest. Sedimentary facies, pollen, and palaeobotanical plant fossils show an overall aridization trend and a shrinking lake cover. During the Neogene cycle, the depocenter migrated back to the south and the former asymmetric foreland basin was reactivated due to thrusting and rapid uplift of the Tian Shan. The maximum thickness of these molasse-type deposits exceeds 5,000 m. Despite its strong potential, there is still a lack of high resolution bio-and cyclostratigraphy, sequence stratigraphy, and palaeoclimate studies in the Junggar Basin to elucidate local versus regional palaeoenvironmental patterns and to better constrain fardistance tectonic forcing.
Zeitschrift der Deutschen Gesellschaft für Geowissenschaften, 2014
ABSTRACT Filtering and storage of precipitation, runoff, and subsequent groundwater recharge is g... more ABSTRACT Filtering and storage of precipitation, runoff, and subsequent groundwater recharge is governed by the structure and properties of the shallow subsurface and the soils formed therein. Hence, detailed knowledge about the three-dimensional structure, thickness and composition of the shallow subsurface is essential to quantify these processes; special benefit can be derived in connection with the hydraulic and material-specific properties. Geobodies can be mapped by complementary, non-invasive, geophysical methods. Associated with lithofacies, geophysical and other properties these "geobothes" can be fingerprinted. A 3D model containing e.g. porosity, field capacity, permeability, grain size and soil chemistry can be build. Geoelectrical resistance tomography and three-dimensional (3D) ground-penetrating radar surveys have been carried out in the catchment of the "Seebach" (Forbach, Bunter, Black Forest, Southern Germany). A test field was established and investigated with respect to the sedimentological and pedological architecture of the shallow subsurface, going along with lithofacies mapping, granulometry, and permeability investigations. The synthesis of all data resulted in a three-dimensional quantitative subsurface model of the shallow subsurface architecture. Together with the associated hydrological characteristics, this can serve as input parameters for water budget and sorption models.
Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen
Spatial relationships of rock and petrophysical properties on a grid block scale (decimeter) are ... more Spatial relationships of rock and petrophysical properties on a grid block scale (decimeter) are poorly known. These however are input to effective property models and near well-bore heterogeneities in geocellular models. To investigate and visualize such relationships slabs of typical clastic and carbonate reservoir rocks were analyzed. To this end rock properties such as grain size, sorting, pore types as well as petrophysical properties like porosity, permeability, ultrasonic speed and resistivity were systematically described. Results are displayed as property maps.
Fluviatile und Schwemmfächerabfolgen, zudem in Kombination mit tektonischer Aktivität, produziere... more Fluviatile und Schwemmfächerabfolgen, zudem in Kombination mit tektonischer Aktivität, produzieren eine extrem heterogene und komplexe Untergrundarchitektur. Um die Qualität von Grundwassermodellen zu verbessern und ingenieurgeologische Fragestellungen mit ausreichender Sicherheit nach Stand von Wissenschaft und Technik beantworten zu können, sind deshalb an den Ablagerungsprozessen orientierte, detaillierte Untergrundmodelle essentiell. Engständige Bohrungsraster können in den meisten Fällen nicht korrekt korreliert werden und kleinräumige Problemzonen erhöhen das gutachterliehe Risiko. Multimethodische Ansätze können dagegen komplexe, mit klassischen Verfahren nicht prognostizierbare Ablagerungsprozesse und Untergrundstrukturen quantifizieren.
In the frame of aquifer studies in Saudi Arabia, we measured porosity and permeability of sandsto... more In the frame of aquifer studies in Saudi Arabia, we measured porosity and permeability of sandstones of the Palaeozoic Wajid Sandstone in order to get a database for a regional groundwater model. The Wajid sandstone is subdivided into five formations, which differ in their dominant depositional environment. From the base to the top these are: (i) Dibsiyah Formation representing a shallow-marine clastic shelf, (ii) Sanamah Formation containing glacial to proglacial sediments most of them deposited in tunnel valleys, (iii) Qusaibah Formation characterized by highstand shales, (iv) Khusayyayn Formation showing large-scale tabular cross-bedded tidal sands, and the (v) Juwayl Formation again containing glacial to proglacial sediments mostly deposited in tunnel valleys and overlain by shallow-marine tidal beds.
Alluvial fans represent sediment sinks directly at the outlet of the source area in mountain land... more Alluvial fans represent sediment sinks directly at the outlet of the source area in mountain landscapes. They contain multiple information on short-term as well as on long-term changes of sediment supply and of environmental parameters like climate and vegetation. However, most studies on alluvial fans are restricted to selective surface analysis and almost no studies exist which aim to clear the subsurface geometry of an alluvial fan in total. Our study is embedded in the SedyMONT research program within the TOPO-EUROPE framework and aims to clarify the subsurface structure of an alluvial fan by a time-controlled 3D architectural model. The Illgraben fan is located in the Central Alps of Switzerland within the Rhone valley and covers an area of about 6.5 km2. Currently construction works for a highway cuts through the fan exposing its deposits (mainly gravel and diamicton) up to 15 m depth and therefore offers the unique opportunity to link ground penetrating radar (GPR) investigat...
Dielectric permittivity is an important parameter for all investigations based on electromagnetic... more Dielectric permittivity is an important parameter for all investigations based on electromagnetic waves (e.g. GPR and TDR measurements). In combination with the electric conductivity, it is crucial for the determination of the propagation velocity, the reflection coefficient and the decay of the electromagnetic wave. The dielectric permittivity depends on several factors like water content, mineralogy, grain size, and bulk density of the material. Our laboratory measurements of dielectric permittivity show quantitative relations between these parameters and that commonly used general algorithms for moisture detection bear significant inaccuracies (up to 200% error for clay substrates). Therefore, it is crucial to determine the permittivity for every specific application. This paper provides new algorithms for some most important substrate types, which can be used to recalibrate TDR-tools for specific applications. However, measurements of the dielectric permittivity are also frequen...
International Journal of Earth Sciences, 2010
This study presents an almost complete Middle Miocene to Pleistocene sequence of synrift sediment... more This study presents an almost complete Middle Miocene to Pleistocene sequence of synrift sediments in the western branch of the East African Rift. The studied succession is exposed in several patches on an eastward tilted block between the northern tip of the Rwenzori Block and the eastern shoulder of the Albert Rift. In this position, it reaches a maximum thickness of 600 m of which 350 m have been logged systematically by analysing lithofacies and sediment architecture. Stratigraphic subdivision of the succession relies on published biostratigraphic data of endemic mollusc associations and their correlation across East Africa. The synrift sediments encountered are siliciclastics ranging from clay to coarse gravel with gypsum and ferrugineous interlayers or impregnations. Lithofacies and architectural analysis indicate alluvial plain, delta plain, nearshore, delta front, or lacustrine depositional environments. Based on the vertical stacking pattern, prograding and retrograding trends of the depositional environments, and climatic indicators (e.g. conservation of feldspar, gypsum, and/or iron hydroxide precipitation), four evolutionary phases can be distinguished: (i) a first phase between ca. 14.5 and 10.0 Ma is characterised by bedload-dominated fluvial environment with massive sandy to gravelly bedforms, feldspar-rich sands, rare iron impregnations and relatively low accommodation space. This phase is interpreted as pre-and early synrift sedimentation under a semiarid climate. (ii) From ca. 10.0 to 4.5 Ma predominantly fine-grained siliciclastics were deposited in a distal fluvial plain to lacustrine setting characterised by limited accommodation space. Fluctuation of thin beds, dominance of clay and frequent iron impregnations point to a more humid climate with seasonality and weak tectonic activity. (iii) During the third phase between 4.5 and 2.0 Ma delta plain and nearshore deposits with frequent ferrugineous impregnations and rich mollusc associations occurred, indicating a humid period with lake-level highstands and accelerated subsidence. (iv) During the final sedimentary interval between 2.0 and 1.5 Ma gravel units reoccurred with less iron-but more carbonate and gypsum impregnations, and arkosic sandstones. This phase recorded a general aridisation trend most probably caused by the upcoming rain barrier of the Rwenzori Mountains together with accelerated rift-flank uplift and strong subsidence of the rift floor. The results of this study are of particular importance for delineating key controls on sedimentation in the Albert Rift.