Dr Daniel Koehn
- Reader (School of Geographical & Earth Sciences)
My research focus is structural geology and tectonics as well as pattern formation in geological systems. I work on a large range of length and time scales and use field observations, numerical simulations and experiments for my research.
- Fracturing, fluid flow and fracture sealing (DGMK funded research group FRACS)
- Flow and Transformation in Porous Media (FP7 Marie Curie Initial Training Network FlowTrans)
- Stylolite Stress Inversion
- Extreme horst uplift in East Africa (DFG funded RiftLink Project)
- Tectonics of the continental margins of Namibia and Brazil (DFG funded project within the SAMPLE group)
- Deep seated Geothermal systems and their relation to faults (cooperation with the School of Engineering)
Fracturing, fluid flow and fracture sealing (DGMK funded research group FRACS)
Prediction of the behaviour of fractured and tight reservoirs is hindered by a lack of understanding of dissolution (forming stylolites) and the formation and sealing of fractures(producing veins). These processes can significantly change geometrical characteristics, mechanical properties, and fluid transport in reservoirs. In the FRACS project (DGMK Project 718) we are working on an understanding of the coupling between sealing of fractures/faults, fluid-flow evolution, and creation of fluidpathways through fracturing. The main objective is to achieve an improved understanding of the dynamic fluid-flow characteristics of a variety of heterogeneous, fractured and resealed reservoirs. Such an understanding can form the basis for the development of predictive tools. FRACS Homepage
Flow and Transformation in Porous Media
The characterization and the understanding of flow of fluids within rocks and granular media has become an ever-increasing problem in Earth Sciences, Physics, and in many industrial applications, including CO2 sequestration, hydrocarbon migration, ore deposit development, and radioactive waste disposal. One of the main problems is the understanding of flows in transforming porous media (PM), where the rocks and fluid pathways evolve spatially and temporally, for example due to chemical interactions with the flow, or due to compaction of the solid matrix. The dynamic feedbacks between flow, destruction of permeability due to compaction or local precipitation, and creation of permeability due to dissolution, chemical reaction or fracturing, makes understanding of such complex systems a challenge. Such feedbacks between flow of fluids and PM in which they are flowing, are important in both relatively slowly deforming PM such as in naturally evolving reservoirs, and in rapidly evolving PM such as fluid-filled fault zones or soils experiencing earthquakes, rapidly flowing grain-fluid mixtures in debris flows, or industrial processes in petroleum production such as pyrolysis or hydrofracking. We propose to study the feedback mechanisms and their impact on the porous media through an interdisciplinary approach between Earth Scientists and Physicists. State of the art analytical and experimental methods will be used on natural systems and rock analogues, and will be complemented by multi-scale dynamical simulations, to develop new basic understanding and new methods that can be directly used in industrial applications. FlowTrans Homepage
Stylolite Stress Inversion
Stylolites are rough surfaces in rocks that develop due to localized stress-induced dissolution. They are very common features especially in limestones and are thus easy to sample. In the last years we have developed a new promising method to use stylolites as stress gauges. The stylolite teeth give the direction of the main compressive stress and the rough interface contains a signature of the absolute value of the stress during stylolite growth. Given a number of assumptions (elastic constants, density of rocks, anisotropy of stress state) a set of stylolites can reveal the full three-dimensional paleostresstensor and the paleodepth of stylolite formation. Stylolites thus represent a new and almost untouched archive of paleostress states within the upper crust of the Earth.
Extreme horst uplift in East Africa
The Rwenzoris in western Uganda are a 5000m high basement block that lies within the western branch of the East African Rift System. As part of a DFG funded Forschergruppe we explored the past and present tectonic history of the mountain. Fault patterns within the mountain are relatively complex and stress inversion indicates extension, strike slip as well as compressional regimes. We have modelled the evolution of the area with several numerical models. Results indicate that the mountain is captured by propagating rift segments and that it is currently rotating clockwise. Numerical models of surface uplift indicate that the Rwenzori comes up in a similar way to a rift flank, however, in order to achieve its extreme height it has to be relatively stiff. We propose that this stiffness is achieved by a palaeoproterozoic fold and thrust belt that strikes across the mountain with the core being an amphibolite wedge that contains the peaks Margerita and Baker. RiftLink Homepage
Tectonics of the continental margins of Namibia and Brazil
As part of the DFG funded SPP SAMPLE we look at the tectonic evolution of the passive continental shelf of Namibia and Brazil. Our work includes a study of the reactivation of basement features during margin related tectonic events as well as a stress inversion study of both margins in order to compare their structural setting and history. SAMPLE Homepage
Lindenfeld, M., Rümpker, G., Link, K., Koehn, D. and Batte, A. (2012) Fluid-triggered earthquake swarms in the Rwenzori region, East African Rift – evidence for rift initiati. Tectonophysics, 566, pp. 95-104. (doi:10.1016/j.tecto.2012.07.010)
Koehn, D. , Ebner, M., Renard, F., Toussaint, R. and Passchier, W. (2012) Modelling of stylolite geometries and stress scaling. Earth and Planetary Science Letters, 341, pp. 104-113. (doi:10.1016/j.epsl.2012.04.046)
Ebner, M., Koehn, D. , Toussaint, R., Renard, F. and Schmittbuhl, J. (2009) Stress sensitivity of stylolite morphology. Earth and Planetary Science Letters, 277(3-4), pp. 394-398. (doi:10.1016/j.epsl.2008.11.001)
Koehn, D. , Aanyu, K., Haines, S. and Sachau, T. (2008) Rift nucleation, rift propagation and the creation of basement micro-plates within active rifts. Tectonophysics, 458(1-4), pp. 105-116. (doi:10.1016/j.tecto.2007.10.003)
- FP7 Marie Curie Initial Training Network FlowTrans, Flow and Transformation in Porous Media, Coordination by the University of Glasgow. Total budget Euro 4.1m, Glasgow budget Euro 1m. 11 PhDs and 4 Postdocs. FlowTrans Homepage
- FRACS Mineral Vein Dynamics Modelling II, started Juli 2012, DGMK funded basic research group. Total budget Euro 0.96m, Glasgow budget Euro 210 k. 4 PhDs and 3 Postdocs. FRACS Homepage
Irfan Ghani, University of Mainz, FRACS Project (DGMK funded): Dynamic development of hydrofracture, defended sucessfully september 2013
Eric Salomon, University of Mainz, SAMPLE Project (DFG funded): Tectonic evolution of the South Atlantic passive continental margin based on onshore structural data Homepage
Anna Vass, FRACS Project (DGMK funded): Large-scale dynamic fracturing and healing of multilayered, high fluid pressure systems. Homepage
Daisy Pataki Rood, FRACS Project (DGMK funded): The role of stylolites in sedimentary basins. Homepage
Ulrich Kelka, FlowTrans (Marie Curie ITN), My research aims to understand the genesis of the so called zebra textures in Dolostones. Homepage
Janis Aleksans, NERC Oil and Gas CDT. Dynamics of hydrofracturing and associated signals (from porous to tight rocks). Homepage
Allan Hollinsworth, NERC Oil and Gas CDT. Understanding porosity-permeability evolution of basement faults using 4D computed X-ray tomography. Homepage
co-supervision of PhD students:
Helen Robinson, School of Engineering, Glasgow University, Geothermal systems in the East African Rift, cooperation with Prof. Paul Younger
Karine Petrus, Univeristy of Warshaw, Poland, FlowTrans (Marie Curie ITN), Modelling the joint effects of flow, dissolution and deformation on the evolution of porous media, Homepage
Stephen Centrella, University of Muenster, Germany, FlowTrans (Marie Curie ITN), The relation between chemistry and texture across shear zones, Homepage
Dr. Nicolas Beaudoin, FlowTrans (Marie Curie ITN), Understanding the nature, origin and migration pathway of fluids that migrated and precipitated as precious ore mineralization in stylolites as observed in granitic rocks and compressive context. Homepage
Dr. Wendy Louise Smith, Homepage
Currently I teach structural geology on Level 1, Level 2 and Level 3 courses including Level 2 and Level 3 practical exercises.
I am also involved in a 1day field trip to Corrieburn, a 1day field trip to Stonehaven and two residential field trips to Ardnamurchan and Oban that last a full week each.
In addition I supervise several Level 4 projects each year.
Currently I am the Exam Officer of the Earth Sciences group.