TY - JOUR A1 - Kaiser, Björn Onno A1 - Cacace, Mauro A1 - Scheck-Wenderoth, Magdalena T1 - 3D coupled fluid and heat transport simulations of the Northeast German Basin and their sensitivity to the spatial discretization - different sensitivities for different mechanisms of heat transport JF - Environmental earth sciences N2 - Based on a numerical model of the Northeast German Basin (NEGB), we investigate the sensitivity of the calculated thermal field as resulting from heat conduction, forced and free convection in response to consecutive horizontal and vertical mesh refinements. Our results suggest that computational findings are more sensitive to consecutive horizontal mesh refinements than to changes in the vertical resolution. In addition, the degree of mesh sensitivity depends strongly on the type of the process being investigated, whether heat conduction, forced convection or free thermal convection represents the active heat driver. In this regard, heat conduction exhibits to be relative robust to imposed changes in the spatial discretization. A systematic mesh sensitivity is observed in areas where forced convection promotes an effective role in shorten the background conductive thermal field. In contrast, free thermal convection is to be regarded as the most sensitive heat transport process as demonstrated by non-systematic changes in the temperature field with respect to imposed changes in the model resolution. KW - Mesh convergence KW - Conduction KW - Advection KW - Convection KW - Thermal field KW - Northeast German Basin Y1 - 2013 U6 - https://doi.org/10.1007/s12665-013-2249-7 SN - 1866-6280 SN - 1866-6299 VL - 70 IS - 8 SP - 3643 EP - 3659 PB - Springer CY - New York ER - TY - JOUR A1 - Kaiser, Björn Onno A1 - Cacace, Mauro A1 - Scheck-Wenderoth, Magdalena T1 - Quaternary channels within the Northeast German Basin and their relevance on double diffusive convective transport processes - constraints from 3-D thermohaline numerical simulations JF - Geochemistry, geophysics, geosystems N2 - The internal geological structure of the Northeast German Basin (NEGB) is affected by intense salt diapirism and by the presence of several stratified aquifer complexes of regional relevance. The shallow Quaternary to late Tertiary freshwater aquifer is separated from the underlying Mesozoic saline aquifers by an embedded Tertiary clay enriched aquitard (Rupelian Aquitard). An important feature of this aquitard is that hydraulic connections between the upper and lower aquifers do exist in areas where the Rupelian Aquitard is missing (hydrogeological windows). Three-dimensional thermohaline numerical simulations are carried out to investigate the effects of such hydrogeological windows in the Rupelian Aquitard on the resulting groundwater, temperature, and salinity distributions. Numerical results suggest that hydrogeological windows act as preferential domains of hydraulic interconnectivity between the different aquifers at depth and enable vigorous heat and mass transport which causes a mixing of warm and saline groundwater with cold and less saline groundwater within both aquifers. In areas where the Rupelian Aquitard confines the Mesozoic aquifer, dissolved solutes from major salt structures are transported laterally giving rise to plumes of variable salinity content ranging from few hundreds of meters to several tens of kilometers. Furthermore, destabilizing thermal buoyancy forces may overwhelm counteracting stabilizing salinity induced forces offside of salt domes. This may result in buoyant upward groundwater flow transporting heat and mass to shallower levels within the same Mesozoic Aquifer. KW - double diffusive convection KW - thermohaline processes KW - numerical simulations KW - salt structures KW - Northeast German Basin KW - quarternary channels Y1 - 2013 U6 - https://doi.org/10.1002/ggge.20192 SN - 1525-2027 VL - 14 IS - 8 SP - 3156 EP - 3175 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Cherubini, Yvonne A1 - Cacace, Mauro A1 - Scheck-Wenderoth, Magdalena A1 - Moeck, Inga A1 - Lewerenz, Björn T1 - Controls on the deep thermal field - implications from 3-D numerical simulations for the geothermal research site Groß Schönebeck JF - Environmental earth sciences N2 - The deep thermal field in sedimentary basins can be affected by convection, conduction or both resulting from the structural inventory, physical properties of geological layers and physical processes taking place therein. For geothermal energy extraction, the controlling factors of the deep thermal field need to be understood to delineate favorable drill sites and exploitation compartments. We use geologically based 3-D finite element simulations to figure out the geologic controls on the thermal field of the geothermal research site Gro Schonebeck located in the E part of the North German Basin. Its target reservoir consists of Permian Rotliegend clastics that compose the lower part of a succession of Late Carboniferous to Cenozoic sediments, subdivided into several aquifers and aquicludes. The sedimentary succession includes a layer of mobilized Upper Permian Zechstein salt which plays a special role for the thermal field due to its high thermal conductivity. Furthermore, the salt is impermeable and due to its rheology decouples the fault systems in the suprasalt units from subsalt layers. Conductive and coupled fluid and heat transport simulations are carried out to assess the relative impact of different heat transfer mechanisms on the temperature distribution. The measured temperatures in 7 wells are used for model validation and show a better fit with models considering fluid and heat transport than with a purely conductive model. Our results suggest that advective and convective heat transport are important heat transfer processes in the suprasalt sediments. In contrast, thermal conduction mainly controls the subsalt layers. With a third simulation, we investigate the influence of a major permeable and of three impermeable faults dissecting the subsalt target reservoir and compare the results to the coupled model where no faults are integrated. The permeable fault may have a local, strong impact on the thermal, pressure and velocity fields whereas the impermeable faults only cause deviations of the pressure field. KW - Thermal field KW - Coupled fluid and heat transport KW - Faults KW - Groß beta Schönebeck Y1 - 2013 U6 - https://doi.org/10.1007/s12665-013-2519-4 SN - 1866-6280 SN - 1866-6299 VL - 70 IS - 8 SP - 3619 EP - 3642 PB - Springer CY - New York ER - TY - JOUR A1 - Cherubini, Yvonne A1 - Cacace, Mauro A1 - Blöcher, Guido A1 - Scheck-Wenderoth, Magdalena T1 - Impact of single inclined faults on the fluid flow and heat transport - results from 3-D finite element simulations JF - Environmental earth sciences N2 - The impact of inclined faults on the hydrothermal field is assessed by adding simplified structural settings to synthetic models. This study is innovative in carrying out numerical simulations because it integrates the real 3-D nature of flow influenced by a fault in a porous medium, thereby providing a useful tool for complex geothermal modelling. The 3-D simulations for the coupled fluid flow and heat transport processes are based on the finite element method. In the model, one geological layer is dissected by a dipping fault. Sensitivity analyses are conducted to quantify the effects of the fault's transmissivity on the fluid flow and thermal field. Different fault models are compared with a model where no fault is present to evaluate the effect of varying fault transmissivity. The results show that faults have a significant impact on the hydrothermal field. Varying either the fault zone width or the fault permeability will result in relevant differences in the pressure, velocity and temperature field. A linear relationship between fault zone width and fluid velocity is found, indicating that velocities increase with decreasing widths. The faults act as preferential pathways for advective heat transport in case of highly transmissive faults, whereas almost no fluid may be transported through poorly transmissive faults. KW - Hydrothermal field KW - 3-D numerical simulations KW - Inclined faults KW - Fault zone KW - Coupled fluid flow and heat transport KW - Finite elements Y1 - 2013 U6 - https://doi.org/10.1007/s12665-012-2212-z SN - 1866-6280 SN - 1866-6299 VL - 70 IS - 8 SP - 3603 EP - 3618 PB - Springer CY - New York ER - TY - JOUR A1 - Cacace, Mauro A1 - Blöcher, Guido A1 - Watanabe, Norihiro A1 - Möck, Inga A1 - Börsing, Nele A1 - Scheck-Wenderoth, Magdalena A1 - Kolditz, Olaf A1 - Hünges, Ernst T1 - Modelling of fractured carbonate reservoirs - outline of a novel technique via a case study from the Molasse Basin, southern Bavaria, Germany JF - Environmental earth sciences N2 - Fluid flow in low-permeable carbonate rocks depends on the density of fractures, their interconnectivity and on the formation of fault damage zones. The present-day stress field influences the aperture hence the transmissivity of fractures whereas paleostress fields are responsible for the formation of faults and fractures. In low-permeable reservoir rocks, fault zones belong to the major targets. Before drilling, an estimate for reservoir productivity of wells drilled into the damage zone of faults is therefore required. Due to limitations in available data, a characterization of such reservoirs usually relies on the use of numerical techniques. The requirements of these mathematical models encompass a full integration of the actual fault geometry, comprising the dimension of the fault damage zone and of the fault core, and the individual population with properties of fault zones in the hanging and foot wall and the host rock. The paper presents both the technical approach to develop such a model and the property definition of heterogeneous fault zones and host rock with respect to the current stress field. The case study describes a deep geothermal reservoir in the western central Molasse Basin in southern Bavaria, Germany. Results from numerical simulations indicate that the well productivity can be enhanced along compressional fault zones if the interconnectivity of fractures is lateral caused by crossing synthetic and antithetic fractures. The model allows a deeper understanding of production tests and reservoir properties of faulted rocks. KW - Fractured carbonate geothermal reservoirs KW - Fault core and damage zone KW - In situ stress field KW - 3D mesh generator KW - OpenGeosys KW - Well productivity Y1 - 2013 U6 - https://doi.org/10.1007/s12665-013-2402-3 SN - 1866-6280 SN - 1866-6299 VL - 70 IS - 8 SP - 3585 EP - 3602 PB - Springer CY - New York ER -