@article{BloecherCacaceLewerenzetal.2010, author = {Bloecher, Mando Guido and Cacace, Mauro and Lewerenz, Bjoern and Zimmermann, G{\"u}nter}, title = {Three dimensional modelling of fractured and faulted reservoirs : framework and implementation}, issn = {0009-2819}, doi = {10.1016/j.chemer.2010.05.014}, year = {2010}, abstract = {Modelling of coupled physical processes in fractured and faulted media is a major challenge for the geoscience community. Due to the complexity related to the geometry of real fracture networks and fault systems, modelling studies have been mainly restricted either to two dimensional cases or to simplified orthogonal fracture systems consisting of vertical and horizontal fractures. An approach to generate three dimensional meshes for realistic fault geometries is presented. The method enables representation of faults in an arbitrary incline as two dimensional planes within a three dimensional, stratified porous matrix of a generic geometry. Based on a structural geological model, the method creates three dimensional unstructured tetrahedral meshes. These meshes can be used for finite element and finite volume numerical simulations. A simulation of a coupled fluid flow and heat transport problem for a two layered porous medium cut by two crossing faults is presented to test the reliability of the method.}, language = {en} } @article{CacaceBloecherWatanabeetal.2013, author = {Cacace, Mauro and Bl{\"o}cher, Guido and Watanabe, Norihiro and M{\"o}ck, Inga and B{\"o}rsing, Nele and Scheck-Wenderoth, Magdalena and Kolditz, Olaf and H{\"u}nges, Ernst}, title = {Modelling of fractured carbonate reservoirs - outline of a novel technique via a case study from the Molasse Basin, southern Bavaria, Germany}, series = {Environmental earth sciences}, volume = {70}, journal = {Environmental earth sciences}, number = {8}, publisher = {Springer}, address = {New York}, issn = {1866-6280}, doi = {10.1007/s12665-013-2402-3}, pages = {3585 -- 3602}, year = {2013}, abstract = {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.}, language = {en} } @article{CacaceKaiserLewerenzetal.2010, author = {Cacace, Mauro and Kaiser, Bjoern Onno and Lewerenz, Bjoern and Scheck-Wenderoth, Magdalena}, title = {Geothermal energy in sedimentary basins : what we can learn from regional numerical models}, issn = {0009-2819}, doi = {10.1016/j.chemer.2010.05.017}, year = {2010}, abstract = {Understanding the interactions between the different processes that control the geothermal and fluid flow fields in sedimentary basins is crucial for exploitation of geothermal energy. Numerical models provide predictive and feasible information for a correct assessment of geothermal resources especially in areas where data acquisition is demanding. Here, we present results from numerical efforts to characterize the thermal structure and its interaction with the fluid system for the area of the North East German Basin (NEGB). The relative impact of the different (diffusive and advective) processes affecting the hydrothermal setting of the basin are investigated by means of three- dimensional numerical simulations. Lithospheric-scale numerical models are evaluated to understand the specific thermal signature of the relevant factors influencing the present-day conductive geothermal field in the NEGB. Shallow and deep structural controls on the thermal configuration of the basin are addressed and quantified. Interaction between the resulting thermal field and the active fluid system is investigated by means of three-dimensional simulations of coupled fluid flow and heat transport. Factors influencing stability and reliability of modeling predictions are discussed. The main effort is to build a physically consistent model for the basin which integrates the impacts of thermal gradients on the regional fluid regime and their coupling with the main geological units defining the basin.}, language = {en} } @article{CherubiniCacaceBloecheretal.2013, author = {Cherubini, Yvonne and Cacace, Mauro and Bl{\"o}cher, Guido and Scheck-Wenderoth, Magdalena}, title = {Impact of single inclined faults on the fluid flow and heat transport - results from 3-D finite element simulations}, series = {Environmental earth sciences}, volume = {70}, journal = {Environmental earth sciences}, number = {8}, publisher = {Springer}, address = {New York}, issn = {1866-6280}, doi = {10.1007/s12665-012-2212-z}, pages = {3603 -- 3618}, year = {2013}, abstract = {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.}, language = {en} } @article{CherubiniCacaceScheckWenderothetal.2013, author = {Cherubini, Yvonne and Cacace, Mauro and Scheck-Wenderoth, Magdalena and Moeck, Inga and Lewerenz, Bj{\"o}rn}, title = {Controls on the deep thermal field - implications from 3-D numerical simulations for the geothermal research site Groß Sch{\"o}nebeck}, series = {Environmental earth sciences}, volume = {70}, journal = {Environmental earth sciences}, number = {8}, publisher = {Springer}, address = {New York}, issn = {1866-6280}, doi = {10.1007/s12665-013-2519-4}, pages = {3619 -- 3642}, year = {2013}, abstract = {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.}, language = {en} } @article{DegenSpoonerScheckWenderothetal.2021, author = {Degen, Denise and Spooner, Cameron and Scheck-Wenderoth, Magdalena and Cacace, Mauro}, title = {How biased are our models?}, series = {Geoscientific model development : an interactive open access journal of the European Geosciences Union}, volume = {14}, journal = {Geoscientific model development : an interactive open access journal of the European Geosciences Union}, number = {11}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1991-959X}, doi = {10.5194/gmd-14-7133-2021}, pages = {7133 -- 7153}, year = {2021}, abstract = {Geophysical process simulations play a crucial role in the understanding of the subsurface. This understanding is required to provide, for instance, clean energy sources such as geothermal energy. However, the calibration and validation of the physical models heavily rely on state measurements such as temperature. In this work, we demonstrate that focusing analyses purely on measurements introduces a high bias. This is illustrated through global sensitivity studies. The extensive exploration of the parameter space becomes feasible through the construction of suitable surrogate models via the reduced basis method, where the bias is found to result from very unequal data distribution. We propose schemes to compensate for parts of this bias. However, the bias cannot be entirely compensated. Therefore, we demonstrate the consequences of this bias with the example of a model calibration.}, language = {en} } @article{FreymarkBottCacaceetal.2019, author = {Freymark, Jessica and Bott, Judith and Cacace, Mauro and Ziegler, Moritz 0. and Scheck-Wenderoth, Magdalena}, title = {Influence of the Main Border Faults on the 3D Hydraulic Field of the Central Upper Rhine Graben}, series = {Geofluids}, journal = {Geofluids}, publisher = {Wiley-Hindawi}, address = {London}, issn = {1468-8115}, doi = {10.1155/2019/7520714}, pages = {21}, year = {2019}, abstract = {The Upper Rhine Graben (URG) is an active rift with a high geothermal potential. Despite being a well-studied area, the three-dimensional interaction of the main controlling factors of the thermal and hydraulic regime is still not fully understood. Therefore, we have used a data-based 3D structural model of the lithological configuration of the central URG for some conceptual numerical experiments of 3D coupled simulations of fluid and heat transport. To assess the influence of the main faults bordering the graben on the hydraulic and the deep thermal field, we carried out a sensitivity analysis on fault width and permeability. Depending on the assigned width and permeability of the main border faults, fluid velocity and temperatures are affected only in the direct proximity of the respective border faults. Hence, the hydraulic characteristics of these major faults do not significantly influence the graben-wide groundwater flow patterns. Instead, the different scenarios tested provide a consistent image of the main characteristics of fluid and heat transport as they have in common: (1) a topography-driven basin-wide fluid flow perpendicular to the rift axis from the graben shoulders to the rift center, (2) a N/NE-directed flow parallel to the rift axis in the center of the rift and, (3) a pronounced upflow of hot fluids along the rift central axis, where the streams from both sides of the rift merge. This upflow axis is predicted to occur predominantly in the center of the URG (northern and southern model area) and shifted towards the eastern boundary fault (central model area).}, language = {en} } @article{KaiserCacaceScheckWenderothetal.2011, author = {Kaiser, Bjoern Onno and Cacace, Mauro and Scheck-Wenderoth, Magdalena and Lewerenz, Bjoern}, title = {Characterization of main heat transport processes in the Northeast German Basin constraints from 3-D numerical models}, series = {Geochemistry, geophysics, geosystems}, volume = {12}, journal = {Geochemistry, geophysics, geosystems}, number = {13}, publisher = {American Geophysical Union}, address = {Washington}, issn = {1525-2027}, doi = {10.1029/2011GC003535}, pages = {17}, year = {2011}, abstract = {To investigate and quantify main physical heat driving processes affecting the present-day subsurface thermal field, we study a complex geological setting, the Northeast German Basin (NEGB). The internal geological structure of the NEGB is characterized by the presence of a relatively thick layer of Permian Zechstein salt (up to 5000 m), which forms many salt diapirs and pillows locally reaching nearly the surface. By means of three-dimensional numerical simulations we explore the role of heat conduction, pressure, and density driven groundwater flow as well as fluid viscosity related effects. Our results suggest that the regional temperature distribution within the basin results from interactions between regional pressure forces as driven by topographic gradients and thermal diffusion locally enhanced by thermal conductivity contrasts between the different sedimentary rocks with the highly conductive salt playing a prominent role. In contrast, buoyancy forces triggered by temperature-dependent fluid density variations are demonstrated to affect only locally the internal thermal configuration. Locations, geometry, and wavelengths of convective thermal anomalies are mainly controlled by the permeability field and thickness values of the respective geological layers.}, language = {en} } @article{KaiserCacaceScheckWenderoth2013, author = {Kaiser, Bj{\"o}rn Onno and Cacace, Mauro and Scheck-Wenderoth, Magdalena}, title = {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}, series = {Environmental earth sciences}, volume = {70}, journal = {Environmental earth sciences}, number = {8}, publisher = {Springer}, address = {New York}, issn = {1866-6280}, doi = {10.1007/s12665-013-2249-7}, pages = {3643 -- 3659}, year = {2013}, abstract = {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.}, language = {en} } @article{KaiserCacaceScheckWenderoth2013, author = {Kaiser, Bj{\"o}rn Onno and Cacace, Mauro and Scheck-Wenderoth, Magdalena}, title = {Quaternary channels within the Northeast German Basin and their relevance on double diffusive convective transport processes - constraints from 3-D thermohaline numerical simulations}, series = {Geochemistry, geophysics, geosystems}, volume = {14}, journal = {Geochemistry, geophysics, geosystems}, number = {8}, publisher = {American Geophysical Union}, address = {Washington}, issn = {1525-2027}, doi = {10.1002/ggge.20192}, pages = {3156 -- 3175}, year = {2013}, abstract = {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.}, language = {en} }