Natural permeable fracture zones are primary exploration and exploitation targets in granitic deep geothermal systems. Such a dataset is crucial to estimate rock property variability and compartmentalisation by faults and fracture networks for deep geothermal and heat storage projects in crystalline units. Thus, the structural investigation of such units is essential. For the Northern Upper Rhine Graben partner von DGE-ROLLOUT published a study on the fracture patterns in the Journal Geoscience.
Combining regional digital elevation model analysis and local outcrop investigation, the study comprises the characterisation of the fracture pattern of a crystalline reservoir analogue, with LiDAR and GIS structural interpretation. This approach provides insights into the 3D architecture of the fault and fracture network, its clustering, and its connectivity. Clustering is marked by long sub-vertical fractures at the outcrop scale, and strongly enhance heterogeneity around weathered fracture and fault corridors. The multi-variable dataset created within this study can be used as input data for accurate discrete fracture networks and fluid-flow modelling of reservoirs of similar type.
The hydraulic yields of geothermal reservoirs in crystalline rocks are controlled by the structural architecture of fault and fracture corridors and its associated hydrothermal alteration history controlling the present-day permeability. A quantification of the fault and fracture network, which can be achieved by analogue investigation, is required to predict such rock media behaviour. The study aims to reach a quantitative knowledge basis of faulted crystalline reservoirs structural architecture, especially at the scale of objects that cannot be resolved with conventional seismic techniques. This near-surface dataset of the Northern Odenwald in the Upper Rhine Graben provides the basis to estimate the input parameters of 3D fractured reservoir models. This study identifies the scale dependence of the clustering of the fracture network around fault zones and their control by the primary fault system orientation.
Geosciences 2021, 11, 371
Multiscale Characterisation of Fracture Patterns of a Crystalline Reservoir Analogue
Claire Bossenne et al.
