Successful across-scale reservoir characterization is a prerequisite for sustainable utilization of the subsurface. Here, we discuss aspects of distributed acoustic sensing (DAS) vertical seismic profiling (VSP) acquisition in Germany and provide an example of data integration for reservoir characterization at the geothermal research platform Groß Schönebeck, aiming to utilize Permian and Permo-Carboniferous reservoir sections at depths below 4 km. At this site, DAS VSP wireline data obtained in two boreholes were processed successfully for 3D interpretation. The data and their interpretation serve as input for a fundamental update of the structural and property characterization of the reservoir zones, relying on the integration of conventional surface 3D seismics and joint core-log analysis. The new model provides a much more detailed characterization of the target reservoirs, allowing for the first time a geological-based (facies-driven) parameterization of the subsurface, considering hydraulic and thermal properties of the reservoir-forming rocks.

In autumn 2017 a network of 14 broadband seismic stations was deployed at the Theistareykir high temperature geothermal field (NE Iceland). This experiment was conducted as part of the current efforts to characterize the field's main structures, and possible short and long term stress variations due to the ongoing fluid injection and extraction operations which started in autumn 2017. In this work, we use two years of continuous seismic records (October 2017–October 2019) to compute a 3D shear wave velocity model of the geothermal field and to detect possible crustal stress changes related to the injection and production activities. From phase cross-correlations of the vertical component recordings, we measure the Rayleigh wave group velocity dispersion curves to obtain 2D group velocity maps between 1 and 5 s. Subsequently, we use a neighborhood algorithm to retrieve the 3D shear wave velocity model of Theistareykir. Mainly, two sets of elongated high and low velocity anomalies can be observed oriented in a NW/WNW direction, parallel to the lineaments of the active Tjörnes fracture zone. Velocity reductions west of Ketilfjall and at Baerjafjall could indicate the location of upflow zones of the magmatic reservoir or hydrothermal system. We analyzed the temporal evolution of phase and amplitude of phase auto-correlations using the stretching technique and discuss their behavior in relation to the geothermal field operations. We notice a slightly stronger long-term velocity decrease in the reservoir region compared to outer regions. This could be related to the mass depletion in that area (higher fluid extraction compared to the water reinjection). In summary, our findings show how a monitoring network can be set up to enable a detailed imaging and monitoring of reservoir behavior in general.