HYDRO-THERMAL MODELING OF A DEEP FAULT-RELATED FRACTURE SYSTEM IN THE UPPER RHINE GRABEN (URG)

The scope of the research project GeoFaces (BMWi: 0324025C) is the analysis of thermo-hydro-mechanic properties of possible geothermal reservoirs in the Upper Rhine Graben (URG) in SW-Germany / E-France. The aim is to quantify the amount of fluid circulation along or through joint faces (factures and faults) under recent geological conditions.

Location and extension of geothermal reservoirs in the URG are well known through geophysical exploration (e.g. 3D seismic survey). A lack of understanding of the thermic, hydraulic, (geo-) mechanic, and chemical (THMC) processes in the reservoir and their mutual influence, might lead to problems concerning geothermal exploration and long-term evaluation of the geothermal potential.

This presentation highlights the combination of different datasets to forecast the physical behavior of an Enhanced Geothermal Reservoir (EGS) in the Upper Rhine Graben. The international geothermal research project in the URG, Soultz-sous-Forêts, targets a fault-related reservoir with preferential geothermal conditions at 5.000 m depth. During the long-term research activities, a large scientific and experimental database has been created, which offers the opportunity to characterize the geothermal reservoir.

These data, e.g. geophysical (including temperature), hydraulic, and seismic measurements, were evaluated and used as input parameters and for the definition of the boundary conditions in a FE-modeling of the geothermal reservoir at the Soultz site. The geophysical, seismological, and hydraulic data allow the determination of the location of faults, resp. fractured zones, as well as the quantification of their hydraulic significance. The tracer tests gave additional information especially concerning the interconnectivity of fractures. We simulated a long-term production scenario with the MOOSE-based application TIGER. The application gives us the opportunity to quantify the geothermal potential by solving hydro, thermal and chemical processes in a fully-coupled manner.