| Abstract |
At the GPK1 and GPK2 boreholes of the HDR test site Soultz-sous-ForÍts (F) the hydraulic properties have been extensively investigated. Especially the multiple level flow rate injection or production experiments conducted between 1994 and 1997 in the open hole sections identified the complex hydraulic regime. A common observation in these tests has been that the downhole pressure response attained quasi-steady state levels within a few days and that the duration of the transient pressure variation seemed to be a function of the flow rate. In attempting a quantitative interpretation of these pressure records, the importance of turbulent-like hydraulic behavior became evident. In the past, forward techniques have been adopted to simulate these experiments. The 2-D models allowed excellent fits to be accomplished assuming non-Darcian flow in the fracture network. Multi-dimensional, inverse modeling procedures are applied for the transient data fit which allow to extract more sophisticated information from these numerical models. Thereby, not only the correlation or sensitivity of individual model parameters but also the confidence interval can be quantified. The results identify matrix diffusivity and fracture aperture as the most sensitive parameters. Further, special attention was paid to constrain the reservoir geometry. Therefore, the distance of the far-field reservoir boundaries which seem to coincide with permeable faults systems was assessed as function of possible flow geometries (parallel flow paths, impedance distribution along flow paths or tortuous flow). These studies improve and assist other methods in developing a conceptual model of the situation in the ~3.5 km deep Soultz reservoir. |