Geoelectrical methods can be part of early warning systems for landslide-prone hillslopes by giving estimates of the water content distribution. Structurally constrained inversions of geoelectrical data can improve the water content estimation by reducing the smoothness constraint along known lithological boundaries, which is especially important for landslides, as often layers with strongly divergent hydrological parameters and varying electrical signatures are present in landslides. However, any a priori information about those boundaries has an intrinsic uncertainty. A detailed synthetic study and a field investigation are combined to study the influence of misplaced structural constraints and the strength of the smoothness reduction via a coupling coefficient on inversion results of electrical resistivity data. While a well-known lithological boundary with a substantial reduction of the smoothness constraint can significantly improve the inversion result, a flawed constraint can cause strong divergences from the synthetic model. The divergence can even grow above the divergence of a fully smoothed inversion result. For correctly placed structural constraints, a coupling coefficient smaller than 10−4 uncovers previously unseen dynamics in the resistivity distribution compared to smoothed inversion results. Uncertain layer boundaries can be included in the inversion process with a larger coupling coefficient to avoid flawed results as long as the uncertainty of the layer thickness is below 20%. The application to field data confirms these findings but is less sensitive to a further reduction of the coupling coefficient, probably due to uncertainties in the structural information.

High-pressure flow-through experiments on solid rock samples are commonly conducted with experimental setups using a confining pressure to restrict the flow to the rock. These setups are often spacious, costly, and difficult to replicate by other researchers due to their individual nature. This work presents the RESECO (resin sealed column) setup which allows flow-through experiments on solid rock without a confining pressure. The column setup is only slightly larger than the sample size and has material costs per sample of a few Euros. The fluid flow is confined to the rock by a cast of epoxy resin using a metal column as an outer casing. The functionality was verified by comparing experimental results with a conventional triaxial cell. Four different rock types with varying hydraulic properties were tested and proven compatible with the setup. Additional endurance tests were performed to investigate the physical limits with regard to pore pressure and temperature. The RESECO setup can be operated with pore pressures of at least 40 MPa and temperatures up to 95 °C, and is therefore suitable for many high-pressure, high-temperature experiments, while being easily reproducible.

<p>Declining permeability of geothermal reservoirs due to fines migration is often considered with regard to existing fines like clay particles that are mobilized. However, fines are also generated due to dissolution and chemical stimulation techniques can induce the generation of fines. For near-wellbore regions, this is uncritical as fines can be extracted after stimulation using cleaning lifts. With the aim of replacing hydraulic stimulations for enhanced geothermal systems by a reservoir-wide chemical stimulation, the penetration depth of the acids needs to be substantially increased. However, cleaning lifts to remove fines are no longer possible in greater distance from the wellbore, so alternative strategies are required.</p> <p>Flow-through experiments with citric acid on dolostone were used to investigate the dependence of fines generation on the reaction conditions. For all dissolution regimes over a range of different Damköhler numbers, fines were generated and could greatly reduce the permeability of the rock samples. Only when large pathways were created by the dissolution process, the generated fines were transported out of the major pathways as well as dissolved therein, thus not interfering with the increase of permeability due to dissolution. The results highlight the great challenges for reservoir-wide chemical stimulations techniques using retarded acid systems, but also indicate possible solutions.</p>