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Physical Properties of the Geothermal Carbonate Reservoirs of the Molasse Basin, Germany - Outcrop Analogue vs. Reservoir Data
| Content Provider | Semantic Scholar |
|---|---|
| Author | Homuth, Sebastian Goetz, Annette Elizabeth Sass, Ingo |
| Copyright Year | 2015 |
| Abstract | The Upper Jurassic carbonates of the Southern German Molasse Basin have been the target of numerous geothermal combined heat and power production projects within the past years. A production orientated reservoir characterization of these carbonates is therefore of particular economical interest. For reservoir predictions parameters such as density, porosity, permeability, thermal conductivity, and specific heat capacity have to be quantified as precisely as possible. Outcrop analogue studies enable the determination and correlation of lithofacies-related thermo- and petrophysical parameters. A thermofacies classification of the carbonate formations serves to identify heterogeneities and production zones. The hydraulic conductivity of the carbonate formations is mainly controlled by tectonic structures and karstification. The type and grade of karstification is also facies related. The rock permeability has only a minor effect on the reservoir’s sustainability except for some grain- and dolostones. Reef bodies show the highest values of thermal conductivity, due to secondary silicified sponge build-ups and dolomitization processes. An increase in permeability can also be observed in the dolomitized areas. Typically physical parameters are determined on oven dried samples. These values have to be corrected applying reservoir transfer models for water saturated and according reservoir temperature and pressure conditions. To validate these calculated parameters a Thermo-Triaxial-Cell simulating the temperature and pressure conditions of the reservoir is used as well as calorimetric and thermal conductivity measurements under elevated temperature conditions are performed. Core and cutting material from a 1,600 m deep research drilling and a 4,850 m (total vertical depth, measured depth: 6,020 m) deep geothermal well (bottom hole temperature of around 170°C) is used as well to validate the reservoir property predictions. Under reservoir conditions a decrease of 2-3 magnitudes in permeability is observed due to the thermal expansion of the rock matrix. For tight carbonates the matrix permeability is therefore temperature controlled. The thermophysical matrix parameters are density controlled. Density increases typically with depth and especially with higher dolomite content. Therefore, thermal conductivity increases, however, the dominant factor temperature also decreases the thermal conductivity. Specific heat capacity typically increases with increasing depth and temperature. The lithofacies-related characterization and prediction of reservoir properties based on outcrop and drilling data demonstrates that this method is a powerful tool for exploration and operation of geothermal reservoirs. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://pangea.stanford.edu/ERE/db/WGC/papers/WGC/2015/11062.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
