| Title | Monitoring Fluid-Rock Interactions at In-Situ Conditions Using Computed Tomography |
|---|---|
| Authors | Mathias NEHLER, Thomas ANDOLFSSON, Ferdinand STÖCKHERT, Jörg RENNER, Rolf BRACKE |
| Year | 2016 |
| Conference | Stanford Geothermal Workshop |
| Keywords | CT scanning, Core flooding experiments, Hydrothermal alteration, Core holder |
| Abstract | The experimentally investigation of the physic-chemical interactions of fluids, rocks and the cementation of geothermal wells is the main goal of the project. The influence of hydrothermal alteration on rock properties like permeability, thermal conductivity and thermal diffusivity is under investigation for typical rock samples like the Bentheim sandstone as well as carboniferous silt- and sandstones of the Ruhr area (Ruhr Sandstone) in Germany. This will help to predict the long-term reservoir development and increase the efficiency of geothermal power plants. The measurements will be performed with newly configured, laboratory devices. A computer tomography- scanner (CT scanner) with a multi-focal x-ray tube of 225 kV for resolutions of around 1 µm (best case scenario) is used for CT scanning. It is possible to scan rock cores up to 600 mm in length and from less than 3 mm up to 100 mm in thickness by the helix CT scanning method. The computerized tomography is a non-destructive technique, which provides 3D reconstructed images of absorbing materials by reconstruction algorithms. Simulation software will enable the 3D visualization combined with numerical simulation capabilities to compute physical properties of the analyzed materials such as absolute permeability and porosity or thermal conductivity. The CT scanning unit will be extended with a setup for flow through experiments at high pressures up to 20 MPa and temperatures up to more than 150°C to simulate reservoir conditions. Pressure gauges and mass flow meters allow the calculation of the effective permeability, which can be compared directly to the results calculated by the scanning software. The segmentation of typical alteration processes (e.g. dissolution and precipitation) will be optimized in the first place. This includes the improvement of imaging quality within the CT scanner by developing a prototype core-holder consisting of layered aluminum and/or carbon fiber epoxy for optimal X-ray scans. In addition the research is focused on the preparation of synthetic brines representing the saline fluids of the northern German basin. |