| Title | Laboratory Setups for Core Flooding and CT-Scanning Experiments at In-Situ HP/HT Conditions |
|---|---|
| Authors | Mathias NEHLER, Thomas ANDOLFSSON, Jörg RENNER, Holger STEEB, Rolf BRACKE |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | CT-scanning, HT/HP experiments, core-flooding, fluid-rock interaction |
| Abstract | The key objective of this research project is to experimentally investigate the physico-chemical interactions of fluids, rocks and the cementation of geothermal wells. The influence of hydrothermal alteration on rock properties like permeability, thermal conductivity and thermal diffusivity is under investigation for typical rock samples like Westerly Granite (USA) as well as carboniferous silt- and sandstones of the Ruhr area in Germany. The changing properties of well grouting materials and interactions with the often highly saline brines are also under research. The measurements will be performed with newly configured, laboratory devices. The direction-dependent permeability is measured with the so called oscillatory pore pressure method. Simultaneous measurements of the upstream and downstream pressures and the upstream fluid flow permit the calculation of permeability and specific storage by two methods, the conventional upstream – downstream pressure analysis and the upstream pressure-flow analysis. The thermal conductivity and thermal diffusivity are measured with a device based on the optical scanning method. The first laboratory experiments will be expanded step by step to get a greater understanding of the physico-chemical interactions. Dissolution experiments at different temperatures, pressures and with different fluids will be performed to get more insights in reaction kinetics and processes within the geothermal reservoir. To achieve the aims also a new prototype of a computer tomography- scanner (CT-scanner) is currently under development with multifocal x-ray tube of 225 kV for resolutions of around 1 µm. It will be possible to scan rock cores up to 600 mm in length and from less than 10 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 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 200 bar 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. A prototype of a core-holder consisting of layered aluminum and carbon fiber epoxy for optimal X-ray scans will be developed. In order to simulate the reactions between different miscible or immiscible fluids, the experiments can be conducted with gases such as CO2 and liquids such as highly saline brines. The two-phase flow leads to changes in the effective permeability by mixing as well as dissolution and precipitation processes. The couplings of chemistry and fluid flow in the porous rocks will be measured by spatial time resolved CT-scans and time resolved sampling of the produced fluids. |