| Abstract |
The video inspection tool GeoKam was developed for providing real insights in deep boreholes in high definition. Its cameras for the front and 360° radial view with adjustable aperture, focus, and lighting allow detailed visual inspection e.g. for the detection of casing leakages. For operations in harsh environments it is designed to withstand 165 °C ambient temperature for a period of around two hours plus two hours travelling time and a pressure of up to 48 MPa. With 95 mm outer diameter it is built in a compact way, regarding the pressure resistant housing and the required heat insulation. Therefore the inspection tool can be used in boreholes with 8 ½ inch (~215 mm) diameter. Thus the temperature, pressure and geometrical parameters cover the operation in most of the geothermal boreholes in Germany. The GeoKam is developed based on the system platform for down-hole tools ZWERG. Most of its components, including housing, heat insulation, temporary cooling system, housing-to-housing connectors, cablehead and electronics including a communication modem are designed in a standardized way and can be reused for the development of further tools in order to reduce costs. This is possible due to a standardization of basic components based on the constraints of the Soultz-sous-Forêts Project in France with 5 km depth, 200 °C ambient temperature and 60 MPa pressure. For the realization of the tool, solutions on several technical challenges had to be developed. One example therefor is the development of a highly loadable metal ceramic composite for the windows in the probe housing. Another is the complicated fabrication of steel and glass Dewar vessels for the heat insulation of tools. In addition to the insulation a cooling module was developed, which allows longer work at deep positions with high temperatures. Furthermore for some components new fabrication methods such as SLM (Selective Laser Melting) are used instead of a conventional cutting fabrication process. This provides further design possibilities and allows advanced useful embodiment designs. In the GeoKam this is the case e.g. at the frame of the camera module or the space-saving lighting system. Besides, the alternative fabrication methods can lead to cost and time reductions. The GeoKam development is almost completed. Currently the complete system is tested under realistic conditions at the Karlsruhe Institute of Technology (KIT) as preparation for planned in situ tests. For this purpose a custom built autoclave has been installed in the geothermal test-hall. In its test space of 2.5 m height and 250 mm diameter a pressure of up to 80 MPa and a temperature of more than 200 °C can be generated with water as media. With the autoclave the conditions of deep boreholes can be closely represented and realistic tests can be conducted. This paper gives an overview over the development process and explains technical details of the complete system and system tests. |