Video Inspection Probe for Deep Geothermal Boreholes - GeoKam

Abstract

GeoKam, an online inspection probe with integrated camera which is developed at the Karlsruhe Institute of Technology will be completed after almost two years development time. The first prototype is suitable for the use in geothermal wells. It is able of transferring live pictures from up to 4000 m depth with an ambient temperature of up to 165 °C to the earth´s surface via wireline. The developments of GeoKam are based on the ZWERG concept, which will be described in the paper of a colleague Dr. Isele: The ZWERG Project, also handed in. it stands for a platform for the fast construction of modular probes. Thus, if required, each probe can be configured individually with different components in order to obtain the desired information of a geothermal borehole. GeoKam is the first prototype. It is composed of cameras, camera electronics, transmitting electronics, cooling device, power supply and lighting system, which are mounted in housing. The housing itself consists of several segments, which are assembled with special connectors for the probe, as required. For optimal investigation of the borehole, several cameras are installed in the GeoKam. In this case each camera is equipped with a lens, wherein the aperture and the focus are adjustable. In order to obtain high quality images, high-quality camera sensors and lenses are installed in GeoKam. By miniature electromotors the lenses can also be adjusted finely to obtain the best quality of image, which also depends on the lighting system. A high image quality, which is unique for a camera probe can be achieved by selecting suitable light sources and a proper positioning on the probe. Due to the high hydrostatic pressure, combined with the relatively high environment temperature and the corrosive fluids in the boreholes, special materials have been selected. For the housing a nickel based superalloy has been chosen. In the area of the camera a high-performance transparent ceramic is used. Both materials with extremely different physical properties especially at high temperatures have been connected by a suitable jointing technology. To ensure a safe operation of the joint in the borehole, a thermal stress analysis, using commercial FEM software and various mechanical tests have been conducted.