5:30 PM - 5:45 PM
[S24-1-05] In-Situ Optical Scanning
Knowledge about the thermal conductivity of rock is essential for accurate design of geothermal plants. Thermal conductivity can be measured in situ, with low precision and coarse spatial resolution, or in a laboratory, where samples are subject to altered conditions and represent only limited sections of the borehole. We developed and evaluated a new technology involving fast, high-resolution and high precision scanning of in-situ thermal conductivity within boreholes. The prototype demonstrated the feasibility of the technology for shallow geothermic wells, with an accuracy of 10%.
The probe is designed for use in open-hole areas of a well. It is fixed and adjusted by a packer system, which consists of fixing, measuring, and centralizing packers (outer casing). Optical sensors are placed in an inner casing in the measuring packer. Pneumatic inflation of the measuring packer purges liquid/mud from the measuring interval; thus, optical scanning is possible in mud filled boreholes. Optical scanning is operated parallel to the borehole axis. A laser heats up the foil of the measuring packer from the inner side, and the heat is transferred to the rock formation by conduction. The laser moves with constant velocity along the profile. An infrared camera and triangulation tool are mounted at a fixed distance to the laser, so that the surface structure and corresponding thermal tail of the wall are scanned. Subsequent data processing leads to the thermal conductivity of the borehole. The probe algorithm enables automatic measurements and corrects for profile and packer rubber foil effects.
Prospecting, the technology can be used in intermediate and deep wells. Furthermore the theories according to Prof. Yuri A. Popov can be applied to measure thermal diffusivity and anisotropy. The tool shows that a tomographic thermal conductivity scanning with shallow penetration depth is possible. Thus, a filter cake and layers of altered rock can be distinguished from original rock.
The probe is designed for use in open-hole areas of a well. It is fixed and adjusted by a packer system, which consists of fixing, measuring, and centralizing packers (outer casing). Optical sensors are placed in an inner casing in the measuring packer. Pneumatic inflation of the measuring packer purges liquid/mud from the measuring interval; thus, optical scanning is possible in mud filled boreholes. Optical scanning is operated parallel to the borehole axis. A laser heats up the foil of the measuring packer from the inner side, and the heat is transferred to the rock formation by conduction. The laser moves with constant velocity along the profile. An infrared camera and triangulation tool are mounted at a fixed distance to the laser, so that the surface structure and corresponding thermal tail of the wall are scanned. Subsequent data processing leads to the thermal conductivity of the borehole. The probe algorithm enables automatic measurements and corrects for profile and packer rubber foil effects.
Prospecting, the technology can be used in intermediate and deep wells. Furthermore the theories according to Prof. Yuri A. Popov can be applied to measure thermal diffusivity and anisotropy. The tool shows that a tomographic thermal conductivity scanning with shallow penetration depth is possible. Thus, a filter cake and layers of altered rock can be distinguished from original rock.