As a formation evaluation tool, its application is limited to conductive muds. It may be run in several configurations and provides up to five resistivity measurements. The RAB tool contains a scintillation gamma ray detector which supplies a total gamma ray measurement. An azimuthal positioning system allows the gamma ray measurement and certain resistivity measurements to be acquired around the borehole.
Additional measurements are chassis temperature and radial and longitudinal shocks.
The RAB tool has a nominal 6.75-in. Designed to be a flexible component of the bottomhole assembly, the RAB tool may be connected directly behind the bit or further back in the bottomhole assembly. The tool may be configured for packed or pendulum assemblies. In this configuration, it provides a bit resistivity measurement, RBIT, with a vertical resolution just a few inches longer than the length of the bit. In addition, the RAB sub has three longitudinally spaced button electrodes that provide staggered depths of investigation.