A temperature-drift-free design for near-bit azimuthal resistivity tool

This paper discusses the challenge of measuring signals for near-bit azimuthal resistivity tools. Current azimuthal resistivity tools present difficulties because of their length and complexity. These issues can be overcome by gathering azimuthal sensitive resistivity data near the bit. However, this still presents space difficulties. Single transmitters and receivers can simplify the structure, but encounter problems with temperature drift. Here, a design is proposed that uses a sensor structure with a single transceiver and two receivers. Real-time calibration and compensation for the analog circuits enables errors in the conditioning channels to be eliminated, with their temperature drift being suppressed across a wide range of temperatures. Experiments were undertaken to test the viability of the proposed measuring system and the results illustrate that its accuracy and reliability meet the requirements for improved azimuthal resistivity measurements.