DEVICE FOR LOGGING WELLS CASED WITH METAL STRING Russian patent published in 2017 - IPC G01V3/20 

FIELD: electricity.

SUBSTANCE: device includes a ground part and a downhole tool with a multi-electrode probe. The ground part consists of an onboard computer, a switching unit, an interface unit, a logging winch, a depth unit and a probe power supply, as well as electrodes B and N_ud. The probe is made in form of a group of five and more units of electrodes arranged in series along the well axis. In extreme units of electrode group, there are current electrodes A1 and A2. The remaining electrode units in the group are measuring ones (M1…Mn). The electrical inputs of the probe are configured to be pressed against the string wall by means of an electric drive with pressing mechanisms and by impact mechanisms built-in into the string body. An electronic unit of a downhole tool includes a gamma logging unit, a coupling locator and an accelerometer. The quality of the impact mechanisms operation is controlled by the accelerometer. The switching unit makes it possible to supply current between current the electrodes A1 and A2 and supply electrodes A1 and A2 relative to electrode b at three measurement cycles. Based on digitised measurement results of the three cycles, specific electric resistance is determined by formula considering the diameter of the casing string.

EFFECT: increased determination accuracy of the specific electric resistance of formations.

2 dwg