METHOD AND DEVICE FOR ELECTRIC LOGGING OF CASED WELLS Russian patent published in 2019 - IPC G01V3/20 

FIELD: geophysics.

SUBSTANCE: invention relates to the field of well geophysical investigations and is intended for determination of electric resistivity of mine rocks surrounding casing string cased with metal string. Invention is based on use of metal column 1.1 of well as grounding of one of poles of source 3.1 of bipolar current pulses, the second pole of which is connected through geophysical cable 5 with current electrodes 2.2 of multi-element submersible probe 2. At current depth of logging in current electrodes 2.2 of probe 2, bipolar pulses of electric current are alternately sent relative to upper part of casing pipe 1.1. After each current supply with measuring electrodes 2.3 of probe 2, potential of one of electrodes 2.3 of probe 2 is measured relative to upper part of casing pipe 1.1 and potential difference (voltage) between electrodes 2.3. Based on measured values of potentials and voltages between electrodes 2.3 and using data on running electrical resistance of casing pipe 1.1, resistivity is calculated. In the probe there are insulating inserts 2.1 between current electrodes 2.2 and group of measuring electrodes 2.3.

EFFECT: expansion of capabilities due to possibility to measure resistivity of rocks in conditions when earth surface is a layer of insulator, for example dry sand in conditions of desert or layer of permafrost, higher accuracy of determination of resistivity and reduced time of logging.

9 cl, 9 dwg