FIELD: resistivity logging in boreholes with current-conducting casing tube. SUBSTANCE: sonde with assemblage of electrodes arranged in positions spaced apart in axial direction and intended for securing electric contact with casing tube is sunk in shaft of well. Electric current is fed between first and second electrodes and measured. First voltage between first and second electrodes of first pair placed in axial direction and second voltage between electrodes of second pair also placed in axial direction outwardly with regard to first pair is measured to find resistance of casing tube between pairs of electrodes. Second difference between first and second voltages is also measured. Current is applied between other electrodes so arranged in axial direction that presence of third pair of electrodes between them is prevented and third voltage between electrodes of third pair is measured to determine wave impedance. Current is fed between first electrode and surface electrode for return of current, fourth voltage between first pair of electrodes is measured, fifth voltage between electrodes of second pair is taken, additional second difference of voltages between fourth and fifth voltages is measured. Specific resistance of formation is found by way of joining of first, second, third, fourth and fifth voltages, measurement of current, second difference and additional second difference of voltages. EFFECT: possibility of employment of single-core electric logging cable. 13 cl, 12 dwg
