METHOD FOR RESISTIVITY LOGGING OF CASED WELLS Russian patent published in 2001 - IPC

FIELD: geophysical explorations of wells, applicable in determination of electrical resistance of rock seams surrounding the well cased by a metal column. SUBSTANCE: used in the method is a sonde having three equidistant measuring electrodes and two measuring electrodes positioned beyond the zone of measuring electrodes symmetrically relative to the middle measuring electrode, current electrodes. Electric current is fed in turn to the column via each of the two current electrodes from the same source pole. At each feeding of current the potential of the column electric field in the point of contact with it of the middle measuring electrode, the first difference of the potentials at the column section between the two extreme measuring electrodes and the second difference of the potentials at the same column section are measured. The specific electrical resistance is measured by the respective formula. EFFECT: enhanced accuracy, expanded measurement range. 12 dwg