METHOD OF ELECTRIC LOGGING OF CASED WELLS Russian patent published in 2003 - IPC

FIELD: geophysical examination of wells. SUBSTANCE: method of electric logging can find use in determination of electric resistance of formations of rocks surrounding well cased by metal string. Method employs sonde comprising three measurement electrodes equidistantly arranged along string and two pairs of current electrodes, one pair being placed above and beyond limits of measurement electrodes and the other pair being positioned beneath them. Two current generators located outside of measurement circuits of sonde and meters are used to feed current into string through both pairs of current electrodes. Potential of electric field of string in point of its contact with center measurement electrode is measured during each current feed as well as first and second differences of potentials across section of string between extreme measurement electrodes. Specific electric resistance is established by corresponding formula. EFFECT: increased accuracy of measurement of specific electric resistance of rocks. 5 dwg