DEVICE FOR ELECTROMAGNETIC LOGGING OF WELLS Russian patent published in 2004 - IPC

FIELD: measurement of electrical characteristics of rocks located around wells bored for oil and gas. SUBSTANCE: technical result of invention lies in increased accuracy of determination of parameters of electrical nonuniformities in beds-collectors while geoelectrical sections are constructed thanks to reduction of error of measurement of phase difference by removal of effect of combination frequencies and noise in intermediate frequency signals and to enhanced measurement accuracy of potentials of spontaneous polarization of well. Proposed device has electrode of signal of well polarization, converter of signal of well polarization, recorder placed on day surface that records signal of well polarization which is connected by logging cable to downhole unit incorporating probes with generator and measurement coils similar one another geometrically and electrodynamically and aid of electromagnetic decoupling on working frequency of probes. Measurement part of downhole unit includes measurement coils, amplifiers-converters and commutator. Generator part of downhole unit includes generator coils, power amplifiers, multiplexer, heterodyne, amplifiers-limiters of intermediate frequency, phase meter, automatic control unit and telemetering system. Device is supplemented with at least two band-pass filters placed between analog outputs of commutator and inputs of amplifiers-limiters and differential amplifier which first input is connected to electrode of signal of well polarization, which second input is connected to grounded electrode located on day surface and which output is connected to analog input of converter of signal of well polarization. EFFECT: increased accuracy of determination of parameters of electrical nonuniformities. 6 cl, 2 dwg