SU627428A1 - Electric geosurvey method - Google Patents

Description

(54) METHOD OF GEO-ELECTRICAL EXPLORATION

2

The essence of the invention is that the ejectromagnetic pope in the Earth is excited by the currents of two coherent infra-low frequencies, and at the receiving point the difference between the delay times of the received signals of the two i frequencies is measured. This difference between the delay times does not depend on the conductivity of the medium and is proportional to the polarizability factor

environment (or phase shift VP).

Let the electro-magnetic pope in the Earth be excited by the currents of two frequencies Ubj and by the help of a ground source and measure the electric field component in the near zone. It is known that in this case the phase angles due to the conductivity of the medium depend directly proportionally on the frequency of the exciting field, and the phase angles caused by the polarizability of the medium change very little with a frequency of 2-10 times. Changes can be neglected. If we imagine the exciting currents in the form

3 aosin) -t; a, 2 a, 5inuj i .;

as shown in FIG. 2, a and buto of the signals received from the earth at the point of reception can be represented as

, sihKt - “... Ma);

f

ai

"AsincAj t-t -

sh

U, -A, (nu;, i - 4 ,,. Asinno), i I ПЛ) nUJ ГДе Vjjf, J% пд ииа,; иЭЭ, respectively, phase angles, due to the volatility (VP) and conductivity (not duktsionnye) medium dp signap two frequencies. The lag time of the signals C is equal, respectively (see Fig. 2, in Af Sn, L. 1-, 1. Ins, wn, d nUJ. To obtain the time difference for arcs from the signals C m-C, a sequence of pulses is formed,

connected in phase with the original signals. The pulses are most easily formed at the moments of the transition of sinusoidal signals through zero from negative to positive values (Fig. 2, e and e. From either positive to negative, or both). In this case, the difference in the delay times is represented as the time interval between a pulse of a sequence of one frequency and the closest in time to it a pulse of a sequence of a different frequency (in Fig. 2, f is the time interval between the moment of zero crossing of a signal of one frequency and the moment next to it Through the zero in the same direction of the signal of a different frequency.) Dp increase in accuracy can be formed the same sequence D b,., according to the moments of zero crossing of signals to another direction (from positive to negative) in this case pulses A С , will follow with a doubled frequency, i.e., the measured value will be 2 times larger. The difference between the delay times is equal to:

ifce -f-out

At5, AVAt,

n "jy.

When changing the frequency of 2-10 times we have:

tp if

R

VP2 BFT VP

INZ

J2lifn. fT-i

(n tj; where T

Claims (2)

ntfij BP p VPVP C4J. Thus, the difference between the times of signaling of two frequencies at the point of reception, in contrast to the difference between the initial phase shifts, is determined only by the polarizability of the medium and is completely independent of its conductivity. Using sensor 1 (which can be used as one IT two grounded lines or a magnetic sensor), at the point of reception, a total two-frequency signal is received, which is excited in the ground by a generator with a grounded line (not shown). Using selective amplifiers 2 and 3, the components of the two frequencies are extracted from this signal (voltage plots of Fig. 2, Vig). Pulse drivers 4 and 5 transform sinusoidal signals into a sequence of pulses corresponding to the transition of signals through a pin from negative values to positive 562 signals (Fig. 2, e and f). These speeds of impulses go to the two inputs of the trigger 6, which you open at the moment when one of the signals crosses through the gate and closes at the next time it passes through the other signal (Fig. 2, g). The time during which the trigger is in the open state is equal to the difference in the delay times of the signals of two frequencies. It is measured using a 7 time interval meter. It is also possible to use other devices; realizing this method. Measurement of the difference between the delay times of two frequency signals for determining the IP parameter during geoelectromagnetic prospection was possible due to the dependence of changes in phase angles VP VP frequency variation in the range of infralow frequencies, as well. There are no changes in the time delay of electromagnetic oscillations of two frequencies, which is caused by the conductivity of the medium. The technical and economic efficiency of the geoelectrical exploration method consists in increasing the accuracy of determining the polarizability parameter of the studied media for eliminating the influence of the conductivity of the medium on the measured polarizability parameter. Measuring devices are also greatly simplified, realizing the method, the invention. An alternating current method of geoelectrical prospecting based on the method of polarization, based on excitation of IB electromagnetic field, currents of two arbitrary coherent Frequencies and measurement of signals at the receiving point, which is , with a ps circuit Improving measurement accuracy by examining the influence of the conductivity of a medium, while studying polarization effects, the difference between the delay times of two frequency signals at the receiving point is measured according to which the polarizability of the medium is judged. Sources of information taken into account in the examination: 1, US Patent No. 27766421, kp, 324-1, 1956. 2 .; Prtsov E, A., et al. Phase measurements of IP in complex geological conditions of the BSSR, Lime, ser. Theologians and Intelligence, No. 3, 1970, 128-133. j (jl CL / y / uiz / 4t, Ih t P .2