EA006537B1

EA006537B1 - Method of marine geoelectro surveying (variants)

Info

Publication number: EA006537B1
Application number: EA200401092A
Authority: EA
Inventors: Николай Иванович РЫХЛИНСКИЙ; Петр Юрьевич ЛЕГЕЙДО; Софья Николаевна ДАВЫДЫЧЕВА; Марк Миронович Мандельбаум; Анатолий Семенович Лисин
Original assignee: Николай Иванович РЫХЛИНСКИЙ
Priority date: 2003-10-07
Filing date: 2004-09-21
Publication date: 2006-02-24
Also published as: RU2236028C1; EA200401092A1

Abstract

The invention relates to geophisical investigation, in particular, to marine geoelectrical surveying using adjustable artificial sources of electromagnetic field and intended for prospecting and contouring oil and gas deposits based on separate determination and mapping peculiar to each of elements (horizons) of rock sediment mass the following three electrophysical parameters required to solve the problem: specific conductance, induced polarization and fall time constant of induced polarization potential difference.In one of the inventive method variants the electromagnetic field is excited in the medium body, sending therein two similar rectangular current pulses: one – with direct passing probing means along investigation profile, the other – with reverse direction. In the second variant – measurement of first and second electric potential differences is carried out using two three-point measuring devices positioned on the profile axis at different distances from dipole source, wherein two similar rectangular current pulses are sent to the medium being investigated in each probing location: one –when passing through this point the first three-point measuring device, and the other – when passing through this point the second three-point measuring device. In the third variant one current pulse is sent in each probing location.In all three variants instantaneous values of first and second axial potential differences are measured at the end of each current pulse and between current pulses in pauses duration. Besides, two adjacent in time instantaneous values of first and second potential differences are singled out in all duration of each pause determining their values differences. Four rated electric parameters are calculated from all said differences and, solving inverse problem based on differential damped wave equation of mathematical physics for intensity of dipole current source in electrochemically polarizing conducting medium a medium model is determined, being most closed by geometric structure and electric parameters to being investigated medium and draw timing sections of the model using electrophysical parameters such as conductance of medium elements, coefficient of induced polarization and fall time constant of induced polarization, said parameters being a part of the equation.

Description

The invention relates to the field of geophysical research, and more specifically to methods of marine geoelectrical exploration using adjustable artificial sources of the electromagnetic field, and is intended to search and delineate oil and gas deposits based on the separate determination and mapping of the following sedimentary rocks of each of the elements (horizons) of the sedimentary rocks three electrophysical parameters necessary for solving the problem posed: specific conductivity caused by polaris and the decay time constant of the potential difference caused by polarization.

There are known methods for geoelectromagnetic exploration, including marine with artificial excitation of the studied medium by electric current (resistance methods for direct and alternating current), which are designed to determine only one electrophysical parameter of the three listed above, namely electrical resistance, which is not enough for prospecting and delineating oil and gas deposits. Among these methods, the most common is the pulsed method at an alternating low-frequency current — a method of becoming an electric field.

According to the results of field measurements using this method, the electrical resistance ρ _{τ is} calculated using the universal formula

Ρτ ^ · ^, (1) where 1 is the measured current jump in the electric dipole source;

DI is the measured voltage at the ends of the receiving groundings ΜΝ;

K is the geometric coefficient of the probing installation (see “Electro-prospecting”, Handbook of Geophysics. Ed. By AG Tarkhov: M.- Nedra, 1980, p. 237 and p. 422-406) [1].

With this approach, which is usually used for all traditional methods of determining electrical resistance in geoelectromagnetic with a controlled artificial current source, only summary information is obtained about all the structural elements of the medium under study, in which the field develops, since nothing in the measured current distribution of the source 1 is not controlled, and there is no information about the specified distribution in actually existing three-dimensional inhomogeneous media. This means that the normalization of the measured electrical parameter Δϋ by the current strength of the power supply 1 of the source is meaningless, since the current 1 does not carry any information about the medium under investigation, but only carries information about the power of the current generator and grounding resistance of the current electrodes of the current dipole.

Thus, resistivity methods are not suitable for prospecting and delineating oil and gas deposits for two reasons: first, only one of the three electrophysical parameters of the medium under study is recorded; the second - the parameter to be recorded is too coarse for the same purpose, since it records the volume resistance of all the geological objects of the studied medium in which the electric field of the current source develops.

In marine geoelectrical exploration, due to the specifics of measurements in motion, a symmetric installation ΑΜΝΒ or dipole-axial ΑΒΜΝ is used.

Attempts to search for hydrocarbons were carried out, in particular, by the SE Soliton and the SNPP Sevmorgeo in the Black and Barents Seas. Only a qualitative interpretation was carried out, signal plots were built, by which the anomalous zones were identified, which, according to the authors of these works, are associated with hydrocarbon deposits. Sometimes anomalies were observed in the signals of the field formation, which in simple geological conditions reflected the presence of shallow gas deposits, for example, in the waters of the Black Sea shelf (A. Petrov. Possibilities of the method of formation of the electric field when searching for hydrocarbons in the shelf zones. Geophysics. No. 5 2000, EAGO. Moscow, p. 21) [2].

In more complex geological conditions, anomalies in the field formation signals obtained using the ΑΜΝΒ and установок units are not necessarily associated with the direct presence of hydrocarbon deposits in the studied medium.

The closest to the proposed method is a ground geoelectromagnetic (N.I. Rykhlinsky et al. Geoelectromagnetic method. USSR author's certificate No. 1436675 of 03/31/87) [3], in which the test medium is excited by a periodic sequence of rectangular current pulses passed through a grounded supply line (grounded dipole electric source), and measure at the points of observation in the pauses between current pulses the first and second axial potential differences, from which the mapped parameter is formed based on the norm not the uninformative total supply current of the dipole source, but the first potential difference proportional to the current density in the Earth under the point of measurement of this difference.

This method cannot be used for marine research due to their specific nature, primarily related to measurements in the process of movement of the craft. Due to the fact that the floating device and with it the probing installation are in constant motion, it is impossible to alternately excite the electromagnetic field at different times with two, located on both sides at the same distance from a fixed observation point, dipole electrical sources. It is also impossible due to the movement of the probe installation to accumulate a signal at a given point.

- 1 006537 observation due to the repeated supply of a series of current pulses. For these reasons, the proposed method has no analogues and prototype in marine geoelectroprospecting.

This method solves the problem of detecting, delineating oil and gas deposits and assessing the quality of their saturation. The technical result, which allows to solve this problem, is to provide the possibility of separating the parameters of electrical conductivity and induced polarization, and also makes it possible to determine the time constant of the decay of the potential difference caused by polarization - an important third along with the first two parameters.

This technical result is achieved by the method of marine geoelectromagnetic, in which the probe field excites an electromagnetic field in the thickness of the medium under study, passing rectangular current pulses through it with pauses after each of them using a dipole electrical source, and sending to the medium under investigation two identical rectangular current pulses: one - with the direct passage of the probe installation along the profile, and the other - with the opposite; and at each sensing point, at the end of each current pulse, the instantaneous value of the first axial electric potential difference is measured, and in each pause, the sequence of the instantaneous values of the first and second axial electric potential differences is measured at discrete points with a constant time interval;

From the values of the measured electric potential differences, three sets of current-independent electric parameters of the dipole source are calculated; ^ ^{2 of} them (ODA, & ² imPR ^ and _x ^ _OBR

ASC (? _O ) _FROM

ASC _| A ² S (G "ASCH _D ,

ASC (G, AG) _FROM ASC (G, Ar) _oya , 'where ίο is the end time of the current pulse;

ΐ; - measuring points in current pauses;

Δΐ is the time interval between two nearest measured instantaneous values of axial differences of electric potentials throughout the existence of transient signals;

Δϋχ (ί ₀ ) πρ, Δϋχΐίομρ are the instantaneous values of the first axial difference of electric potentials at the end of the current pulse, measured when the currents are fed into the dipole source, respectively, when the probe installation moves in the forward and reverse directions;

Δϋ ^ ΐί) ^, Δϋ ^ ΐί) ^, Δ ^ ΐί) ^, Δ ^^ ί;) ^ - instantaneous values of the first and second axial differences of electric potentials measured in current pauses throughout the existence of transient signals at regular intervals time Δΐ, respectively, when moving the probe installation in the forward and reverse directions;

Δϋ _χ (ΐ ;, D1) _pr , Δϋ _χ (;, Δΐ) ^, Δ ² ϋχ (ΐ;, D1) pr, Δ ² ϋχ (ΐ ;, Δΐ) ^ - the difference of values between the separated time intervals Δΐ by two the nearest instantaneous values of the first and second axial differences of the electric potentials of the transition process;

using the values of these normalized parameters and the differential equation of mathematical physics for the electric field strength of a dipole source in an electrochemically polarized conducting medium ““

V ² Ε (ίω) = ΐωμ · σ {ιωσ ϋ ητ) · Ε (ίω), where V - Hamiltonian operator;

the electric field strength of the dipole source, expressed in the equation for the case of a harmonic change in the magnitude of the electric field over time;

σ (ιωσ _ο ητ) is the frequency-dependent electrical conductivity of the elements of the medium;

σ ₀ is the electrical conductivity of the elements of the medium without taking into account the effect of the induced polarization;

η is the coefficient of their induced polarization;

τ is the time constant of the decay of the potential difference caused by polarization;

solve the mathematical inverse problem and determine the three electrophysical parameters inherent in each element of the medium: the electrical conductivity σ ₀ , the induced polarization η and the time constant for the decay of the potential difference induced polarization τ, and build three time sections using these parameters.

In addition, according to the invention, a fourth set of dipole source independent of the current strength of the normalized electrical parameters is calculated.

- 2 006537

Δυ.ΛΟ ,, ρ _| Δί // ρ ₀ „and use it along with the other three in solving the inverse problem.

The same technical result is achieved by the fact that in the method of marine geoelectromagnetic, in which the probe profile excites an electromagnetic field in the thickness of the medium under investigation, passing rectangular current pulses through it with pauses after each of them with the help of a dipole electrical source two identical rectangular current pulses are sent: one - with the direct passage of the probe installation along the profile, and the other - with the opposite; and at each sensing point, at the end of each current pulse, the instantaneous value of the first axial electric potential difference is measured, and in each pause, the sequence of the instantaneous values of the first and second axial electric potential differences is measured at discrete points with a constant time interval;

From the values of the measured differences of electric potentials, three sets of normalized electrical parameters independent of the current intensity of the dipole source are calculated _| s ² and _x (1) _OEP 'PM / w) _0№ im _"p Αυ ^ ι,) ,,, · ^ υ χ (ι,) πρ Lu _x (z) _O8R'

Δ ² υ _χ (ι „Δί) _{ΠΡ |} ΔΉ, ", Δ /) _Ο „,

Δσ _ν (ί „Δί)„, Δ ^ (/ „Δί) οερ where ΐ ₀ is the end time of the current pulse;

ίΐ - measurement points in current pauses;

Δυ _χ (ΐ ₀ ) πρ, Δυ _χ (ΐ ₀ ^ φ are the instantaneous values of the first axial electric potential difference at the end of the current pulse, measured when the currents are fed into the dipole source, respectively, when the probe installation moves in the forward and reverse directions;

Δυ ^ ΐ,) ^, Δυ ^ φ, Δ ^ χ ^) ^, Δ ^ χ ^) ^ - instantaneous values of the first and second axial differences of electric potentials measured in current pauses throughout the existence of transient signals at equal time intervals Αΐ, respectively, when the probe is moving in the forward and reverse directions;

Δυ _χ (ΐ ₁₅ Δΐ) ^, Δυ _χ (ΐ ₁₅ Δΐ) ^, Δ ² υχ (ΐ15 Δΐ) ^, Δ ² υχ ( ₁₅ Δ) ^ - the difference of values between the separated time intervals Δΐ by the two nearest instantaneous values of the first and second axial differences of electric potentials of the transition process;

at the same time they carry out group sounding in several neighboring points on separate sections of the profile along its entire length and the normalized electrical parameters determined for each group of points are summed up between themselves, obtaining the following amounts:

for Δ ² ^ χ (ζ) / 7Ζ " ₊ ^Δ2 ^, ν (<) θ5 />

• \ _ ^ _X M _OL Μ7 _χ (ί ₀₎ _οερ _ y \ ² υχ {ΐχρ 1 ² Δ δ / Χ (Γ) ^ r \ _x ^ _i} _OL Lu _x (t _OBR.

y £ υ _χ ^) _{ΠΡ |} Δ ² σ _Λ , (Λ, Δ /) ^ ^ [ΔίΖ / ί, ΔΟ ^ Δσ _ν (,., Δί) _{0 £ />} where η is the number of sounding points in each of the sounding groups;

using the values of these sums and the differential equation of mathematical physics for the electric field strength of a dipole source in an electrochemically polarized conducting medium

V ² Ε (ΐω) = ίωμ σ (ΐωσ _ο ητ) (ΐω), where V is the Hamiltonian operator;

Е (1ш) is the electric field strength of a dipole source, expressed in the equation for the case of a harmonic change in the magnitude of the electric field with time;

σ (ΐωσ _ο ητ) is the frequency dependent electrical conductivity of the elements of the medium;

η is the coefficient of their induced polarization;

- 3 006537 τ is the time constant of the decay of the potential difference caused by polarization;

This technical result is also achieved by the method of marine geoelectromagnetic, in which the probe field excites an electromagnetic field in the thickness of the medium under study, passing rectangular current pulses through it with pauses after each of them using a dipole electrical source, and on the axis of the profile at different distances from the dipole electric source of two three-point measuring systems, measure the first and second differences of the electric potentials Alov, and two identical rectangular current pulses are sent to the test medium: one - when the first three-point measuring installation passes through the sensing point, and the other - when the second one passes, measuring the instantaneous value of the first axial electric potential difference at the end of each current pulse and also in each pause after switching off the current pulse throughout the lifetime of the transient signals at discrete points with a constant time interval, the instantaneous values of the first and second axial differences of electric potentials;

From the values of the measured differences of electric potentials, three sets of normalized electrical parameters that are independent of the current intensity of the dipole source are calculated.

Mm, Mm ₂ Mm, Mm ₂

MM) imA mm mm _g '

Μ _χ (ι „& ί), Μ _χ (ι„ & ι \ №, (ι „α \ 'where ΐ ₀ is the end time of the current pulse;

1, - measuring points in current pauses;

Δϋχ (ΐ ₀ ) ι, Δϋχ (ΐ ₀ ) ₂ - instantaneous values of the first axial difference of electric potentials at the end of each current pulse, measured when current is supplied to a dipole source, respectively, when passing through the sensing point of the first and second three-point measurement settings;

Δϋ _χ (ΐι) ι, Δϋ _χ (ΐ () ₂ , Δ ² ϋχ (ΐ1) ι, Δ ² υχ (ΐ0 ₂ - instantaneous values of the first and second axial differences of electric potentials, measured in current pauses throughout the existence of transient signals process at equal time intervals Δΐ, when passing through the sensing point, respectively, of the first and second three-point measurement systems;

Δυ _χ (ΐι, Δΐ) ι, Δυ _χ (ΐι, Δΐ) ₂ , Δ ² υχ (ΐι, Δΐ) ι, Δ ² χχ (ΐι, Δΐ) ₂ - differences of values between the separated time intervals Δΐ of the two nearest instantaneous values of the first and second axial differences of electric potentials of the transition process;

using the values of these normalized parameters and the differential equation of mathematical physics for the electric field strength of a dipole source in an electrochemically polarized conducting medium

where V is the Hamilton operator;

E (1st>) is the electric field strength of the dipole source, expressed in the equation for the case of a harmonic change in the magnitude of the electric field with time;

σ (ΐωσ ₀ ητ) is the frequency-dependent electrical conductivity of the elements of the medium;

σ0 is the electrical conductivity of the elements of the medium without taking into account the effect of the induced polarization;

η is the coefficient of their induced polarization;

solve the mathematical inverse problem and determine the three electrophysical parameters inherent in each element of the medium: the electrical conductivity σ0, the induced polarization η and the time constant for the decay of the potential difference caused by polarization τ, and build three time sections using these parameters.

- 4 006537

D ", Yu, DCH",) _g Δί /. _ν (Ζ ₀ ), Δ £ / _ν (ί „), and use it along with the other three in solving the inverse problem.

From the values of the measured electric potential differences, three sets of normalized electrical parameters, independent of the current strength of the dipole source, are calculated, _g (r ₀ ), Δί // ί ₀ ) ₂ 'Δί / up, Δσ _Λ . (0 ₂ '

Δ ² ί / ν Δί), Δ ² [/ ν (/,., Δ /) ₂

Δί / ^ / ,, Δ /). ΔίΖ. _ν (/ „Δ /) ₂ 'where ίο is the end time of the current pulse;

ΐι - measuring points in current pauses;

Δυ _χ (ΐ ₀ ) ι, Δυ _χ (ΐ ₀ ) ₂ are the instantaneous values of the first axial electric potential difference at the end of each current pulse, measured when the current is fed into the dipole source, respectively, when passing through the sensing point of the first and second three-point measurement settings ;

Δυ _χ (ίΐ) ι, Δυ _χ (ίΐ) ₂ , Δ ² χ χ (ΐι) ι, Δ ² υχ (Τ) ₂ - instantaneous values of the first and second axial differences of electric potentials, measured in current pauses throughout the existence of transient signals process at equal time intervals Δΐ, when passing through the sensing point, respectively, of the first and second three-point measurement systems;

Δυ _χ (ίΐ, Δΐ) ι, Δυ _χ (ίΐ, Δΐ) ₂ , Δ ² υχ (ΐι, Δΐ) ι, Δ ² χ χ (ΐι, Δΐ) ₂ - the difference of values between the separated time intervals Δΐ by the two nearest instantaneous values of the first and second axial differences of electric potentials of the transition process;

AShch /,),

Δ <7 _χ (Ζ ₀ ).

AShch /) ₂ δ ^ (/ ₀ ) ₂ .

Δ ² σν «), δ ² ι / λ · (,) ₂

Δί / _χ (Ο, Δί7 _χ (Ο ₂ _

Δ ² σ _Γ (/ „Δζ),

Δσ _ν (/, Δί),

D ² 1 / _g (/ _,., A) ₂

Δσ _ν (ί., Δ /) ₂ where η is the number of sensing points in each of the sensing groups;

where V is the Hamilton operator;

Е (1ш) is the electric field strength of a dipole source, expressed in the equation for the case of a harmonic change in the magnitude of the electric field with time; σ (ΐωσ _ο ητ) is the frequency dependent electrical conductivity of the elements of the medium;

σ ₀ is the electrical conductivity of the elements of the medium without taking into account the effect of the induced polarization; η is the coefficient of their induced polarization;

- 5 006537 τ is the time constant of the decay of the potential difference induced polarization;

This technical result is also achieved by the method of marine geoelectrical exploration, in which the probe field excites an electromagnetic field in the thickness of the medium under study, passing rectangular current pulses through it with pauses after each of them using a dipole electrical source, and sending to the medium under investigation one rectangular current pulse;

and at each sensing point, at the end of each current pulse, the instantaneous value of the first axial electric potential difference is measured, and in each pause, the sequence of the instantaneous values of the first and second axial electric potential differences is measured at discrete points with a constant time interval;

From the values of the measured differences of electric potentials, three sets of normalized electrical parameters that are independent of the current intensity of the dipole source are calculated:

JH / TO Δ ^; σ _χ (Ο Δ ^ / Ζ ,, Δί)

Δί / Д /,) 'ΔδΖ _Λ . (Ζ,)' ΔΖ7 _ν (ί ,, Δζ) 'where ΐ ₀ is the end time of the current pulse;

ΐι - measuring points in current pauses;

Δυ _χ (ΐ ₀ ) is the instantaneous value of the first axial difference of electric potentials at the end of the current pulse, measured when the current is supplied to the dipole source;

Δυ _χ (ΐι), Δ ² υ _χ (ΐθ - instantaneous values of the first and second axial differences of electric potentials, measured in current pauses throughout the existence of transient signals at equal time intervals Δΐ;

Δυχ (ΐι, Δΐ), Δ ² υχΑΔΐ) are the differences of values between the separated time intervals Δΐ by the two nearest instantaneous values of the first and second axial differences of the electric potentials of the transient process;

where V is the Hamilton operator;

σ (ΐωσοητ) is the frequency-dependent electrical conductivity of the elements of the medium;

η is the coefficient of their induced polarization;

DU. (/,) DGSch,) and use it along with three others in solving the inverse problem.

The same technical result is achieved by the fact that in the method of marine geoelectromagnetic, in which the probe profile excites an electromagnetic field in the thickness of the medium under investigation, passing rectangular current pulses through it with pauses after each of them with the help of a dipole electrical source send one rectangular current pulse;

- 6 006537 and at each sensing point, at the end of each current pulse, the instantaneous value of the first axial difference of electric potentials is measured, and in each pause, the sequence of instantaneous values of the first and second axial differences is measured at discrete points with a constant time interval electrical potentials;

Mu,) Δ ² υ _χ (ι „Δί)

Δί / _ν (/ ₀ ) 'Δί / _Λ . (Ί,)' Δΐ / DG ,, Δ /) 'where ΐ ₀ is the end time of the current pulse;

ΐ; - measuring points in current pauses;

Δϋχ (ΐ ₀ ) is the instantaneous value of the first axial difference of electric potentials at the end of the current pulse, measured when current is supplied to a dipole source;

Δϋ _χ (ΐ;), Δ ² ϋ _χ (ΐ;) are the instantaneous values of the first and second axial differences of electric potentials measured in current pauses throughout the existence of transient signals at equal time intervals Δΐ;

Δϋ _χ (ΐ;, Δΐ), Δ ² ϋ _χ (ΐ;, Δΐ) are the differences between the separated time intervals Δΐ by the two nearest instantaneous values of the first and second axial differences of the electric potentials of the transient process;

y-ι δ ² and _x (ί.) y "δ and _x (y) uk δ and _x (ι., δ /)

ΤΔσ _ν (/ ₀ ) 'ΤΔί / _Α . «)' ΝΔσ _ν (/, Δ /) 'where η is the number of sounding points in each of the sounding groups;

where V is the Hamilton operator;

Ε (ίάΐ) is the electric field strength of the dipole source, expressed in the equation for the case of a harmonic change in the magnitude of the electric field with time;

η is the coefficient of their induced polarization;

The invention is illustrated by drawings.

FIG. 1 is a block diagram of a device for implementing a variant of the proposed method using a three-electrode sensor of the first and second differences of electric potentials.

FIG. 2 shows a block diagram of a device for implementing a variant of the proposed method using two measuring three-electrode sensors of the first and second differences of electric potentials placed at different distances from a dipole electric source.

FIG. 3 shows the forms of single pulses as a function of time ΐ: a) - the shape of a single rectangular current pulse I in the network of a dipole source AB; b) - the shape of the pulses of the first and second differences of electric potentials.

The device (Fig. 1) contains 1 feeding electrodes 2 and 3 of a dipole electrical source (current dipole AB) immersed in water and connected to the generator 4 rectangular current pulses. To ensure synchronization of the moments of switching on and off the current pulses, the generator 4 is connected to the radio receiver 5 with the antenna 6 for satellite binding of the sensing point.

The receiving electrodes 7-M ₁ , 8-Ν and 9-M ₂ sensors of the first and second differences are successively arranged on the axis of the profile at equal intervals on the determining size of the probe installation

- 7 006537 given distances from the supply electrodes 2 and 3. The matching amplifier 10 is designed to measure the first potential difference ΔϋΜ ₁ Μ ₂ , between the outermost receiving electrodes 7 and 9; matching amplifier 11 - for measuring the second potential difference Δ ² υΜ1Μ2 between electrodes Μ1ΝΜ2 equal to the difference of the two first differences of electric potentials ΔυΜ1Ν and ΔυΝΜ2 (Δ ² υΜ1Μ ₂ = ΔυΜ ₁ Ν ΔυΝΜ ₂ ); the inputs of analog-to-digital converters (ADC) 12 and 13 are connected to matching amplifiers 10 and 11, and the outputs to the inputs of digital filters 14 and 15; the outputs of the digital filters 14 and 15 are connected to a computer processing and recording unit 16, which is also connected to the radio receiver 5 to synchronize it with the source 4.

The device (Fig. 2), performed in the embodiment using two measuring three-electrode sensors of the first and second differences of electric potentials, contains the same elements from 1 to 16 as the device according to (Fig. 1), and additionally - elements 17-25 of the second channel measurements.

Here, the 17-Μ ₁ , 18-Ν and 19-M ₂ electrodes of the sensors of the first and second differences are placed on the axis of the profile at equal intervals defining the smaller size of the second probe installation distances from the supply electrodes 2 and 3. The matching amplifier 20 is designed to measure the first difference potentials ΔυΜ ₁ Μ ₂ between the extreme receiving electrodes 17 and 19; matching amplifier 21 - for measuring the second potential difference Δ ² υΜ ₁ ₂ between the electrodes 17, 18 and 19; the inputs of analog-to-digital converters (ADC) 22 and 23 are connected to matching amplifiers 20 and 21, and the outputs to the inputs of digital filters 24 and 25; the outputs of the digital filters 24 and 25 are connected to a computer processing and recording unit 16.

For the third option, the device of FIG. one.

FIG. 3 (a) shows the shape of a single rectangular current pulse I in the circuit of a dipole source AB as a function of time ΐ. Here T is the current pulse period.

FIG. 3 (b) shows the shape of one of the pulses Δυ _χ and Δ ² υχ. Here, at time ΐ0, the instantaneous value Δυχ ()0) at the end of the existence of a rectangular current pulse in the current dipole is shown. Also shown is one of the instantaneous values of Δυχ (ΐ0, Δ ² υχ (ΐ0 in the current pause. Also shown is one of the values of Δυ _χ (ΐι, Δΐ), Δ ² _{χ χ} (ΐι, Δΐ) at one of the time intervals Δΐ in the current pause .

Consider the basics of the proposed method, its implementation and new opportunities for marine geoelectrical exploration.

In the proposed method of marine geoelectrical exploration, the elimination of the distorting effect on the soundings of variable depth and electrically highly conductive layer of sea water, as well as other local inhomogeneities of the geological section, is performed by sounding at a given point a profile with two single required power rectangular current pulses: through the sensing point in the forward direction; the second is at the reverse; or by probing at a given point of the profile with two three-point measuring installations located at different distances from the dipole source.

The distorting effect of the above local inhomogeneities of the geological environment is achieved by eliminating the horizontal component of the current density C under the sensing point. For this, the measurement of the second axial potential differences Δ ² υχ is carried out at the extremum point of the electric field υ, at which the first axial potential difference Δυ _χ and, accordingly, C are equal to zero.

Note that there is no need to create an extremum of potential at the sensing point by selecting currents in each of the two current dipole sources, and it is sufficient to supply currents of arbitrary magnitude separately into these dipoles at different times and measure the first [Δυ _χ (Ι ₁ ), Δυ _χ (Ι ₂ )] and second [Δ ² υχ (Ι1), Δ ² υχ (Ι ₂ )] axial differences of electric potentials, where 1 ₁ is the current of the first current dipole source, 1 ₂ is the current of the second current dipole source. Based on the measured first electric potential differences, the coefficient K obtained from the equation κ · Δυ _χ (ΐ ₁ ) + Δυ _χ (ΐ ₂ ) = ο, (2) resulting from the necessity of the presence of the extremum of the potential of the electric field along the X coordinate within the zone measuring electrodes of the probe installation in order to zero there the axial component of the current density C.

In determining the amount of a relationship

or the sum of the ratios of their differences in time, the coefficient K, which follows from (2), is included in the numerator and denominator of the second term of the above sum (2a) and regardless of the magnitudes of the currents 1 ₁ and 1 _{2 is} always reduced, i.e. during the operation of division, both denominators Δυ _χ (Ι ₁ ) and Δυ _χ (Ι ₂ ) become equal to each other, and, specifically, equal to one.

Thus, at the sensing point in a plane perpendicular to the axis of the profile, there is no horizontal component of the current density C. This means that the electric current is vertically focused.

- 8 006537

Further, it is known that the electromagnetic field in a poorly conducting physical medium propagates in time ΐ according to the differential damped wave equation of mathematical physics for the electric field strength resulting from the first and second Maxwell equations, including in the case of its pulse variation

where V is the Hamilton operator (V ² is the Laplace operator); E - electric field strength, V / m .;

μ - magnetic permeability - a constant value for non-magnetic media, which include sedimentary geological rocks, and is 4π · 10 ^-7 Henry / m;

σ ₀ - electrical conductivity of non-polarizable medium, Siemens;

ε is the dielectric constant, Farad / m. (V. A. Govorkov. Electric and magnetic fields. M .: Gosenergoizdat, 1960, pp.257-263) [4].

In the case of a highly conductive medium, to which sedimentary rocks belong, due to the fact that σ _{0 is} numerically many times greater than ε, the second term in the right-hand side of equation (3) is small compared to the first, and it is discarded (L. L. Van'yan The fundamentals of electromagnetic soundings.- M .: Nedra, 1965, p.28-30) [5]. Physically, this means that bias currents in conducting media are neglected due to their smallness compared with conduction currents. Then equation (3) takes the form

When solving this equation, it allows one to determine only one electrical parameter of the elements of the medium — the electrical conductivity σ0.

Equation (4) is the electromagnetic field propagation equation in a conducting nonpolarizable medium, which coincides with the heat conduction or diffusion equation known in mathematical physics and which is used in geophysics in resistivity methods to study the propagation of an alternating electromagnetic field deep into the geological rocks under study this, it is considered that the electrical conductivity σ0 of one or another geological horizon is the main and practically the only determining factor of electric properties, has its constant value for each horizon, and is independent of the excitation frequency of the electromagnetic field. However, geological sedimentary rocks when they are excited by alternating low-frequency electric current used in geophysics are characterized by the polarization η caused by them. The induced polarization is a dimensionless quantity depending on the electrochemical activity of sedimentary rocks. It is defined as the ratio of potential differences measured on a sample of the rock under investigation after switching off the current pulses after 0.5 s (Livp) and before switching off (Δϋ). This ratio is usually expressed as a percentage.

The induced polarization of sedimentary geological rocks has a unique stability among physical parameters and practically does not depend on the composition of rocks and their temperature. It for ion-conducting (sedimentary) rocks depends on many factors: humidity and porosity, the composition and concentration of the solution in the pores of the rock, the structure and size of pores, the content of clay minerals, etc. (VA Komarov. Electrical prospecting by the method of polarization. L.- Science, 1980, p. 392) [6]. And, most importantly, as shown by extensive practical geoelectric studies by the proposed method on geological objects, the induced polarization carries basic information about the presence in the geological environment of oil and gas deposits with a high degree of polarization.

It was established (\\ '. Ι I. ReIop, 8.N. ^ agb, R.O. Na11o £, Δ'. 8111 apb R.N. №1zop. Yediupsu 1P, Oörbuster 43, 1978, pp.588-603) [7] that the electrical conductivity of sedimentary rocks is not constant, but depends on the induced polarization and on the frequency of excitation of the electric field on the proposed K.8. Cole and K.N. Cole in the form of its harmonious change in time by the empirical formula σ (ίωσ _ο ητ) = σ _ο 1 - --—, (6) to 1 + (1bUg) 0 in which this electrical conductivity depends on ω, σ ₀ , η and τ, where η - induced polarization of rocks, a dimensionless quantity, usually expressed as a percentage;

τ is the time constant, which determines the rate of decay of the potential difference associated with the induced polarization, s;

ω - harmonic frequency of electrical excitation, G;

c is a dimensionless exponent, which, although not a physical parameter of rocks, also depends on it σ (0ωσ ₀ ητ).

- 9 006537

The induced polarization η at low frequencies of electrical excitation, unlike the dielectric constant ε, is not numerically small compared to the electrical conductivity σ ₀ for sedimentary geological rocks, measured, for example, at high frequency currents (ω ^ · ο>), when this is evident from formula (6), the induced polarization does not manifest itself. Consequently, the induced polarization, when studying for the purpose of searching and delineating oil and gas deposits, the geoelectric parameters of sedimentary geological rocks on low-frequency alternating current, cannot be neglected. Known (Electro-prospecting. Handbook of geophysics. Ed. By V.Khmelevsky et al., M.- Nedra: 1989, Book Two,

p.99-102) [8] that for certain sedimentary geological rocks 0.5 s after turning off the exciting current pulse, the magnitude of the potential difference caused by polarization, despite its intense decline, still retains levels whose numerical values range from 0 , 2 to 10% of the numerical values of the potential difference of the direct field associated with the electrical conductivity σ ₀ , measured, as noted above, at high frequency currents, when the induced polarization is not manifested. To keep the formula (6) in shape, the thermal equation (4) is written for the case of a harmonic change in the magnitude of the electromagnetic field over time, bearing in mind that

Ε (ίω) = Ε _η · β ^{ίω 1} and taking into account that

(7) view

Then equation (4) for a conducting non-polarizable medium with the transformation (7) will take

V ² Ε (ΐά>) = \ ωμσ _α · (ΐύ)).

(9)

But since the electrical conductivity of sedimentary rocks is not constant, and depends on the induced polarization and on the excitation frequency according to formula (6), equation (9) taking into account this formula acquires four parameters defining the properties of a polarizing medium σ ₀ , η, τ and c instead of one σ ₀ and for the case of a harmonious change in the magnitude of the electromagnetic field in time takes the form

V ²

Ε (ίώ?) = \ Ωμσ ₀ 1 - ---.--- · (ΐίθ), _ 14- (160 g) _ (10) but in general form, taking into account (6)

Equation (10) becomes already close, in essence, to the damped wave equation (3) for the electric field at low frequencies, according to the laws of which an alternating electromagnetic field penetrates into the medium under study not only due to diffusion induction currents caused by electrical conductivity σ ₀ , but also thanks also to the “displacement” currents caused by the polarization η of these same rocks. The latter circumstance suggests that the geoelectrical exploration capabilities for prospecting and delineating oil and gas deposits at low frequency alternating (harmonic or pulsed) currents are higher than previously thought. These opportunities are realized only under two conditions: first, when the range of measured electrical normalized parameters expands to four necessary for correct solution of equation (10), and second, when their measurement accuracy increases to such an extent as to reveal the features of the transitional field formation curves in the pauses current associated with induced polarization. Moreover, it is not allowed as a parameter normalizing such a parameter measured by traditional geoelectromagnetic surveys, as the current strength I of a controlled artificial source that does not carry any information about the current density distribution over depth in a three-dimensional non-uniform geological environment. The latter is already due to the presence of an oil and gas deposit limited in horizontal coordinates.

The implementation of new opportunities for marine geoelectrical is achieved by the proposed method. And the fact that equation (10) is close, in essence, to the damped wave equation for electric field strength, equation (3) is easy to verify by expanding formula (6) into a Taylor series relative to the frequency difference ω-ω0 (where ω0 is the repetition rate excitation current pulses), using, in particular, only two members of this series due to its rapid convergence at ω ₀ <τ ^-1 (which is usually the case in practice). Under this assumption, we obtain the equation

- 10 006537

As can be seen, equation (11) does not differ in form from the damped wave equation for the electric field strength (3) for the case of a pulsed change in the magnitudes of the electromagnetic field. And although the coefficient at “ ^ω · Ε (ίω) is less than the coefficient at ~ ^ω Е (ιω) is less than the coefficient at _{n0 is still not as much as ε n0} compared to σ ₀ in a conducting non-polarizable medium, and neglect the second member of this equation no longer acceptable.

Equation (10) is considered to be close in its essence to equation (3), and not analytically equal to it because its derivation used the empirical formula (6) due to the lack of an analytical formula for the relationship between the electrical conductivity σ (ΐωσ ₀ ητ) and the polarization caused η.

For the proposed method, the problem of detecting oil and gas deposits in the studied rock mass as a mathematical inverse problem is solved according to equation (10a) as a function of time, i.e., as a function of time-dependent penetration depth of the electromagnetic field, three parameters of the environment independent of each other: the electrical conductivity σ ₀ caused by polarization η, the time constant τ of the decay of the difference in electric potentials caused by polarization; and on the fourth, non-environmental parameter, exponent c, which follows from the empirical formula (6).

This problem, as the inverse mathematical problem is solved for a proposed first embodiment of a method with measuring sensors of the first and second differences by using the entire array defined in this way at least three independent of current sources of normalized electrical parameters d ² n, - "to _L , _|

ΔΠ _ν (ί „Δ /)„, Δ (/ _ν (ί ,, Δζ) _οί , 'in the current pauses at times ΐ ₁ (0 <ί <π) equal to ₀ , ΐ ₀ + Δΐ, ΐ ₀ + 2Δΐ, ΐ ₀ + 3Δΐ, etc. to ΐ ₀ + πΔΐ, that is, until the end of the life of the transient signals and the differential equation of mathematical physics (10a) for the electric field strength of a dipole source in an electrochemically polarized conducting medium, In particular, for example, one of the methods for solving an inverse mathematical problem is the selection method (A.N. Tikhonov, V.Ya. Arsenin. Methods for solving ill-posed problems. - Moscow: Nauka, 1979, pp. 37-43) [9]. this m to reduce the number of selection options use the available data on the model of the geological environment under study, for example, drilling data from reference or parametric wells, which, as a rule, are drilled everywhere with a rare step, or seismic data, if the latter has already been carried out in the study area. or a priori data on the geological section that, as a rule, in exploratory research is found most often, the inverse problem is also solved, but with an increased number of options ora

In the final result, by solving the inverse problem, a medium model is obtained that is closest to the real in terms of its geometric structure and the values of the parameters σ ₀ , η and τ for each of its elements, and, as a result, they separate these three parameters. And finally, three time sections σ ₀ , η and τ are built: along the vertical coordinate - as a function of the transition time in the current pause, functionally related to the depth of field penetration, and, consequently, to the depth of each horizon, found as a result solving the inverse problem of the environmental model; along the horizontal coordinate, as a function of the distance between sensing points on the sea surface along a given profile; and the values included in the equation (10a) of the electrophysical parameters σ0, η and τ are represented by the digital scale attached for each section in a color image by color gamut.

For the purpose of a more correct solution of the inverse problem, the fourth set of dipole sources of the normalized electrical parameters, independent of the current strength, are additionally calculated. (O _{YAR |} d. (G ,.) _№

ΔΓ _Λ . (Ζ _Ο ) „, DSH (M _{0 £} / ⁽¹³⁾ and use it in this solution along with three others (12).

In the presence of intense interference, for example telluric currents, group sensing is performed successively at several neighboring points in separate sections of the profile along its entire length. The normalized electrical parameters for this variant determined at each point of the sensing group are summed up between themselves, obtaining the following sums:

- 11 006537

where η is the number of probing points in each of the probing groups;

and use these amounts in solving the inverse problem.

Similarly, the inverse mathematical problem is solved for the third variant of the method, where the whole array of three sources of normalized electrical parameters determined by this method is also used.

And, in order to more correctly solve the inverse problem, the fourth set of dipole sources of normalized electrical parameters independent of the current strength is additionally calculated.

and use it in this solution along with three others (15).

If there is any interference, group sounding is carried out in succession at several neighboring points in separate sections of the profile throughout its continuation. The normalized electrical parameters determined at each point of the probing group summarize among themselves, obtaining the following sums:

where η is the number of probing points in each of the probing groups;

and use these amounts in solving the inverse problem.

Similarly, the inverse mathematical problem is solved for a variant of the method, which is used in the conditions of a constant thickness of the sea layer and the absence of other local inhomogeneities. In this case, the presence of the axial component of the current density) _x does not have a significant distorting effect on the measurement results. This method also uses the entire array of three sources of rated electrical parameters that are independent of current strength

and use it in this solution along with three others (18).

where η is the number of probing points in each of the probing groups; and use these amounts in solving the inverse problem.

- 12 006537

Research by the proposed method in oil and gas fields has established that in the presence of an oil or gas reservoir, regardless of the type of trap and its geometric shape, all three parameters (electrical conductivity σ ₀ , induced polarization η and time constant τ) within the contour of the reservoir take on an anomaly in the depth of the cut, where this deposit is located.

A specific example

FIG. 1 and 2 presents a block diagram of the apparatus for the implementation of the proposed method. In particular, in FIG. 1 shows a block diagram of the apparatus for implementing the first variant of the proposed method. The block diagram shows a current dipole AB (2 and 3) placed in water, powered by a generator of 4 rectangular current pulses. On the dipole axis at a certain distance from it, using the measuring electrodes Μ1, Ν, Μ2 (7, 8 and 9) measure the instantaneous values of the first and second axial differences: one at the end of each current pulse and in the current pause after a set time Δΐ all differences throughout the existence of transient signals. All the above measured differences are amplified by amplifiers 10 and 11. To ensure the accuracy of the measurement necessary to reveal the characteristics of the transition process of field formation in current pauses, which are measured by amplifiers 10 and 11, associated with the polarization of the studied rocks, the differences are digitized by analog-digital converters (ADC ) 12 and 13 with a bit depth of 24 or more. To implement the proposed method, a measuring device with a twenty-four-bit ADC has been developed and manufactured. In this device, after twenty-four-digit digitizing of measured signals, the latter are filtered out from random noise using multi-tier digital filters 14 and 15. Filtered useful signals from the outputs of the digital filters 14 and 15 are fed to the input of the computer processing and recording unit 16.

To ensure the binding of the probe installation to a given point of sensing and synchronization of the moments of switching on and off of the current pulses with the moments of measurement in the receiver of the receiving signals, a radio receiver 5, respectively, directed to the navigation satellites, is used with the receiving antenna 6.

To determine the six normalized electrical parameters (12), (13), (14), (15), (16), (17), (18), (19) and (20) that are present in the variants of the method of marine geoelectromagnetic, measure instantaneous values first potential differences Δυ _χ (ΐ ₀ ) at the end of the current pulse and a series of instantaneous values of the first and second potential differences of transients Δυ _χ ( ₁ ) and Δυ ² _χ ( ₁ ) during pauses throughout the lifetime of the transient signals. Also determine a series of differences in the values of every two adjacent instantaneous values of the first and second potential differences along the entire lifetime of the transient signals. The plots of one of the current pulses and the measured ί-th instantaneous values of the first and second potential differences in one of the pauses are shown in FIG. 3. Indices pr. And arr. for the first and second variants of the method in formulas (12), (13) and (14) indicate that the measurement of electrical parameters at each sensing point is carried out when the probe installation moves in the forward and reverse directions. And the indices 1 and 2 for the third and fourth variants of the method in formulas (15), (16) and (17) denote that the measurement of electrical parameters at each sensing point is carried out using two three-point points located on the profile axis at different distances from the dipole source. measuring installations.

The proposed method is implemented in the form of a complex of supply, measuring and processing equipment. As noted above, research by the proposed method on a variety of oil and gas fields has established that, in the presence of an oil or gas reservoir, regardless of the type of trap and its geometrical shape, all three parameters σ0, η and τ within the contour of the reservoir take on the form that reflects the anomaly in the depth of the section there where this deposit is located. The method provides a significant economic effect in the search and exploration of hydrocarbon accumulations.

Claims

1. A method of marine geoelectrical exploration, in which an electromagnetic field is excited along the axis of the sounding profile in the thickness of the medium under investigation, passing rectangular current pulses through it with pauses after each of them using a dipole electric source, and two identical rectangular current pulses are sent to the medium under study: one - with the direct passage of the probe installation along the profile, and the other - with the opposite; and at each sounding point at the end of each current pulse the instantaneous value of the first axial difference of electric potentials is measured, and in each pause throughout the entire time of existence of the transient signals at discrete points with a constant time interval, a sequence of instantaneous values of the first and second axial differences of electric potentials is measured;

from the values of the measured electric potential differences, three sets of normalized electrical parameters independent of the current strength of the dipole source are calculated

- 13 006537 δ ^ _τ (ο „, 'Δ ² σχ (ρΟ5? Δ ² « χ (/,) „ _ρ , l ² <7, _r ( _oo , * im„, 4th name _No. 4υ _χ (ι, ) „, \ And _x ^ _oer '

Δ ² σ. _Γ (ζ, Δ /) „,, ^. (7 ,, Δ /) _ο „

Δ! / _Ν (ί „Δί)„ Δυ _χ ((„Δΐ) _οα , 'where ΐ ₀ is the end time of the current pulse;

Ϊ! - measuring points in pauses of current;

Δί is the time interval between the two closest measured instantaneous values of axial differences of electric potentials throughout the entire existence of transient signals;

Δυ ^ ΐ ^, Δυχ ^^ ρ - instantaneous values of the first axial difference of electric potentials at the end of the current pulse, measured when currents are supplied to the dipole source, respectively, when the probe installation moves in the forward and reverse directions;

Δυχ ^, Δυχζ ^ φ, Δ ² ^^ Δ ^ χζ ^ φ - instantaneous values of the first and second axial differences of electric potentials, measured in pauses of current throughout the existence of transient signals at equal time intervals Δί, respectively, when the probe installation in the forward and reverse directions;

Δυχ (Ϊ !, Δΐ) ^, Δυχ (ΐί, Δΐ ^, Δ ² ΓΧ (1 ,, Δΐ) ^, Δ ² Γχ (1 ,, Δΐ ^ are the differences between the separated time intervals Δΐ by the two closest instantaneous values of the first and second axial differences in the electrical potentials of the transition process;

using the values of these normalized parameters and the differential equation of mathematical physics for the electric field strength of a dipole source in an electrochemically polarized conducting medium where V is the Hamilton operator;

E (1O>) is the electric field strength of the dipole source, expressed in the equation for the case of a harmonic change in the magnitude of the electric field over time;

σ ₀ is the electrical conductivity of the elements of the medium without taking into account the effect of induced polarization;

η is the coefficient of their induced polarization;

τ is the decay time constant of the potential difference caused by polarization;

they solve the mathematical inverse problem and determine three electrophysical parameters inherent in each element of the medium: electrical conductivity σ ₀ caused by polarization η and the decay time constant of the potential difference caused by polarization τ, and three time sections are constructed from these parameters.

2. The method of marine geoelectrical exploration according to claim 1, characterized in that the fourth set of normalized electric parameters δ and _x (ί ₀ ) pr δ and _x (ζθ) _OBR, independent of the current strength of the dipole source, is calculated and used along with three others to solve inverse problem.

3. A method of marine geoelectrical exploration, in which an electromagnetic field is excited along the axis of the sounding profile in the thickness of the medium under investigation, passing rectangular current pulses through it with pauses after each of them using a dipole electric source, and two identical rectangular current pulses are sent to the medium under investigation: one - with the direct passage of the probe installation along the profile, and the other - with the opposite; and at each sounding point at the end of each current pulse the instantaneous value of the first axial difference of electric potentials is measured, and in each pause throughout the entire time of existence of the transient signals at discrete points with a constant time interval, a sequence of instantaneous values of the first and second axial differences of electric potentials is measured;

from the measured values of the electrical potential differences is calculated from three independent sets of current dipole source normalized electrical parameters ₊ ^k2 _x and w _0BR _m Mm ₊ MMO »№ M _X _n, ^ HMO _BR 'Δ ^ / 0 / t /. ΔίΖ _Ύ (Γ) _Ο5 / ά ² υχ (ι, Μ.) Πρ , Δ ² σν «, Δ;.) Regarding _R

4 и _х (1 „м)„ _г & υ _χ (ί „& ί) О _{Р Р} where ΐ0 is the end time of the current pulse;

14 006537

1, - measuring points in pauses of current;

Δΐ is the time interval between the two closest measured instantaneous values of axial differences of electric potentials throughout the entire existence of transient signals;

Δυ _χ (ΐ ₀ ) _Π ρ, Δυ ^ ΐο) ^ - instantaneous values of the first axial difference of electric potentials at the end of the current pulse, measured when currents are supplied to the dipole source, respectively, when the probe installation moves in the forward and reverse directions;

Δυ ^ ΐ ^, Αυ _χ (1,) _arr , ASF / G, Δ ² ^^) ^ - instantaneous values of the first and second axial differences of electric potentials, measured in pauses of current throughout the existence of transient signals at equal time intervals Δΐ , respectively, when the sounding installation moves in the forward and reverse directions;

Δυ _χ (ΐί, Δΐ) ^, Δυ _χ (ΐί, Δΐ) ^, Δ ² υχ (ΐι, Δΐ) ^, Δ ² υχ (ΐι, Δΐ) ^ are the differences between the separated time intervals Δΐ by the two closest instantaneous values of the first and second axial differences in the electrical potentials of the transition process;

in this case, group sensing is carried out at several neighboring points in separate sections of the profile along its entire length and the normalized electrical parameters determined for each group of points are summed up among themselves, obtaining the following amounts:

Δ4, (ί.) „, Д4, (< ₀ ) _from _ т | D4 _g (/ “Д /)”, where η is the number of sounding points in each of the sounding groups;

using the values of these sums and the differential equation of mathematical physics for the electric field strength of a dipole source in an electrochemically polarized conducting medium where V is the Hamilton operator;

- the electric field strength of the dipole source, expressed in the equation for the case of a harmonic change in the magnitude of the electric field over time;

σ (ΐωσ _ο ητ) is the frequency-dependent conductivity of the elements of the medium;

η is the coefficient of their induced polarization;

4. A method of marine geoelectrical exploration, in which an electromagnetic field is excited along the axis of the sounding profile in the thickness of the medium under investigation, passing rectangular current pulses through it with pauses after each of them with the help of a dipole electric source, and with the help of located on the profile axis at different distances from the dipole the electric source of two three-point measuring installations measure the first and second differences of electric potentials, and two identical ones are sent to the test medium rectangular current pulse: one - when passing through the sounding point of the first three-point measuring installation, and the other - when passing the second, while measuring at the end of each current pulse the instantaneous value of the first axial difference of electric potentials and also in each pause after switching off the current pulse throughout during the time of existence of transient signals at discrete points with a constant time interval — instantaneous values of the first and second axial differences of electric potentials;

from the values of the measured differences of electric potentials, three sets of normalized electrical parameters independent of the current strength of the dipole source are calculated

- 15 006537

ДСО, Δ ² ί7χ (Ο2 Δ ² ί / γ (Ο, Δ ² σ _Λ , (Ο ₂

Δυ _χ (ί ₀ \ Δί / _Λ . (Ί ₀ ) ₂ 'Δί / D / D Δί / _Λ . (Ο ₂ '

ΔνΑζ., Δζ), Δ ² ^ (ζ., Δ0 _;

Δσ _ν ", Δί), ΔίΖ _Λ . (Ζ.Δ /) ₂ 'where ΐ ₀ is the end time of the current pulse;

ΐί - measuring points in pauses of current;

Δυ _χ (ΐ ₀ ) ι, Δυ _χ (ΐ ₀ ) ₂ are the instantaneous values of the first axial difference of electric potentials at the end of each current pulse, measured when a current was applied to a dipole source, respectively, when passing through the sounding point of the first and second three-point measuring installations ;

Δυ _χ (ΐι) ι, Δυ _χ (ΐι) ₂ , Δ ² υχ (Τ) ι, Δ ² υχ (Τ) ₂ are the instantaneous values of the first and second axial differences of electric potentials, measured in pauses of current throughout the existence of transition signals process at equal time intervals Δΐ, when passing through the sensing point, respectively, of the first and second three-point measuring installations;

Δυ _χ (ΐι, Δΐ) ι, Δυ _χ (ΐι, Δΐ) ₂ , Δ ² υχ (ΐι, Δΐ) ι, Δ ² υχ (ΐι, Δΐ) ₂ - the difference between the separated time intervals Δΐ by the two closest instantaneous values of the first and second axial differences in the electrical potentials of the transition process;

E (1sh) is the electric field strength of the dipole source, expressed in the equation for the case of a harmonic change in the magnitude of the electric field over time;

η is the coefficient of their induced polarization;

they solve the mathematical inverse problem and determine three electrophysical parameters inherent in each element of the medium: electrical conductivity σ0 caused by polarization η and the decay time constant of the potential difference caused by polarization τ, and three time sections are constructed from these parameters.

5. The method of marine geoelectrical exploration according to claim 4, characterized in that the fourth set of normalized electrical parameters independent of the current strength of the dipole source is calculated

DTSCH), DTs, (/,) _g

Δ ^ (ί ₀ ), DLSL and use it along with three others when solving the inverse problem.

6. A method of marine geoelectrical exploration, in which an electromagnetic field is excited along the axis of the sounding profile in the thickness of the medium under investigation, passing rectangular current pulses through it with pauses after each of them with the help of a dipole electric source, and with the help of located on the profile axis at different distances from the dipole the electric source of two three-point measuring installations measure the first and second differences of electric potentials, and two identical rectangular current pulse: one - when passing through the sounding point of the first three-point measuring installation, and the other - when passing the second, while measuring at the end of each current pulse the instantaneous value of the first axial difference of electric potentials and also in each pause after switching off the current pulse throughout the time of the existence of transient signals at discrete points with a constant time interval — instantaneous values of the first and second axial differences of electric potentials;