SU1329630A3 - Method of electromagnetic logging of rock and device for effecting same - Google Patents

Abstract

The disclosure is directed to an apparatus and method for determining dielectric constant and/or conductivity of earth formations surrounding a borehole. Electromagnetic energy is generated at a first location by transmitter T in the borehole and the relative attenuation thereof is detected at a second location in the borehole using a first or "close" differential receiver arrangement R1, R2. The relative phase of the electromagnetic energy is also detected at a third location in the borehole, the second location being between the first and third locations, by a second or "far" differential receiver arrangement R3, R4 located at the third location in the borehole. Means 100 are provided for determining the dielectric constant and/or the conductivity of the formations as a function of the detected relative attenuation and relative phase. In a further embodiment of the invention, the attenuation of the electromagnetic energy is also detected at the third location and then combined with the other information to obtain an "ultra deep" conductivity value. <IMAGE>

Description

a pair of receiver coils, and the phase comparator is connected to the second pair of receiver coils.

6. The device according to claim 5, characterized in that the first information processing channel includes a phase comparator connected to the first sampling and storage circuit for detecting and storing the relative phase of the electromagnetic field received by the remote receiving coil of the second receiver pair, phase comparator and the second circuit sampling and storage, either for detecting and storing the phase of an electromagnetic field received by the near receiving coil of the second pair of receivers, a unit for determining the difference between the stored phases, connected to the first and second sampling and storage schemes.

7. The device according to claim 5, wherein the second information processing channel includes an amplitude measurement unit and a third selection circuit 1; and and storage for detecting and storing the amplitude of the electromagnetic wave received by the remote device.

n

The invention relates to the study of the properties of rocks surrounding the well, in particular, to a device and method for determining the dielectric constant and / or specific conductivity of the rocks surrounding the well using high-frequency electromagnetic energy.

The purpose of the invention is to improve the accuracy of measurements of parameters of rock.

FIG. 1 shows a block diagram of a device; FIG. 2 is a block diagram of an amplitude comparator; FIG. 3 is a block diagram of a phase detector; in fig. 4 is a sectional view showing the lines of the equal phase of the electromagnetic WAVE; in fig. 5 is a cross-section of a well, which shows lines of equal amplitude of the electromagnetic wave in FIG. 6–8 are simplified models used to determine normalized phase and damping values 29630

the first receiver pair's front receive coil, the amplitude measuring unit and the fourth sampling and storage scheme for detecting and storing the amplitude of the electromagnetic wave received by the near receiving coil of the first receiver pair, as well as a ratio driver connected to

fourth and fifth sampling and storage schemes for determining the ratio of the stored amplitudes ..

8. The device according to claim 7, wherein the third information processing channel includes a second phase comparator and a fifth sampling and storage circuit for determining and storing the relative phase of the electromagnetic wave received by the remote receiving coil of the first pair of receiver, the unit for determining the difference between the stored phase determined by the near receiving coil of the second pair of receivers, and the stored phase determined by the remote receiving coil of the first pair of receivers connected to the fifth sampling and storage circuit.

neither; in fig. 9 is a graph of normalized amplitude and phase versus model diameter; in fig. 10 is a simplified algorithm for programming a computing device} in FIG. 11 is a plot of attenuation versus phase for various values of f and 6; in fig. 12 is a block diagram of the device option.

The device is designed to explore underground formations 1 intersected by well 2, which can be filled with air or drilling mud based on water or oil. The well may be open or closed non-conductive material. The investigated borehole d 3 is suspended in bore 2 on an armored cable 4, the length of which is almost equal to the depth of the well. The length of the cable is controlled by a device on the surface, such as a drum. Armored KAG) ol1, t uslP Shaets.y on blr LPan when lifting equipment 1 Yes 1: 0 nepxHocTi. r.oc. Ie measurements characterize the breed. Depth) is; ; (1 meteor. Roller 5, globersh-l. With gamoniyushim device glu And And, I; OTO

) .Ul JAPLE. TCIA SOURCE 11Nfo; A ai1I

about the depth.

Well bore d 3 may be presetted ;; a probe with a transmitter 6, a first or a short pair of transmitters 7 and 8, a second or a long pair of receivers 9 and 10. The transmitter and receivers 7-10 are preferably circular. The location of the transmitter in the well is labeled L,

1 m (JSTOPoJ A liai liapi liapi. Receivers - L, I /. Points and LT and L, denote the average levels of receiver pairs 7-10, respectively. Distance D., between the transmitter 6 and the pair of receivers 7 and 8 should be approximately equal half the distance D between the transmitter 6 and napoii receivers 9 and 10.

Transmitter 6 is excited by a circuit that includes a generator 11, which can be quantified and which GK 1 generates a high-frequency signal in the range of 10-100 MGP, preferably about 20 MHz. The output signal of generator 1I is amplified by amplifier 12 and fed to transmitter 6 through a matching balance circuit 1tur 13. Generator 14, which is desynchronized with generator I1, produces an output signal with a frequency different from generator frequency 11 by a relatively small amount, for example, 80 kHz. The output signal of generator 14 is mixed with the receiver signal in order to generate a new signal, the amplitude and phase of which correspond to the amplitude and phase of the signal from the receiver output, and the frequency is much lower (80 kg2), which greatly facilitates the determination of amplitude and phase.

Amplitude meter — Amplitude comparator 15 measures the relative attenuation of electromagnetic waves received by receivers 7 and 8, and generates an amplitude ratio signal / (L- / L,), where Ln and L are peak values of the amplitude. received by P; 1 ismki-1. 8 and 7 respectively. F: .KV: ib ;; ; the detector 16 measures the phase difference hs tdu -iju 1: magnetic and beam

ten

15

2963 (;

IS .1, ill) them: 1O .1 Om receivers 9 and 1P. L Daip: - In a variant, the output signals of receivers 9 and 10 can be received on the low frequency (amplitude comparator 17, ", (th; h, 1: used for measurements

with and with i x deep; specific pro-11

7I.

The generator and other devices of the device are placed inside the snapshot. The circuits, electrically, with conductors 18-20 of armored cable 4 are connected to the ground equipment, which includes the numeral device 21.

In ycTpoitCTse 21, the relative attenuation signal from the amplitude comparator 15 and the phase difference signal from the phase detector I (S are processed together. As a result, the dielectric constant f and the specific conductivity of the rock occurring on a certain club in the well under study are calculated. Similarly, Thus, the output signal of the amplitude comparator 17 can be processed along with the calculated dielectric constant value to calculate the superdeep conductivity value for the given formation. dielectric values (5V constant and conductivity are recorded by the recorder

25

thirty

rum

99

together with the signal from measure0

five

0

five

5. The device 22 accumulates a volume of information from the dielectric constant and specific conductivity of the rocks surrounding the well formation as a function of. depths, Computing recording and storage devices can be located far enough from the well.

FIG. 2 shows one of the variants of the amplitude comparator 15, the signal from receiver 7 is fed to the input of the first tuning and matching circuit 23, and the signal from receiving 8 is fed to the input of the second tuning and matching circuit 24, the outputs of the circuits 23 and 24 are amplified in preamplifiers 25 and 26. To facilitate the amplitude detection process, the outputs from the preamps 25 and 26 are connected to mixers 27 and 28, respectively, on the second inputs of which the signal is f, t 80 kHz from generator 14, i.e., the signal whose frequency

80 kHz more or less transmitter frequency. As a result of mixing these two signals at the outputs of the mixers, signals are generated that in amplitude and phase correspond to the signals received by the respective receiver, but the frequency of these signals produced by the mixers is 80 kHz.

27 and 28 are filtered by a band-pass filter to be performed similarly to FIG. 2, For

Frames 29 and 30, and then go through intermediate frequency amplifiers 31 and 32 to peak detectors 33 and respectively, signals that are the energy envelope of the wave are captured from the outputs of peak detectors. The outputs of the peak detectors are connected to the dividing circuit 35, which outputs to the core (line) 18 (Fig. 1) a signal corresponding to the ratio of the amplitudes of the wave received by the receivers 8 and 7.

FIG. 3 shows one of the variants of the phase detector 16 (FIG. O. The signals from receivers 9 and 10 are fed to the inputs of the tuning matching circuits 36 and 38, respectively. The output signal from circuit 36 passes through preamplifier 38, mixer 39, filter 40 and intermediate amplifier 41 Frequency. The signal from the output of circuit 37 passes through preamplifier 42, mixer 43, filter 44 and intermediate frequency amplifier 45. The outputs of amplifiers 41 and 45 are connected to zero detectors 46 and 47 From the output of detector 46, the signal goes to the switching input of trigger 48, and from the detector output ora 47 - at the entrance

15

To increase design efficiency, the comparator 17 may have common circuit elements with circuits 15 and / or 16.

FIGS. 4 and 5 show a well filled with a drilling fluid with a specific conductivity of 6 and a dielectric constant E, the penetration zone of the drilling fluid with a specific

20

ho

and the dielectric zone is unaffected by penetration of the drilling fluid, with

constant conductivity

) fp

and dielect30

conductivity C, a constant constant of 6,

FIG. 4 shows the general form of 25 lines of a constant phase of an electromagnetic wave emitted by a vertical magnetic dipole located at the starting point O. The lines of a constant phase practically have the shape of circles and reflect, for example, the fact that the phase phase between signals received in the points of the well designated G and G. correspond to the phase difference in the rock between the lines 50 and 51, t, e, mainly in the invaded zone. Similarly, the phase difference between the signals received at the points rj and G4 of the well corresponds to the phase difference in the rock concluded between 35

trigger irradiation 48. Zero detec- tions of lines 52 and 53, including the polotor, produce an output signal only when crossing zero in the positive direction.

Consequently, the output of the trigger 48 produces a pulse, the duration of which corresponds to the phase difference between the two signals. The output signal of the trigger 48 is fed to the integrator 49, the output of which is the signal from the core 19, i.e. An analog signal corresponding to the phase difference between the signals from receivers 10 and 9. When using downhole noise-compensating equipment from another side of the receivers, another generator can be placed, and pairs of receivers can be adapted for

switch and alternate change of functions depending on the switching of the transmitters.

The signals in conductors 18-20 can, if necessary, be converted to discrete signals before broadcasting them to the surface using conventional telemetry equipment.

Amplitude comparator 17 may

To increase design efficiency, the comparator 17 may have common circuit elements with circuits 15 and / or 16.

FIGS. 4 and 5 show a well filled with a drilling fluid with a specific conductivity of 6 and a dielectric constant E, the penetration zone of the drilling fluid with a specific

ho

and the dielectric zone is unaffected by penetration of the drilling fluid, with

constant conductivity

) fp

and dielect0

conductivity C, a constant constant of 6,

Fig. 4 shows the general form of 5 lines of a constant phase of an electromagnetic wave emitted by a vertical magnetic dipole located at the starting point O. The lines of a constant phase practically have the shape of circles and reflect, for example, the fact that the phase phase between signals received in the points of the well designated G and G. correspond to the phase difference in the rock between the lines 50 and 51, t, e, mainly in the invaded zone. Similarly, the phase difference between the signals received at the points rj and G4 of the well corresponds to the phase difference in the rock concluded between

0

su not affected by rock penetration, indicated by hatching. The difference in the nature of signal comparison contributes to the elimination of the influence of non-shaded areas.

FIG. 5 shows the points G, G, wells. Amplitude difference

g;

between the points of T,

iG

corresponds to

differences of amplitudes in the rock, lying between lines 54 and 55, so that the hatched areas (Fig. 5) designate areas of the rock that are not affected by penetration, the amplitude difference in which is represented by measurements at points G and G. The difference in amplitude between the points rj and G corresponds to the difference in amplitude in the zone of the rock that is between lines 56 and 57,

W. Klyuchayushchey - shaded rocks, not affected by penetration

Thus, the attenuation measurements carried out using the receivers located in the borehole depend on the properties of the rock located in another zone. The attenuation measurements allow one to sink deeper (both in the radial direction and in the direction parallel to the well) than the phase measurements. The attenuation values measured at points G and G are strongly dependent on the zone not affected by penetration, while the values of the phase difference at the same points depend on the penetration zone.

Consider a vertical magnetic dipole in a homogeneous medium with conductivity (J, magnetic permeability / -i, relative dielectric constant 5, the voltage at a distance of 4 from the source is expressed by

V (L) Kj 1 - JKL

Hi) Li

KL

constant value; source angular frequency; imaginary uniti is a complex constant distribution, defined by the formula

K2 j U) f d

jL-il- e with

(2)

where C is the speed of light; L - base of observations

K a + jb,

where a and b are the coefficients of the th number. Substituting (3) into (1),

V (L) K j s 1 - jaL + bL x

-bL

L

For a pair of spaced receivers located at points 1. and L, and being more distant from the transmitter than L,, the ratio of 1 to tel.nor attenuation is determined by the ratio

(five)

maybe express

) - to U ML (1 +

1 -1- L,

(aL,). )

(6)

Similarly, / V (L) / can be

+

expressed as

Kpw i-bL:

-

,

f (+ bLj (7)

+

From expressions (5) - (7) are relevant

+

rillbLi) .il (aLz.) yjf (L,., -bCS-i-i GA 1g G9 T7Tt 1

1 + LP,) 2+ (a1), 2

(eight)

+

To determine the relative phase between the radiation received by the two receivers, first calculate the phase angle Φ, the radiation perceived by the first receiver located at a distance L,

- (bUUj

one; arctg.- | - - -i Vbir

thirty

+ aL-,

Then

f arctg 1

+ aL

2

(9)

(ten)

Similarly, the phase of radiation perceived by a receiver located at a distance L, is

f ,, arctg -; - - aL ,. (eleven)

The relative phase or phase difference is expressed

4F p - (aCLj - L,)

H Ubb, 1 - ri + bL, - | x ,, s arctg (12)

Dependencies (8) and (12) are expressed in the indices a and b of equation (3). Using equations (2) and (3), justifying their real and imaginary parts, we get

but. .ll. (h) t

2ab lotff. (C) 50 A joint solution of equations (13) and (14) gives,

 . (and, ko) - -CT

(., o "--- b

W

(15)

1D (16)

These values a and b can be substituted in dependence (8) and (12) ..

at i

Suppose that the distances and LJ and the angular frequency ij are known. Since the rocks of interest to us are mostly non-magnetic, then. can be considered constant. Thus, if the attenuation and lf values are measured, the unknowns and b can be calculated from equations (8) and (12).

After the general equations have been obtained, it should be pointed out that in the embodiment of FIG. 1, attenuation information is obtained from the near pair of receivers 7 and 8, while phase information is obtained from the far pair of receivers 9 and 10. Thus, in equation (8), the distances L and L denote the distances from transmitter 6 to receivers 7 and 8 respectively. In equation (12), the distances L and LJ denote the distances from transmitter 6 to receivers 9 and 10, respectively. Typical values will be given below.

To obtain the knowledge; (and / or 6 from equations (8) and (12) and their recording) various equipment can be used, installed both in close proximity to the well, and at a considerable distance from it (it should be remembered that input values for these equations must be obtained from different pairs of receivers. For example, you can use a small universal calculator, the memory of which contains a table of values and 6 corresponding to specific values of attenuation and LF. This can be done, for example, by entering into equations (8 ) and (12 ) alternately and in pairs, the values of E and B. For each pair of input values, the equations are solved for attenuation and d f. Specific pairs of values and 4, which are used to obtain the attenuation values and f, are then entered in a table (Fig. 11). During the execution of work, when specific attenuation values and / jf are obtained on lines 18 and 19, the calculator searches for the corresponding table values of u.These values are then recorded by the recorder itself from the output of the computing device 21 (Fig. one).

A simplified programming algorithm for the device 21 for a full table is shown in FIG. 10. Pervon Chal 29630 O

The values of f and 6 are selected using block 58. Usually, the minimum possible values of and 6 are chosen as initial values. Block 59 performs the function of solving equations (8) and (12) for attenuation and iF values. The current values of g and 6, corresponding to the calculated

The Q attenuation and /) "values accumulate and this operation is represented by block 60. Then the value of B is stepwise changed. This operation is reflected in block 61. After this value is checked (rhomb 62), it is not determined whether it exceeds the current value is the maximum possible to use. If the current value has exceeded the maximum 20 but possible, then as a result of the operation indicated by rhombus 62, the signal Yes is generated, which enters block 63, which reflects the increment d. The current value and test (diamond 64) are examined to see if its value does not exceed the maximum possible value for use. If not, then the signal is returned to the input of block 59 and the whole set of values is again calculated (5 with a step change in b within the full range of possible values. This procedure continues until it reaches its maximum value at which the program ends and the whole table of values accumulates. at F. The graph itself shows the family of outputs by parameters, and 6. Obviously, if such a schedule is built once, then it can be used to adjust the values and b for any given pair of measurements of the output of the gauge and the terminal as well as simply to determine the output data graphically.

One can use the coincidence method with the tabular method.

gg using the least squares method. Another possibility lies in the solution of equations (8) and (12) by the method of successive approximations, given by some values, a.

then changing them, by matching the similarities of the solution. One can apply a specialized analog or digital calculator, at the output of which one can obtain data corresponding to the family of curves shown in FIG. 11. Thus, using the logging equipment described, it is possible to empirically obtain data for plotting FIG. eleven.

FIG. Figures 6-9 depict the wellbore surrounding rocks that influence the attenuation and phase changes. Consider “Other words” can be a table of values for dL / V / fCxy,

20

Dj) and a value table for V g (x D ..).

Zi

A grooved model (Fig. 6), in which 15 of the receiver X. with several values, shows a well 65 having a diameter of the diameter of the transition zone D. (including a mudcake) of 200 mm and filled with a drilling fluid with a dielectric constant j 70 and conductivity - 1, which is typical of a solution based on relatively fresh water. Washed area 66 of variable thickness has a dielectric constant.

) f5 11 and conductivity

6 63 Mr / m. Area 67, also having a variable thickness, is affected to some extent by penetration and is called a transition zone. Natural breed 68 has the following parameters: dielectric constant 5.2 m; The conductivity is 20 M (j / M. The average diameter of the transition zone is d, and its parameters smoothly change from one boundary to another, which is approximately reflected in this model in eight equal steps. The diameter of the fully flushed zone 66 is marked D and is part of the diameter of the transition zone is 67. In this model, it is 11/20 D. The dielectric constant and conductivity in different zones are shown by curves 69 and 70, respectively.

Consider next a transmitter made in the form of a coil 38 mm in diameter wound on a hollow mandrel and located along the axis of the well at an initial depth that we denote as X 0. Now consider the same coil that serves as a receiver and is located in the well at a distance X from the transmitter. With the selected average diameter of the transition zone D. at the selected frequency, for example 20 MHz, the magnitude of the phase angle of the voltage at the receiver location point x can be calculated) 1a using the equation After the table of values is compiled, you can consider the relative depth of investigation using measurements phases and amplitudes using pairs of receivers located at different distances. Before this, however, it is useful to consider the second and third theoretical models in order to obtain

30 reference line from which the normalized depth of research can be calculated. The second theoretical model (Fig. 7) has an intrusion area 71 of unorganized extent, i.e. zone 66 (fig. 6) is extended to infinity. Using the second model, you can create a table of values similar to the one described above, except that

40

In this case, all rocks are infiltration zones of infinite diameter, i.e. tables of values for / V./ f (x, D,) and for R (X., D), where Bn is the diameter g of the infinitely extended penetration zone.

Suppose now that a pair of distances, denoted by Xd, is chosen

50 X., on which receivers are located Using the table of values associated with the second model (Fig. 7), you can get the expected attenuation value, indicated and expected

55 is the value of the relative phase, indicated from the magnitude and phase of the voltage, taken from the previously compiled table for the distances Hu and X,

Maxwell’s work for the multilayer model using the recursive method, i.e. a calculation wire for the reflection coefficient at the far edge using a general wave equation, and then solving the successive problems for the reflection coefficients at successively approaching boundaries. Using this technique and changing the location of the receiver and the diameter of the transition zone, a table of voltage values and its phases can be compiled for each position. In other words, tables of values for / V / fCxy can be compiled

Dj) and a value table for V g (x D ..).

 receiver X. at several values of the diameter of the transition zone D.

/

After a table of values has been compiled, the relative depth of investigation can be considered using measurements of both phase and amplitude using pairs of receivers located at different distances. Prior to this, however, it is useful to consider the second and third theoretical models in order to obtain

reference line from which you can calculate the normalized depth of research. The second theoretical model (Fig. 7) has an intrusion area 71 of unorganized extent, i.e. zone 66 (fig. 6) is extended to infinity. Using the second model, you can create a table of values similar to the one described above, except that

40

In this case, all rocks are infiltration zones of infinite diameter, i.e. tables of values for / V./ f (x, D,) and for R (X., D), where Bn is the diameter g of the infinitely extended penetration zone.

Suppose now that a pair of distances, denoted by Xd, is chosen

X., on which the receivers are located. Using the table of values associated with the second model (Fig. 7), it is possible to obtain the expected attenuation value, indicated and the expected

the value of the relative phase, indicated from the magnitude and phase of the voltage, taken from the previously compiled table for the distances Hu and X,

13

/ VfeccJ

 7v,

f

01 bo.

. v, - i.

In particular, the normalized attenuation values,) and phases for receivers located

at points X.

  and x / and for average diaff .f

meters of the transition zone (, fig, o) are presented in the form

, Aab (Di) - Aatt A «bn (D,) -

Ayi

In the third theoretical model (Fig. 8), the penetration is absent and the characteristics of the rock lying around the well are dielectric constant ft and the specific dependence t. Using the third one, it is possible to create tables similar to those that were compiled for the second model, i.e. tables for iv. t I where Аа (В-) and,.) are obtained f (x, D,) and V-t g (x, D.), where. the original table (Fig. 6) I 15 according to the formulas

. .. h ab (Di) -iCott

. - - f:;: F:; g

Ya

(D) -1YY1 .. - /Ve(D.)r

20

25

thirty

D - refers to the absence of a tool, i.e. to the case in which there is only natural rock around the well. Assuming that the pair of receivers is located respectively at distances x and x, it is possible, taking in magnitudes and phase angles of voltage for distances x, and x from the tables compiled earlier, to obtain the expected values of attenuation He, and phase a ot,

d

- -bf-7v;, / -.

 iVj, - If, for normalizing values, we take the obtained attenuation and phase difference values for the second model (unrestricted penetration zone) and for the third model (no penetration zone), then we can obtain normalized attenuation and phase shift values between receivers located at points x

their. Perform this operation, you can 40 1320 mm, and dashed lines and get an idea about the dependencies of the curves of dependences A, b and the depth of the study (in cases F., for a pair of receivers, is located - unrestricted zone of penetration and „Distance x 1900 mm and its absence”, without experiencing an excessively 2540 mm. These normalized effects of a particular 45 curves make it possible to make a number of observations of a parameter, for example, a specific conduction. First, we consider solid bridges (for example, specific conducted curves A and Φ. For a pair of receivers, these can give completely different distance over distances x 700 mm and dependences of 700 mm and x 1320 mm. Measurements of the difference and attenuation from the diameter attenuations lead to a significant meter of the transition zone for specifically deeper into the rock than measurements of the phased placement of the receivers, if not (f 4 and 5) to carry out normalization). The normalization operation allows us to get &amp; More When in the model (Fig. 6) D. the objective data on the depth of the study is approximately 1270 mm normalized, avoiding a strong influence the phase end is almost equal to one. These are specific values of the specific conductance — meaning that changes in the relative and dielectric constant of this phase at such a distance to the formation. Receivers produce almost such values of (01) (D.) - 0 „(П ).

From the expression for Ad (B.), it can be seen that the normalized attenuation value is one if Aa (0,) is equal to Ad, (the case of an unrestricted penetration zone), while the normalized attenuation value is zero if Aj, t, (D. ) equal to (the case of the zone unaffected by penetration). From the expression) it follows that the normalized phase phase is one, if D (D.) Is Dobo, and is zero, if Bd (0, -) is equal to One.

FIG. Figure 9 shows a plot of the normalized amplitude and phase 35 Apj, and Fd for various diameters for the model shown in Fig. 6. The solid curves reflect the Aflj, and ato pairs of receivers located at points Hc 700 mm and x

1329630

In particular, the normalized attenuation values,) and phases for receivers located

at points X.

  and x / and for average diaff .f

meters of the transition zone (Fig, o) where Aa (B-) and,.) obtained the original table (Fig. 6) 5 by the formulas

harvested in the form of

where Aa (B-) and the initial formulas

, Aab (Di) - Aatt A «bn (D,) -

Ayi

B-) and.) Obtained the initial table (Fig. 6) of llamas

a (B-) and,.) are obtained from the initial table (fig

. .. h ab (Di) -iCott

. - - f:;: F:; g

Ya

(D) -1YY1 .. - /Ve(D.)r

1320 mm, and the dashed lines show the curves of dependences A, B, and F. For a pair of receivers, located —– —– distances Xd 1900 mm and 2540 mm. These normalized curves allow us to make a series of observations. We first consider the solid curves A, and φ. for a pair of receivers located at distances x x 700 mm and x 1320 mm. Attenuation measurements are guided significantly deeper into the rock than measurements of ph- (ф 4 and 5). When in the model (Fig. 6) D. is approximately 1270 mm, the normalized phase value is almost equal to one. This means that changes in the relative phase at such distances to receivers give almost such values of (01) (D.) - 0 "(П).

From the expression for Ad (B.), it can be seen that the normalized attenuation value is one if Aa (0,) is equal to Ad, (the case of an unrestricted penetration zone), while the normalized attenuation value is zero if Aj, t, (D. ) equal to (the case of the zone unaffected by penetration). From the expression) it follows that the normalized phase phase is one, if D (D.) Is Dobo, and is zero, if Bd (0, -) is equal to One.

FIG. Figure 9 shows a plot of the normalized amplitude and phase Apj, and Fd for various diameters for the model shown in Fig. 6. The solid curves reflect the Aflj, and ato pairs of receivers located at points Hc 700 mm and x

15.3

relative phase, as in the case of unlimited zone of penetration. Thus, phase changes usually do not swallow deeper than 1270 mm into the penetration zone, since the curves show that at a depth of more than 1270 mm, the results are practically the same as for an unrestricted penetration zone at such distances to receivers . Thus, for a penetration zone of 1270 mm or more in depth and for the parameters of the model of FIG. 6, the phase measurements are practically unaffected by the presence of the natural rock penetration zone. On the other hand, from the solid curves for the standard attenuation values, it follows that for 1270 mm, the measured attenuation value approaches a normalized attenuation value of not less than 0.3. This means that the attenuation values with a penetration diameter of 1270 mm are still under the significant influence of natural rocks. As can be seen from the curve, the normalized attenuation value approaches unity only when the penetration depth is 2000 mm, i.e. the effect of natural rocks ceases to have an effect on the attenuation measurement results with the model parameters of fig. 6 only at a penetration depth of about 2000 mm.

The dashed lines, respectively, reflecting the normalized values of the phase decay f g for a pair of receivers located at distances of mm and x) 2540 mm, also show that the attenuation measurements are deeper than the phase measurements. For example, when the diameter of the injected zone D is 2000 mm, the normalized phase value is approximately equal to unity, i.e. the measurements are carried out almost completely in the penetration zone. In contrast, the normalized attenuation value is still almost zero, which means that the attenuation measurement at this penetration rate is determined by natural rocks.

The curve for the normalized phase values when placing the receivers at distances x ,, 1900 mm, x, 2500 mm and the curve for the normalized attenuation values when placing

9630

receivers at distances x 700mm and X, 1320 mm coincide quite well over the entire range of penetration diameters. The curves also give a good match in the range of diameters of the penetration zone for different models with different parameters and other transition zone profiles (this

10 fact is established by calculating curves for various models). The specific distances given are for the preferred option, but various options are possible. For example,

15, the choice of the distance depends in part on the choice of operating frequency. It should also be borne in mind that it is possible to calculate other families of curves from which one can choose coinciding.

0 When choosing an operating frequency, consideration should be given to a number of considerations. As the frequency increases, the energy absorption by the rock increases, as a result of which the level of the received signal decreases. In addition, as the frequency increases, the depth of investigation decreases. However, at higher frequencies, the conductivity has a smaller effect on

0 the measurement results and the resolution of the dielectric measurement is increased. In connection with the foregoing, the frequency is selected in light of these conflicting conditions. A frequency of about 20 MHz provides a fairly good resolution when determining the dielectric constant, despite the fact that the signal at the input of the receivers is sufficient for taking measurements at a satisfactory depth of investigation.

The choice of the distance to the receivers also depends on a number of factors. However, the choice of these distances

g leaves some freedom. In this regard, the reasoning below regarding the choice of preferred distances to receivers should be considered as an example. In order to obtain the maximum depth of investigation, the distant receiver 10 should be positioned as far as possible, as far as the design and operational conditions allow. When choosing the location of this receiver 10, the limiting factors are the physical logging device of the logging device (which should go well inside an uneven well)

five

0

17

and attenuation of the signal at a selected distance to the receiver 10. Taking these factors into account, the distance from the transmitter to receiver 10 is chosen to be 2540 mm, at which the level of the signal received in relatively well-conducting rocks is close to the minimum threshold of the signal. Then the location of the receiver 9 of the far pair of receivers is selected. In order to obtain good resolution when measuring phase and / or attenuation, receiver 9 should be located sufficiently

The position between the receivers of the near pair is chosen almost the same as the distance between the receivers of the far pair, i.e. about 640 m so both pairs have approximately one ac resolution

FIG. Figure 11 shows a plot of the attenuation versus phase at different values and 6, plotted for the preferred placement of prints 7 and 8 (685 mm, 1320 mm), 9 and 10 (1900 mm, 2540 mm) in accordance with FIG. 8 and 9. Curves can be

ten

far from the receiver 10. On the other hand, 15 are calculated from equations (8) and (12)

The ROS distance from the receiver 10 should not be too large so as not to introduce ambiguity into the phase measurements. So, spacing for too long a distance impairs the destructive ability of logging, i.e. reduces the ability to distinguish rock characteristics varying over relatively short distances (for example, in the case of thin layers). In the described embodiment, the point of location of the receiver 9 is selected at a distance of 640 mm from the point of location of the receiver 10, i.e. at a distance of about 1920 Mrt from the transmitter. After the locations of the receivers of the far pair are selected, from which, in the basic version, the relative phase information is obtained, the locations of the receivers of the near pair are determined. It is desirable to select these points in such a way that the depth of the relative attenuation measured by the receivers of the near pair coincides with the depth of the relative phase of the receivers measured by the receivers of the far pair. The above described methodology for presenting a normalized depth of investigation for different cases of the location of pairs of receivers for a theoretical generalized model can be successfully used to achieve such a match.

Placing the receiver of the near pair (Fig. 9) at a distance of 685 and 1320 mm from the transmitter provides a fairly good match (within the range of possible diameters of the transition zone of average size) of the depth of the attenuation study using the receivers 7 and 8 with the depth of the relative phase exploring using the receivers 9 and 1C. In this case, the ras29630 18

The position between the receivers of the near pair is chosen almost the same as the distance between the receivers of the far pair, i.e. about 640 mm, so both pairs have approximately one resolution

FIG. Figure 11 shows a plot of attenuation versus phase at various values and 6, constructed to preferentially accommodate receivers 7 and 8 (685 mm, 1320 mm), 9 and 10 (1900 mm, 2540 mm) in accordance with FIG. 8 and 9. Curves can be

ten

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for f and b for each pair of attenuation values and j f, the solution of which is carried out in accordance with the algorithm shown in FIG. 10. In particular, in equation (8), the distances L and L are 685 and 1320 mm, respectively (since the closest pair of receivers is used to obtain attenuation information), and for equation (12), the distance 1, and Lj, respectively, is 1900 and 2540 mm (since far-pair receivers are used to obtain phase information). As described above, the original values. and 6 (in accordance with the algorithm of FIG. 10) are entered into the computing device 21. Then the tables are viewed by the attenuation and LF values present on the lines 18 and 19 and the output is the E and 6 values for recording. For this purpose, an iterative method, a curve matching method or an analog transmitter can be used. Another aspect of the invention is ultradepth determination of conductivity using receivers 9 and 10. To do this, it is necessary to determine the dielectric constant rock, i.e., using attenuation measurements using the near pair of receivers 7 and 9 in combination with With the help of the far pair of receivers 9 and 10 and substituting the measured values in equations (8) and (12), we obtain the value of the dielectric constant (dielectric permeability) of the rock. Next, taking f into a known value and substituting the attenuation value measured with the aid of a far pair of receivers and the distance between receivers 9-10 instead of 7-8 into equation (8), the conductivity 6 is calculated, which in this case is designated 6. It should be remembered that the substitution in the equation for (the value of the dielectric constant refers to rocks that lie less deep than those rocks to which the attenuation measured by the distant pair receivers 9 and 10 is related. However, in most cases this does not lead to significant percentage error in determining f,

FIG. 12 depicts one embodiment of the invention in which the attenuation and phase information from each of a plurality of receiver pairs is processed by a single processing channel. The measurement of the amplitude and / or phase of a wave received by one of the receivers of a pair is carried out by one of the processing channels connected to the receiver in question. The obtained amplitude and / or phase value is recorded and stored in the same processing channel is connected to another receiver of this pair. The amplitude and phase values obtained as a result of processing information from the second receiver are recorded and the two filled phase values are then used to determine the attenuation value and / or the relative phase difference of the waves received by a particular pair of receivers. FIG. a diagram is shown which is used to measure the attenuation and phase difference for each of the three pairs of receivers, namely 7 and 8, 8 and 9 and 10. This scheme is applied to the generalized case where any or all of the values obtained can be used in accordance with the invention. In some cases, not all information may be required and, accordingly, only a part of the circuit and part of the outputs can be used. You can use either the outputs on the recorder, or on the computing device 2 1. The embodiment shown in FIG. 12 also allows one of the parameters to be replaced, usually obtained from a remote receiver by a parameter received from a near receiver, which may be required if the information from this remote receiver does not meet a certain standard.

Such a situation may occur in the case of rocks with relatively high

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conductivity, in which the signal received by remote receivers is too weak due to increased attenuation.

FIG. 12 shows the transmitter 6 and four receivers 7-10. These receivers have coils located at a distance from each other along the probe. In this embodiment, the transmitter is excited at 20 MHz by the signal from generator 72. The generator output through amplifier 73 and matching tuning circuit 74 is connected to transmitter 6. The time signals used to switch receivers and their circuits are obtained by dividing the frequency 20 MHz by 250 and then by 1000 dividers of 75 and 76 frequencies. The signal from the first divider then passes through a bandpass filter 77 and is converted to a rectangular by circuit 78. As a result, the output line 79 has a 80 kHz rectangular signal, which is fed to the input of phase detector 80. The signal on line 79 also goes to a divider 76 per 1000, from the output of which the signal goes to the generator 81 and to the output line 82. The signals from lines 83 and 82 are used in the receiver circuit. Phase detector 80 is part of the circuit that includes controlled oscillator 84 and frequency divider 85. The generator 84, controlled by voltage, has a nominal frequency of about 19.92 MHz, i.e. 80 kHz less than the oscillator frequency 72-20 MHz. A frequency of 19.22 MHz is divided by 249 in divider 85 to obtain a frequency of 80 MHz, and a signal of this frequency is fed to another input of phase detector 80. If a difference appears between the frequencies of two 80 MHz signals. An error signal appears at the output of the phase detector 80, which corrects the output frequency of the oscillator 84, controlled by the voltage, so that the difference between the frequencies of the oscillator signals 72 and 84 is maintained at 80 kHz.

The outputs of receivers 8 and 7 are connected to the input terminals of switch 86. In the same way, receivers 8 and 9 are connected to switch 87, and receivers 9 and 10 are connected to switch 88. Each of these switches 86-88 is designed to connect

211

one of its inputs to its output and switches are controlled by a time signal of 30 kHz on line 83. The outputs of switches 88-86 are respectively connected to the inputs of processing channels 89-91. Processing channel 89 includes a tuned tuned circuit 92 connected to a preamplifier 93 having a gain control input. The output of the pre-installed 1 body 93 is connected to the mixer 94, to another input of which a signal is supplied from LIKIN 95. This signal has a frequency of 19.92 MHz, which differs from the frequency of the transmitter by 80 kHz. In relation to the variant shown in FIG. 1, it was noted that this equipment facilitates the measurement of the amplitude and / or phase by the fact that detection occurs at a lower frequency, and the amplitude and phase of the received signal is preserved. The output of mixer 94 through a band-pass filter 96 of the proper frequency band, the average frequency of which is 80 kHz, is connected to the intermediate-frequency amplifier 97. The output of amplifier 97 is connected to a peak detector 98 and a circuit 99 generating a square wave signal. The output of the peak detector 98 is connected to the automatic gain control circuit 100, the output of which is connected to the control input of the preamplifier 93 as feedback. The output of the peak detector 98, which generates the signal of the envelope wave of electromagnetic energy, is received by the receiver to which the processing channel 89 is currently connected, is also connected to the storage device 101. The storage device has two selection and storage circuits 102 and 103 that select the input signal by controlling the time signal signals in lines 83 and 82. In particular, the selection and storage circuit 102 switches to selection of the input signal for positive signals in line 83, and circuit 103 is turned on by gigals of opposite polarity in line 82. Two outputs itrl 10 connected to the dividing circuit 104, an output signal which corresponds to an envelope filled with electromagnetic energy AI, the receiver being taken Yu, to the envelope wave received designated recipient 9, i.e. attenuation), OH means 11H (mu A.j ,,.,.

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The output (1D adapter or 97 is also connected to the circuit of 99 square signals, the output of which is connected to the detector 105 zero. The output of the detector is connected to the input of the installation Zero trigger 10.6. The switching input of the trigger 106 receives the signal from line 79, the Output SIGNN .1L of the trigger 106 is integrated by the integrator 107, producing an output signal that is proportional to the width of the output pulse of the trigger 106 and is accordingly proportional to the time of the excited

5 states of the trigger 106. The integrator 107 is returned to zero by the delay unit 108 under the action of both a positive and negative 80 kHz signal from line 83.

the output of the integrator 107 is connected to

drive 109, similar to drive 101 in that it also has two selection and storage circuits 110 and 111, which respectively

5 are switched to the selection by oppositely directed rectangular signals from lines 83 and 82. Two outputs of accumulator 109 are connected to a differential amplifier 112, generating an output signal, denoted d4 3.4. During operation, it is easy to see that f 3,4 corresponds to the phase difference between the received (- {by 9 waves of electromagnetic energy received by receivers 9 and 10). During the time that receiver 9 is connected to processing channel 89, the phase is measured relative to the reference signal which is the signal frequency

Q 80 kHz on line 79, which is related to the signal that excites transmitter 6. This reference signal sets trigger 106 and it returns to its initial state with a signal coming from channel 9 through channel 89. Thus, in each period of a square signal at 80 kHz trigger 106 produces an output pulse, the duration of which corresponds to the relative phase of the wave of electromagnetic energy received by receiver 9. The pulses are averaged by integrator 107 so that the value filled in selection circuit 110 and stored (neither accumulator 109, corresponds to the measured phase of the wave of electromagnetic energy supplied to the input of the receiver 9. If the processing channel is switched to the receiver 10, to set

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Trigger trigger uses the same reference signal again, but in this case it is reconstructed by the signal generated by the wave of electromagnetic energy received by receiver 10. The difference between these two phases is obtained by using a differential amplifier 112, the output signal of which is denoted by the index f 3,4.

Channels 90 and 91 can have a structure similar to that of channel 89. Determination of the dielectric constant and / or conductivity according to the method described above is usually done using signals and 1 f 3.4. FIG. 12 shows these signals, as well as the signal of the LF 2.3, transmitted through block 113 to the computing device 21 (Fig. 1), Block 113 turns on the switch 114, which connects to the device 21 either a signal f 3,4 or F 2,3 in depending on the output of the threshold detector 115. The output of the threshold detector 115 is supplied with a signal from the automatic gain control circuit 100, i.e. a signal corresponding to the amplitude of the energy wave received by receivers 9 and 10. If the system gain is automatic5

The gain control exceeds the predetermined threshold, the signal level at receivers 9 and 10 is considered to be insufficient, and an LF 2.3 signal is connected to the computing device 21. The output of threshold detector 115, which detects the state of switch 114, is also transmitted to the surface and recorded. So it is always known what a pair of receivers are used for.

To determine the attenuation, a differential receiver setup is used, as the preferred option, and direct amplitude measurement is also possible. Differential installation of receivers is preferred because it minimizes the effect of borehole effects on measurement results. The graph in Fig. 11 is applicable to wells of different diameters, while the corresponding graph of the phase difference versus amplitude (direct measurement) can be used to apply one specific diameter to the well and for each diameter of the well a different schedule is required.

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Editor G. Volkova

Compiled by N. Bibin

Tehred M. Khodanich Proofreader L. Patay

Order 3500/59 Circulation 730 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, Projecto st., 4

Claims (8)

1. The method of electromagnetic logging, providing for the excitation at a given point in the well of an electromagnetic field, measuring the attenuation of the field energy at the second point of the well and determining the dielectric constant and / or conductivity of the rocks, characterized in that, in order to improve the accuracy of measurements, the relative phase shift of the electromagnetic field measured at a third point between a pair of receivers or between a field meter located at the first point, and between a single receiver located at a third point, while the second the piece is placed between the first and third points, 2. The method according to p. 1, in which the dielectric constant and / or conductivity of the rocks is determined by measuring the attenuation of the electromagnetic field by means of a first pair of detectors located at a second point, characterized in that the relative phase shift of the electromagnetic field is measured by a second pair of spaced detectors placed at the third point. 3. The method according to π. 1, characterized in that the attenuation of the electromagnetic field is measured at a third point, which determines the conductivity of the rocks in the form of a function of the dielectric constant and attenuation. 4. Device for electromagnetic logging of rocks, containing a generator coil located at the first point of the well, a first detector coil connected to an amplitude meter to determine the attenuation of the electromagnetic field and placed g at the second point of the well, a second detector coil connected to a phase comparator for determining the relative phase of the electromagnetic field, and the unit for measuring the dielectric constant and / or conductivity of rocks in fixing the measured values of the relative phase and the attenuation of the electron a magnetic field, characterized in that, in order to obtain rock parameters from one depth relative to the well wall, a second detector coil is installed in the well at a third point, and the second point is located in the middle between the first and third points. 5. The device according to Π. 4, characterized in that the amplitude and phase detectors are made in the form of two pairs of receiving coils spaced a predetermined distance and placed respectively in the second and third points of the well, while the amplitude meter is connected to SU 1329630 A 3 pair of receiving coils, and the phase comparator is connected to a second pair of receiving coils. 6. The device according to claim 5, wherein the first information processing channel includes a phase comparator connected to the first sampling and storage circuit for detecting and storing the relative phase of the electromagnetic field received by the remote receiving coil of the second receiver pair, the phase comparator and the second sampling and storage scheme for detecting and storing the phase of the electromagnetic field received by the nearest receiving coil of the second pair of receivers, a unit for determining the difference between the stored phases, connected to the first and Ora sampling schemes and storage. 7. The device according to claim 5, characterized in that the second information processing channel includes an amplitude measuring unit and a third sampling and storage circuit for detecting and storing the amplitude of the electromagnetic wave received by the removed receiver coil of the first pair of the receiver, the amplitude measuring unit and the fourth sampling circuit and storage for detecting and storing the amplitude of the electromagnetic wave received by the near receiving coil of the first pair of the receiver, as well as a shaper, connected to the fourth and fifth circuits in sampling and storage to determine the ratio of stored amplitudes. 8. The device according to p. 7, characterized in that the third information processing channel includes a second phase comparator and a fifth sampling and storage circuit for determining and storing the relative phase of the electromagnetic wave received by the remote receiving coil of the first receiver pair, a unit for determining the difference between the stored phase, determined by the near receiving coil of the second pair of receivers, and the stored phase determined by the remote receiving coil of the first pair of receivers connected to the fifth sampling and storage circuit.