DE2440676A1 - METHOD AND DEVICE FOR DETERMINING THE ELECTROMAGNETIC PROPERTIES OF THE MATERIALS IN THE AREA OF A DRILL HOLE - Google Patents

Description

Patent assessor Hamburg, 15th - 8th 1974

Dr. Gerhard Schupfner 770 / ik _{/ n}

Deutsche Texaco AG "2440676

2000 Hamburg 13 T 74 057

Middle way 180

SUBSCRIBED

TEXACO DEVELOPMENT CORPORATION

135 East 42nd Street,. New York, N.Y, 10017 U.S.A.

Method and device for determining the electromagnetic properties of the area a borehole located materials

The invention relates to a method and a direction for determining the electromagnetic properties of those located in the area of a borehole Materials, in particular a method and a device for borehole measurement by means of high-frequency dielectric induction, where the, specific Y / resistance (or specific conductivity) and the dielectric constant the formation, clearly identifiable by a device for in-house measurements, which is in Borehole is carried out.

For many years it was common practice, the electric Properties of earth formations in the area of a borehole for the purpose of local determination to determine an oil-bearing horizon.

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This type of determination was through in the past the use of electrical resistance measurements in "bores with highly conductive (low spec. resistance) Borehole fluids and through the use of induction logging in boreholes made by means of oil-based drilling muds or drilling fluids with

possibly higher resistivities were drilled / · In normal borehole measurements that determine the resistivity, a current-emitting electrode or an electrode arrangement is used to focus the emitted current in order to inject either a direct current or an alternating current of low frequency (e.g. 60 Hz) into the surrounding area of the borehole Send formation via contact electrodes. These currents flow through an area of the earth formations and are determined at a current return electrode which is arranged at a certain distance from the electrode which emits the current. The size of the determined currents can then be taken as the value of the specific resistance of the earth formations in the area of the borehole. In some cases

with. the current electrodes are used in connection / potential measuring electrodes for the purpose of determining the resistivity of the formation.

In induction electrical measurements, it was in the past, common practice to use a measuring probe, which has a transmitter coil (or coil assembly) and disposed at a certain distance to the receiver coil.

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Usually a high frequency alternating current was carried through sent the encoder coil (usually at a frequency of around 20 kHz). The resulting electric fields in the earth's bma- tion, were about the Receiver coil determined as induction currents or ~ induction voltages ...

The usability of the two aforementioned systems resulted from the fact that with hydrocarbon molecules filled pore spaces of the earth formations have higher resistivity than earth formations, whose pore spaces are filled with either salt water or other conductive liquids.

Various problems arose in the interpretation the induction or resistance measurement record in Horizons 'containing' fresh water (with a sodium chloride content of less than 10,000 ppm). Such sands or earth formations containing fresh water show specific Resistances of almost the same level as formations carrying hydrocarbons. In these cases e.s very difficult, if not impossible, to be alone on the To determine on the basis of the measurement data whether it is a freshwater zone or a hydrocarbon zone. It would be It is therefore very welcome to provide a borehole logging system which is based on a single measurement of some physical properties of the earth formations in the borehole area between freshwater layers and hydrocarbons containing zones can distinguish. . ·.

The invention is based on the object of creating a method and an apparatus for making a distinction of freshwater layers and hydrocarbon-bearing layers in the borehole area, whereby a electrical borehole measuring system is to be created which is able to simultaneously measure the conductivity and to measure the dielectric constant of the earth formations in the borehole area and also an induction measuring system which operates at such high frequencies that the dielectric properties of the Materials surrounding the borehole influence the measurement together with the conductivity properties of these materials, the measurement of the dielectric properties and conductivity properties being relatively unaffected the geometry of the borehole, the conductivity of the drilling fluid used when the borehole was created or the Incidence of drilling mud filtrate from the borehole into the surrounding earth formation.

This problem is solved by a borehole measuring system that uses a dual high-frequency dielectric inductive ' tion measuring system included. In the logging system of the present invention, a logging probe is provided, which contains two different high-frequency dielectric measuring devices. The first high frequency dielectric Induction measuring apparatus has a 16 MHz single transmitter coil together with a receiver coil arranged a little further away from it.

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The second high-frequency dielectric induction measuring apparatus has a focused 30 MHz double transmitter coil and one of the aforementioned corresponding 16 MHz receiver coil on. At these high frequencies, the physical properties include those in the borehole area located earth formations, which the induced by the two transducer coils in these formations high-frequency alternating currents affect the dielectric constant (or absolute dielectric constant) of earth formations along with the conductivity properties (or resistivity properties) of these formations. By measuring the Amplitude of the received signal for each of the two High frequencies can affect the dielectric and conductivity properties of those in the borehole area Earth formations are determined. In order to carry out these measurements or to obtain these measured values, the Device created that also provides an interpretation of the measured at the two high frequencies Enables signal amplitudes.

An embodiment of the invention, from which follows inventive features result is in the drawing shown. Show it: ·

Fig. 1 - a schematic overall view of the device in block form,

FIG. 2. - a schematic block diagram of FIG

underground transmitter and receiver equipment,

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Fig. 3 A and 3 B circuit diagrams of the high-frequency

Transmitting and receiving equipment,

4 - a theoretically obtained graphical representation of the amplitude curve a 64 MHz single high frequency induction probe for borehole diameters from 0 to 0.35 meters,

5 - a theoretically obtained graphical representation of the amplitude curve a 130 MHz single high frequency induction probe for borehole diameters from 0 to 0.4 meters,

Fig. 6 - a theoretically obtained coordinate representation of the amplitude of a 16 MHz single high frequency induction probe and a focused 32 MHz dual high frequency induction probe (similar to that shown in Fig. 1), wherein the probe was embedded in a homogeneous material, and

Fig. 7A - :: 7D theoretically obtained coordinate representations the amplitude of high-frequency induction measurements using a double-frequency probe (similar to the shown in Fig. 1), which originate from boreholes with a diameter of 203.2 mm and 304.8 mm

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land in a fresh water sludge and an oil-based slurry.

Hydrocarbons have a characteristic low dielectric constant £ _r , which is less than 5. Fresh water, on the other hand, has a relatively high dielectric constant <5 _r of approximately 80. The dielectric material constant O, is defined as the natural electrical polarization of this material. In the following description, the terms "relative dielectric constant" and "dielectric constant 6" _r "are used with the same meaning. This quantity is based on the absolute dielectric constant of free space £ by the relationship according to equation 1:

in which ^ ₀ = 8.854 pF per meter, the absolute dielectric constant of free space,

According to the electromagnetic field theory and in particular according to the theory of a point-shaped oscillating magnetic Dipole, can express the behavior of high-frequency fields in the area of a cylindrical borehole are according to equation 2 (which represents the Helmholtz equation with the usual cylinder coordinates £, 0 and Z).

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±
β te,

7 ^(w)

(m)

in the V / _ den hertz'sehen magnetic Dektor, J / _m \

- ■ represents the magnitude of the current and j =] / - 1.

K is the complex circular wavenumber, expressed by, the Equation J5i

K = W ^ AtC + 0 WXtO ^

In equation 2, the values α and <* ( _z ) represent Dirac's momentum functions.

W = 2 Wf, where f represents the oscillation frequency of the point magnetic dipole.

is the dielectric material constant.

JU is the designation for the magnetic induction coefficient of the material surrounding the magnetic dipole and (~ jf the designation for the electrical

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Conductivity of the medium.

It should be noted that three physical constants are associated with the material surrounding the point magnetic dipole in the aforementioned equations. These constants are the relative magnetic. Induction coefficient / t, the material constant C and the electrical conductivity 6 *. For most earth formations, the magnetic induction coefficient A * can be assumed to be constant in a frequency range of interest - from 10 to 60 MHz. Variations in this coefficient in the materials of interest fall essentially within a range of 0.001 to 0.1 % . Thus, only the other two constants S and (o show significant changes when changing from one formation material to another at the frequencies in question. These two physical properties have a direct influence on any high-frequency alternating current flowing in the media. Both these physical properties of the media have an effect on the size and phase with respect to the donor of these formation-induced or eddy currents.

Assuming a point magnetic source in a cylindrical borehole and with reference to the Helmholtz equation, the total field is defined as that field of the source that is generated by a receiver coil

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in any medium. The whole field .can be divided into a primary field and a secondary field. The primary field is defined as that field the source, which is determined by the receiver coil in some reference media (e.g. in a vacuum or in air) was, The secondary field is defined as the field that, when vectorially added to the primary field, makes up the total field forms. The primary field has · - an amplitude and a Phase that is equal to the amplitude and phase of the total field in the comparison medium. Is the probe in one If a medium is placed that differs from the comparison medium, the secondary field is added vectorially to the Primary field and creates the total field within the new medium. The primary field serves as an amplitude and phase comparison for determining the secondary field.

The currents that flow in the medium surrounding the punctiform magnetic dipole are called eddy currents. The eddy currents generate secondary fields which, in the case of a highly conductive medium, act against the primary or comparison field. However, if V / £ (angular velocity of the operating frequency multiplied by the dielectric constant) approaches the size of (& (the electrical conductivity), the eddy currents are out of phase and can actually deflect into secondary fields which increase the size of the total field. when working at frequencies that essentially include the high frequency range from 10 to 60 MHz.

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Since changes in the two values of C and G / cause changes in eddy currents at any given frequency, measuring a single amplitude cannot separate the effects of the two effects. In accordance with the principle of this invention, the measurement of the amplitude of the total field at two different frequencies f.- and fp can be combined to simultaneously obtain the values <5 and Q? to be able to derive. Other techniques can also be used for this purpose, but they are not intended to be discussed in the context of this application.

The Helmholtz equation (equation 2) applies to every cylindrical Location of a layered medium that surrounds the point-shaped magnetic dipole in the borehole. at Use of a computer program to carry out numerical Integration of the solutions of equation 2 in different cylindrical positions around the dipole and when applied of boundary conditions at the interface of these regions and at the source, this can be done by a distance Z along The total field offset from the borehole axis from the magnetic dipole can be derived at the receiver coil.

By investigating the numerical solution of the Helmholtz equation (Equation 2) in boreholes of different diameters, graphical representations of the field amplitude can be made on the receiver coil as a function of the borehole diameter for different borehole sizes.

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Such a graphic representation is shown in FIG. 4 for a 64 MHz single ^{transmitter coil and receiver system and for a 32-1 1} IHz double transmitter coil and single receiver coil system. It can be seen from Fig. 4 that at a 64 MHz frequency, an abnormal resonance effect occurs at a borehole radius of about 254 mm. It can also be seen that the 32 MHz double walker coil amplitude frequency does not exhibit this resonance effect with appropriately large boreholes.

Fig. 5 shows a graph of the normalized total field amplitude at the receiver coil on the z-axis of the borehole as a function of the borehole radius for an operating frequency of 130 MHz. In this The case shows the resonance effect with a borehole radius of about 100 mm and again with a borehole radius of about 250 mm. So should try to ground the dielectric and conductivity properties of the To measure the materials surrounding the borehole at frequencies as high as 64-MHz, it is from the graph 4 and 5 it can be seen that some corrections are necessary for these resonance effects. On the other hand it should be remembered that · for the purpose of. determination the electrical conductivity and the material constant (or the dielectric constant) of the borehole surrounding materials, measurements of the amplitude of the received signal at at least two different Frequencies for the purpose of interpreting the resulting

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Amplitude measurements in the values of the dielectric constant £ and the conductivity (j of the materials surrounding the borehole must be carried out. In order to avoid the resonance effects shown in FIGS Theoretical calculations showed that measurements at these frequencies are more accurate than those made at higher frequencies due to the resonance effect in the borehole -MHz are similarly not insensitive to errors that could occur due to the eccentric arrangement of the probe in the borehole.

1 shows a dual frequency induction dielectric borehole logging system schematized. A borehole probe 11, the probe body of which is preferably made of fiberglass material or another non-conductive material with sufficient strength properties depends on a measuring cable 12 in an uncased borehole 13. The borehole 13 is filled with a borehole fluid 14 and surrounded by earth formations 15, whose dielectric., and conductive properties are to be measured.

The lower part of the borehole probe 11 has an electronic transmitter part 16 and associated transmitter coils 17, 18 and 19, which are wound around a central winding mandrel 20.

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This winding mandrel 20 is preferably also made of a non-conductive material. The encoder coil 17 operates at a frequency of 16 MHz and is described in more detail below. The encoder coils 18 and 19, which are helically wound in opposite directions to produce a reversed polarity pair have a focussed or double transmitter coil arrangement operating at a frequency of 30 MHz is working. A receiving coil 21 is in a longitudinal direction of the borehole probe 11 is located away from the transmitter coils and sits approximately one meter from the center of the 16 MHz encoder coil 17 removed. The receiver coil 21 is approximately 81.28 cm from the center of the 32 MHz transducer coil pair 18.19 · arranged away, the centers of which are in turn 10.32 cm apart. It is evident to the person skilled in the art that other coil distances between the transmitter and receiver coils are also possible and are within the scope of the invention.

The radial depth of investigation of the borehole measuring system is influenced by the distance between the transmitter and receiver coils. In general, it can be said that the greater the distance between the transmitter and receiver coils, the greater the distance greater is the radial depth of investigation in the earth formation. It should be noted, however, that it it is necessary to arrange the transmitter and receiver coils close enough together in order to receive usable signal levels of earth formations of different dielectric

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· ^Γ; _ 15- 2440076

and conductive properties / to ensure. As a highly conductive Material in the borehole area is the high-frequency Attenuates signals, it is necessary, "a '" higher ^ energy Im Use the encoder part if the distance is between Transmitter and receiver coils enlarged Λδΐ ..

A conventional host arrangement ^ 22; is provided on the surface of the earth for the movement "of the :: Bohrlo: ch ^ Sonde-i1? 1 through the" borehole during measurement ". IBie; Wind.e; 22 can be electric or mechanically imitating devices 24 and 25 or measuring devices 24 and 27, which record the signals from the borehole probe as: function of the depth of borehole 13, such as through the dashed line 23 is indicated. The energy required for the precision work of the receiver electronics arranged in the borehole probe 13 is supplied via lines in the measuring cable 12 from an overactively arranged energy source -28. The electrical measurement signals, which are determined by the receiver electronics 36, are amplified by an input amplifier 29 and forwarded by this to signal processing circuits 37 or 38 *

The receiver output signals of the receiver electronics 36 are described in more detail below, but it can generally be stated that these signals are two amplitude measurements which are transmitted via lines of the measuring cable 12 and are arranged in the above-ground ^ Processing facility separated by frequency discrimination will. *

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This means that the amplitude information of the one working frequency is transmitted via the measuring cable 12 with a first intermediate frequency f., And the amplitude information of the second working frequency is transmitted _{via the measuring cable 12 with a second intermediate frequency f 2.}

Upon closer inspection of the signal processing circuit 37, it can be seen that the double-frequency input signal from the measuring cable 12 is amplified by the input amplifier 29 and fed to a signal splitter circuit 30. The signal splitter circuit 30 can have high-frequency filter devices, for example those which split the signal into its two frequency components f., And $. The signal of frequency f. Is transmitted to an amplitude detector 31. The information contained in the amplitude is then fed to a recording device 24 which records the amplitude with the frequency fp as a function of the borehole depth. The second amplitude detector 32 determines the amplitude information, which is determined with the frequency fp and then fed to the second recording device 25, which also records this information as a function of the borehole depth.

Alternatively, the arrangement of the signal processing circuit 38 can be used. In this signal processing circuit 38, the double frequency input signal a signal splitter circuit 33 which is similar to the signal splitter circuit described above 30 is formed, and in two different intermediate

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frequency components f ^ and fp divided. An analog / digital circuit 34 is used to determine the amplitude generated at the frequency f * and to convert this signal into digital form The digital signals generated by the analog-to-digital circuits 34 and 35 can then be fed to a computer 39, such as a PDP 11 computer from the Digital Equipment Company of Cambridge, Massachusetts. The information entered into the computer 39 can then be output, using an appropriate program, directly in the form of values which indicate the specific resistance and dielectric constant of the earth formation surrounding the borehole 13. The output signals of the computer 39 can be fed to the digital recording devices 26 and 27 as a function of the borehole depth. The type of determination of the specific The resistance and the dielectric constant within the computer are explained in more detail below.

In Figure 2, in schematic block form, is the downhole probe 11 together with the transmitter and receiver electronics. From a battery 51 and a regulator 52 a direct current voltage is used to apply the Encoder circuits out. The transmitter circuit for the 16 MHz transmitter coil contains a crystal-controlled one

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Oscillator 53 operating at the encoder frequency of 16 MHz is working. The output of the oscillator 53 is connected to a control circuit 54 whose "gain in takes place in a manner explained in more detail below. The amplified .16 MHz output of the control circuit

54 an amplifier stage 55 is supplied to the ert the signal to a ^RT of approximately one watt amplified.

The 16 MHz output of the amplifier stage © 55 is via a Balun 56 coupled to the transmitter coil 17. The encoder output current in the balun 56 is a Encoder winding 58 monitored and by a direct current - ^ - Circuit 59 detects which generates an output signal that is used by the power control circuit 60 for controlling the Amplification of the control circuit 54 is used. In this way there is a constant output current at the Amplifier stage 55 for transmitter coil 17 is generated.

The 30 MHz encoder circuit has a crystal controlled Oscillator 61, which operates at a frequency of 30 MHz and - transmits a 30 MHz output signal to amplifier 62, which amplifies the signal to a value of approximately one watt. The 30 MHz output from amplifier 62 is via a balun 63 and shielded lines 67 and 68 with coils 18, 19 of the 30 MHz double encoder coil tied together. The dual encoder coils 18, 19 are also housed in electrostatic shields 69, 70. The output current of the amplifier 62 is monitored via a transmitter winding 64 in the balun 63 and connected to direct current

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Current detector 65 transmitted. The output signal from this detector 65 is connected to a power control circuit 66 applied, which applies a control voltage to the supply -. stronger 62 and to the crystal controlled oscillator '61 gives away. In this way, the output current of the 30 MHz encoder is kept at an approximately constant value.

The operating voltage for the receiver circuit shown in FIG. 2 is generated by a controlled current source 71 which generates a voltage of £ 15 volts. The input current of the current source 71 is supplied via lines in the measuring cable, which are acted upon by the surface current source. The receiver coil 21, which is also arranged in a shield 72, simultaneously receives signals from currents which have been induced in the formation by the 16 MHz transmitter arrangement and the 30 MHz transmitter arrangement. The received signals emanating from the two transmitter arrangements are fed from the receiver coil 21 via a signal splitter circuit 73 to receiver electronics. The signal splitter circuit 73 has a. Secondary windings that are matched to the 16 MHz and 30 MHz frequencies of the received signals. The signal from the 16 MHz winding of the signal splitter circuit is sent to a mixer lh . The mixer 74 is also connected to a crystal-controlled oscillator 75, which emits an output signal - (16, .010 MHz). After the mixing has been carried out in the mixer stage, a signal is generated in a first intermediate frequency range

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of approximately 10 KHz is fed to amplifier stages 76 and 77. Likewise, the signal is from the 30 MHz winding of the signal splitter circuit 73 is fed to a mixer 78, which also has a crystal controlled oscillator 79 is connected and from this with a 30.025 MHz output signal is applied. After the signal has been mixed in the mixer 78, an output signal in emits an intermediate frequency range of approximately 25 KHz, which is fed to the amplifier stages 80 and 81. The 10 KHz output signal of amplifier stage 77 and the 25 KHz output signal of amplifier stage 81 are both one Summing amplifier 82 supplied to the two aforementioned Output signals added and a corresponding output signal to a conductor in the measuring cable 12 for forwarding transmitted after days. This sum signal sent after the carry thus contains the amplitude information of the signals received by the receiver coil 21 from the formation currents transmitted by the transmitter coils' (16- and 30-MHz) were induced.

The circuit shown in block form in FIG. 2 is shown in greater detail in FIGS. 3A and 3B. In Fig. 3B is a regulator 52 is drawn, which regulates the voltage of the battery in a temperature-compensated manner. The controller 52 has a Working amplifier 83, a transistor 84, a diode 85 and a sensistor 86. The controller 52 is used for the maintenance shark Creation of a +15 volt comparison voltage of the 32 volt battery 51, while the control circuits are in working position are.

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It is understandable that the battery voltage of the battery 51 can vary in the operating position of the transmitter circuits. Keeping the + 15-volt DC voltage constant ensured by the regulator 52 by means of a comparison voltage. This equivalent stress is in 'the Encoder circuits, as explained in more detail below, used. The 16 MHz crystal controlled oscillator 53 of Fig. 2, as seen in Fig. 3B, includes a transistor 87, and a 16 MHz crystal 88 and associated Switching components. The crystal 88 is connected to a control circuit (in Fig. denoted by the reference number 54), which has a transistor 90 and associated switching elements, connected. The amplified output of transistor 90 "is also Connected via a transformer 91 to an amplifier stage, which has a transistor 92 'and the associated Has switching elements. The amplifier stage including transistor 92 produces an output value of approximately one watt at 16 MHz. This output signal is one thing with the 16 MHz transmitter coil 17 via the balun 56 Has bifilar winding connected. This balun 56, which is designed as a converter, is a Impedance matching device, which the output signal of the amplifier stage 55 (Fig. 2) to the impedance of the transmitter coil 17 (approximately a 4: 1 impedance conversion). The use of a Symmetriergleides 56 enables the Transmitter coil 17 to work ungrounded instead of any Point of the coil to have an earth return. -.- ■ -

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However, the shield 57 of the transmitter coil 17 is grounded, so that only the emitted output signal of the transmitter coil itself the earth formation surrounding the borehole achieved. The encoder winding 58 is placed at the center tap of the bifilar winding of the balun 56, which is designed as a toroidal transformer and determines the current. A circuit for discovery a peak value, which includes a diode 93 and a resistor 94, is connected to the output of the encoder winding 58 connected and performs the function of the DC circuit 59 of Fig. 2. The peak voltage, the proportional to the current in the bifilar winding of the balun 56 is determined in this way and transmitted to an input of a working amplifier 95. A comparison voltage is sent to the other input of the Working amplifier fed from the potentiometer 96. Everyone Difference between the equivalent voltage from the potentiometer 96 and the peak voltage from the encoder winding 58, is amplified by the working amplifier 95 and the base voltage-controlling transistor 96 A supplied to the Function of the power control circuit 6O in FIG. 2 fulfilled. Since the battery voltage of the battery 51 is the Collector of transistor 90 via the voltage-controlling Transistor 96 A is fed, controls the base of the The control signal fed to transistor 96 A determines the level of the voltage fed to the collector of transistor 90. This increases the gain of the control circuit containing transistor 90 and the associated switching elements.

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circle to a value as determined by the encoder winding 58, maintained to a constant Output current from the transistor 92 and its associated To generate switching elements containing amplifier stage 55.

The crystal controlled oscillator 61 comprises a transistor 97 and a 30 MHz crystal 98 '. The 30-14Hz output signal of the oscillator is coupled via a transformer 99 to an amplifier stage containing a transistor 100 ′ and associated switching elements 100 with the associated switching elements corresponds to the amplifier stage 62 according to FIG. 2 and serves for the direct amplification of the signal from the 30 MHz oscillator a value of about one watt. The output signal from transistor 100 is connected to the 30 MHz transmitter coil 18, 19 About the bifilar winding of the balun 63 and the shielded lines 67 and 68 connected. That with the Bifilar winding provided balun 63 serves as Impedance matching device between the amplifier stage and the transmitter coils 18 and 19 (with an approximate Impedance conversion of about 4: 1). The output current of the transistor 100 is supplied by the balun 63 via a transmitter winding 64, which corresponds to the encoder winding 58. The one generated in the secondary winding of the encoder winding 64 Peak voltage is detected by a circuit comprising a diode 101, a filter circuit 106 and a resistor 102 and the direct current ^ f -Detector .65 in Fig. 2 corresponds. This peak voltage, which is proportional to the output current of transistor 100, becomes

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fed to an input of a working amplifier 103. A signal that is proportional to the difference between the Comparison voltage and the peak voltage that is determined in the secondary winding of the encoder winding 64, is generated at the output of the working amplifier 103 and the base of a transistor controlling the series voltage 105 supplied. As the working voltage for transistor 97 of the oscillator and transistor 100 for the amplifier stage is given via the aforementioned transistor 105, controls the output signal from the working amplifier 103 the size of these voltages and thus regulates the 30 MHz encoder output in order to ensure a constant output current, how it is monitored by the encoder winding 64 to ensure. Here, too, the bifilar winding enables the Symmetrier 63 the transmitter coils 18 and 19 to work ungrounded, since the shields surrounding the transmitter coils 69 and 7Q are grounded.

The regulated working voltages for the receiver circuit are supplied by the controllable current source 71, which has transistors 107, 108, working amplifiers 109, 110, diodes 111, 112 and sensors 113, 114. The Sensi gates 113 and 114 are used for temperature compensation of the voltages generated by the power source 71 due to any temperature effects on the transistors 107 and 108 and the work amplifiers 109 and 110. The current source 71 is a regulated output voltage of - 15 volts DC for operation of the receiver -

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Circuit from, with the power source 71 .Its. Receives input voltage via lines of measuring cable 12. ·.

The locked measuring cable is designed as a triaxial cable and has an outer shield, an insulation layer, a coaxial shield, a second insulation layer and an inner conductor, as indicated in Fig. 3A. Of course, a corresponding other can also be used Find measuring cable use.

From Fig. 3A it can be seen that the two transducer coils 16 MHz and 30 MHz signals induced in the formation can be received at the receiver coil 21 housed in the electrostatic shield These combined signals are assigned to the signal splitter ^ ' Circuit 73 is supplied which has a high Q secondary resonant circuit for the 16 MHz and 30 MHz frequencies of the two Has encoder coils. The 16 MHz signal from the signal splitter circuit 73 is fed to a field effect transistor 115, which serves as a mixer stage, that of mixer stage 74 in Fig. 2 corresponds. The gate of the field effect: Transistor 115 is also on a 16.010 MHz signal applied to the one transistor 116, one Crystal 117 and associated switching elements having crystal controlled oscillator. That is because of the Mixing effect of the field effect transistor 115 occurring 10 KHz output signal is the temperature compensated Two-stage amplifier fed to the working amplifier 118 and 119 and associated switching elements, with the

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Has sensistors 120 and 121. Any drift in the working characteristics of the working amplifiers 118 and 119 is compensated by the action of the sensors 120 and 121. ·

Likewise, the 30 MHz component of the signal received at receiver coil 21 becomes the gate of a field effect transistor 122, which has the function of the mixer stage in FIG. A 30.025-MHz is used by a crystal controlled ones comprising a transistor 123 and a crystal 124 and associated switching elements Oscillator supplied, the 30.025 MHz signal is also supplied fed to the gate of the field effect transistor 122. · Due to the mixing effect of the field effect transistor 122, a 25 KHz output signal at the output of the field effect transistor 122 generated, which is fed to a temperature-compensated two-stage amplifier, which is controlled by sensistors 127 and 128 temperature-stabilized working amplifiers 125 and 126. The 10 KHz and 25 KHz output signals the working amplifiers 119 and 126 are fed to a summing amplifier similar to that shown in FIG corresponds to reference numeral 82 and has a working amplifier 128. The working amplifier 128 is used for summing these two intermediate frequency signals and generation of an amplified output signal of the summed signal for the purpose of transmission via the inner conductor of the triaxial measuring cable 12 to the surface. The signals are above ground reinforced and in one of the alternative procedures

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determined as it is in the description of Fig. ' 1 is disclosed. '""' · ^{: Γ} · " ^:

6 shows a theoretically derived graph of a result obtained by means of the above-described borehole measuring system, in which the measuring probe was embedded in a homogeneous material. The normalized · 'field amplitudes at the receiver coil on the basis of the ^32-MHz: Doppelgeberauspendung received signals are plotted along the abscissa, while the ordinate contains a record of the normalized field amplitude .of the received 16 MHz signal. By "normalized" it is meant that the received signals are related to their corresponding values in air; that is, the amplitude of the signal received at a frequency of 30 MHz due to transmission in air is divided into the received signal of the total field in the formation due to the transmitted 30 MHz signal. Similarly, the formation signal received at 16 MHz at the receiver coil is divided by the amplitude of the 16 MHz signal received in air. - · "·"'■' .-

The curves shown in FIG. 6 are a function of the conductivity properties and the dielectric properties of the homogeneous medium in which the measuring probe is embedded for the purpose of a graphic representation according to FIG. From Fig. 6 it can be seen that the 16 MHz and 32 MHz frequencies of the amplitudes of the normalized field

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Functions of both conductivity and dielectric Properties of the earth formation are that the amplitude of the 16-Mfiz signal is more dependent on the conductivity properties of the earth formation than 32 MHz frequency amplitude. Against this is the 32 MHz signal in a homogeneous medium noticeably stronger due to the dielectric ■ properties of the earth formation than the normalized one 16 MHz signal affected.

The use of a double transmitter coil arrangement according to Figures 1, 2, 3A and 3B backs up at a 30 MHz frequency a Focuszierurigseffekt on the 30 MHz signal, from which a deeper penetration of the 30 MHz signal into the das Formation surrounding the borehole results. The unfocused 16 MHz signal normally speaks on formation materials that are not that far from the borehole. · Since, however, the 16 MHz encoder coil continues from the receiver coil as the 30 MHz dual transmitter coil remotely, approximately the same radial zone is examined from each system in a homogeneous medium. It should be noted, however, that due to varying dielectric and conductivity properties of the earth formations surrounding the borehole, this does not always have to be the case. In some cases that will 30 MHz frequency signal through the highly conductive invasion zones, conductive media from the borehole, prevented from penetrate as deep as would normally be the case with a less conductive medium.

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In any case, it can be seen that by creating normalized total field amplitude measurements at two different frequencies (16-MHz and 30-MHz), as with 1, 2, 3A and 3B and by reference to the creation of a coordinate representation of theoretically derived values for them Amplitudes such as those shown in Figures 6 and 7A-7D it is possible to have a unique value for both the conductivity and the dielectric Derive constant of the material surrounding the borehole.

In FIGS. 7A-7D four graphic representations are given which are similar to the representation in FIG. the Graphics show the normalized field amplitudes at 32 MHz in relation to the normalized field amplitudes at 16 MHz. In The graphs show the result as it would theoretically using one in FIGS. 1, 2, 3A and The induction dielectric borehole logging system shown in FIG. 3B in 203.2 mm (8 ") and 304.8 (12") boreholes a freshwater slurry (Figures 7A and 7B) and an oil-based slurry (7C and 7D) can be derived; A graph of this type can be found in tabular form in the memory of a small general-purpose computer such as e.g., the computer 39 in FIG. These representations can then be used to derive the specific Resistance and the dielectric constant of the earth formations in the area of the borehole directly from the amplitude measurement of the normalized total field at 16 and 30 MHz frequencies can be used.

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The small universal computer 39 can be used to carry out the Calculations are easily preprogrammed when stored with the information about the borehole diameter and the dielectric properties of the borehole fluid which are known in advance.

Alternatively, the logging system can be calibrated in test wells with formations of known characteristics will. The calibration curves resulting therefrom (similar to those shown in FIGS. 7A-YD) can then be similar Way to be used in the calculator 39;

509827/0160

Claims (31)

2UÖB7S τ lh P a t e η t a ■ m Sp / i *! %. ■ & fee ■ - ■. ·. ·; . ■ 1) Procedure for determining who. Electromagnetic properties of the materials located in the area of a borehole, in which an alternating electromagnetic field is generated and determined at locations that are remote from one another in the longitudinal direction of the borehole, thereby g; & K m z e Ii: e-Jl g ^ti: - r net that a first radio frequency; elektiOmag- · - "-netic. Alternating field with a frequency: is produced in the range of 10 to 20 MHz in the borehole That a second high-frequency electromagnetic alternating field with a .Frequency in the range of 20-Ms 40-MHz is generated, that in a location in the longitudinal direction of the borehole away from the places where the first and second electromagnetic alternating fields are generated, the voltage amplitudes of the total electromagnetic field in the first and second frequency range can be determined / generally signals are generated which are representative of the total field voltage amplitudes of the <total electromagnetic field in the first and second frequency range and signals are generated which are representative of the total field voltage amplitudes are that the creation and determination steps at different borehole depths are repeated and 50 982 7 / G16Ö that the total field voltage amplitude signals or the signals derived therefrom are recorded as a function of the borehole depth, 2) Method according to claim 1, characterized in that the second higher electromagnetic alternating field Frequehz is selected from the frequency range in such a way that especially interference from harmonic components of the second order of the first lower electromagnetic alternating field frequency are switched off. 3) Method according to claim 1 or 2, characterized characterized in that the first alternating electromagnetic field frequency is at approximately 16 MHz and the second alternating electromagnetic field frequency is selected at approximately 30 MHz, 4) Method according to one of the preceding claims, characterized in that that at least one of the electromagnetic alternating fields, preferably the second alternating field, as radially focused electromagnetic alternating field is generated. 50 9827/0160 . 33 - 'Z44067Ö 5) Method according to one of the preceding / claims, characterized in that for determining the specific resistance and the dielectric properties of the ... of the borehole located materials these properties corresponding signals, according to a predetermined relationship of the signals obtained in the first and second frequency ranges of the Total field voltage amplitudes, and that the resistivity and the Signals representing dielectric properties are recorded as a function of the borehole depth. 6) Method according to one of the preceding claims, characterized , that the generated during the generation of the first and second electromagnetic alternating field electromagnetic flux is stabilized at a constant value. 7) Method according to one of the preceding claims, characterized, that the first and second alternating electromagnetic field in a homogeneous medium outside the borehole is generated that removed in a longitudinal direction of the homogeneous medium outside the borehole from the places of creation of the first and second 5 0 9827/0160 electromagnetic alternating field, the voltage amplitudes of the overall electromagnetic field these voltage amplitudes can be determined in the first and second frequency ranges corresponding normalization signals are generated, the amplitudes of which define a unit that within of the borehole, the generation and determination steps in the first and second frequency range be repeated in the case of a plurality of depths in the borehole that the first for each of these depths and second total field voltage amplitude signals are generated which represent the normalized relative amplitudes of the total field at the first and second frequency with respect to the first and second normalization signals represent, and that the first and second representative total field signals as a function the, borehole depth are recorded. 8) Method according to claim 7, characterized that the generation and determination steps in the homogeneous medium in air before admitting the devices comprising the measuring probe for generating and determining the first and second frequency signals in the borehole. 509827/0160 9) Device for carrying out äes geke η η ζ ei ch-.net "'u r ά ¹ ^ ¹ ai / ^ ^{-'; J} a device (17) for generating a first ^c ″ ^; high-frequency electröi &agnetisO'toen ife (& s £ i £ e & ü £ S '5m ■ borehole in a Frexiuenz1b; e: reabcih Mh;' tte ^ geiaStt ¹ 1.0- ■ ° to 20-MHz, by a Einric ^ htöng tÄ ;, 19t: 2ür ER ^';:'; a second generation: hochfope duck ^ * i Aeifctromagaetischen alternating field in Bönrlioolh "IATA etitem ■ frequency range of about 20 to # Ö ^ ffi [% iaarch feiiie means (21) determining ziir 'JäerSpanni ^{^^;} amplitudes of the electromagnetic ftesamtfetLaes in the first and second frequency range in 'a in'Längsrichtung of the bore hole remote from the places of production of the first and second elefctromagnetischen ~ ~ / ■ ~ alternating field location and generating signals representative of the Gesamtfeid-Spaimungsamplituden the elec- tromagnetic - GeSaatfeldes are at 'the first and second frequency range, and by means (24,25 or 26,27) for recording the total field amplitude signals or signals derived therefrom as a function of the drilling depth. 10) Device according to claim 9, dad ü r c h 'characterized in that the device (17,18,19) a device (53 :) for generating the first and second alternating electromagnetic fields of the first alternating electromagnetic field 50 9827/0160 ■ -. ' at a frequency of about ΐ6 · * -ΜΗζ and one Device (.61) for generating the second alternating electromagnetic field in a Has a frequency of approximately 30 MHz. 11) Apparatus according to claim 9 or 10, characterized in that the g e k e η η ζ e i c h η et Device for generating the first and second alternating electromagnetic fields, a single transmitter coil (17) tuned to a frequency of approximately 16 MHz and focused radially Has double encoder coil (18,19), the coils have opposite polarities and each on are tuned to a frequency of approximately 30 MHz. 12) Device according to one of claims 9 to 11, characterized, that the device for determining the voltage. amplitudes of the total electromagnetic field has a single receiver coil (21) at the first and second frequencies and that a signal splitter circuit (30) for separating the two signal components induced in the receiver coil (21) is provided. 50 98 27/0180 13) Device according to one of claims 9 to 12, .marked by Amplitude detectors (31,32), which are used as double from
Superhet to achieve 'two intermediate frequency signals are used which are representative of the amplitudes of the overall field signals in the first and second frequency range. 14) Device according to one of claims 9 to 13, characterized by means for deriving signals according to a predetermined relationship from which the total field voltage amplitudes signals representing the first and second frequencies which correspond to the specific Resistance and the dielectric properties of the .in the area of the borehole Represent formation materials, and by recording means (26 x, 27) for recording that for the resistivity and dielectric properties of the formation materials representative signals as a function of the borehole depth. 15) Device according to claim 14, characterized marked that the facility to derive the representative of the specific resistance and the dielectric properties Signals analog / digital switching devices (34,35) 50 98 27/0160 for converting the total field voltage signals into digital form and a digital universal computer (39) for comparing the digitized signals to a predetermined relationship is. 16) Device according to one of claims 9 to 15, characterized by Power control circuits (60, 66) to stabilize the entire electromagnetic flow, that of the devices for generating the first and second alternating electromagnetic fields was emitted to a constant value. 17) Device according to one of claims 9 to 16, characterized in that that the means for generating the first and second electromagnetic fields one crystal controlled electromagnetic frequency transmitter with an oscillator (53,61) and a Output amplifier stage (55,62) and is connected to the transmitter coil arrangement '(17,18,19), 18) Device according to one of claims 9 to 17, characterized in that that the power control circuits (60,66) means for monitoring the current intensity in the Output amplifier stages (55,62) and generation 509827/0160 a "signal" representing this stream. seen is that a ^ icflltiing-ziM "Compare. this current signal 3e? s: with ;: elnenl ·: predetermined. Comparative stream signals and ": for the. Generation of a corresponding; difference-signal:. Provided is-t?, - and that a facility; for control; of the type- the-output-amplifier stages: 055 * 62), stored voltage ^ . in response to the Di ££ erenz> sign ;. for the purpose of Minimizing dessellies provided. is ± v " 19) Device according to claims einem.der% "^ to 18, .. characterized geke nr ^mz; e i, C:. H · η et: that the output amplifier stages (55 * 62) with the transmitter coil arrangement ( 17,18,19) over a first; 'and second impedance-matching balun (56,63) is connected. 20) Device according to claim 19, / da ^; d: URC, characterized h that the baluns have (56,63) bifilar windings, the ratio of the input winding for Aüsgangswicklung corresponding to an effective matching of the input impedance of the transmitter coil arrangement (17,1 ^{8 »1} 9) ^mi" t of the output impedance of the output Amplifier stages (55,62) is determined. 50 9 827/0160, 21) Device according to claim 19 or 20, characterized in that that the baluns (56,63) have taps between the input and output winding, the one with the primary windings of the encoder windings monitoring the current strength (58,64) are connected, their secondary windings with DC-c * -circuits (59,65) are connected, which by the balun (56,63) generate signals representing flowing currents. 22) Device according to claim 21, characterized • marked that the current monitoring encoder windings (58,64) input and Have output windings wound around annular shaped ferrite cores. 23) Device according to one of claims 9 to 22, characterized in that that the facilities for generating one of the Output amplifier stages (55> 62) flowing currents representing current signal encoder windings (58,64) for checking the alternating current in the output amplifier stages and that devices to determine the peak voltage in the secondary winding and to generate a DC 509827/0160 current signal, which represents the peak voltage, is provided. 24) Device according to one of claims 9 Ms 23, characterized by-work amplifiers (95,103) for comparing the direct current signal with a comparison signal, the Have potentiometers (96, 104) for generating a "variably selectable comparison signal, and the two input terminals and means for supplying the direct current signal to one of the input terminals and have devices for feeding the comparison signal to the other input terminal, thereby making the working amplifiers (95,103) DC output signals for each difference between the direct current signal and the comparison signal. . ■ 25) Device according to one of claims 9 to 24, characterized by a device that acts on the representing the difference DC output signals responding to control the voltage supply to the output amplifier stages, which has a transistor (105), the emitter and collector of which in series between a Battery (51) and the output side of the working amplifier (103) of the output amplifier stage and 509827/0160 the device for supplying the direct current output signal representing the difference the base of the transistor (103), whereby the. Voltage drop across the transistor (103) through the Value of the DC output signal a controller experiences and also the applied voltage to the transistors (92, 100) on the output side "of the output amplifier stages. 26) Device according to one of claims 9 to 25, characterized by electrostatic shields (57, 69) around the transmitter coil arrangement (17, 18, 19). 27) Device according to one of claims 9 to 26, characterized in that the determining device has a receiver coil (21) in a location remote from the generation location of the first and second alternating electromagnetic fields in the longitudinal direction for receiving the first and second frequency ranges induced electromagnetic alternating field voltages that mixer stages (7A-, 78) are provided for converting the induced voltage signals in the first and second frequency range into two intermediate frequency voltage signals in a range from 1 to 40 KHz and that a Summing Amplifier (82) 50 9827/0160 for forwarding the voltage signals representing the intermediate frequencies from the borehole measuring probe (11) arranged underground to the signal processing line device arranged above and generating signals representing total field amplitudes in the case of the first and second. second Frequency range of the intermediate frequency signals. is provided. . 28) Forrichtung according to claim 27, Φ; ä d ti r c: h g e k e η η ζ e i without t that the mixing stages (74, 78) have crystal-controlled oscillators (75, 79), one of which is an oscillator in the first frequency plus or minus the first intermediate frequency and the other oscillator on the second. Frequency plus or minus the second intermediate frequency is working. 29) Device according to claim 27 or 28; thereby g e k e η η ζ e i c h, η e t that the mixer stages (74, 78) have output stages, which are matched to the acceptance only of output signals in the first and second intermediate frequency range appear. 30) Device according to one of the. Claims 27 to 29, characterized, that a triaxial measuring cable "(12) is used to transmit the intermediate frequency signals to the surface. 50 9827/0160 • It is provided that an inner conductor, an inner insulation layer, one coaxial with the inner conductor arranged shield, 'an outer insulation layer and has at least two outer reinforcement layers which compensate for the torsional forces. 31) Device according to one of claims 9 "to 30, characterized ge characterizing t, that the determination device has a device for generating signals which the total field voltage amplitudes at values which, with reference to the corresponding signals, by normalizing the outside of the borehole in a homogeneous medium generated and determined electromagnetic alternating fields are generated. 509827/0160 Blank page