DE3318656A1 - Induction-logging measuring method and device for geophysical borehole measurements - Google Patents

Description

FROM KREISLER SCHONWALD EISHOLD FUES FROM KREISLER KELLER SELTING WERNER

PATENT LAWYERS

Dr.-Ing. by Kreisler 11973

Dr.-Ing. K. Schönwald, Cologne

BPB INDUSTRIES PLC "Dr.-Ing. K. W. Eishold, Bad Soden

Ferguson House Dr. J. F. Fues, Cologne

15/17 Marylebone Road DipL-Chem. Alek von Kreisler, Cologne

London DipL-Chem. Carola Keller, Cologne

Xt ₁ VT ₁ ς jp Dipl.-Ing. G. Selting, Cologne

«Ou ·! - · ^Dr - HK. Werner, Cologne

Great Britain

DEICHMANNHAUS AT THE MAIN RAILWAY STATION

D-5000 COLOGNE 1

Sg-Da / Fe May 20, 1983

Induction log measurement method and device for geophysical borehole measurements

The invention relates to an induction log measuring method for geophysical borehole measurements and a measuring device therefor.

The induction log measuring method is a known measuring method. An instrument, hereinafter referred to as a probe, is suspended from a cable in a borehole to obtain information about the type of soil in the area of the borehole, in particular with regard to the possible occurrence of minerals and crude oil, to obtain. The probe has a winding, referred to below as a transmitter coil, which is wrapped around an insulating Coil core is wound. The transmitter coil is operated with alternating current to create an electromagnetic field to generate in the kilohertz frequency range. The influence of the surrounding earth formations on the electromagnetic The field is examined by means of the

The second winding, called the catch coil, is measured. The second winding is also wound on the insulating coil core so that it is coaxial with the transmitter coil and spaced longitudinally is arranged by the transmitter coil. This arrangement is referred to below as a transmitting / receiving unit.

The signal from the receiving coil in the above measuring system gives a general measure of the specific resistance the earth formation in the area of the borehole. There are numerous methods for "focusing" the measurements has been proposed such that the signal is representative of the relative resistivity narrow sectors of the earth formation. For example, the signal can be representative of the specific resistance an annular earth area at a certain lateral distance from the borehole (radial or lateral focusing) and / or a relatively narrow horizontal strip of earth whose central axis is at a point between the transmitter and receiver coils (vertical or longitudinal Focusing). Such focusing is achieved through a multi-coil system by adding more than one transmitter coil and / or more than one receiving coil is used. The signals from the various send / receive combinations are brought together in the probe and as a composite signal via the cable to the earth's surface transfer. The output signals of the various send / receive combinations can be algebraic can be added up, with a weighting if you wish is used to obtain the measurement characteristics of the earth formations in certain sectors. It is also, known to process a logging signal by first storing it and then a predetermined one

algebraic combination of selected fractions of the Measurement signal which was obtained at different times and which corresponds to different depths of the borehole, to calculate.

in all cases where multi-coil systems are used the output signals are combined in the probe itself and one or more such composite ones Transmitting signals to the earth's surface. The possibilities of further processing such compound Signals that can be carried on the surface of the earth are restricted. Hence it is with one information obtained from a single probe in a single pass through a borehole. If more Information needed is an additional pass through the borehole with one probe, the other Has send / receive combinations, required.

The invention is based on the object of providing a measuring method of the type mentioned at the beginning, which is a subsequent evaluation of the measurement signal data for any Measurement signal combination allowed, and a measuring device of the type mentioned to create the transmit the measurement signal of each individual transmitter / receiver coil combination separately in unchanged form and can save.

To solve this problem, the method is that of the introduction named type characterized by

Positioning of an induction log measuring device in several borehole depths, the measuring device from consists of at least two transmitter / receiver units in order to receive separate electrical signals,

transmission of the separate electrical signals to the Surface of the earth,

Store the separate signals so that the signals from each unit are preserved in their original form stay and

Composition of the separate electrical signals in any way to generate one or more screen displays, which depends on the borehole depth for the electrical properties of the earth formation are representative in the area of the borehole.

A device of the type mentioned is characterized by

at least two transmitter / receiver units for induction log measurements, which are contained in a probe that can be guided through the borehole to each separate electrical Receive signals

a cable to hold the probe in the borehole and to carry the separate electrical signals to the surface of the earth transferred to,

a storage device on the earth's surface for storing the separate electrical signals and

a device for combining the separate electrical signals in any way to generate a or several screen displays, which are dependent on the depth of the borehole for the electrical properties are representative of the earth formation in the area of the borehole.

The separate electrical original signals can be on the earth's surface For example, they can be stored indefinitely on magnetic tapes or magnetic disks. The production a screen display with the inclusion of a

The correct combination of these signals does not affect the storage of the original signals, which are still retained in their original form. The invention enables hence, to be flexible and generate a plurality of screen displays based on the same original data. It is even possible to generate a screen display some time after the original data has been acquired, by using software programs that were not yet available at the time the data was collected.

The current supplied to the transmitter coil is sinusoidal and the electromagnetic field generated is customary in the frequency range between 1 kHz and 100 kHz, preferably between 10 kHz and 50 kHz. Due to the electromagnetic field generated in the surrounding geological formations in the receiving coil induced voltage, which forms the desired signal component, is 180 ° relative to the voltage in the Transmitting coil out of phase. A relatively high and undesirable voltage is also induced directly. These unwanted component is phase shifted by 90 ° in relation to the voltage in the transmitter coil. The 90 ° phase shifted Component can be suppressed by suitable electronic devices. Preferably the 90 ° phase-shifted component suppressed by a small one referred to below as a dummy coil Auxiliary winding is provided, for example between the transmitting coil and the receiving coil can be inserted. Such a dummy coil cancels the largest one Part of the 90 ° phase-shifted component of the signal induced in the receiving coil. The dummy coil does not necessarily need to be arranged between the transmitter coil and the corresponding receiver coil. One single dummy coil can be used to turn the order

To delete 90 ° phase-shifted components in different sender / receiver units. Any rest of the A signal component phase-shifted by 90 ° is filtered by a phase detector, as described below.

In the following, a preferred embodiment of the invention is explained in more detail with reference to the drawings explained.

Show it:

Fig. 1 is a schematic representation of a probe in. a borehole with the arrangement of the coils,

as well as a block diagram of the probe electronics and the electronics on the earth's surface and

2 shows an enlarged section of the probe with the windings of the coils.

As shown in Fig. 1, a probe consists of an insulated coil part 1 and a probe electronics part It is held from the surface of the earth by a cable 3. Various transmitting, receiving and dummy coils are wound on an insulating coil core in the insulated coil part 1. As shown in Fig. 2 is each winding 4 is wound on an insulating fiberglass core 5 and electrostatically attached to the inner and outer winding surfaces are shielded by shields 6 and 7, respectively. The coil area is inside an outer insulating glass fiber tube 8, which the Forms coil part 1, surrounded with insulating oil. It has been found suitable to have a single transmitter coil T and four receiving coils R1, R? .R3 and R4 to be used. Between the transmitting coil and the corresponding receiving coils are four dummy coils D1, D2, D3 and D4 arranged. As shown in Fig. 1, the dummy coils D1, D2 and D3 are between the transmitting coil T and the receiving

AO

Coil R1 arranged, while the dummy coil D4 is arranged between the receiving coils R1 and R2. The distance between the transmitting coil and the receiving coils is such, that suitable combinations of the separate signals received at the surface of the earth will achieve the desired Can give information about the resistivity of different sectors in the area of the borehole.

The following table shows the distance between the receiving and dummy coils and the transmitting coil as well as the number of Turns and the diameter of each coil.

TABEL

Coil 15

T D1 D2 D3 R1 D4 R2 R3 R4

Distance from the
Transmitter coil
(mm) number of
Turns diameter
(mm) _ 236 71 220 4th 71 313 4th 71 389 4th 71 470 114 71 669 9 71 704 114 71 937 114 71 1350 114 71

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A transmitter 9 supplies the transmitter coil T with alternating current. This generates an electromagnetic field with a frequency of 20 kHz in the vicinity of the transmitter coil T. A receiving amplifier 10 takes up the electromagnetic force (emf) induced in the receiving coil R1 and the dummy coil D1 as an alternating voltage V _n in the micro-volt range and amplifies it into the millivolt range before a phase investigation. A predominant portion of the component phase-shifted by 90 ° has been deleted from the dummy coil D1. The phase detector 11 has a dual function. On the one hand, it receives a current phase reference signal 12 from the transmitter 9 and filters out any residual component V remaining in the current signal, phase-shifted by 90 °.

On the other hand, it converts the amplifier output signal from an AC voltage signal to a DC voltage signal. A low-pass filter 13 removes the 20 kHz component of the output signal of the phase detector 11 and feeds the resulting signal to an analog multiplexer 14. Each receiving and dummy coil has its respective components 10, 11 and 13 / around the respective signal to the analog multiplexer 14 feed. The analog multiplexer receives each of the four filtered DC voltage signals from the respective receiving and dummy coils and also from any other analog measuring transducers in series and feeds them to an analog / digital converter 15 which is controlled by a data acquisition microprocessor 16. The output signals from the microprocessor 16 are applied to a cable communication device 17, the data transfer between the probe and d r ^a surface carried by commands received from the surface and data is transmitted back to the surface. A power supply 18 draws power from the

Cable 3 and provides supply connections with smoothed DC voltage for general use within available for the probe.

On the earth's surface, the signal from the cable 3 is received by a cable communication device 19, which is the counterpart to the cable communication device 17, the two units exchanging information in both directions. A probe interface 20 recognizes the signal received by the probe and converts the digital data format that is in the communication line is used in nominal conductivity units, in a format defined by the central processing unit 21 is recognized. A plotter 22 makes it possible to use the calculated results of the combinations to draw the four separate receiving coil output signals depending on a depth coordinate or assign. A magnetic tape unit 23 provides the system software and is used at the same time as a storage unit. A control console 24 has a screen unit and a keypad via which the operator operates the system and controls the probe. A power supply unit 25 forms the Voltage source for supplying the probe with power via the cable.

The coil arrangement can also differ from the exemplary embodiment shown in FIG. 1. For example, can the dummy coil in a transmitter / receiver unit on the lower side of the transmitter coil relative to the receiver coil be arranged. The receiving coil can also be arranged below the transmitting coil and the dummy coil above the transmitter coil. The transmitting / receiving units can be rotated in a manner similar to that shown in FIG. 1

so that the transmitter coil points towards the tip of the probe. In addition, it is possible / more to be provided as a transmitter coil, although preferably only one transmitter coil is provided. A coil arrangement can be formed and combined as required by interchanging all of the above-mentioned transmitting and receiving elements will.

The system described above transmits the original signal ¹ data from each transmitter / receiver unit in its original form to the earth's surface. These data are stored on magnetic tape and can be combined with one another in various ways and processed in any desired way. All data is generated by a single pass through the borehole with a single probe. The predominant response signal of a single transmitter / receiver unit depends mainly on the distance between transmitter and receiver. The four Urmeßsignale can be accordingly combined at the surface with appropriate weightings to achieve a radial focusing. Vertical focusing is achieved by introducing a time factor (the time depends on the probe depth) so that the signals at the earth's surface are combined with suitable depth information.

With suitable programming, a large number of induction logs can be generated directly on site from the door data (Borehole measurement diagrams) can be generated. In addition, more information can be easily accessed can be obtained by changing the program without the need for another pass through the borehole is because the original data has been saved. It is also possible to use the same probe by suitable adaptation the computer software in a multitude of different

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geological conditions. This flexibility was not achievable with previous systems.

If, as in the known devices, the radial focusing by combining the measurement signals in the If the probe itself is reached, it is generally necessary to use several transmitter coils, as well as several Receiving coils to achieve a focus on one or more radial distances from the borehole. That The same result can be achieved with the device described here with a system comprising a single transmitter and multiple recipients can be reached. This device therefore requires a shorter coil part, so that the probe is both shorter and lighter than previously known instruments.

Claims (6)

EXPECTATIONS Induction log measurement method for geophysical Borehole measurements ,, characterized by Positioning of an induction log measuring device in several borehole depths , the measuring device consisting of at least two transmitter / receiver units (T / R1 to R4) in order to receive separate electrical signals, transmission of the separate electrical signals to the earth's surface, Store the separate signals so that the signals from each unit are in their original form be preserved and Composition of the separate electrical signals in any way to generate one or more Screen displays that show the electrical properties as a function of the borehole depth are representative of the earth formation in the area of the borehole. 2. The method according to claim 1, characterized in that the induction log measuring device at least has two transmitter / receiver units (T, R1 to R4) with a single common transmitter coil (T) 3. The method according to claim 1 or 2, characterized in that that the receiving coils (R1 to R4) of the respective transmitting / receiving units are all on the are arranged on the same side in relation to the transmitter coil (T). 4. The method according to any one of claims 1 to 3 / characterized characterized in that each transmitting / receiving unit (T, R1 to R4) has an auxiliary coil (D1 to D4) between the transmitting and receiving coils, around the induced in the receiving coil directly from the transmitting coil To extinguish tension. 5. The method according to any one of the preceding claims / characterized in that the induction log measuring device comprises a multiplexing device to serially process the measurement signals from the respective receiving coils, whereby the processed Signals are transmitted separately to the earth's surface. 6. Induction log measuring device for geophysical Borehole measurements, characterized by at least two transmitting / receiving units (T, R1 to R4) for induction log measurements that are in one through the borehole guidable probe (1,2) are included to each separate electrical signals obtain, a cable (3) to hold the probe (1,2) in the borehole and to carry the separate electrical signals to be transmitted to the surface of the earth, a storage device (23) on the earth's surface, for storing the separate electrical signals and a device (22) for combining the separate electrical signals in any way, for Generation of one or more screen displays, - yc - which depends on the borehole depth for the electrical properties of the earth formation in the Area of the borehole are representative.