RU2831753C1 - Complex magnetometer-inclinometer for survey of wells of various purposes - Google Patents

Abstract

FIELD: measuring.

SUBSTANCE: invention relates to measurement geophysical equipment and is intended for logging when searching for and exploring iron-ore deposits, as well as weakly magnetic objects, investigating parametric and oil-and-gas wells. Complex magnetometer-inclinometer contains three mutually orthogonal rigidly fixed accelerometers, three mutually orthogonal rigidly fixed ferroprobe, sensor signals conversion unit, magnetizing and compensation coils, quartz generator, frequency divider, analogue-to-digital converter of double integration (ADC), shift register, signal modulator. Device additionally includes a control pulse distributor, an ADC integrator charge and discharge clock generator connected to the control pulse distributor, a differential ferroprobe connected to the sensor signal conversion unit. Differential ferroprobe is installed at a distance from the magnetizing coil and inside the compensation coil, which are connected to a control pulse distributor, to which a pulse generator for controlling charge and discharge cycles of the ADC integrator is also connected.

EFFECT: wider range of the channel for measuring magnetic susceptibility without reducing sensitivity and high speed of detecting other channels.

1 cl, 2 dwg

Description

The proposed invention (a complex magnetometer-inclinometer for studying wells of various purposes) relates to the field of measuring geophysical equipment and is intended for conducting borehole magnetometry during prospecting and exploration of iron ore deposits, weakly magnetic objects (deposits of nickel, gold, diamonds, etc.) and studying parametric and oil and gas wells. In one trip, the complex borehole magnetometer-inclinometer measures the magnetic susceptibility of rocks intersected by the well, three components of the geomagnetic field vector, the zenith angle and the magnetic azimuth of the well with a depth discretization step of 0.1 m. In this case, the values of the magnetic susceptibility of rocks with different degrees of magnetic mineralization change in a very wide range (from 0.001 to 1-2 SI units), which is significantly greater than the range of variation of the geomagnetic field components. To solve this problem, with digital recording, more time must be allocated to the magnetic susceptibility measurement channel compared to other channels. On the other hand, by using certain circuit solutions, it is possible to reduce the time for measuring the remaining channels, which will significantly increase the logging speed and reduce the registration errors that occur when the downhole tool rotates after being torn away from the bottomhole.

A device is known [1] containing magnetizing and compensating coils located along the axis of the borehole tool at some distance from each other, a single-element ferroprobe located inside the compensating coil, a measuring circuit of the magnetometer and other units. The disadvantages of the device include the use of a single-element ferroprobe, which has higher intrinsic noise compared to a differential ferroprobe, as well as the significant complexity of the measuring circuit of the magnetometer. In addition, this device measures only the axial (along the axis of the borehole tool) component of the geomagnetic field, which is only practical in vertical wells.

A device [2] is known that contains single-element ferroprobes. One of them is vertically weighed (Z), the other two (Hx, Hy) are horizontally weighed using additional weights. The magnetic susceptibility sensor contains an axial ferroprobe, a magnetizing coil, compensation resistors, a measuring circuit of the magnetometer, and two synchronous detectors. The disadvantages of this device include the use of single-element ferroprobes for both measuring the components of the geomagnetic field and the magnitude of magnetic susceptibility, which significantly complicates the signal extraction and amplification unit. In addition, compensation of the primary field of the magnetizing coil with voltage from the resistors may not be stable enough.

The closest technical solution to the proposed invention is a device [3] containing three rigidly fixed and orthogonally installed single-element ferroprobes, three rigidly fixed and orthogonally installed accelerometers, a magnetic susceptibility sensor, a measuring circuit of the magnetic susceptibility channel, a measuring circuit of the magnetometer, an analog-to-digital converter, and a control unit. The disadvantages of the device include the fact that the operating time of the integrating ADC when measuring both the field components and magnetic susceptibility is the same (40⋅10 ^-3 s), but much more time is needed to measure the value of magnetic susceptibility.

The first significant point in this application is the introduction of a differential ferroprobe into the circuit of the magnetic susceptibility measurement unit, which significantly simplifies the measuring circuit of the magnetometer and helps to reduce its own noise.

The second significant point in this application is the introduction of two more electronic units 15 and 16 into the device, which make it possible to extend the discharge time of the integrator at the moment of measuring the magnetic susceptibility.

The device operates as follows: the output signal of the quartz generator 13 with a frequency of 2048 kHz is fed to the input of the frequency divider 14, which generates a series of frequencies: 32 and 64 kHz - to control the operation of the magnetometer circuit; 2400, and 400 Hz - to operate the shift register and other blocks. Block 15 generates current pulses into the magnetizing and compensation coils, controls the keys of the accelerometers and ferroprobes, organizes the discharge pulse of the ADC integrator during the measurement of magnetic susceptibility, as well as a pause in the transmission of information by modulator 19. Block 16 generates charge clock signals and discharge integrator ADC, coming from block 15, taking into account the increase in discharge time when measuring the value of magnetic susceptibility. The parallel output code of the ADC of block 17 goes to the inputs of the shift register 18, is converted into a serial code and goes to the input of the modulator 19, where the single bits of the serial code are filled with a frequency of 32 kHz and are fed to the logging cable and then to the logging recorder. The supply voltage of the downhole tool is also fed through this cable.

Brief description of the drawings

Fig. 1 shows the functional diagram of the device. The device contains:

1, 2, 3 - rigidly fixed and orthogonally located accelerometers;

4, 5, 6 - rigidly fixed and orthogonally located ferroprobes, the sensitivity axes of which coincide in direction with the sensitivity axes of the accelerometers;

7, 8, 9 - differential ferroprobe of magnetic susceptibility sensor;

10 - compensation coil of the magnetic susceptibility sensor;

11 - magnetizing coil of the magnetic susceptibility sensor;

12 - a unit for converting signals from accelerometers 1, 2, 3, signals from flux gates 4, 5, 6 and signals from magnetic susceptibility sensors 7, 8, 9 into direct current pulses required for feeding to the ADC input;

13 - quartz generator;

14 - frequency divider;

15 - distributor of control pulses of block 12;

16 - pulse generator for controlling the charge and discharge cycle;

17 - integrating push-pull analog-to-digital converter (ADC);

18 - shift register;

19 - shift register output signal modulator;

20 - power supply unit of the well tool;

21 - single-core logging cable.

Fig. 2 shows the timing diagrams of the device:

- pause in the transmission of information via the logging cable;

- opposite polarity current pulses supplied to magnetizing coil 11 and compensation coil 10;

- output signal of block 15;

- signals for controlling the ADC integrator discharge clock (low level);

- signals for controlling the ADC integrator charge cycle (low level);

- output signal of the ADC integrator;

- output signal of the magnetic susceptibility channel;

- output pulses of the ferroprobe signal conversion unit;

- output signals of the accelerometer channel;

- output signals of modulator 19.

Sources of information

1. Astrakhancev Yu.G., Ponomarev V.N. Device for measuring the magnetic susceptibility of rocks. // A.S. No. 1299315, 1985.

2. Ponomarev V.N., Astrakhantsev Yu.G., Legotin L.G., Gritchin A.G. Autonomous magnetometer for measurements in ultra-deep wells // A.S. No. 1294137, 1985.

3. Yu. G. Astrakhancev, N. A. Beloglazova Hardware and software complex for continuous inclinometry of oil and gas wells // Practice of instrument making. No. 1. 2003, Ekaterinburg, pp. 17-21.

Claims (1)

A complex magnetometer-inclinometer for studying wells of various purposes, comprising three mutually orthogonal rigidly fixed accelerometers, three mutually orthogonal rigidly fixed ferroprobes, a sensor signal conversion unit, a magnetizing and compensation coil, a quartz generator, a frequency divider, a double-integration analog-to-digital converter (ADC), a shift register, a signal modulator, characterized in that a control pulse distributor, a charge and discharge cycle former of the ADC integrator connected to the control pulse distributor, and also a differential ferroprobe installed at a distance from the magnetizing coil and inside the compensation coil, which in turn are connected to the control pulse distributor, to which a charge and discharge cycle control pulse former of the analog-to-digital converter integrator is also connected, and the ferroprobe itself is connected to the sensor signal conversion unit.