SU1133577A1 - Device for logging magnetic susceptibility - Google Patents

Abstract

A MACHINE FOR DRIVING A MAGNETIC SENSITIVITY containing a generator coil connected to a sinusoidal voltage generator, focusing and measuring coils connected in series with a breakdown and connected to the input of a signal conversion circuit whose output is connected to the recorder, while the coils are coaxially located on a predetermined sweep, and the coils are aligned on the other, characterized in that, in order to improve the accuracy in logging wells with variable diameters, the distance between the centers of the generator and measuring cells uschek ki between the centers of the generator and the focusing coils L ^ bonded relation P 9 -jJ-linl; - 0 U, LK by where is the length of the measuring coil; F is the length of the focusing coil, and the number of turns of the focusing coil i Wf and the number of turns of the measuring coil WH are related by the ratio (L 0.2 Wf / W and 0.5 00 oo SP

Description

The invention relates to geophysics and is intended for measuring the magnetic susceptibility of rocks and ores in natural occurrence, in particular for logging magnetic susceptibility.

A device for continuous measurement of magnetic susceptibility is known, comprising an oscillating, measuring, and focusing coil with a given number of turns of the focusing coil and a given distance between the coils 1.

The disadvantage of the device is low resolution.

The closest in technical essence to the invention is a device for logging magnetic susceptibility, comprising a generator coil connected to a sinusoidal voltage generator, focusing and measuring coils connected in series and connected to the input of a signal conversion circuit, the output of which is connected to the recorder, the rollers are located coaxially at a given distance from one another 2.

A disadvantage of the known device is the low accuracy in the logging of wells with variable diameter.

The purpose of the invention is to improve the accuracy when logging wells with variable diameter.

This goal is achieved by the fact that in a device for logging magnetic susceptibility, containing a generator coil connected to a sinusoidal voltage generator, focusing and measuring coils connected in series and opposite to and connected to the input of a signal conversion circuit, the output of which is connected to the recorder, the coils are located coaxially at a given distance from one another, the distance between the centers of the generating and measuring coils LK and between the centers of the generating and focusing coils k bfs are called

n r, .j. 1g, -1f g, g.F- Cu u, 2 LH

where and is the length of the measuring coil; (p is the length of the focusing coil, and the number of turns of the focusing roll Wcip and the number of turns of the measuring roll WH are related by

0.2 0.5.

FIG. 1 shows a functional diagram of a device for logging magnetic susceptibility; in fig. 2 - theoretical curves of the dependence of the output signal increments on the diameter of the well.

The device contains a generator coil 1 (Fig. 1) connected to the generator 2 of sinusoidal voltage.

focusing 3 and measuring 4 coils, connected in series and counter and connected to the input of the signal conversion circuit 5. The output of the circuit 5, 5 signal conversion is connected to the recorder 6. The power supply unit 7 is connected to the signal conversion unit 5 and the sinusoidal voltage generator 2. Plots 8-17 (Fig. 2) are obtained by calculation to increment the output signal of the borehole diameter dcKB, where d is the increment of the emf measured

chains; about - the initial EMF measuring

coils;

5G-magnetic susceptibility of the medium.

Chart 18, represented by points, obtained experimentally.

The operation of the device is as follows.

The generator coil 1, fed by the generator 2 of sinusoidal voltage, creates an alternating magnetic field in the surrounding space. Under the conditions of a non-magnetic and non-conducting medium in the focusing 3 and measuring 4 coils, the magnitude and direction of the EMF is induced by the action of the field of the generating coil 1. When the device is placed in a well intersected by magnetic rocks, the field of the generating coil 1 interacts with the explosive magnetic medium . As a result of this interaction, the EMF on the focusing 3 and measuring 4 coils, due to their different distance from the generator coil, varies according to different laws. The resulting increment of the difference signal, depending on the magnetic susceptibility of the medium, is fed to the input of the signal conversion circuit 5 and further to the recorder 6. The measured signal, besides the measured parameter $, also depends on the measurement conditions, in particular, on the changing diameter of the well and design features of the induction converter.

When the focusing 3 and measuring 4 coils are at a distance of 1f / b) 0.7, it has. the location of the relationship between the increment of the difference of 0 EMF and design parameters

 G "-i4S-- fG .;

L is the increment of the EMF differences under the influence of a medium with magnetic susceptibility ze; EMF of the primary floor of the measuring coil;

GK is the geometric factor of a probe consisting of a generator and a measuring coil;

Of - the geometric factor of the probe, consisting of the exciting and focusing coils.

The formula is used when plotting the dependence of the increment of the measured signal 4 / oH-3t on the variable diameter of the well (Fig. 2) for different W $ / WM ratios, from which it can be seen that the lower the curve maximum, the smaller the Curve on V4b / lA / KL coils 0,130,18 0,24 0,31 0,36

the degree of the measured signal depends on the ratio dcKB / L. The curvature of the graphs is estimated by the following construction. For each curve, an area is determined in which the magnitude of the measured signal varies by no more than 5 ° / o from the maximum value. This interval is shown on the curves with a dashed line. The magnitude of the Dyok interval (expressed in units of b) for various ratios of the number of turns on the focusing 3 and measuring 4 coils is shown in the table.

10 EnillllCniLlZIZCIT 0.43 0.48 0.55

The interval value is 0.282 0.312 0.350 0.354 .J 1. 0.266 A “., D //„

The larger the interval (iDoKs), the wider the exclusion range for measurements of a variable borehole diameter and the smaller the measurement error in wells with a variable diameter.

If a compensated measurement scheme is used, the number of turns on the measuring and focusing coils is selected so that the emf in air is zero. FIG. 2, the sensitivity curve of such a compensated probe is curve 9, and the value of the Lyokv / Lu interval for such a probe is 0.280 (see table). Devices characterized by a large AdcKB / LH interval are less dependent on the output signal on the variable diameter of the well. At the same time, with the ratio, the exclusion range for measuring the variable diameter of the well also depends on the ratio Lf / L. Interval D. dcna. in which the readings of the instrument vary by no more than 5 ° / o of the maximum value, increases with increasing ratio.

The minimum distance between the coils is limited by the length of the EF of the focusing 3 and IT of the measuring 4 coils and is determined by the expression 0.5 (f + 1i). It follows from the calculations that the range of values of W J / WMN at which the devices differ in a large AdcKB interval is determined by the expressions

U / LH 0.85 (see FIG. 2); 0.18 W $ / WH 0.6;

L $ / LH 0.8; 0.2 / WH 0.5;

Bf / bc 0.7; 0.22 0.31. Devices with the LflL parameter less than 0.7 are characterized by a smaller AdcKB interval, in which the value of the measured signal varies by no more than 5% of the maximum value.

A positive effect is observed in devices where the ratio is

0, W}, 5; and, 8. Taking into account 0ф and РИ, a ratio is obtained defining the distance between the centers of the coils

o.,.,

In accordance with the obtained ratios, a device was fabricated and tested, where the number of turns on the focusing is 0, 0.329 0,, 0

Claims (1)

MAGNETIC SUSCEPTIBILITY DEVICE, comprising a generator coil connected to a sinusoidal voltage generator, focusing and measuring coils, connected in series and connected to the input of the signal conversion circuit, the output of which is connected to the recorder, while the coils are located coaxially at a predetermined distance from each other, characterized in that, in order to increase accuracy when logging wells with variable diameter, the distance between the centers of the generating and measuring coils uu between centers generating and focusing coils are connected by the relation η rp 9 - * coils; coils, coils p W # and the number of turns of the measuring coil - © coils Wk are related by 0.2 <W ^ / Wj, <0.5 where is the measuring length is the focusing length and the number of turns of the focusing εεϊΤ ’ns sl m FIG. 1