RU2579177C1 - Device for generation of electromagnetic field of toroidal coil in geological environment - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention relates to the field of geophysical research in oil wells, namely to a device for studying the electrical properties of the rock (reservoir) surrounding a borehole, the method of electromagnetic logging. Technical effect: The device comprises a base in the form of conductive nonmagnetic metal pipe and generating at least one toroidal coil structure, situated concentrically ground, and is provided with a sealed enclosure of a nonmagnetic metal which is electrically connected to the substrate. Near the generator on the same base near the toroidal coil a measuring toroidal coil is placed. Both coils are installed inside the housing with an insulating gap. Measuring toroidal coil comprises at least two windings, signal and compensating. Signal winding of the measuring coil is connected to the input of feedback converter-amplifier. Compensating winding of the measuring coil is connected to the output of feedback converter-amplifier. Between the generator and the measuring coils a electrostatic shield is located which is electrically connected to the base and the housing of the device.

EFFECT: increasing measurement accuracy while simplifying the construction.

5 cl, 3 dwg

Description

A device for generating an electromagnetic field with a toroidal coil in a geological environment (hereinafter referred to as the invention, technical solution) relates to the field of geophysical research in oil and gas wells, namely, devices for studying the electrical properties of rocks (reservoirs) surrounding a well by probes (downhole emitters) by electromagnetic logging.

Currently, a number of analog devices are known from the prior art that are closest to the invention, of which the prototype is a device for measuring lateral resistivity and specific propagation resistance according to RF patent No. 2398112 (priority date: 01/01/2004). The disadvantages of the prototype include the following:

- the electric current flowing in the generator coil not directly excites the electromagnetic field in the environment, part of the current will magnetize the toroidal core (see Fig. 1, where Er is the emf generator, Ig is the primary current, r1 is the active resistance windings, Ls - leakage inductance, Lm - magnetization inductance, Im - magnetization current, Rн, Lн - active and inductive load resistances, In - load current (these values are complex);

- the impossibility of measuring the electric current delivered to the load;

- external pressure directly affects the cores of the generator coils, which leads to a change in their magnetic permeability;

- the technological complexity of mounting the generator coils and their low maintainability due to the fact that the winding of the core and windings must be performed in a small volume of grooves of an integral pipe.

The technical goal (task) of the claimed invention is to eliminate the above drawbacks, and its technical result is the creation of a device for electromagnetic well logging, which provides more accurate measurement of the desired values and values, while simplifying the design, which positively affects the installation and maintainability of the device.

This object is achieved by the fact that the inventive device containing a base in the form of a non-magnetic conductive metal pipe and at least one generator toroidal coil of known design, located coaxially to the above base, is structurally equipped with a sealed housing of non-magnetic metal, which is electrically connected to the base, while on the base next to the generator toroidal coil there is a measuring toroidal coil, both coils are installed inside the housing with an insulating As a result, the measuring toroidal coil contains at least two windings, one of which is signal, the other is compensating, while the input of the feedback amplifier-converter is connected to the signal winding of the measuring coil, and the feedback amplifier-converter output is connected to the compensating winding of the measuring coil (in bold the essential features of the invention that distinguish it from the prototype). It is the above set of features that provides the invention with the claimed technical result.

An invention, in its particular cases of execution, is characterized by the features specified in the previous paragraph, in conjunction with the following features:

1) An electrostatic screen is located between the generator and measuring toroidal coils, which is electrically connected to the base and the housing of the device;

2) Two or more generator toroidal coils are used, located next to each other;

3) The generator toroidal coil is located between two measuring toroidal coils with gaps in which electrostatic screens are located;

4) The body of the device is made collapsible.

The list of graphic drawings explaining the essence of the claimed invention:

FIG. 1 is an equivalent circuit for exciting an electromagnetic field of a device with toroidal coils;

FIG. 2 is a feedback circuit of a measuring coil;

FIG. 3 - a General view of the structural scheme of a technical solution.

A device for generating an electromagnetic field by a toroidal coil in a geological environment includes the following elements (Fig. 3): housing 1, generator coils 2, electrostatic screen 3, measuring coil 4, base 5, insulating ring 6, sealing coating 7, amplifier transformer feedback (not shown conditionally), signal generator (not shown conditionally), measuring equipment block (not shown conditionally).

The housing 1 of the proposed device is made in the form of a collapsible hollow pipe of a given diameter sealed from non-magnetic metal.

Generator coils 2 are coaxially placed on the base 5, represented by toroidal coils of a well-known design with a ferromagnetic core.

The electrostatic screen 3 is located between one of the generator coils 2 and the measuring coil 4, is electrically connected in a known manner with the base 5 and the housing 1.

The measuring coil 4 is coaxially placed on the base 5 with a predetermined distance from the generator coils 2, is represented by a toroidal coil of a well-known design with a ferromagnetic core.

The base 5 is presented in the form of a single hollow metal pipe of a given diameter of non-magnetic conductive metal. Fixed in a known manner inside the housing 1.

The insulating ring 6 is represented by a closed ceramic ring fixed in a predetermined manner on the housing 1.

The sealing coating 7 is made in the form of a closed rubber ring, mounted on the housing 1 and is structurally designed to seal the main components of the claimed invention inside this housing.

The inventive device operates as follows: an alternating electric current is supplied to the winding of the generator coils 2 from a signal generator (not shown conventionally), whereby an alternating electric field is excited in the environment, penetrating to a depth sufficient for the study. Then, a block of measuring equipment (not shown conventionally) measures the electric current at the terminals of the measuring coil 4. In this case, the electric current in the signal winding Wc of the measuring coil 4 (Fig. 2) is proportional to the electric current flowing along the base 5. The electric current in the compensating winding Wk the measuring coil 4 (Fig. 2), created by the feedback amplifier A1, is equal in magnitude to the electric current in the signal winding Wc of the measuring coil 4 and is out of phase with it. The voltage at the output of the amplifier-converter A1 will be proportional to the current flowing along the base 5. Due to the flow of two identical antiphase electric currents in the two windings of the measuring coil 4, its effect on the voltage drop on the base 5 is minimized.

Claims (5)

1. A device for generating an electromagnetic field with a toroidal coil in a geological environment, containing a base with a coaxially located generator toroidal coil of known design, characterized in that it is equipped with a sealed housing of non-magnetic metal, which is electrically connected to the base, while on the base next to the generator a measuring toroidal coil is placed in the toroidal coil, both coils are installed inside the housing with an insulating gap, the measuring toroidal coil with it contains at least two windings, one of which is signal, the second compensating, while the feedback amplifier of the feedback transformer is connected to the signal coil of the measuring coil, and the feedback amplifier of the converter is connected to the compensating winding of the measuring coil. 2. A device for generating an electromagnetic field with a toroidal coil in a geological environment according to claim 1, characterized in that between the generator and measuring toroidal coils is an electrostatic screen that is electrically connected to the base and the housing of the device. 3. A device for generating an electromagnetic field with a toroidal coil in a geological environment according to claim 2, characterized in that two or more adjacent toroidal generator coils are located nearby. 4. A device for generating an electromagnetic field with a toroidal coil in a geological environment according to claim 2, characterized in that the generating toroidal coil is located between two measuring toroidal coils with gaps in which the electrostatic screens are located. 5. A device for generating an electromagnetic field with a toroidal coil in a geological environment according to claim 2, characterized in that the housing is collapsible.

Images