RU2801354C1 - Method for increasing the noise immunity of the technology for locating sleeve joints of casing strings of geological exploration wells and a device for its implementation - Google Patents

Abstract

FIELD: geophysics; oil and gas production.

SUBSTANCE: invention is related to the exploration wells in oil and oil and gas fields. The proposed method consists in applying an exciting electromagnetic field in the environment with alternating current in a generator inductive coil located coaxially between two measuring coils with equal moments, turned on in opposite directions and moving along the investigated well. By the magnitude of the measured difference in the EMF, the position of the coupling connection is determined. To eliminate the effect of non-uniform magnetization of the casing ferromagnetic metal, two additional external coils are installed, connected in series and powered by direct current, or two neodymium magnets that magnetize the metal to a state of magnetic saturation, which allows for high-quality location of coupling joints.

EFFECT: increased noise immunity of the technology for locating sleeve joints of casing strings of geological exploration wells.

2 cl, 3 dwg, 1 tbl

Description

The invention relates to field geophysics, in particular to devices and methods for non-destructive monitoring of the technical condition of well casing ferromagnetic pipes.

Known locator couplings, patent RU 2191365 dated 20.10.2002 (CJSC "Geofizmash") - analogue. It consists of a downhole tool and a surface part connected by a logging cable. The ground part contains blocks for processing telemetric information coming from the logging cable, and a computer. The downhole tool contains n induction transducers connected to an information processing device, which consists of n/2 differential amplifiers, a summing device, n + 1 analog switches, a controller, an analog-to-digital converter, a transmitter to a ground logging station. At the same time, induction transducers are reinforced by means of non-magnetic inserts along the diameter of the device.

The operation of this device does not take into account the rotation of the tool around the longitudinal axis during movement and the alternate separation and contact of the induction transducers with the casing wall. For this reason, false signals appear, similar to signals from couplings.

In this invention, the sleeve locator is a rather cumbersome system that is difficult in industrial operation, and also does not take into account the occurrence of intervals of variations in the values of the magnetic permeability of the pipe metal.

The variant (RU 2191365) also completely ignores the main interfering factors, which often lead to intense variations in the magnetic permeability of the pipe metal.

A known method of locating sleeve connections (patent RU 2715090 C2), based on the selection of the most reliable data, namely the data from the transducers closest to the wall of the casing, while the selection of transducers occurs using data received from a device for determining the position of the device relative to the well; as well as improving the accuracy and reliability of the indication of casing collars due to the physical spacing of the induction transducers for the induction transducer for indicating couplings.

The problem is solved due to the fact that the locator of ferromagnetic casing couplings consists of a control microcontroller, a device for determining the position of the device in space (for example, a gyroscope or an accelerometer), a coupling locator, while the coupling locator contains one induction transducer located in the center of the device and comparable in diameter to the body of the device, which together significantly reduces its sensitivity up to the exclusion of their influence.

The variant (RU 2715090 C2) also does not take into account the main interfering factors, which often lead to intense variations in the magnetic permeability of the pipe metal.

One of the modifications of the coupling locator (https://studopedia.ru/20_115929_magnitnie-lokatori-muft) - (prototype) is a simplified differential magnetic system, which consists of a multilayer coil with a core and two relatively weak permanent magnets installed only to create a coil and around it of a weak constant magnetic field.

When moving the locator along the column in places of violation of the homogeneity of the column (for example, thickening due to the coupling connection), the value of the measured EMF ε changes, induced by increasing the flux of magnetic induction F according to Faraday's law:

due to an increase in the area of the coupling interval and, accordingly, the magnetic flux. Considering the magnetic permeability of the materials of the column and the sleeve are close, the change in the EMF value occurs due to a change in the area of the magnetic material crossed by the magnetic field

where D _M - sleeve diameter, D _O - casing diameter.

To assess the quantitative values of the system parameters of the proposed method, we present the data of the main used casing pipes and coupling joints in oil wells (GOST 632-80):

For example, the additional area ΔS in the interval of the coupling joint, crossed by the magnetic flux, for pipes with a diameter of 146 mm will be ΔS=S _M - S _O =4 901 mm ² .

The measurement quality is mainly affected by variations in the magnetic permeability of the column metal due to two reasons:

• development of metal corrosion processes, when centers of oxides appear in the metal structure, partially disturbing the orientation system of magnetic domains;

• change in the geometrical parameters of the column under the influence of external multidirectional pressure from the side of the enclosing rock mass, which also leads to a violation of the complex orientation of the magnetic domains that determine the value of the magnetic permeability of the metal.

In the event that there are no variations in the magnitude of the magnetic permeability of the pipe metal (μ _rel \u003d const), the measured EMF in the interval of the sleeve connection manifests itself as a contrasting sign-changing effect (the value of the magnetic flux changes sharply) against a relatively calm background (receiving coils are switched on differentially) of an extended section of the sleeveless interval pipes.

In the event that it is present from the causes of variations in μ, a high level of intense signal interference appears, against which the measured EMF from pipe couplings is practically indistinguishable.

The purpose of the proposed technical solution is to increase the noise immunity of the technology for locating sleeve joints of casing strings during geophysical surveys.

The method of locating coupling joints of casing strings is based on the principle of electromagnetic induction in electric current conductors. The measurements are performed by a clutch locator device, which is an electromagnetic system consisting of a generator 1 that creates an alternating electromagnetic field, a meter 2, a generator coil 3 and two receiving coils 4 and 5 with a common core, connected differentially.

The generator coil 3 is supplied with a supply current from the alternator 1. Measurements are made by two receiving coils with equal effective areas, switched on differentially, which makes it possible to obtain an EMF practically equal to zero if, opposite to each of the measuring coils, there is an unchanged pipe (background value ). The value of the measured EMF differs from zero (the complex differential signal increases sharply) in the event that one of the receiving coils is located in the interval of the unchanged pipe, and the second - in the interval of the coupling connection. When carrying out measurements, the main physical parameter that determines the magnitude of the alternating magnetic field is the electrical conductivity c. A sharp change in the value of the longitudinal electrical conductivity S=σ⋅h (См) at the transition from the casing string to the sleeve connection occurs due to a change in the thickness h in the places where the sleeve connection is installed.

For a qualitative determination of the position of the sleeve joint of the columns, it is necessary to exclude the influence of variations in the value of the magnetic permeability of the metal of the column.

This goal is achieved by the fact that the investigated interval of the column is subjected to magnetization to the saturation level (A.G. Stoletov’s curve is the dependence of magnetic susceptibility on the magnetic field strength in a ferromagnet. At certain large values of the external magnetic field, its value will not affect the change in the magnetization of the metal of the column, and magnetic saturation occurs).

Saturation occurs because the random arrangement of the structure of a molecule in a material (the magnetic domains) changes when the moments of the magnetic domains in the material become "aligned".

As the magnetic field strength H increases, these moments of the magnetic domains become more and more oriented along the direction of the field until they reach perfect alignment, creating maximum flux density, and any increase in magnetic field strength due to an increase in electric current in the coil will have little or no effect at all.

In order to achieve the effect of magnetic saturation in practice, it is necessary to create a constant magnetic field with an induction of the order of 1.2-1.6 Tesla at the measurement intervals with LM receiving coils connected differentially.

At the same time, a constant magnetic field of any magnetization source practically does not create interference of an inductive nature on measurements by receiving coils.

Creating a magnetic field with such an induction value is possible in two ways.

1. Application of permanent magnets. For such a task, only neodymium (Nd) magnets can be used, which create magnetic fields with an induction of the order of 1.2-1.6 Tesla, and at the same time practically do not lose their properties at high temperatures up to 150°C. One of the main advantages of using neodymium permanent magnets for solving the problem is the absence of energy consumption during their operation, which is important when conducting borehole surveys;

2. The use of an electromagnet, which is tightly wound turns of wire that create a magnetic field when a direct electric current passes. It is known that the polarity and strength of the magnetic field generated by an electromagnet can be adjusted by changing the direction and magnitude of the current flowing through the wire. The main core for amplifying the magnetic field is a ferrite core (Fig. 1) made of a magnetically soft ferromagnetic material, such as, for example, mild steel.

The purpose of the proposed technical solution is a small-sized autonomous device based on an effective technological method for increasing the noise immunity of the casing collar locator in the ranges of high variations in the magnetic susceptibility of the casing metal caused by various reasons.

The problem is solved by one of the following methods:

1. In the LM, additional external coils are installed at two intervals of the receiving coils, connected in series and fed with direct current (Fig. 2). The amplitude of the current in the additional supply coils is set in such a range as to create a constant magnetic field of the order of 1.2-1.6 T in the intervals of the receiving coils. The supply voltage of the additional coils is supplied through the logging cable.

In this case, the metal of the casing string is magnetized to a saturation level, which reduces almost to zero all interference caused by the inhomogeneity of the magnetic permeability of the metal, caused both by the development of oxidative processes and external external pressure in the intervals of plastic rocks of the geological section.

It should be noted that a constant magnetic field does not interfere with the operation of the receiving coils, since the current is induced in the receiving closed circuits only when the external magnetic field changes (in this case, the signal of the main generator coil).

The proposed device works as follows.

From the source 6, direct current is supplied to the magnetizing coils 7-8, located on a ferrite core common for all coils, the constant magnetic field of which magnetizes the interval of the column in the area of action of each of the two receiving coils.

The intervals of the examined pipe in the areas of action of the measuring coils are magnetized to the level of magnetic saturation, while all magnetic inhomogeneities of the metal of the column of different nature are practically leveled.

The device allows you to confidently fix the coupling connections of the steel column in conditions of strong magnetic interference.

2. Two permanent neodymium magnets (Nd) with a high coercive force are installed in the LM at two intervals of the receiving coils, retaining their properties at temperatures of about 140°C.

The main purpose of the magnets is to create a constant magnetic field of 1.2 - 1.6 T in the measurement intervals of the LM receiving coils. In this case, the metal of the string enters a state of magnetic saturation, in which the variations in magnetic permeability imposed during the operation of the well do not affect.

The intervals of the examined pipe in the areas of action of the measuring coils are also magnetized to the level of magnetic saturation, while the magnetic field of inhomogeneities of the column metal of various nature is practically leveled almost to zero.

The device allows you to confidently fix the coupling connections of the steel column in conditions of strong magnetic interference.

A constant magnetic field of 1.2 - 1.6 T also does not create any interference when receiving coils register magnetic fields of changing eddy currents in the casing string metal. The practical result of the invention is a high-quality determination of the location of the coupling joints of casing strings in any operating conditions.

Bibliography

1. Patent No. 2191365 of the Russian Federation. Locator of perforations and couplings of casing ferromagnetic pipes. / Polovko M.P., Khodakovsky A.V., Permyakov A.G., Golovko L.I., Melnikov A.V. IPC G01N 3/18(2006.01) G01N 27/82(2006.01) 2002.10.2020.

2. Patent No. RU 2715090 C2 RF. Locator of perforations and couplings of casing ferromagnetic pipes and method of its use. / Permyakov A.G., Khodakovsky A.V., Petrusova A.N., Polovko M.P., Khodakovsky A.V., Permyakov A.G., Golovko L.I., Melnikov A.V. IPC G01N 27/82(2006.01), 05/22/2017.

3. Magnetic locators of couplings and sticking determinant. https://studopedia.ru/20_115929_magnitnie-lokatori-muft-i-prihvatoopredelitel.html?ysclid=1981uhe5q7260080784.

4. Saveliev I.V. Course of general physics. T. 2. Electricity. M.: Nauka, 1970. 432 p.

5. GOST 632-80. Casing pipes and couplings to them. Specifications. - M. 1980. Introduction date 1983-01-01. The limitation of the validity period was removed by the Decree of the State Standard of 09.09.92 N 1146.

A method for increasing the noise immunity of the technology for locating sleeve joints of casing strings of geological exploration wells and a device for its implementation

Fig. 1. Scheme of the main device of the clutch locator: 1 - alternator, 2 - meter, 3 - generator coil, 4-5 - receiving coils.

Fig. Fig. 2. Diagram of the device of the clutch locator 1 according to the proposed method: 1-alternating current generator, 2 - meter, 3 - generator coil, 4-5 - receiving coils, 6 - direct current source, 7-8 - magnetizing coils.

Fig. 3 Diagram of the device of the clutch locator 2 according to the proposed method: 1 - alternator, 2 - meter, 3 - generator coil, 4-5 - receiving coils, M - magnetizing permanent Nd magnets.

Claims (2)

1. A method for locating coupling joints of casing strings and tubing, which consists in creating an alternating electromagnetic field by a current generator using a generator coil and registering a differential EMF from two identical receiving coils connected differentially, characterized in that, in order to increase noise immunity, an additional method is used magnetization of the metal of the columns to the level of magnetic saturation in the interval of the receiving coils, and in the complete absence of numerous interferences in the magnitude of the EMF, a conclusion is made about the actual position of the coupling joints. 2. A device for locating coupling joints of casing strings and tubing, containing a current generator that creates an alternating electromagnetic field, a meter, a generating coil and two receiving coils with a common core, connected differentially, characterized in that the device at two intervals of the receiving coils additionally contains a solenoid that includes two additional external coils connected in series and powered by direct current, or two permanent neodymium magnets (Nd), which provide magnetization of the pipe metal to obtain a constant magnetic field of 1.2-1.6 Tesla in the range of receiving coils, and the external coils are located on a single for all ferrite core coils.

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