RU2661505C1 - Coaxial induction cable, heating device and heating method - Google Patents

Abstract

FIELD: electrical equipment; heating.

SUBSTANCE: group of inventions relates to the field of electric heating by induction currents and can be used in the hydrate paraffin and asphalt-tar formations elimination and prevention devices in oil and gas wells and pipelines, as well as for the viscous products heating. Induction cable comprises central load-carrying element, coaxially arranged above it inner multiwire conductor, inner insulation layer, coaxially located above them soft magnetic material layer of variable cross-section, central insulating layer, coaxially located above them outer multiwire conductor and outer insulating layer. Inner and outer conductors, inner, central and outer insulating layers and the soft magnetic material layer are made flexible. Heating device includes linear heating element in the form of a tubing string in the borehole, pipeline or container and placed therein induction cable section, in which the outer and inner conductors are closed to each other in the head part. From the outside, one of the variable frequency power supply source terminals is connected to the induction cable central conductor, and the AC source other terminal is connected to the induction cable outer conductor. Heating method consists in the tubing string in well, pipeline or container induction heating performance using the induction cable outer conductor generated induction field by the current supply from industrial network to the alternating current source input.

EFFECT: increases the wells cleaning productivity with provision of the heat power output adjustment, reliability, provides easy maintenance.

3 cl, 2 dwg

Description

The invention relates to the field of electric heating by induction-resistive currents excited by a coaxial induction cable, and can be used in devices for eliminating and preventing the formation of paraffin hydrate and asphalt-tar deposits in oil and gas wells and pipelines, as well as for heating viscous products in pipelines and tanks with the aim of transportation and pumping.

A known method of cleaning oil and gas wells from the formation of plugs and their elimination, in which the geophysical cable is lowered into the well, loaded onto an electrode thermal device and an alternating electric current of industrial frequency is passed through it [G.A. Pavlenko. Experience in the industrial use of new technical means for the elimination of hydrate-paraffin formations in wells. - NTV "Logger". Tver: GERS. 1998. Issue. 58. S. 88-91].

A device for implementing this method contains an isolation transformer, a cable, the cores of which are connected to the transformer at one end and, to the electrode, with the other, to the electrode thermal device.

The disadvantage of the described method is the possibility of thermal effects only on the local volume of oil in the pipeline and, as a result, low cleaning efficiency and the re-formation of plugs in the well sections already passed by the heat device, which prevents further advancement due to cable setting.

A known method of cleaning wells with high-frequency currents using an induction heating device in the form of a cylindrical coil (inductor) [Shilov A.A., Khakimov T.G. et al. Thermal impact on the bottomhole formation zone using a high-frequency heater. - NTV "Logger". Tver: GERS. 1999. Issue. 64. P. 53-55], which induces heating eddy currents by its high-frequency electromagnetic field.

The disadvantage of the described method is the possibility of thermal effects only on the local section of the pipeline and, as a consequence, the risk of re-formation of plugs in the cleaned areas and it is impossible to use the above device for heating the well over the entire depth of the formation of deposits.

There is a method of eliminating and preventing the formation of deposits and plugs in oil and gas wells, in which a heating system from a linear heating element and a supply core is immersed in a well to a depth of formation of deposits, the heating is carried out by passing electric current through the heating element through the supply core and the heat generation is regulated by the depth of formation deposits by changing the electrical power in relay mode so that the temperature in the well is within 5-50 ° C higher than the melting point of paraffins, at the same time control the temperature of the electrical insulation of the heating elements, limiting it to the melting temperature, and change the speed of the product through the well to heat it sufficiently [RU, patent No. 2166615, IPC 6 ЕВВ 37/00, 36/04 from 11.10.99] .

A device for implementing this method in various embodiments contains one or more insulated linear heating elements and a conductive supply core, as well as a current contact between them, the heating elements and conductive core being combined by common electrical insulation in one structure in the form of a multicore cable.

In one embodiment of the device, it is indicated that a tubing can be used as a linear heater.

The disadvantage of this method and device for its implementation is the possibility of the main thermal effect only on the oil product, which leads to high energy consumption.

There is a method for preventing the formation of paraffin hydrate formations in oil and gas wells and pipelines, as well as for heating viscous products in pipelines and tanks for the purpose of transporting and pumping, consisting in the implementation of heating using the skin effect in the external conductor of the heating cable by supplying current from an industrial power supply network to the input of the AC source of the heating device. [RU, patent C1 No. 2589553, IPC Н05В 3/56 (2006.01) F16L 53/00 (2006/01)].

A device for implementing this method in various embodiments consists of a piece of a heating cable operating on the basis of the skin effect, comprising a central conductor, an inner insulating layer and a ferromagnetic outer conductor located coaxially on top of them, the inner insulating layer is made of a polymeric material, and the outer conductor is made in the form corrugated steel pipe with a wall thickness of less than three skin layer thicknesses at the operating frequency of the supply voltage and two-phase AC source, in with a torus, the first output of the AC source is connected to the proximal end of the central conductor, and the second to the proximal end of the external conductor, and at the distal end of the specified length of cable, the central and external conductors are closed to each other.

The disadvantage of this method and device for its implementation is the possibility of the main thermal effect only on the oil product, which leads to high energy consumption.

Closest to the claimed method in technical essence and the achieved effect is a method of eliminating and preventing the formation of deposits and plugs in oil and gas wells, in which the heating is carried out to the depth of formation of deposits using a heating system containing a linear heating element in the form of a pipe string in the well or a metal conductor immersed in the well, and the supply core immersed in the well, through which an electric current is passed, ensuring its closure in th the main part of the heating system to the linear heating element, while regulating the heat. A high-frequency electric current is passed through the supply core and the metal of the linear heating element is exposed to the high-frequency field of the supply core, while the frequency of the electric current is set at the lower threshold so that the penetration depth of the high-frequency field into the metal of the linear heating element is less than its thickness, and heat generation is regulated so that they provide preferential heat dissipation along the length of the linear heating element by reducing the gap between the last and the supplying residential and by increasing the frequency of the electric current from this lower threshold [Patent No. 2248442, cl. ЕВВ 37/00, 36/04, publ. 2005].

A device for its implementation comprises a heating system consisting of a supply core and a linear heating element in the form of a pipe string in the well or a metal conductor with a cross section selected sufficient to support the weight of the heating system immersed in the well, as well as an electric current closure between them in the head of the heating system. As a metal conductor, the device contains a bare metal conductor, the supply core is made of twisted and insulated conductors, and the electric current closure is made either in the form of a winding from a high-frequency wire wound on a ferrite core and placed inside the metal shell so that the ferrite core is closed by end parts on this shell, and the brand of core ferrite is selected from the condition that its temperature exceeds the loss of magnetic properties over the melting temperature deposits in the well, but not higher than the temperature of their ignition or coking, or in the form of a bare electrode connected to the supply core, equipped with protective insulating sleeves installed at intervals along the length of the bare electrode, and the bare electrode is located with the formation of a duct along its axis fluid between it and the heating element [Patent No. 2248442, class. ЕВВ 37/00, 36/04, publ. 2005].

A common disadvantage of devices for implementing the method is low reliability due to the possibility of breakdown of the head contact, as well as the bulkiness of the structure.

The objective of the invention is to increase the cleaning performance of wells, pipelines or tanks by ensuring the most complete coverage of the required heating zones and by regulating the released heat power on the surface of the pipeline of the well or other heated object, ensuring ease of maintenance and improving the reliability of the heating system.

In the part of the supply core and the main contactor, the problem is solved, and the technical result is achieved by the fact that it is proposed to use a coaxial induction cable containing the central conductor and the inner insulation layer, coaxially located flexible layers of soft magnetic material, the central insulation , external conductive and external insulating layers.

In terms of the heating device, the problem is solved, and the technical result is achieved by the fact that the proposed heating device consists of a linear heating element in the form of a pipe string in a well, a pipeline or a tank and, in contrast to the prototype, a piece of a coaxial induction cable immersed in the well, providing a short circuit the inner and outer conductors of the coaxial induction cable in the head and connecting the inner and outer conductors of the coaxial induction th cable in the outer portion to the terminals of different frequency AC source, wherein the coaxial cable has a different induction constructive inductance along its length.

In terms of the heating method, the problem is solved, and the technical result is achieved by the fact that the proposed method consists in carrying out heating by inductive currents excited in the pipe string of the well, pipeline or vessel by the external conductor of the coaxial induction cable by supplying current from an industrial network to the input of an alternating current source of various frequency of the above heating device. After supplying current from the industrial network, the operating frequency and output voltage of the AC source are preferably controlled.

The central conductor can be made in the form of a braid of non-ferromagnetic conductors with high conductivity or a load-bearing element braided by conductors with high conductivity. The inner insulating layer may be made of a polymeric material. The layer of soft magnetic material can be made with the possibility of changing the cross section along the longitudinal axis of the cable. The specified layer can be made in the form of a braid of soft magnetic wire and or a set of soft magnetic sleeves and or a spiral wound tape of soft magnetic material. Polymer insulation is applied over a layer of soft magnetic material. The external conductor can be made in the form of a braid of non-ferromagnetic conductors with high conductivity. On top of the outer conductor, an outer polymer sheath is preferably located. External polymer insulation can be made of reinforced non-conductive material.

The invention is illustrated by drawings.

In FIG. 1. shows a cross section of an induction cable.

In FIG. 2 shows an installation for processing a well, comprising a device for implementing a method for eliminating and preventing the formation of deposits and plugs in oil and gas producing wells.

The coaxial induction cable (Fig. 1) consists of a central load-bearing element 1 located coaxially on top of the central conductor 2, an inner insulating layer 3 of a heat-resistant polymer material, located coaxially on top of them a layer of magnetically soft material (magnetic core) 4, located on top of them of the middle insulating layer 5, the outer conductor 6 and the outer polymer sheath coaxially located on top of them 7. On one side of the cable, the inner and outer conductors are closed per 8 sliver and insulated, and on the other hand the inner and outer conductors are connected to terminals 9 and 10 of different AC frequencies.

The installation (Fig. 2) contains an AC source 11, a heating system of a central conductor of a coaxial induction cable 2, a distributed magnetic circuit of a coaxial induction cable 3, an outer conductor of a coaxial induction cable 4 and a linear heating element in the form of a pipe string of a well 12. In the head part, the central and the outer conductors of the coaxial induction cable are closed and externally insulated, and from the outer part, the outer and inner conductors are connected to the AC source current of various frequencies.

The operation of the linear heating system is as follows.

When you turn on the AC source 11 (Fig. 2), an alternating electric current begins to flow through the inner 2 and 4 outer conductors of the induction cable, creating a magnetizing force, under the influence of which divided wires are induced in the distributed magnetic circuit 3 of the induction cable and the distributed magnetic circuit of the pipe string in the well 12 variable magnetic fluxes. The magnetic core 3 of the induction cable provides a separation of the electromagnetic fields of the inner and outer conductors of the induction cable and minimizes the mutual influence of the alternating currents of the above conductors, on the one hand, and improves the magnetic coupling between the outer conductor of the induction cable and the heated pipeline. Under the action of an alternating magnetic flux induced by the outer conductor of the induction cable, eddy currents are induced in the pipe 12 to heat these pipes.

Thus, the proposed invention allows to achieve high productivity and quality of well cleaning, as well as to ensure ease of installation and reliable operation of the device.

Claims (3)

1. Coaxial induction cable comprising a central load-bearing element, an inner multi-wire conductor located coaxially on top of it, an inner flexible insulating layer of polymeric material coaxially located on top of them, characterized in that a flexible layer of soft magnetic material of variable cross section is coaxially located on top of them over of them, the central insulating layer of flexible polymer material is coaxially located; on top of them is an external multi-wire mammary conductor and disposed on top of them reinforced flexible outer insulating layer. 2. A heating device consisting of a linear heating element in the form of a pipe string in a well, a pipeline or a tank, a piece of a coaxial induction cable placed in it according to claim 1, and an alternating current source of various frequencies, in which the first output of the alternating current source is connected to the external end the Central conductor of the coaxial induction cable, and the second to the outer end of the outer conductor of the coaxial induction cable, and in the head of the specified length of cable outer conductors closed together and externally insulated. 3. The heating method, which consists in heating a pipe string in a well, pipe or tank using an induction field created by the external conductor of a coaxial induction cable by supplying current from an industrial network to the input of a variable frequency current source of different frequencies of the above-described heating device according to claim 2.

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