CA2949555C

CA2949555C - Inductor and method for heating a geological formation

Info

Publication number: CA2949555C
Application number: CA2949555A
Authority: CA
Inventors: Dirk Diehl; Andreas Koch
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2014-05-21
Filing date: 2015-04-23
Publication date: 2018-09-25
Anticipated expiration: 2035-04-23
Also published as: EP3146149A1; EP2947261A1; EP2947261B1; AR100534A1; WO2015176910A1; EA201692351A1; CA2949555A1

Abstract

The invention relates an inductor (1) for heating a geological formation, in particular a deposit (100) of a hydrocarbon-containing substance, for example a deposit of tar sand, oil shale, or heavy oil reserves, by means of electromagnetic induction, in particular for obtaining the hydrocarbon-containing substance from the deposit (100). The inductor (1) comprises at least one conductor (2), wherein the conductor (2) has at least one interruption point (4), wherein a rounded conducting body (40) is applied at least on one end region (6) of the conductor (2) at the interruption point (4). In particular, an individual wire can be interrupted and connected to the rounded conducting body (40). A sleeve can preferably be used which surrounds the rounded conducting body. The invention further relates to an operating method and a production method for the inductor.

Description

Description Inductor and method for heating a geological formaeion For in-situ extraction of hydrocarbons from an underground reservoir, for example for extraction of heavy oils, ultra-heavy oils or bitumen from oil sand or oil shale deposits, it is necessary to achieve the greatest possible flowability of the hydrocarbons to be extracted. One option for improving the flowability of The hydrocarbons during their extraction is to increase the temperature obtaining in the reservoir.
An applied method for increasing the temperature of the reservoir is inductive heating by means of an inductor, which is introduced into the reservoir (i.e. into the ground). By means of the inductor eddy currents are induced in the electrically-conductive reservoirs by electromagnetic fields which form, which heat up the reservoir, so that this consequently results in an improvement of the flowability of the hydrocarbons present in the reservoir. Eddy currents are induced in such cases, especially in the pore water of the reservoir, which through sales dissolved therein has an electrical conductivity. The heat is transferred from the water to the hydrocarbon by thermal conduction.
In order to achieve a sufficient heating power in the surroundings of the inductor for the required temperature increase large alternating current strengths of a few 100 A
are typically needed, since the reservoir surrounding the inductor mostly only has low electrical conductivity. By operating the inductor with a high alternating current strength a high inductive voltage drop is produced along the inductor, wherein the inductive voltage drop can be of the order of magnitude of a few 100 kV. Such high voltages can only be handled with difficulty in practice, so that it is expedient Lo compensate for said voltages.

Compensation for the inductive voltage drop is made possible, as described in patent DE 10 2007 040 605, by capacitors connected in series for example (reactive power compensation).
In the solution presented in said document the current-carrying conductors of the inductor are interrupted to form the capacitors and thus have a plurality of interruption points.
Series connection of capacitors can have the disadvantage that the interruption point can form weak points of the inductor.
For example partial discharges can occur at the interruption points in the event of a fault. Because of the inaccessibility of an inductor introduced deep into the reservoir, especially high demands are to be placed on the reliability of the inductor. In particular the aim is a continuous and maintenance-free operation over ten to twenty years. Should a capacitor of the inductor fail, because of the series connection of the capacitors, the whole inductor would cease to function and would have to be replaced.
The underlying object of the present invention is consequently to improve the reliability of an inductor.
The invention relates to an inductor for heating a geological formation, especially a reservoir of a substance containing hydrocarbons, for example an oil sand, oil shale or heavy oil reservoir, by means of electromagnetic induction, especially for recovering the substance containing hydrocarbons from the reservoir, comprising at least one conductor, wherein the conductor has at least one interruption point, characterized that a rounded conductive body is attached at least in an end area of the conductor at the interruption point.
Preferably both end areas of an interrupted conductor are embodied as described above at the interruption point.
The inventive fitting of a rounded conductive body is especially to be understood as contact between the rounded conductive body and the end area of the conductor. In this case the rounded conductive body represents a separate element. It is not simply a matncr of reshaping the end area of the conductor.
The inductor represents a current conductor. The current conductor is preferably manufactured, in a similar manner to a cable, from a plurality of individual wires insulated electrically in relation to one another. With the repeated application of interruption points on the inventive inductor an electrical series resonant circuit can be obtained, wherein the design is preferably implemented so that a resonant frequency ranging from around 13 kHz to 200 kHz is obtained, which also represents the preferred operating frequency of the inductor. The inductor is preferably activated via a generator which is at least operated with the said frequency range in this case.
The inventive interruption point is used to form conductor sections acting capacitively (in the sense of capacitors).
This is done by the capacitive coupling of the adjacenn conductor groups over a defined conductor length - for example to 50m - for reactive power compensation. The capacitances are preferably arranged as a series circuit. In a series circuit, if a capacitor fails, depending on the fault involved, the complete inductor can cease to function. This problem is reduced in accordance with the invention by a parr_ial discharge resistance of insulated individual wires being increased in relation to adjacent continuous wires and the opposite wire ends.
A further inventive advantage is that sharp edges which would otherwise lead to an excessive field strength increase (excessive increase in the electrical field strength) at the interruption point are avoided by the inventive embodiment.
Advantageously the reliability of the inductor is further improved by the avoidance of the excessive field strengths, which can lead over the period of continuous operation of the inductor to a destruction of the insulation layer at the interruption point and consequently to a failure of the inductor.
One embodiment of the invention is intended to provide each individual wire - a core - which is preferably individually insulated, with such an interruption point. Each wire preferably has such interruption points at repeated spacings.
This embodiment is advantageous if a wire is prepared for an inductor in a first step and is only subsequently stranded with further wires, together with a sequence of interruption points.
Another embodiment of the invention is aimed at providing a bundle of wires with such an interruption point, wherein the wires are preferably individually insulated. At one position in the inductor all wires of a bundle are interrupted and not just one wire. The interruption points occur over the length of the inductor at repeated spacings. This embodiment is advantageous if an already completely stranded cable without interruption points is present and is post-processed in a subsequent step for obtaining an inductor in which a bundle of wires on the cable is repeatedly separated at specific points.
In an embodiment of the invention the rounded conductive body can comprise a hemispherical surface or a continuously curved collar-shaped surface.

In a further embodiment the conductor can consist of a number of, preferably single - i.e. individual - insulated wires.
Wire ends of the end area of the conductor can be connected to the rounded conductive body by means of pressing and/or crimping and/or soldering and/or welding and/or electrically-conductive glue ing.
Furthermore the conductor can consist of a single wire. A
plurality of conductors can form the inductor.
Furthermore the rounded conductive body can be embodied at one end as a sleeve. The end area of the conductor can be introduced into the sleeve.
In particular the sleeve can have a blind hole or a through-hole into which the end area of the conductor is introduced into the sleeve.
Preferably a mechanical connection between the sleeve and the end area of the conductor can be made by means of pressing and/or crimping and/or soldering and/or welding and/or electrically-conductive glueing.
In one embodiment a further rounded conductive body can be attached to a further end area of the conductor at the interruption point. An insulating spacer can be positioned between the rounded conductive body and the further rounded conductive body.
Furthermore the insulating spacer can have a surface section embodied such that the surface section of the insulated spacer is connected mechanically and preferably by a form fit to a surface section of the rounded conductive body.
Furthermore the insulating spacer can be embodied and surface shapes of the insulating spacer can engage into surface shapes of the rounded conductive body and into surface shapes of the further rounded conductive body so that the rounded conductive body and the further rounded conductive body are fixed to each other without any offset and at a pre-specified distance from one another.
Preferably a mechanical connection can be made between the rounded conductive body and the insulating spacer by means of pressing and/or crimping and/or soldering and/or welding and/or glueing.
Furthermore the rounded conductive body and the further rounded conductive body and the insulating spacer can be introduced into a hollow-cylindrical further sleeve, wherein the further sleeve is embodied as an insulator or as a conductive sleeve.
Wires of a further conductor can in this case be routed through the materlal of the further sleeve embodied as an insulator.
Preferably wires of a further conductor can be conductively connected to the material of the conductive sleeve.
The inductor can also have at least two conductor bundles, wherein a first of the two conductor bundles can comprise at least the first conductor and a second conductor and a second of the two conductor bundles can comprise at least a third conductor and a fourth conductor, wherein a first hollow-cylindrical sleeve is embodied in one piece such that a jacket element of the first hollow-cylindrical sleeve and a jacket element of the second hollow-cylindrical sleeve are combined with one another for one secelon. A sleeve is thus produced which in cross-section has the shape of a number 8.
In addition the inductor can comprise at least three conductor bundles. A first of the three conductor bundles can comprise at least the first conductor and a second conductor. A second of the three conductor bundles can comprise at least a third conductor and a fourth conductor. A third of the three conductor bundles can comprise at least the fifth conductor and sixth conductor. A first hollow-cylindrical sleeve can be embodied in one piece with the second hollow-cylindrical sleeve and with a third hollow-cylindrical sleeve such that:
- a jacket element of the first hollow-cylindrical sleeve and a jacket element of the second hollow-cylindrical sleeve are combined with one another for a first section, and - the jacket element of the first hollow-cylindrical sleeve and a jacket element of the third hollow-cylindrical sleeve are combined with one another for a second section, and - the jacket element of the second hollow-cylindrical sleeve and the jacket element of the third hollow-cylindrical sleeve are combined with one another for a third section.
In this way an especially compact sleeve element comprising three hollow cylinders is produced.
In a development of the invention the interruption point of the conductor and conductor sections adjoining the interruption point and components provided at the interruption point can be surrounded by an outer sleeve.
Preferably the inductor can be errhodied as a multifilament conductor. In particular the conductor can form a conductor or a wire of the multifilament conductor.
With a plurality of conductors which each have an interruption point, the respective interruption points of the conductors can have an offset in relation to each other along a longitudinal extent of the inductor.
Preferably the conductors can form an interlaced and/or stranded structure which extends along the longitudinal extent of the inductor.

Invention further relates to an operating method for heating a geological formation, especially a reservoir of a substance containing hydrocarbons, for example an oil sand, oil shale or heavy oil reservoir, by means of the electromagnetic induction, especially for recovering the substance containing hydrocarbons from the reservoir, in which an inductor with at least one conductor disposed in the geological formation is activated such that an electromagnetic field forms in the geological formation, wherein the conductor has at least one interruption point for this purpose, wherein a rounded conductive body is fitted to at least one end area of the conductor at the interruption point.
Preferably alternating current can he supplied to the conductor, preferably with a frequency ranging from 10 kHz to 200 kHz.
The hemispherical embodiment of the ends advantageously compensates for the sharp edges or corners which can arise when the introduction point is produced, for example from the separation of the conductor with a cutting tool. The partial discharge resistance at the interruption point of the conductor is further improved. This is the case since the hemispherical even and/or smooth embodiment of the end prevents excessive field strengths, as occur for example with edge shapes. Preferably both ends of the interruption point are embodied in a hemispherical shape.
An embodiment of the end area is preferred in which the radii of curvature are greater than or equal to a radius of the cross-section (cross-sectional radius) of the conductor.
Excessive field strengths are further reduced by this, so that the partial discharge resistance of the conductor at the interruption point is additionally increased.

in accordance with an advantageous embodiment of the invention the conductor forms one conductor of a multifilament conductor.
There is provision here in particular for all conductors of the multifilament conductor to have an interruption point, the end areas of which are embodied in accordance with the invention. By designing a multifilament conductor from a plurality of conductors with inventive end areas an especially advantageous inductor for inductive heating is made possible.
Here the filaments of the multifilament conductor are formed by the plurality of conductors. Preferably a multifilament conductor comprises a plurality of at least 10 and at most 5000 conductors. The heating power of the inductor is advantageously increased by this.
In accordance with an advantageous embodiment of the invention the interruption point of the conductor is enclosed by an electrically-insulating outer sleeve.
The outer sleeve is used for mechanical, force-fir connection of the two ends of the conductor, which ends are formed by the interruption point of the conductor. The outer sleeve is expediently embodied as an electrically-insulating sleeve here to avoid a short-circuit at the interruption point. Preferably it is an outer sleeve molded from insulating material and/or insulating plastic which surrounds both ends of the interruption points. An outer sleeve is provided here of which the external diameter is significantly larger than the diameter of the cross-section of the conductor.
An outer sleeve in the sense of the invention is an electrically-insulating sealing element. It can involve a molded sleeve which is produced when a hollow shape is molded.
It has an insulating effect and lends mechanical stability.

An outer sleeve in this case is a connection element, and especially also an insulation and/or protection element. The outer sleeve is preferably connected firmly to the introduced cable. It surrounds an interruption point. Embodiments as cast-resin sleeves, gel sleeves, shrink sleeves - hot shrink or cold shrink sleeves - are conceivable.
An inductor with a plurality of conductors is preferred, wherein the interruption points of the conductors of a conductor group have a mutual offset along a longitudinal axis of the inductor. The offset is preferably small by comparison with the distance to the adjacent interruption points of the second conductor group.
Through this an inductor is advantageously formed of which the individual conductors are coupled capacitively to one another.
The series connection of the capacitors which are embodied by the capacitively-coupled conductors advantageously reduces the reactive power of the inductor and/or almost compensates for it in a resonant circuit.
Especially preferred is an inductor consisting of a plurality of conductors, wherein the conductors extend in parallel along the longitudinal axis of the inductor.
Advantageously the parallel course of the conductors means that an approximately constant capacitance between the conductors is made possible, so that there is an even and equally-distributed loading of the conductors of the inductor.
In accordance with an advantageous embodiment of the invention the conductors form an interlaced and/or stranded structure which extends along the longitudinal axis of the inductor.
This advantageously makes possible a cable arrangement of the conductors of the inductor which, through an interlacing and/or stranding, on the one hand is mechanically stabilized and on the other hand is suitable for formation of capacitances between the individual conductors.
In accordance with an advantageous embodiment of the invention alternating current is supplied to the conductor. If the conductor corresponds to a conductor group the conductor group is supplied with alternating current.
Advantageously all conductor groups of the inductor are supplied with alternating current.
This means that advantageously, by means of the inductance of the conductor and the capacitances which are formed by the interruption point and by means of the adjacent conductors, an electrical resonant circuit with a resonant frequency specific to the resonant circuit is embodied. Advantageously, through the embodiment of a resonant circuit, especially in the resonance of the resonant circuit, the reactive power which must be provided for the operation of the inductor is reduced.
Here the offset of the interruption point, which offset continues periodically along the conductors or the inductor, corresponds to the resonance length of the inductor.
Supply of an alternating current of which the frequency ranges from 10 kHz to 200 kHz is expedient.
Advantageously the resonant frequency of the resonant circuit lies in the said range of 10 kHz to 200 kHz here.
The invention also relates to a manufacturing method for an inductor for heating a geological formation, especially a reservoir of a substance containing hydrocarbons, for example an oil sand, oil shale or heavy oil reservoir, by means of electromagnetic induction, comprising the following manufacturing steps for at least one longitudinal position of a cable:

- Providing the cable with at least two conductor bundles Lwisted with one another;
- Soreading out a first of the two conductor bundles at the longitudinal position of the cable;
- Separating all wires of a second of the two conductor bundles at the longitudinal position of the cable;
- Removing insulation from cable ends of the separated wires;
- Connecting rounded conductive bodies to a de-insulated cable end in each case;
- Inserting a respective spacer between pairs of rounded conductive bodies;
- Optionally inserting a hollow-cylindrical shaped sleeve, wherein wires of the first conductor bundle are routed in a jacket surface of the sleeve;
- Optionally fitting an outer sleeve mold, injecting the outer sleeve mold into an outer sleeve, wherein the outer sleeve surrounds the rounded conductive bodies and a section of the two conductor bundles, and removing the outer sleeve mold.
As an alternative the invention relates to a further manufacturing method for an inductor for heating a geological formation, especially of a reservoir of a substance containing hydrocarbons, for example an oil sand, or oil shale or heavy oil reservoir, by means of the electromagnetic induction, comprising the following manufacturing steps:
a) Carrying out the following working steps for at least one longitudinal position of a wire:
- Providing the, preferably insulated, wire;
- Separating the wire at the longitudinal position of the wire;
- Removing insulation from the two cable ends of the separated wire;
- Connection of rounded conductive bodies in each case to a respective de-insulated cable end;

- Inserting a respective spacer between pairs of rounded conductive bodies;
- Optionally fitting an outer sleeve mold, injecting the outer sleeve mold into an outer sleeve, wherein the outer sleeve surrounds the rounded conductive bodies and two end areas of the separated wires, and removing the outer sleeve mold;
b) Winding the processed wire and/or stranding a plurality of wires processed in this way to form an inductor.
In the present method the rounded conductive bodies are preferably first connected to the de-insulated cable ends.
Subsequently the respective spacers are inserted between pairs of rounded conductive bodies.
These last mentioned steps can also be reversed as an alternative, so that first of all an already connected unit consisting of a spacer and a pair of rounded conductive bodies connected to said spacer are provided. This unit is preferably already connected using a force fit. Subsequently this unit can be connected to the two de-insulated cable ends.
b) Winding the processed wire and/or stranding a plurality of wires processed in this way to form an inductor.
The manufacturing method can preferably be implemented so that the connection of rounded conductive bodies to a respective de-insulated cable end in each case is carried out with the following steps:
- Pushing sleeves onto the respective cable ends, wherein the sleeves :In each case surround the rounded conductive bodies;
- Force-fit connection, especially crimping, of the respective sleeve with the respective de-insulated cable end.

In addition the aforementioned twisting of a plurality of wires processed in this wat to form an inductor can be carried out with the following steps:
Arranging a number of processed wires in relation to one another so that at least two bundles of wires are formed, whereby the wires of a first of the two bundles are aligned in a longitudinal alignment to one another so that separation points of the separated wires of the first bundle largely come to lie next to one another and the wires of a second of the two bundles in the longitudinal alignment are aligned in relation to one another so that separation points of the separated wires of the second bundle largely come to lie next to one another, wherein the separation points of the first bundle are disposed offset in relation to the separation points of the second bundle to one another;
Stranding the wires thus disposed so that the wires of the first bundle and of the second bundle are stranded alternately to one another.
According to one aspect of the present invention, there is provided an inductor for heating a geological formation, by means of electromagnetic induction, comprising at least one conductor, wherein the conductor has at least one interruption point, wherein a rounded conductive body is fitted to at least to one end area of the conductor at the interruption point, and the rounded conductive body is embodied at one end as a sleeve and the one end area of the conductor is introduced into the sleeve.
According to another aspect of the present invention, there is provided an operating method for heating a geological 14a formation, by means of electromagnetic induction, in which an inductor disposed in the geological formation with at least one conductor is activated such that an electromagnetic field forms in the geological formation, wherein the conductor has at least one interruption point, wherein a rounded conductive body is attached at least to one end area of the conductor at the interruption point.
According to still another aspect of the present invention, there is provided a manufacturing method for an inductor for heating a geological formation, by means of electromagnetic induction, comprising the following manufacturing steps: a) carrying out the following working steps for at least one longitudinal position of a wire: providing, the wire;
separating the wire at a longitudinal position of the wire;
removing insulation from two cable ends of the separated wire;
connecting rounded conductive bodies in each case to a respective de-insulated cable end; inserting a respective spacer between pairs of rounded conductive bodies; b) winding the processed wire and/or stranding a plurality of wires processed in this way to form an inductor.
According to yet another aspect of the present invention, there is provided a manufacturing method for an inductor for heating a geological formation, by means of electromagnetic induction, comprising the following manufacturing steps: a) carrying out the following working steps for at least one longitudinal position of a wire: providing the wire; separating the wire at the longitudinal position of the wire; removing insulation from the two cable ends of the separated wire; providing an already 14b connected unit consisting of a spacer and a pair of rounded conductive bodies connected to said spacer; connection of the unit to the two de-insulated cable ends; b) winding the processed wire and/or stranding a plurality of wires processed in this way to form an inductor.
Further advantages, features and details of the invention emerge from the exemplary embodiments described below as well as with reference to the drawings. In the drawings, in schematic diagrams:
Figure 1 Shows an inductor section which has a conductor with spherical terminations of an interruption point, after a first manufacturing step;
Figure 2 shows a cross-sectional drawing of Figure 1 with a spacer, after a second manufacturing step;
Figure 3 shows a cross-sectional drawing of Figure 2 with an additional hollow-cylindrical surrounding insulation body, after a third manufacturing step;
Figure 4 shows a three-dimensional diagram of Figure 3;

Figure 5 shows a three-dimensional diagram of Figure 2 with an additional hollow-cylindrical surrounding insulation body, after an alternate third manufacturing step;
Figure 6 shows a diagram of three conductor sections with additional hollow-cylindrical surrounding insulation bodies attached in each case, which are part of the inductor as a whole;
Figure 7 shows a diagram of an alternate embodiment of three conductor sections with attached additional hollow-cylindrical surrounding insulation bodies in each case, which are part of the inductor as a whole;
Figure 8 shows a schematic diagram of an inductor section comprising two multifilament conductors;
Figure 9 shows a sectional drawing of an alternate inductor section in which an interruption point is connected mechanically via two sleeves, a spacer and an outer sleeve;
Figure 10 shows a sectional drawing of a further alternate inductor section in which an interruption point is connected mechanically via two alternately designed sleeves, a spacer adapted thereto and an outer sleeve;
Figure 11 shows a schematic diagram of a perspective view of an inductor in a reservoir.
The same elements can be provided with :he same reference characters in the figures.
The figures relate to an inductor 1 for the exploitation of oil sand and heavy oil reservoirs, which is provided for heating up a reservoir in order to improve the flowability in-situ of the hydrocarbons to be extracted. The electromagnetic heating method presented is also called inductive heating, in which one or more conductor loops to which alternating current is supplied are introduced into the reservoir. Subsequently eddy currents, which then heat up the reservoir, are induced in the electrically-conductive reservoirs. In accordance with the present invention the current conductors, in a similar way to cables, are manufactured from a plurality of electrically-insulated individual wires.
Half of the individual wires are interrupted alternately and at defined spacings. Thus the electrical current is forced to penetrate the individual wire insulation as displacement current. The cable inductor - inductor 1 - thus acts in sections as a capacitance, through which the inevitable inductance of the conductor arrangement can be compensated for explicitly for a frequency. The conductor loop with the periodically arranged interruptions acts electrically as a series resonant circuit. In which is resonant frequency can be operated without reactance, i.e. without reactive power.
The embodiment of interruption points in the cable inductor discussed below has the advantage that sharp-edged wire ends can be avoided. Since especially high electrical field strengths can arise at sharp-edged wire ends it is advantageous to avoid such embodiments.
Figures 1 to 7 relate to an embodiment in which a conductor in the sense of the invention consists of a plurality of individual wires. All these individual wires belonging to a conductor are separated at one interruption point.
Figure 1 shows a section of an inductor 1, wherein the inductor 1 comprises a conductor 2 with an interruption point 4. In the exemplary embodiment shown the inductor 1 is thus embodied by means of the conductor 2 and further conductors not shown in the figure, wherein a plurality of conductors embodied in the same way is preferred for the inductor 1 for adaptation to the resonant frequency for example. To form a suitable capacitance a second conductor largely running in parallel to conductor 2 (not shown in Figure 1 but illustrated in Figure 4) is provided. Here the second conductor (labeled with reference characters 3 in Figure 3 and 4) has an interruption point 4 offset in relation to the conductor 2, wherein the offset is continued periodically and corresponds to the resonance length.
At the interruption point 4 the conductor 2 has two end areas 6 to each of which a rounded conductive body 40 and 40' is attached. The rounded conductive bodies 40 form ends of the conductive cable-type structure.
The rounded conductive bodies 40, 40' are embodied in accordance with Figure 1 in a hemispherical shape or a three-quarter spherical shape, wherein the rounded parts of the two rounded conductive bodies 40, 40' lie opposite one another and are at a distance from one another and are thus not touching.
The hemispherical embodiment or shape of the ends means that excessive field strengths are avoided at the ends and consequently at the interruption points 4, so that through this the partial discharge resistance of the interruption points 4 is increased.
In accordance with Figure 1 a number of twisted wires form the conductor 2.
The conductor 2 extending along a longitudinal axis A is preferably surrounded by a layer of insulation (not shown), which surrounds the conductor 2. Individual wires are likewise preferably provided with an individual layer of insulation.

The rounded conductive bodies 40, 40' are each full bodies which are embodied conductive. In particular metals or metallic alloys are considered as material.
The rounded conductive bodies 40, 40' can be called electrodes. They are preferably massive bodies and/or solid bodies. They are rounded in the same direction in which the separated cable end would otherwise point.
Ends of the individual wires are connected to the respective conductive bodies 40 or 40', especially on a rear side of the rounded conductive bodies 40 or 40', which for their part can form an even surface. The mechanical and conductive connection of the wires with a respective rounded conductive body 40, 40' can be made by soldering, welding, crimping or another connection technology. Penetration of a wire end into the rear side of a rounded conductive body 40, 40' to achieve a firm and conductive connection is illustrated in Figure 2 for example.
In operation the rounded conductive bodies 40, 40' are at the same electrical potential as the conductor 2.
The rounded conductive body 40 (or also 40') can also be seen as an electrode of a capacitor. In accordance with Figure 1 there are pairs of spherical electrodes into which all or at least a number of wire ends are merged and electrically connected. This avoids sharp-edged wire ends as well as the resulting high electrical field strengths at these sharp-edged wire ends, at which partial discharges would strike by preference.
A force-fit and form-fit paired fixing of the rounded conductive bodies 40, 40' can be provided. This is illustrated in Figure 2 in a cross-sectional drawing. This figure shows an insulating body as an insulating spacer 32. This is preferably made of ceramic and/or mineral and/or plastic-based material.

It comprises, at least partly, a pair of rounded conductive bodies 40, 40'. The surface shape of a section of the insulating spacer 32 in this case is adapted to the surface shape of one of the rounded conductive bodies 40, 40'.
Preferably - as shown in Figure 2 - the insulating spacer 32 has two opposing recesses into which in each case a rounded conductive body 40, 40' can he introduced at least partly.
The insulating spacer 32 can in such cases be a solid body which has been manufactured in advance and is merely connected to the rounded conductive bodies 40, 40'. As an alternative the insulating spacer 32 can also be applied in liquid form by means of injection-molding and/or filling technology, wherein the material subsequently hardens. The insulating spacer 32 (also called the insulating layer) can be attached to the surface of the conductor 2 by means of extrusion.
The insula,:ing spacer 32, which can preferably be ceramic or mineral-based or can also be plastic-based, encloses the electrodes, keeps them at a defined distance, centers them relative to the conductor structure passing through them (not shown in Figure 1 and 2, but shown in Figure 3) and thus insures a defined electrical field distribution without excessive fields (i.e. low relative peak values).
The rounded conductive bodies 40, 401, together with the insulating spacer 32 simultaneously make possible a mechanical and electrical stability of the insulation at the interruption points 4 of the conductor 2.
In accordance with the invention the rounded conductive body 40 or 40' represents a separate element or a separate body before assembly, which only forms a unit when joined to the conductor 2. The rounded conductive body 40 or 40' is in particular not merely the cable end of a separated conductor.

Figures 1, 2, and 3 can be understood such that they illustrate the inductor 1 at different consecutive stages of its manufacture.
Figure 3 illustrates, in a cross-sectional drawing, how two conductors 2 and 3 are advantageously disposed at an interruption point 4 of one of the conductors 2. An inner conductor corresponds to the conductor 2, which has an interruption point 4 with a pair of rounded conductive bodies 40, 40' and an insulating spacer 32 disposed between them. A
further conductor 3 - likewise embodied by a number of twisted wires - is routed - in a largely annular manner - past the interruption points 4 :o the outside. For this purpose a surrounding hollow-cylindrical insulation body 34 can be provided at the interruption points 4, wherein the wires of the further conductor 3 are routed through a jacket surface of the hollow-cylindrical insulation body 34. For this purpose the hollow-cylindrical insulation body 34 can have grooves into which the wires of the conductor 3 can be inserted.
For the section of the drawing shown the conductor 2 represents an inner conductor. The further conductor 3 represents an outer conductor. For another section however the conductor 2 can represent the outer conductor and the conductor 3 the inner conductor.
Figure 4 shows the same arrangement as Figure 3 in a three-dimensional view from outside.
The overall structure of the interruption in accordance with Figure 3 and 4 is achieved by routing the two conductor groups (2 and 3) away from each other into an inner group and an outer group. The inner wires (i.e. the conductor 2) are interrupted and merged on both sides into spherical electrodes, while the outer continuous wires (i.e. the further conductor 3) are routed in a defined manner in an insulating body. The entire arrangement can additionally be encapsulated with an insulating mass or enclosed by shrink tubing.
Figure 3 and 4 illustrate how a twisted cable consisting of two groups of wires can be processed, in which a first group of wires is widened and/or spread out in order to make an interruption for a second group of wires. In the axial course the two groups will be merged together again, so that at the two edges of the diagram of Figure 4 a largely normal twisted cable is to be seen. Were Figure 4 now to be extended, which is not shown however, the second group of wires would now be widened and/or spread out at the resonance link distance, in order now to make an interruption for the first group of wires.
The hollow-cylindrical insulation body 34, through the jacket surface of which the wires of the further conductor 3 are routed, insures a defined distance of the wires of the further conductor 3 from the rounded conductive bodies 40, 40. In this way danger of electrical flashover is prevented. The wires of the further conductor 3 are not interrupted by the hollow-cylindrical insulation body 34 but run through the insulation body 34.
Largely identical in its outer embodiment to Figure 3 and 4, the hollow-cylindrical insulation body 34 can also be replaced by a hollow-cylindrical conductor piece 33. This is illustrated with reference to Figure 5.
Figure 5 represents an alternative to Figure 3 and 4 and shows that the continuous outer wires of the further conductor 3 (thus the outer conductor for the section of the drawing shown) are merged mechanically and electrically in a hollow-cylindrical-shaped conductor 33. The inner insulation body which still exists - the spacer 32 - holds the spherical electrodes in position in relation to one another and relative to the outer conductor (3) or to the hollow-cylindrical-shaped conductor 33. Once again defined electrical field distributions with small excessive fields are achieved, for which preferably the edges of the hollow-cylindrical-shaped conductor 33 are also rounded.
In a similar way to the hollow-cylindrical insulation body 34, the wires of the further conductor 3 can be simply routed through the hollow-cylindrical-shaped conductor 33 so that the hollow-cylindrical-shaped conductor 33 and the wires of the conductor 3 have the same potential.
As an alternative the wires of the further conductor 3 can be separated at the interruption point. Subsequently the separated ends can be connected mechanically and electrically to the hollow-cylindrical-shaped conductor 33. This method of operation has the advantage that the complete inductor can be separated on the spot, then the rounded conductive bodies 40, 40' and the spacer 32 can be inserted for the conductor 2, and subsequently the wires of the conductor 3 can be connected again via the hollow-cylindrical-shaped conductor 33.
Processing is thus simplified.
The cable inductor (inductor 1) can be constructed from a number of conductor bundles. Figure 6 shows the inductor 1 with a three conductor bundles, which each have an outer insulator (34) in accordance with Figure 3 and 4. In Figure 6a a conductor bundle is largely covered in the three-dimensional view by a further conductor bundle. Figure 6b shows the view of the three conductor bundles from the axial direction. All conductor bundles each have an interruption point 4, wherein the interruption points 4 are made at a different longitudinal position along the inductor 1. The positioning of the interruption points 4 is illustrated with reference to Figure 8.
The cable inductor in accordance with Figure 6 is constructed from a number of conductor bundles which are all interrupted within a short axial distance in relation to one another (e.g.
within 1m). The inner conductors of the bundle can be interrupted individually, wherein the interruptions are made with a small axial offset. The interruptions (i.e. the interruption points 4) could then be encapsulated together in a an outer cable sleeve (not shown).
As an alternative - not shown - all wires of a respective outer conductor (corresponding to the further conductor 3 as shown in the figures) can now be formed from different bundles into a common outer conductor. Likewise not illustrated, the common outer conductor could be routed through a common cuter insulating body.
Figure 6 shows a diagram with a number of hollow-cylindrical insulation bodies 34. In a similar way an embodiment with metal cylinders (from Figure 5) can also be embodied in accordance with Figure 6. I.e. in this case hollow-cylindrical insulation bodies 34 are not involved but rather a number of hollow cylindrical metallic bodies 33. Otherwise the embodiment in accordance with Figure 6 applies correspondingly.
Figure 6b shows a cross-section through an inductor on an inductor section in which the wires are not spread out. The cross section is thus taken through a section in which the wires are twisted in a compact manner. The cross-sectional plane would be outside the area illustrated in Figure 6a.
Figure 6b therefore also additionally shows that the wires of the conductor 2 and the wires of the further conductor 3, in the sections of the inductor in which they are not spread out, are twisted such that the wires of the conductor 2 and the wires of the further conductor 3 are arranged alternately.
In a similar way to Figure 6, Figure 7 shows the inductor 1 with three conductor bundles, which each have an external insulator (34) in accordance with Figure 3 and 4. In Figure ia a conductor bundle is largely hidden in the three-dimensional view by a further conductor bundles. Figure 7b shows the view of the three conductor bundles from the axial direction. All conductor bundles each have an interruption point 4, wherein the interruption points 4 can occur at different longitudinal positions along the inductor 1 or at the same longitudinal position. The diagram in Figure 7 is to be understood such that, for the insulation body 34 shown, just one conductor is interrupted. As an alternative a number of conductors can also be interrupted for the insulation body 34 shown.
The cable inductor in accordance with Figure 7 is constructed from a number of conductor bundles. The inner conductors of the bundle can be interrupted individually. The interruptions can then be encapsulated together in an outer cable sleeve (not shown).
The three separately embodied hollow-cylindrical insulation bodies 34 from Figure 6 are now embodied in accordance with Figure 7 as a common body 34', in which three hollow cylinders are connected via their jacket surface with one another.
Figure 7b illustrates in this case that the central axes of the three hollow cylinders are disposed offset in relation to each other by 1200 in each case, in relation to a central axis of the insulation body (34'). This type of arrangement does not lead to any lateral offset and thus leads to a very compact construction.
Figure 7 shows a diagram with a number of combined hollow-cylindrical insulation bodies 34'. In a similar manner an embodiment with a common metallic cylinder (combined from the individual metallic cylinders from Figure 5) can also be embodied in accordance with Figure 7. I.e. in this case a body made of a number of hollow-cylindrical insulation bodies is not involved but rather a body made of a number of hollow cylindrical metallic bodies. Otherwise the embodiment in accordance with Figure 7 applies correspondingly.

It can be seen from Figures 4, 5, 6 and 7 that the inductor 1 per se is a twisted cable comprising a plurality of individually insulated wires, wherein the twisting may possibly he widened out for the interruption points. In the said figures two conductor bundles - labeled 2 and 3 - are shown, wherein all wires of a conductor bundle are at the same potential. The wires of the conductor bundle are twisted so that wires of the first conductor bundle are adjacent to wires of a second conductor bundle and then once again adjoin wires of the second conductor bundle. Through this adjacency of different phases of the wires the capacitive effect between the wires can be improved.
Also conceivable are inductors with more than two conductor bundles. Then, for N conductor bundles one wire of each of the different conductor bundles is disposed adjacent to one another, to which the next N wires are then adjoined by a wire in each case of the different conductor bundles.
All these wires run in an extent of the inductor 1 but are twisted together however.
It is also conceivable to form different groups of wires and to twist each group individually, wherein the inductor 1 includes all twisted groups.
Figure 8 shows an inductor 1 which has at least two multifilament conductors 21, 22, wherein the multifilament conductors 21, 22 are formed in each case from a plurality of conductors 2.
Each conductor 2 of the multifilament conductors 21, 22 consequently has interruption points 4, wherein the end areas 6 of the conductors 2 not shown are embodied in accordance with the invention at the interruption points 4. In other words the multifilament conductors 21, 22 are made up of a plurality of conductors 2 in accordance with Figure 1.
The conductors 2 of the multifilament conductor 21, 22 essentially run in parallel to one another. Through the interruption points 4 and an offset 14 of the interruption points 4 of the first multifilament conductor 21 in relation tc the interruption points 4 of the second multifilament conductor 22, the conductors 2 of the first multifilament conductor 21 are advantageously coupled capacitively with the conductors 2 of the second multifilament conductor 22. The offset 14 here essentially corresponds to a resonance length, wherein the offset 14 continues periodically along the conductor 2. The conductor 2 here has a plurality of interruption points 4, wherein the interruption points 4 of each conductor 2 have a constant spacing from one another.
The partial discharge resistance of the inductor 1 is advantageously improved by the end areas 6 of the conductor 2 of the multifilament conductors 21, 22 not shown in any greater detail and embodied in accordance with the invention.
In addition the mechanical strength at the interruption points 4 is increased.
Figure 9 shows a schematic cross-sectional diagram in which the rounded conductive body 40, 40 is placed as a sleeve 31 on a cable end of a respective wire of the inductor.
Figures 9 and 10 relate here to an embodiment in which a conductor in the sense of the invention consists of a single individual wire - a single strand. Each individual wire is separated at an interruption point and the two ends produced are each individually provided with one sleeve 31.
In accordance with Figure 9 an interruption point 4 is shown as an alternate embodiment to Figure 1 to 5. An end area 6 of the conductor 2 - this can involve a plurality of twisted strands - has its insulation removed. Otherwise the conductor

2 is surrounded by an insulation 55. A largely cylindrical and largely rotation-symmetrical sleeve 31 surrounds a recess for receiving the end area 6 of the conductor 2. The other end of the sleeve 31 forms the rounded conductive bodies 40, 40'. By accepting the end area 6 of the conductor 2 into the recess of the sleeve 31 and establishing a firm connection, the rounded conductive body 40, 40' is thus applied to the conductor 2.
The firm connection - conductive and making a form fit - is preferably made by means of pressing and/or crimping and/or soldering and/or welding and/or electrically-conductive glue ing.
The other end of the interrupted conductor likewise receives a corresponding sleeve 31.
The sleeve 31 - also called the screening sleeve below - is in this case a molded part, preferably made of copper or of another electrically-conductive material.
The sleeve 31 corresponds to a cable shoe which can be pushed during manufacturing of the inductor over a wire end - the end area 6.
The sleeve 31 is thus at the same electrical potential during operation as the conductor 2.
In accordance with the surface shape of The rounded conductive bodies 40, 401 an insulating spacer 32 with two opposing recesses is provided, which each correspond to the surface shape of the rounded conductive body 40, 40'.
In this way the insulating spacer 32 can be connected via a form fit and/or force fit to the rounded conductive bodies 40, 40'.

The insulating spacer 32 in accordance with Figure 9 has a recess into which the rounded conductive body 40, 40 can penetrate. The insulating spacer 32 surrounds the sleeve 31 Preferably also transverse to the axial extent of sleeve 31, so that the sleeve 31 is disposed coaxially with the conductor 2 and/or the insulating spacer 32.
In accordance with Figure 9 the entire arrangement of the interruption points 4 is enclosed by an electrically-insulating outer sleeve 30. The outer sleeve 30 in this case is especially a molded outer sleeve. A molded outer sleeve has the advantage that voids and air pockets can be avoided. The outer sleeve 30 has an insulating effect and at the same time lends mechanical stability.
The outer sleeve 30 in particular surrounds the two end areas 6 of the conductor 2, the two sleeves 31 and the spacer 32.
Preferably the outer sleeve 30 surrounds sections of the conductor 2 already insulated, but also especially the sections of the conductor 2 in the end areas 6 in which insulation has been removed. The outer sleeve 30 in this case is especially a rotation-symmetrical body.
In order to explain the manufacturing mer_hod reference is further made to Figure 9. The two wire ends which are produced when a wire is interrupted are introduced into the insulation elements in order to connect them to each other mechanically in a defined position and insulate them electrically. The insulation element consists of two conductive screening sleeves (31) (for example as a molded copper part), an electrically-insulated spacer 32 mechanically connecting the screening sleeves (31) and an insulating envelope acting outwards which is especially embodied as a molded outer sleeve (30). Each screening sleeve (31), which consists of material which conducts electricity well - for example copper, aluminum, other metals or alloys, graphite, possibly electrically-conductive plastics such as CF PEEK (carbon fiber reinforced polyetheretherketone) has a hole into which the individual wire end from which a few millimeters of insulation has previously been stripped back is introduced. The mechanical and electrical connection of the individual wire end and screening sleeve (31) can be made by deforming the collar of the screening sleeve (31) by means of a suitable press/crimp tool, wherein the tool is designed such that no burrs or edges occur on the screening sleeve (31). As an alternative the connection can be made by soldering, welding or electrically-conductive glueing. The spacer 32 is made of a high-temperature-resistant and electrically-insulating material, for example a plastic such as PFA (Perfluoro Alkoxy Aikene), PTFE (Polytetrafluorethylene) or PEEK
(Polyetheretherketone) or a ceramic. The screening sleeves (31) are introduced mechanically rigidly, preferably with a form fit, into the spacer 32. The spacer creates a defined axial distance between the screening sleeves (31), crier= the screening sleeves (31) coaxially and centers them. The production of the insulating element is concluded by a gas-free enveloping (in the form of the said molded outer sleeve) of screening sleeve pair (31) and spacer 32 through a high-temperature-resistant insulation material, which is already on the individual wire insulation. Preferably insulating plastics (for example those mentioned above) can be used for this purpose. Especially suitable are those which can be applied by an injection (vacuum) molding or extruding method. In particular the same thermoplastic can be used which already forms the outer layer of the individual wire insulation and/or the spacer 32, for example PFA.
Figure 10 shows an alternative embodiment to Figure 9, in which the arrangement is embodied analogously to that shown in Figure 9, except for the shape of the sleeves 31 and the spacer 32. The transition between the sleeve 31 and the spacer 32 is however largely inverse to Figure 9, i.e. concave surfaces are now convex and vice versa.

The rounded conductive body 40, 40' has a hemispherical convex surface in Figure 9. In accordance with Figure 10 it now has a continuously curved collar-shaped surface (40B). The surface of the sleeve 31 is concave in sections. Since the sleeve 31 is preferably rotationally-symmetrical, the shape of the a)dal end side directed towards the spacer 32 can also be referred to as toroidal, more precisely as semi-toroidal.
The spacer 32 is again adapted to the surface of the sleeve 31. Consequently the insulated spacer 32 has a rounded pin.
The pin in this case can be introduced into the recess of the central collar-shaped surface (40B) of the sleeve 31, so that a stable connection between sleeve 31 and spacer 32 arises.
Preferably the spacers 32 in Figure 9 and 10 are embodied axis-symmetrically and rotation-symmetrically. However it is also possible to provide individual shapes so that the spacer 32 and the sleeve 31 engage into one another so that only a specific position is possible. It should be insured here however that the surfaces of the conducting elements are as even in shape as possible and the conductive body is rounded, so that a flashover of an arc can be avoided.
The spacer 32 creates a defined axial distance between the surfaces (40A) of the screening sleeves (31) facing towards one another. It orients the screening sleeves (31) coaxially to one another. It centers them in relation to one another.
The embodiment of Figure 10 differs from that of Figure 9 in that the spacer 32, similar to the wire ends, is introduced into a screening sleeve (31) modified for its part with blind holes on both sides. As an alternative - not shown - a through-hole with possibly different radii on both sides of a screening sleeve (31) can be used. The connection of screening sleeve (31) and electrically-insulating spacer 32 can be made by pressing or crimping (possibly in one operation together with the wire ends) or glueing. Theinjection-molded outer sleeve finally applied - i.e. the outer sleeve 30 - once again insures insulation radially outwards, especially to the adjacent continuous wires.
Figures 1 to 7 relate to an embodiment in which the conductor 2 in the sense of the invention consists of a plurality of individual wires. All these individual wires belonging to a conductor are separated at one interruption point. This is advantageous if a twisted cable already exists and interruption points are to be inserted retroactively.
Figures 9 and 10 by contrast relate to an embodiment in which the conductor 2 in the sense of the invention consists of a single individual wire. This individual wire can for example have a cross-section of around 1 mm2. Each individual wire is separated at an interruption point and the two ends produced are each provided with a sleeve 31. This embodiment is advantageous if individual wires are provided with interruption points beforehand and only subsequently is a twisting or stranding or winding into a common cable comprising a number of these individual wires undertaken. The stranding has the effect of relieving the strain on the inductor 1.
The use of rounded surfaces (cf. 40, 40') at the interruption point 4 has the following advantages:
The arrangement makes it possible to avoid local peaks of the electrical field strengths at conductor edges and points which would otherwise be present which could lead to partial discharges and thus to the failure of the inductor 1. It is further advantageous that the number of critical conductor ends is drastically reduced, which likewise serves to enhance reliability.
A positive side effect is that the inductor cable (in a first step however without interruptions) can be continuously manufactured like a normal cable and the interruptions can be made retroactively. It is thus especially possible to subject the still uninterrupted cable to a partial discharge test beforehand in order to identify possible weak points of the individual conductor insulation in advance.
Furthermore the determination of the resonant frequency, which depends like the inductor loop geometry on the distance between the interruptions, can be tuned after the cable manufacturing to the respective reservoir and does not have to be known before the cable manufacturing. I.e. the cable can be manufactured within limits independent of the individual reservoir and the adaptation is only made by the retroactive insertion of the interruption points at an individually defined distance (resonance length).
The advantages of the insulation element are also as follows:
The screening sleeves (31) envelope the individual wire ends which, because of the separation/cutting without further measures, generally have sharp edges and burrs and avoid peaks of the electrical field at the individual wire ends because of the screening effect caused by equal potential of wire end and screening sleeve (31).
Excesses of the electrical field do not occur on the outer surfaces of the screening sleeves (31), since the screening sleeves (31) in accordance with the invention do not have any edges, but only roundings.
The spacers 32 insure that the electrical field strength between a screening sleeve pair (reference character 31 in each case) do not exceed any critical values.
Critical field strengths at the end of the individual wire insulation of the wire end are avoided or reduced by the overhang of the screening sleeve (31) provided. This point is critical since it may not be able to be insured that they can be surround-molded in a gas-free manner.
The insulation element creates a connection with tensile strength from one wire end via first screening sleeve (31), spacer 32, second screening sleeve (31) to the other wire end.
This is needed for subsequent s-,1-randing steps.
The spacer according to Fiaure 9 guarantees a minimum layer thickness of the insulation thickness in the radial direction, even if the molded outer sleeve - i.e. the outer sleeve 30 -is attached axially offset, since the spacer during the injection molding process can rest at a maximum on the inner wall of the injection mold.
With the spacer 32 according to Figure 10 a more rational production may possibly be achieved, in that the wire ends can be pressed simultaneously with the spacer 32 with the screening sleeve (31).
Figure 11 shows a perspective cross-section of an oil sand reservoir as the reservoir with an inductor 1, which can also be referred to as an electrical conductor loop, running largely horizontally in the reservoir. An oil sand deposit referred to as a reservoir is shown, wherein for the specific considerations a cuboid unit 100 with the length 1, the width w and the height h is chosen as an example. The length 1 can amount to up to a few multiples of 500 m, the width w 60 up to 100 m and the height h about 20 to 100 m. it should be taken inLo account that, starting from the earth surface E, an "overburden" of depth s of up to 500 m can be present.
Also shown is an arrangement for inductive heating of the reservoir section 100. This can be formed by a long, i.e. a few 100 m to 1.5 km, conductor loop 120 to 121 laid in the ground, wherein the outwards conductor 120 and return conductor 121 are routed next to one another, i.e. at the same depth, and are connected to one another at the end via an element 15 inside or outside the reservoir. At the start the conductors 120 and 121 are routed vertically or at a slight angle downwards and are supplied with electrical power by a high-frequency generator 60 which can be accommodated in an external housing. The high-frequency generator 60 or medium-frequency generator preferably covers a range of 10 kHz to 200 kHz or a sub range thereto and can preferably be set to any given frequencies in this frequency range. Also conceivable is an operating range of 1 kHz to 500 kHz.
In Figure 11 the conductors 120 and 121 run next to one another at the same depth. They can also be routed above one another. Below the conductor loop (i.e. the conductor 120 and 121), i.e. on the floor of the reservoir unit 100, an extraction pipe 102 is shown, via which the liquefied bitumen or heavy oil can be collected and/or transported away.
Typical distances between the outwards and return conductors 120, 121 are 5 to 60 m for an external diameter of the conductors of 10 to 50 cm (0.1 to 0.5 m).
The outwards conductor 120 and the return conductor 121 from Figure 11 are, at least in the area of their largely horizontal extent, preferably embodied with interruptions in accordance with Figures 1 to 10.
Typical operating parameters are for example an inductively introduced heating power of 1 kW per meter of double conductor. A current amplitude of 300 A to 1000 A can be provided for example. An individual wire can for example have a diameter of 0.5 to 1 mm. Overall the wires in the inductor can have a cross-section of 1000 to 1500 mm2. For example the inductor can consist of 2500 to 3500 individual massive wires.
Copper can be provided as the material for the wires. Teflon can be provided for example as insulation for each individual wire. Wall thicknesses of the insulation can for example amount to 0.2 to 0.3 mm. The doubled resonance length through typical inductor can e.g. amount to 35 to 50 m. The wires are arranged in the longitudinal direction with an offset of the interruption points by the resonance length.
The invention in accordance with the figures relates to an arrangement and a method for application of heat to a geological formation, especially to a reservoir present in a geological formation, especially for recovering a substance containing hydrocarbons - especially crude oil - from the reservoir. An inductor is proposed which is designed for in-situ extraction with underground reservoirs, approximately as from a depth of around 75 m. this means that with this technique the oil sand - i.e. the sand and the stone with the oil contained therein - remains in place. The oil or the bitumen is separated from the grains of sand by means of electromagnetic waves and possibly further different methods and is made more filowahle, so that it can be extracted. The "in-situ" method presented has the principle of increasing the temperature underground and thus reducing the viscosity of the bound oil or of the bitumen and making it more flowable in order to subsequently pump it out. The heating effect especially causes the long-chain hydrocarbons of the highly-viscous which in to fracture. The inductor - i.e. an electrical conductor which is embodied as an induction line -can be operated with low losses as a resonant circuit. Since preferably both ends cf the inductor are connected to the frequency generator, the induction line forms an induction loop. The technical realization of the electrical line is carried out as a resonant circuit. The frequency generator can preferably be embodied as a frequency converter, which converts a frequency of 50Hz or 60Hz from the mains into a voltage with a frequency in the range of 1 kHz to 500 kHz. The frequency converter can be installed on the surface.
Furthermore in the reservoir zone heated by the induction loop preferably at least one extracLion hole can be drilled. In addition at least one injection hole for injection of hot steam can be provided optionally between two continuous quasi-parallel holes in which the induction loop is disposed.
After the inductor has been laid as an induction loop into at least two holes and the induction loop has been connected to the frequency generator, the supply of power to the conductor begins in operation and thus the inductive heating underground with the resultant formation of a heating zone which is characterized by an increased temperature. The conductor loop or induction loop acts in operation as an induction hearer in order to introduce additional heat into the reservoir. The active area of the conductor, in the essentially horizontal direction within the reservoir, can describe a practically closed loop (i.e. an oval). An end area - possibly laid above ground - can be joined to the active area. The parts of the start and end area of the conductor laid above ground can be electrically contacted with a current source - the frequency generator. There is preferably provision to compensate for the line inductivity of the conductor in sections by series capacitances. In this case there can be provision for the line with integrated compensation that the frequency of the frequency generator is tuned to the resonant frequency of the current loop. The capacitance in the conductor can be formed between cable sections. A dielectric present can be selected in such cases such that it fulfills the requirement for a high dielectric strength and a high temperature resistance.
Insulation of the inductor from the surrounding soil is advantageous in order to prevent resistive currents through the soil between the adjacent cable sections, especially in the area of the capacitors. The insulation further prevents a resistive current flow between outwards and return conductor.
The longitudinal inductance can be compensated for in operation by means of cross capacitances. The capacitance per unit length - which a two-wire line, such as for example a coaxial line or multi-wire line, provides over its entire length in any event - can be used to compensate for the longitudinal inductances. For this purpose the inner and outer conductor are interrupted at equal distances alternately and thus the current flow is forced via the distributed cross capacitances.
The temperature in operation in the heating zone depends on the introduced electromagnetic power, which is produced by the geological and physical (e.g. electrical conductivity) parameters of the reservoir and also the technical parameters of the electrical arrangement, especially consisting of the inductor and the high-frequency generator. This temperature can reach up to 300 C and is able to be regulated by changing the current strength through the loop of the inductor. The regulation is undertaken via the frequency generator. The electrical conductivity of the reservoir can be increased by additional injection of water or of another fluid, e.g. an electrolyte.
The temperature initially develops as a result of the induction of eddy currents into the electrically conductive underground areas. During the course of the heating temperature gradients arise, meaning locations at a higher temperature than the original reservoir temperature. The higher temperature locations occur where eddy currents are induced. The output point of the heat is therefore not the induction loop or the electrical conductor but is the eddy currents induced by the electromagnetic field in the electrically-conductive layer. Through the temperature gradients arising over the course of time, depending on the thermal parameters such as thermal conductivity, thermal transfer also arises, through which the temperature profile equalizes. With a greater distance to the conductor the strength of the alternating field reduces so that only a lesser heating is made possible there.

If on the other hand the fluids or the electrically-conductive liquids made fluid are transported away immediately as soon as they have been made fluid, then at the emptied points there is less heating by electrical eddy currents the more the soil with its electrical conductivity has been also transported away. Although the electromagnetic field is still there, Eddy currents can only form however where there is still conductivity present. However a flowing away of a liquid can have the effect of another liquid flowing in.
The power provided is preferably set to between 100 kW and several megawatts.
The invention merely relates to one inductor. However a number of inductors next to one another and at a distance from one another can be laid in a reservoir, depending on its size.
Although the invention has been illustrated in greater detail and described by exemplary embodiments, the invention is not restricted by the disclosed examples and other variat_ions can be derived herefrom by the person skilled in the art without departing from the scope of protection of the invention.

Claims

CLAIMS:

1. An inductor for heating a geological formation, by means of electromagnetic induction, comprising at least one conductor, wherein the conductor has at least one interruption point, wherein a rounded conductive body is fitted to at least to one end area of the conductor at the interruption point, and the rounded conductive body is embodied at one end as a sleeve and the one end area of the conductor is introduced into the sleeve.

2. The inductor as claimed in claim 1 for heating a geological formation that is a reservoir of a substance containing hydrocarbons.

3. The inductor as claimed in claim 1 for heating a geological formation that is a reservoir containing an oil sand, oil shale or heavy oil reservoir.

4. The inductor as claimed in claim 2 for extracting the substance containing hydrocarbons from the reservoir.

5. The inductor as claimed in claim 1, wherein the rounded conductive body comprises a hemispherical surface or a continuously curved collar-shaped surface.

6. The inductor as claimed in claim 1, wherein the sleeve has a blind hole or a through-hole into which the one end area of the conductor is introduced into the sleeve.

7. The inductor as claimed in claim 1 or 6, wherein a mechanical connection between the sleeve and the one end area of the conductor is made by means of pressing.

8. The inductor as claimed in any one of claims 1 to 7, wherein a mechanical connection between the sleeve and the one end area of the conductor is made by means of crimping.

9. The inductor as claimed in any one of claim 1 to 8, wherein a mechanical connection between the sleeve and the one end area of the conductor is made by means of soldering.

10. The inductor as claimed in any one of claim 1 to 9, wherein a mechanical connection between the sleeve and the one end area of the conductor is made by means of welding.

11. The inductor as claimed in any one of claim 1 to 10, wherein a mechanical connection between the sleeve and the one end area of the conductor is made by means of electrically-conductive glueing.

12. The inductor as claimed in any one of claims 1 to 11, wherein a further rounded conductive body is fitted to a further end area of the conductor at the interruption point and that an insulating spacer is positioned between the rounded conductive body and the further rounded conductive body.

13. The inductor as claimed in claim 12, wherein the insulating spacer has a surface section, wherein the surface section of the insulating spacer is connected mechanically to a surface section of the rounded conductive body.

14. The inductor as claimed in claim 13, wherein the surface section of the insulating spacer form fit to the surface section of the rounded conductive body.

15. The inductor as claimed in claim 12 or 13, wherein the insulating spacer is embodied and surface shapes of the insulating spacer engage into surface shapes of the rounded conductive body and into surface shapes of the further rounded conductive body such that the rounded conductive body and the further rounded conductive body are fixed in relation to one another without an offset and at a pre-specified distance.

16. The inductor as claimed in any one of claims 12 to 15, wherein a mechanical connection between the rounded conductive body and the insulating spacer is made by means of pressing.

17. The inductor as claimed in any one of claims 12 to 16, wherein a mechanical connection between the sleeve and the one end area of the conductor is made by means of crimping.

18. The inductor as claimed in any one of claims 12 to 17, wherein a mechanical connection between the sleeve and the one end area of the conductor is made by means of soldering.

19. The inductor as claimed in any one of claims 12 to 18, wherein a mechanical connection between the sleeve and the one end area of the conductor is made by means of welding.

20. The inductor as claimed in any one of claims 1 to 19, wherein a mechanical connection between the sleeve and the one end area of the conductor is made by means of soldering.

21. The inductor as claimed in any one of claims 1 to 16, wherein the interruption point of the conductor and conductor sections adjoining the interruption point and components provided at the interruption point are surrounded by an outer sleeve.

22. An operating method for heating a geological formation, by means of electromagnetic induction, in which an inductor disposed in the geological formation with at least one conductor is activated such that an electromagnetic field forms in the geological formation, wherein the conductor has at least one interruption point, wherein a rounded conductive body is attached at least to one end area of the conductor at the interruption point.

23. The method as claimed in claim 22 for heating a geological formation that is a reservoir of a substance containing hydrocarbons.

24. The method as claimed in claim 22 for heating a geological formation that is a reservoir containing an oil sand, oil shale or heavy oil reservoir.

25. The method as claimed in claim 23 for extracting the substance containing hydrocarbons from the reservoir.

26. A manufacturing method for an inductor for heating a geological formation, by means of electromagnetic induction, comprising the following manufacturing steps:
a) Carrying out the following working steps for at least one longitudinal position of a wire:
Providing, the wire;
Separating the wire at a longitudinal position of the wire;
Removing insulation from two cable ends of the separated wire;
Connecting rounded conductive bodies in each case to a respective de-insulated cable end;
Inserting a respective spacer between pairs of rounded conductive bodies;
b) Winding the processed wire and/or stranding a plurality of wires processed in this way to form an inductor.

27. The manufacturing method as claimed in claim 26 for heating a geological formation that is a reservoir of a substance containing hydrocarbons.

28. The manufacturing method as claimed in claim 26 for heating a geological formation that is a reservoir containing an oil sand, oil shale or heavy oil reservoir.

29. The manufacturing method of any of claims 26 to 28, wherein providing the wire comprises providing insulated wire.

30. The manufacturing method of any of claims 26 to 29 further comprising fitting an outer sleeve mold, injecting the outer sleeve mold into an outer sleeve, wherein the outer sleeve surrounds the rounded conductive bodies and two end areas of the separated wire, and removing the outer sleeve mold.

31. A manufacturing method for an inductor for heating a geological formation, by means of electromagnetic induction, comprising the following manufacturing steps:
a) Carrying out the following working steps for at least one longitudinal position of a wire:
- Providing the wire;
- Separating the wire at the longitudinal position of the wire;
- Removing insulation from the two cable ends of the separated wire;
- Providing an already connected unit consisting of a spacer and a pair of rounded conductive bodies connected to said spacer;
- Connection of the unit to the two de-insulated cable ends;
b) Winding the processed wire and/or stranding a plurality of wires processed in this way to form an inductor.

32. The manufacturing method as claimed in claim 31 for heating a geological formation that is a reservoir of a substance containing hydrocarbons.

33. The manufacturing method as claimed in claim 31 for heating a geological formation that is a reservoir containing an oil sand, oil shale or heavy oil reservoir.

34. The manufacturing method of any of claims 31 to 33, wherein providing the wire comprises providing insulated wire.

35. The manufacturing method of any of claims 31 to 34 further comprising fitting an outer sleeve mold, injecting the outer sleeve mold into an outer sleeve, wherein the outer sleeve surrounds the rounded conductive bodies and two end areas of the separated wire, and removing the outer sleeve mold.

36. The manufacturing method according to claim 26 or 31, wherein the connection of rounded conductive bodies is carried out in each case at a respective de-insulated cable end with the following steps:
Pushing sleeves onto the respective cable ends, wherein the sleeves in each case surround the rounded conductive bodies;
Force-fit connecting, of the respective sleeve with the respective de-insulated cable end.

37. The manufacturing method according to claim 36, wherein force-fit connecting comprises crimping.

38. The manufacturing method according to any one of claims 26 to 36, wherein the stranding of a plurality of wires processed in this way to form an inductor is carried out with the following steps:
- Arranging a number of processed wires in relation to one another so that at least two bundles of wires are formed, whereby the wires of a first of the two bundles are aligned in a longitudinal alignment to one another so that separation points of the separated wires of the first bundle largely come to lie next to one another and the wires of a second of the two bundles in the longitudinal alignment are aligned in relation to one another so that separation points of the separated wires of the second bundle largely come to lie next to one another, the separation points of the first bundle are disposed offset in relation to the separation points of the second bundle to one another;
- Stranding the wires thus disposed so that the wires of the first bundle and of the second bundle are stranded alternately to one another.