EP2250858B1 - Apparatus for inductive heating of oil sand and heavy oil deposits by way of current-carrying conductors - Google Patents

Abstract

An apparatus for the inductive heating of oil sand and heavy oil deposits by way of current-carrying conductors is provided. The conductors include individual conductor groups, wherein the conductor groups are designed in periodically repeating sections of defined length defining a resonance length, and wherein two or more of the conductor groups are capacitively coupled. In this way, each conductor can be insulated and can include a single wire.

Description

The invention relates to an arrangement for inductive heating of oil sands and heavy oil deposits by means of live conductors.

For conveying heavy oils or bitumen from oil sands or oil shale deposits by means of pipe systems which are introduced through drilling, their flowability must be increased considerably. This can be achieved by increasing the temperature of the deposit, which is referred to as a reservoir below. Used exclusively or inductive heating or in addition to support the known SAGD method, the problem arises that the inductive voltage drop along the long length of the inductor of z. B. 1000 m can lead to very high voltages up to a few 100 kV, which can be controlled neither in the insulation against the reservoir or the soil nor the generator with respect to the reactive power.

To support the reservoir heating by steam injection according to the known SAGD (S team Assisted G ravity D rainage) method or as a complete replacement of the steam injection various electromagnetic acting Induktoren- and electrode configurations may be used, which in the non-prepublished applications of the applicant With AZ 10 2007 036 832 . AZ 10 2007 008 292 and AZ 10 2007 040 606 are described in detail.

In general state of the art of induction heating, the construction of high inductive voltages can be prevented by a series circuit consisting of inductor sections and integrated capacitances which are to be tuned to the operating frequency as a series resonant circuit. In the not previously published application of the applicant with AZ 10 2007 040 605 are a concentrated capacitance coaxial conductor arrangement and distributed capacitance principle based on the published German patent application DE 10 2004 009 896 A1 described in detail. The former conductor arrangement has various peculiarities, such as low flexibility, high production costs, expensive high-voltage ceramics. The latter conductor arrangement is not aligned for the intended purpose stated above.

Object of the present invention is in contrast to provide a conductor arrangement which can be used as an inductor for the purpose of oil sand heating.

The object is achieved by the totality of the features of claim 1. Further developments are specified in the subclaims.

According to the invention, it is proposed to capacitively couple two or more conductor groups in periodically repeated sections of defined length ('length of resonance'). Each conductor is insulated individually and consists of a single wire or a plurality of wires, which in turn are insulated for themselves. In particular, a so-called. Multifilament conductor structure is formed, which has already been proposed in electrical engineering for other purposes. Optionally, a multi-band and / or multi-foil conductor structure can be realized for the same purpose.

In practical application, inductive heating for the intended purpose of the oil sand heating at excitation frequencies of eg 10 - 50 kHz typically requires two conductor groups of 1000 - 5000 filaments if effective resonance lengths in the range of 20 - 100 m are to be obtained. But there may also be more than two conductor groups.

In the arrangements according to the invention, the resonant frequency is inversely proportional to the distance of the interruptions of the conductor groups. The construction of a capacitively compensated multifilament conductor can be done by means of specific RF strands. The construction of a capacitively compensated multifilament conductor can also be done alternatively by means of solid wires.

In the invention, a compensated multifilament conductor is advantageously constructed of transposed or intertwined individual conductors in such a way that each individual conductor within the resonance length on each radius is equally common. Similar to conventional Milliken-type conductors, a compensated multifilament conductor may be constructed of a plurality of conductor groups arranged around the common center.

The individual compensated conductor sub-groups are advantageously made of stranded solid or HF stranded wires. In this case, the cross sections of the conductor subgroups may deviate from the round or hexagonal shape and be, for example, sector-shaped. The central ladder free area within the cross section of a compensated Milliken type multifilament conductor can be used for mechanical reinforcement to increase tensile strength. For this purpose permanently inserted or removable synthetic fiber ropes or removable steel ropes can be used.

The central, ladder-free region within the cross-section of a compensated Milliken-type multifilament conductor can be used for cooling by means of a circulating liquid, in particular water or oil. Furthermore, there may advantageously be accommodated temperature sensors which can be used for monitoring and controlling the energization and / or liquid cooling.

To install the inductor, which consists of capacitively compensated multifilament conductor in the reservoir, it is proposed preferably to draw the inductor into a previously introduced plastic tube of larger inner diameter. It can be z. B. an oil can be introduced as a lubricant.

During operation, i. Energization of the conductor arrangement according to the invention, the space between the inductor and plastic pipe with a liquid, in particular water of low electrical conductivity or z. B. transformer oil, which may also previously serve as a lubricant, be flooded.

If an active cooling of the inductor by means of a circulating coolant is desired, it is proposed according to the invention to pump the coolant in the intermediate space and central conductor-free region, namely in opposite directions.

• Die ineinander und räumlich eng beieinander liegenden Leitergruppen sind stark kapazitiv verkoppelt. Damit wird ein Serienresonanzkreis aufgebaut, bei dem sich bei der Resonanzfrequenz die Phasenverschiebungen von Strom und Spannung durch die Leitungsinduktivitäten durch Kapazitäten zwischen den Leitergruppen gerade kompensieren.
• Über den Abstand der Unterbrechungen wird die Resonanzfrequenz des Leiters eingestellt. Weiterhin bestimmt diese Länge den induktiven Spannungsabfall und legt die Anforderungen an die Spannungsfestigkeit der Isolation bzw. des Dielektrikums fest.
• Die Verwendung von HF-Litze reduziert bzw. vermeidet die ohmschen Zusatzverluste aufgrund des Skin-Effekts.

The above-mentioned further developments and concretizations of the invention have in particular the following advantages:

• The interconnected and closely spaced conductor groups are strongly capacitively coupled. Thus, a series resonant circuit is constructed in which the phase shifts of current and voltage through the line inductances by capacitances between the conductor groups just compensate at the resonant frequency.
• About the distance of the interruptions, the resonance frequency of the conductor is set. Furthermore, this length determines the inductive voltage drop and specifies the requirements for the dielectric strength of the insulation or of the dielectric.
• The use of HF litz reduces or avoids the additional ohmic losses due to the skin effect.

If small resonance lengths are to be achieved in the multifilament conductor according to the invention, high capacitance coverings are required. This is a division of the total conductor cross-section in a variety of individual conductors, for example, up to several thousand individual conductors necessary. Advantageously, then the diameter of the individual conductor is already so small that an increase in resistance by skin effect no longer occurs.

In the invention, the interlacing or transposition of the individual conductors within the resonance length avoids ohmic additional losses due to the so-called proximity effect. Furthermore, it reduces the dielectric strength requirements of dielectric isolation by more homogeneous displacement current densities. The arrangement of several conductor subgroups around the common center allows the use of stranded wires - instead of intertwined or transposed wires without sacrificing the reduction of ohmic additional losses due to the proximity effect - while simplifying manufacturing.

In the proper installation of the inductor in the reservoir of oil sands deposits tensile loads of some 10 tonnes are expected to overwhelm the weakened by interruptions compensated conductor, such. B. could reduce the dielectric strength of the dielectric. Therefore, a mechanical reinforcement is desirable.

In the design of the inductor with a small conductor cross section, in particular cross section of copper, an active cooling of the arrangement according to the invention may be necessary, for which there are advantageously open spaces or spaces in the arrangement. A plastic tube is used to keep open the hole, the protection of the inductor during installation and operation. Thus, it reduces the tensile load on the inductor during retraction by reducing the friction. A liquid in the gap makes the good thermal contact with the plastic tube and the reservoir, which is needed for passive cooling of the inductor. At an ambient temperature of the reservoir of z. B. 200 ° C can ohmic losses in the inductor to about 20 W / m by heat conduction be discharged without the temperature in the inductor exceeds the critical for Teflon insulation values of 250 ° C.

With the countercurrent coolant flow inside and outside the conductors, a more uniform temperature along the inductor, which may be about 1000 meters long, is achieved than would be the case for rectified coolant flows.

Further details and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the drawing in conjunction with the claims.

Figur 1

einen perspektivischen Ausschnitt aus einem Ölsand- Reservoir mit einer horizontal im Reservoir verlau- fenden elektrischen Leiterschleife,

Figur 2

ein Schaltbild eines Serienresonanzkreises mit kon- zentrierten Kapazitäten zu Kompensation der Lei- tungsinduktivitäten,

Figur 3

ein Schema einer kapazitiv kompensierten Koaxiallei- tung mit verteilten Kapazitäten,

Figur 4

ein Schema der kapazitiv verkoppelten Filamentgrup- pen in Längsrichtung,

Figur 5

den Querschnitt eines Multifilamentleiters,

Figur 6

die Verteilung des elektrischen Feldes eines 2-Grup- pen-60-Filamentleiters im Querschnitt,

Figur 7

graphische Darstellung von Kapazitätsbelag zweier Leitergruppen in Abhängigkeit von der Leiteranzahl,

Figur 8

graphische Darstellung von Frequenzabhängigkeit der ohmschen Widerstands für verschiedene Drahtdurchmes- ser,

Figur 9

einen Querschnitt eines verseilten kompensierten Multifilamentleiter vom Milliken-Typ,

Figur 10

eine Alternative zu Figur 9,

Figur 11

eine perspektivische Darstellung eines Vier- Quadrantenleiters,

Figur 12

den Querschnitt eines verseilten kompensierten Mul- tifilamentleiters vom Milliken-Typ in einem Füh- rungsrohr und

Figur 13

eine graphische Darstellung von Abhängigkeit der In- duktorbestromung von der Frequenz für verschiedene Heizleistungen.

It show in a schematic representation

FIG. 1

3 shows a perspective detail of an oil sand reservoir with an electrical conductor loop running horizontally in the reservoir,

FIG. 2

a circuit diagram of a series resonant circuit with concentrated capacitances for compensation of the line inductances,

FIG. 3

a diagram of a capacitively compensated coaxial line with distributed capacitances,

FIG. 4

a diagram of the capacitively coupled filament groups in the longitudinal direction,

FIG. 5

the cross section of a multifilament conductor,

FIG. 6

the distribution of the electric field of a 2-group 60 filament conductor in cross section,

FIG. 7

graphical representation of the capacitance of two conductor groups as a function of the number of conductors,

FIG. 8

graphical representation of frequency dependence of the ohmic resistance for different wire diameters,

FIG. 9

a cross section of a stranded compensated Milliken type multifilament conductor,

FIG. 10

an alternative to FIG. 9 .

FIG. 11

a perspective view of a four-quadrant ladder,

FIG. 12

the cross-section of a stranded compensated Milliken type multi-filament conductor in a guide tube and

FIG. 13

a graphic representation of the dependence of the Induerkorbestromung of the frequency for different heat outputs.

The same or equivalent elements of the figures have the same or corresponding reference numerals. The figures are described below in groups together.

In the FIG. 1 is a designated as a reservoir oil sands deposit shown, with the specific considerations always a cuboid unit 1 with the length 1, the width w and the height h is taken out. The length 1 may for example be up to some 500 m, the width w 60 to 100 m and the height h about 20 to 100 m. It has to be taken into account that starting from the earth's surface E there can be an overburden of thickness s up to 500 m.

In FIG. 1 an arrangement for inductive heating of the reservoir cutout 1 is shown. This can be formed by a long, ie some 100 m to 1.5 km, laid in the ground conductor loop 10 to 20, the Hinleiter 10 and return conductor 20 side by side, ie at the same depth, are guided and at the end via an element 15 inside or outside of the reservoir are interconnected. Initially, the conductors 10 and 20 are led down vertically or at a shallow angle and are powered by an RF generator 60 which may be housed in an external housing.

In FIG. 1 the conductors 10 and 20 run side by side at the same depth. But they can also be performed on top of each other. Below the conductor loop 10/20, ie on the ground the reservoir unit 1, a delivery pipe 1020 is indicated, can be transported through the liquefied bitumen or heavy oil.

Typical distances between the return and return conductors 10, 20 are 5 to 60 m with an outer diameter of the conductors of 10 to 50 cm (0.1 to 0.5 m).

The electric double line 10, 20 off FIG. 1 with the typical dimensions mentioned above has a longitudinal inductivity of 1.0 to 2.7 μH / m. The transverse capacitance is only 10 to 100 pF / m with the dimensions mentioned, so that the capacitive cross currents can initially be neglected. At the same time wave effects should be avoided. The shaft speed is given by the capacitance and inductance of the conductor arrangement. The characteristic frequency of the arrangement is due to the loop length and the wave propagation speed along the arrangement of the double line 10, 20. The loop length is therefore to be chosen so short that no disturbing wave effects result here.

It can be shown that the simulated power loss density distribution in a plane perpendicular to the conductors - as it forms in opposite-phase energization of the upper and lower conductor - decreases radially.

For an inductively introduced heating power of 1 kW per meter of double cable, a current amplitude of about 350 A for low-impedance reservoirs with resistivities of 30 Ω · m and about 950 A for high-resistance reservoirs with resistivities of 500 Ω · m is required at 50 kHz. The required current amplitude for 1 kW / m falls quadratically with the excitation frequency. i.e. at 100 kHz, the current amplitudes fall to 1/4 of the above values.

At a mean current amplitude of 500 A at 50 kHz and For a typical inductance coating of 2 μH / m, the inductive voltage drop is about 300 V / m.

• Ein konkretes Beispiel einer Auslegung eines kapazitiv kompensierten Multifilamentleiters sieht wie folgt aus: Zwei Leitergruppen haben zusammen beispielsweise 1200 mm² Kupfer-Querschnitt. Dieser Querschnitt wird verteilt auf 2790 einzelne massive Drähte mit einem Durchmesser von je 0,74 mm.
• Jeder der Drähte erhält eine Isolation aus Teflon mit einer Wandstärke von etwas mehr als 0,25 mm und wird auf die doppelte Resonanzlänge von 2*20,9 m = 41,8 gebracht. Die Anordnung der Drähte in Längsrichtung erfolgt mit einem Versatz um die Resonanzlänge entsprechend der weiter unten beschriebenen Figur 4.

In the following, an electrical and thermal design of a blind power compensated Multifilamentinduktors will be described in detail. In the older not previously published German patent application AZ 10 2007 040 605 already the basic principle of the partial compensation of a coaxial line with distributed capacitances is described above. The relevant description of the earlier application is referred to below:

• A concrete example of a design of a capacitively compensated multifilament conductor is as follows: Two conductor groups together have, for example, 1200 mm ² copper cross section. This cross-section is distributed over 2790 individual solid wires with a diameter of 0.74 mm each.
• Each of the wires is given a Teflon insulation with a wall thickness of slightly more than 0.25 mm and is brought to twice the resonance length of 2 * 20.9 m = 41.8. The arrangement of the wires in the longitudinal direction is carried out with an offset by the resonance length corresponding to that described below FIG. 4 ,

The conductor arrangement results in a hexagonal grid in cross section and is in FIG. 5 played. It is doing a compression in the cross-sectional plane made such that the wires are brought to a mutual distance of 0.5 mm. The superfluous insulation fills the gussets in the hexagonal grid. The two groups of conductors have, when arranged alternately, the wires on the rings accordingly FIG. 5 then a capacity coverage of 115.4 nF / m. With the resonant length of 20.9 m, the conductor is then capacitively compensated at 20 kHz. The ohmic resistance at 20 kHz is then 30 μΩ / m. With an AC amplitude of 825 A (peak), an inductive heating power of 3 kW / m (rms) can be introduced into a reservoir of a specific resistance of 555 Ωm if the return conductor is at a distance of 106 m and this configuration is continued periodically. The ohmic losses in the conductor averaged over a resonance length amount to 15.1 W / m (rms). These lead depending on the underlying thermal model of the reservoir zrs, T = 200 ° C constant in 0.5 m or 2.5 m distance from the conductor, to a heating of the conductor 230-250 ° C, which still requires no additional liquid cooling becomes. The insulation would have to withstand a voltage of 3.6 kV. For Teflon, dielectric strengths of 20-36 kV / mm are specified. That is, with an insulation thickness of 0.5 mm, about one third of the dielectric strength is required.

As shown in the diagram in FIG. 2 is provided to compensate the line inductance L sections by discrete or continuously running series capacitances C. This is in FIG. 2 shown in simplified form. Shown is a substitute schematic image of a circuit operated with an AC power source 25 with complex resistor 26, in each of which sections inductances L _i and capacitances C _i are present. There is thus a partial compensation of the line.

Although the latter type of compensation is known from the prior art in systems of inductive energy transfer to translationally moving systems. In the present context, this results in particular advantages.

The peculiarity of compensation integrated in the line is that the frequency of the HF line generator must be matched to the resonance frequency of the current loop. This means that the double line 10, 20 of the FIG. 1 for the inductive heating appropriate, ie with high current amplitudes, only at this frequency can be operated.

The decisive advantage of the latter approach is that an addition of the inductive voltages along the line is prevented. If in the above example - ie 500 A, 2 μH / m, 50 kHz and 300 V / m - for example, every 10 m each a capacitor C _{i introduced} in the return conductor of 1 uF capacitance, the operation of this arrangement can at 50 kHz resonant done. Thus, the occurring inductive and correspondingly capacitive sum voltages are limited to 3 kV.

If the distance between adjacent capacitors C _{i is} reduced, the capacitance values must increase in inverse proportion to the distance-proportional to the distance of the reduced voltage-resistance requirement of the capacitors-to obtain the same resonant frequency.

In FIG. 3 an advantageous embodiment of capacitors integrated in the line with respective capacitance C is shown. The capacitance is formed by cylindrical capacitors C _i between a tubular outer electrode 32 of a first portion and a tubular inner electrode 34 of a second portion, between which a dielectric 33 is located. Likewise, the adjacent capacitor is formed between subsequent sections.

For the dielectric of the capacitor C in addition to a high dielectric strength continue to demand a high temperature resistance, since the conductor in the inductively heated reservoir 100, the temperature of z. B. can reach 250 ° C, and the resistive losses in the conductors 10, 20 can lead to further heating of the electrodes. The requirements for the dielectric 33 are met by a large number of capacitor ceramics.

In practice, for example, the group of aluminum silicates, ie porcelains, have temperature resistances of several 100 ° C. and electrical breakdown strengths of> 20 kV / mm at permittivity numbers of 6. This allows the above cylinder capacitors with the required capacity be realized and have a length of for example 1 to 2 m.

If the length should be shorter, is a nesting of several coaxial electrodes according to the FIGS. 2 to 4 to provide a clarified principle. Other common capacitor designs can be integrated into the line, as long as they have the required voltage and temperature resistance. This is the purpose of the radial structure of the conductor arrangements, which is illustrated by the cross-sectional representations.

In the FIG. 4 the schematic diagram of two capacitively coupled filament groups 100 and 200 in the longitudinal direction is shown. It can be seen that individual wire sections of predetermined length repeat periodically and that in this first structure 100 a second structure 200 is arranged with individual wire sections, wherein in each case the same length is given and wherein the first group of wire sections and the second group of wire sections in overlap a given distance. This defines a resonance length R _L which is significant for the capacitive coupling of the filament groups in the longitudinal direction.

In the FIG. 5 the entire inductor arrangement is already surrounded by an insulation 150. Insulation against the surrounding soil is necessary to prevent resistive currents through the soil between the adjacent sections, especially in the area of the capacitors. The insulation also prevents the resistive current flow between the return and return conductors. However, the requirements with respect to the dielectric strength to the insulation are compared to the uncompensated line of> 100 kV dropped in the above example, slightly above 3 kV and thus meet by a variety of insulating materials. Like the dielectric of the capacitors, the insulation must withstand higher temperatures permanently, which in turn offers ceramic insulating materials. The insulation layer thickness must not be too low be selected, otherwise capacitive leakage could flow into the surrounding soil. Insulation thickness greater z. B. 2 mm are sufficient in the above embodiment.

Sectional views of a corresponding arrangement with 36 filaments, which in turn consists of two filament groups are in the Figures 5 . 9 . 10 and 12 shown. This illustrates in particular FIG. 5 the construction and the combination of the nested arrangement of 36 filaments. In detail, the filament conductors of the first group are denoted by 101 to 118 and the filament conductors of the second group are denoted by 201 to 218. In the structure of a hexagonal arrangement, a central area 150 in the center of the conductors is exposed.

Overall, this results in given insulation according to the intensity structure. In FIG. 6 For example, a two-group 60 filament conductor assembly is shown in cross-section, again having a hexagonal structure construction. The conductors 401 to 430 (hatched on the left) belong to the first group of filament conductors and the conductors 501 to 530 (shaded to the right) belong to the second group of filament conductors. The conductor groups are embedded in an insulating medium. The specific structure of the conductor groups results in individual conductors, which are connected in groups via a high-intensity electric field and are each connected to other conductors via a low field, which can be confirmed by model calculations.

In the hexagonal structure according to FIG. 5 and FIG. 6 the central area 150 is field-free. This region 150 can be used for introducing coolants or else for introducing mechanical reinforcements in order to increase the tensile strength. For this example, permanently inserted or removable synthetic fiber ropes or removable steel cables are used. This will be discussed in detail below.

In the graph according to FIG. 7 is - in each case logarithmic scale - the abscissa represents the number n of the individual wires and the ordinate represents the longitudinal capacitance in μF / m. Graphs 71 to 74 for different conductor cross sections are shown, namely 71 for a cross section of 600 mm ² , 72 for a cross section of 1200 mm ² , 73 for a cross section of 2400 mm ² and 71 for a cross section of 4800 mm ² .

The individual graphs 71 to 72 run parallel with the same, monotonous slope: As expected, the litz wire capacitance increases exponentially with the number of wires, but linearly with the cross section.

Out FIG. 7 It can be deduced that the capacitive compensation can be adjusted on the one hand depending on the number of conductors and on the other hand on the total cross section. It was a geometry of the ladder according to the FIGS. 4 and 5 based on the same Teflon insulation. For a given cross-sectional area, therefore, the necessary number of stranded conductors can be determined.

In the graph of the FIG. 8 the frequency dependence of the ohmic resistance for different wire diameters is shown. On the abscissa the frequency is plotted in Hz and on the ordinate the resistance per unit length R is in Ω / m, again for both coordinates the logarithmic scale is chosen. Graphs 81 to 84 for different wire diameters are shown as parameters, 81 for a diameter of 0.5 mm, 82 for a diameter of 1 mm, 83 for a diameter of 2 mm and 84 for a diameter of 5 mm.

The graphs 81 to 84 are parallel to the abscissa in the initial region and then increase monotonically with essentially the same slope: as expected, the resistance increases exponentially with the frequency on the one hand and the wire diameter on the other hand. It is energized by a temperature assumed 260 ° C.

From the graph of graphs 81 to 84 in FIG FIG. 9 In particular, the influence of the skin effect at the indicated temperature can be removed. It can be seen from the graphs 81 to 84 that the ohmic resistance is initially substantially constant in the range up to different cutoff frequencies between 10 ³ and 10 ⁵ Hz, the resistance being inversely proportional to the wire diameter and then the resistance also increases with increasing frequencies ,

In FIG. 9 Six conductor bundles 91 to 96 are arranged in hexagonal geometry around a central cavity 97. In FIG. 10 on the other hand, six conductor bundles 91 'to 96' are arranged in approximately pie-like manner as segments around a central cavity 97 '. The free spaces 97 and 97 'contain possibilities for accommodating cooling devices or mechanical reinforcement devices. Corresponding means are not shown in detail in FIGS. 9 and 10.

Out FIG. 11 it follows that, in a basic arrangement accordingly FIG. 10 With sector-like elements made of individual conductors it is advantageous that the individual conductors are twisted in the longitudinal direction of the entire cable. Thus, lines of, for example, C to D, which illustrate the azimuthal twisting of the individual conductors, result on the circumference of the conductor. In the sectional area results in the left quadrant a field profile corresponding to the arrows.

In the FIG. 12 plastic pipe 120 is shown, in which an arrangement is introduced with stranded conductors. The tube 120 can be made of plastic, for example, with a gap 121 in the tube 120 resulting in which the insulator with the hexagonal conductor structures 122 is introduced. Essential here again is a centric conductor-free region 123 in which necessary aids are introduced for the intended use of the conductors described can be. In particular, such an arrangement with the conductor-free center 123 allows the use of stranded wires instead of intertwined or transposed wires, without having to sacrifice the reduction of ohmic additional losses by the proximity effect. As a result, a comparatively simple production is possible.

For the intended use of the particular with reference to FIGS. 4, 5 and 9 to 12 described in detail conductor arrangements for heating oil sand reservoirs of some 100 m expansion, the respective boundary conditions are observed. When laying the inductor in particular considerable tensile loads are expected, which can be in the range of some 10 tons. As a result, the interruptions in accordance with FIG. 4 Weakened compensated conductors are overwhelmed to the extent that the dielectric strength of the dielectric is reduced. For this purpose, mechanical reinforcements are provided, which can be done in particular by steel cables. Furthermore, active cooling may be necessary.

In the arrangement according to FIG. 12 In particular, the outer plastic tube 120 serves to keep the bore open, as well as to protect the inductor during installation and operation of the system with the arrangement for inductive heating of the oil sands deposit. This reduces the tensile load on the inductor during retraction by reducing friction.

Especially in the arrangement according to FIG. 12 For example, the liquid may be disposed within the plastic tube 120 for cooling an annular space 120. Here, the liquid makes a good thermal contact with the plastic tube 120 and above to the reservoir, again at least a passive cooling of the inductor is required. For example, at an ambient temperature of the reservoir of z. B. 200 ° C, the ohmic losses in the inductor of about 20 W / m are dissipated by the heat conduction, without the temperature in the inductor itself exceeding the value of 250 ° C. which is critical for Teflon insulation.

The arrangement according to FIG. 12 furthermore offers the possibility of an opposite cooling. In this case, the central cavity 97 is used for the one direction of the flowing liquid and the annulus 121 within the plastic tube 120 for the other direction of the flowing liquid.

In FIG. 13 are - in a linear representation - on the abscissa the frequency in kHz and plotted on the ordinate of the inductor current in amperes. The dependence of the inductor current on the frequency is reproduced, whereby the parameters given are different heating powers, for the graph 131 1 kW / m, for the graph 132 3 kW / m, for the graph 133 5 kW / m and for the graph 134 10 kW / m.

The individual graphs 131 to 134 each have an approximately hyperbolic course. It follows that the dependence of the Induktorbestromung of the frequency becomes stronger with increasing heating power, provided that constant power losses are assumed in the reservoir. In this respect, graphs 131 to 134 show the currents / or frequencies required for certain heating powers.

The arrangements described in detail with reference to the figures with the capacitively compensated multifilament conductors allow effective inductive heating of oil sands or other heavy oil deposits. Calculations and tests have shown that an effective heating of the reservoir is achieved, whereby the viscosity of the sand bound bitumen or the heavy oil is lowered and thus a sufficient flowability of the previously highly viscous raw material is achieved.

Claims (19)

1. Apparatus for the inductive heating of oil sand and heavy oil deposits by way of current-carrying conductors that consist of individual conductor groups, characterised in that the conductor groups are formed in periodically repeated portions of defined length that define a resonance length (R_L), and in that two or more conductor groups of this type are capacitively coupled, forming a multifilament, multiband and/or multifilm conductor structure.
2. Apparatus according to claim 1, characterised in that each conductor is individually insulated and consists of a single wire.
3. Apparatus according to claim 1, characterised in that each conductor consists of a large number of insulated wires that form a 'HF litz wire'.
4. Apparatus according to claim 3, characterised in that two groups, each comprising 1000 to 5000 filaments, are provided and resonance lengths (R_L) ranging from approximately 20 to approximately 100 m are obtained.
5. Apparatus according to either claim 3 or claim 4, characterised in that a capacitively compensated multifilament conductor of transposed and/or woven individual conductors is formed in such a way that each individual conductor within the resonance length (R_L) is found the same number of times on each radius of the apparatus.
6. Apparatus according to one of claim 3 or claim 4, characterised in that, similarly to conventional conductors, a compensated multifilament conductor is formed of a plurality of conductor sub-groups that are arranged about a common centre.
7. Apparatus according to claim 6, characterised in that the individual compensated conductor sub-groups consist of stranded solid or HF litz wires.
8. Apparatus according to claim 6, characterised in that the cross-sections of the conductor sub-groups are round or hexagonal. (Figs 9 to 12)
9. Apparatus according to claim 8, characterised in that the conductor sub-groups are segment-shaped.
10. Apparatus according to any one of the preceding claims, characterised in that the central conductor-free region within the cross-section of a compensated multifilament conductor is used to provide mechanical reinforcement and to increase tensile strength.
11. Apparatus according to claim 10, characterised in that plastics material fibre cables or glass fibre cables or steel cables are used to provide reinforcement and are insertable and/or removable at least temporarily.
12. Apparatus according to any one of the preceding claims, characterised in that the central conductor-free region within the cross-section of a compensated multifilament conductor comprises means for cooling.
13. Apparatus according to claim 12, characterised in that a liquid, in particular water or oil, is provided or can be introduced as means for cooling.
14. Apparatus according to claim 12, characterised in that temperature sensors, in particular glass fibre sensors or Bragg fibres, are arranged in the central region and can be used to monitor and/or control the current feed and/or the liquid cooler.
15. Apparatus according to any one of the preceding claims, characterised in that the inductor is inserted in a plastics material pipe having a larger inner diameter.
16. Apparatus according to claim 15, characterised in that lubricant is provided between the plastics material pipe and the inductor.
17. Apparatus according to claim 15, characterised in that a liquid, for example water, of low electric conductivity and/or a lubricating liquid or insulating liquid is provided during operation between the inductor and the plastics material pipe.
18. Apparatus according to claim 16, characterised in that a coolant is pumped into the gap and/or into the central conductor-free region, in particular in opposite directions.
19. Apparatus according to any one of the preceding claims, characterised in that a defined inductance and a defined capacitance per unit length of the inductor are provided in such a way that the apparatus can be operated in a serially compensated manner at a previously determined frequency.

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