CA2812711C

CA2812711C - Process for the "in situ" extraction of bitumen or ultraheavy oil from oil-sand deposits as a reservoir

Info

Publication number: CA2812711C
Application number: CA2812711A
Authority: CA
Inventors: Dirk Diehl
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2010-09-28
Filing date: 2011-09-28
Publication date: 2019-01-29
Anticipated expiration: 2031-09-28
Also published as: EP2633153A1; EP2633153B1; DE102010043302A1; WO2012041877A1; CA2812711A1

Abstract

The present invention relates to a process for the in situ extraction of bitumen or ultraheavy oil from oil sand deposits (100) as reservoir (1). The reservoir (1) is inductively heated by means of at least one electrical current-passing conductor (3) in order to achieve a reduction in the viscosity of the bitumen or ultraheavy oil. At least one perforated fluid guide (30), which surrounds or encloses the at least one conductor (3) at least in certain portions, is used to introduce a fluid (45) into the reservoir (1) via the perforation in the fluid guide (30). The fluid (45) reduces an electrical conductivity in the reservoir (1), at least in the surroundings of the fluid guide (30).

Description

ak 02812711 2013-03-26 Description Process for the "in situ" extraction of bitumen or ultraheavy oil from oil-sand deposits as a reservoir The present invention relates to a process for the "in situ"
extraction of bitumen or ultraheavy oil from oil-sand deposits as a reservoir. The reservoir is inductively heated by means of at least one electrical current-passing conductor in order to achieve a reduction in the viscosity of the bitumen or ultraheavy oil. At least one perforated fluid guide, which surrounds or encloses the at least one conductor at least in certain portions, is used to introduce a fluid into the reservoir via the perforation in the fluid guide.
For the extraction of hydrocarbons, such as for example heavy oils or bitumen, from deposits with oil-sand or oil-shale reserves, referred to hereinafter as a reservoir, open-cast methods or "in situ" methods may be used. One "in situ" method is the SAGD (Steam Assisted Gravity Drainage) process. In this case, a pipe is used to introduce steam under high pressure into the ground, through a pipe running horizontally within the reservoir. The steam heats up the heavy oil or bitumen in the reservoir, the oil or bitumen becoming flowable. The heated, flowable ultraheavy oil or bitumen seeps under gravity down to a second pipe, arranged for example about 5 m lower, through which it is pumped away or extracted.
Alternatively or in addition, the reservoir may be inductively heated, for example by an insulated, current-passing conductor loop, which induces currents in the ground of the reservoir in the area around it. The induced currents are carried in particular by the ionic conductivity in liquids. The amount of the magnetic flux density around the conductor of the conductor loop decreases approximately in inverse proportion to the distance from the conductor. In the case of homogeneous CA 02812711,2013-03-26 , PCT/EP2011/066814 - la -electrical conductivity of the surrounding ground, this leads approximately , CA 02812711.2013-03-26 to a decrease in the heating output density around the conductor. The heating output density around the conductor is inversely proportionate to the square of the distance from the conductor. Consequently, the highest heating output density occurs in the area directly surrounding the insulated conductor. This leads initially to strong heating up of the ground in the area directly surrounding the conductor, which by heat conduction also leads to a correspondingly high temperature TL of the conductor itself. This takes place even if the resistive losses in the conductor itself are very small.
The conductor for the inductive heating of the reservoir, which is also referred to as an inductor and is known for example from DE 102007040605 B3, consists of a series of materials. In particular, dielectrics are used in the conductor for capacitive compensation, in order to keep the electrical losses in the conductor itself as low as possible. For the insulation of the electrically conductive material, in particular with respect to the surrounding ground, insulating material that consists for example of PFA, PTFE and/or PEEK, or comprises or contains such material, is used. The dielectric and the insulating material are generally thermally stable up to a maximum of 150 C, even over a relatively long time such as hours, days, months and years.
In order to be able to extract ultraheavy oil and/or bitumen reliably over relatively long periods of time, assisted by inductive heating of the reservoir by means of at least one conductor loop with an insulated electrical conductor, the temperature of the conductor must be kept below a critical temperature of for example 150 C. Only in this way can it be ensured that the insulation and the dielectric are thermally stable over time and that the conductor is not damaged by high temperatures. This is difficult specifically with regard to the high electrical voltages of greater than 10 kV and heating outputs in the range of MW.

CA 02812711.2013-03-26 PCT/EP2011/066814 - 2a -The object of the present invention is therefore to provide a process in which the temperature of a conductor for the inductive heating of the ground of a reservoir does not exceed a critical value.
The stated object is achieved with respect to the process for the "in situ" extraction of bitumen or ultraheavy oil from oil-sand deposits as a reservoir by the features described herein.
Advantageous refinements of the process according to the invention for the "in situ" extraction of bitumen or ultraheavy oil from oil-sand deposits as a reservoir are provided by the assigned dependent subclaims. At the same time, the features of the main claim can be combined with features of the subclaims and features of the subclaims can be combined with one another.
The process according to the invention for the "in situ"
extraction of bitumen or ultraheavy oil from oil-sand deposits as a reservoir comprises that the reservoir is inductively heated by means of at least one electrical current-passing conductor to reduce the viscosity of the bitumen or ultraheavy oil, and that at least one perforated fluid guide, which surrounds or encloses the at least one conductor at least in certain portions, is used to introduce a fluid into the reservoir via the perforation in the fluid guide. The fluid reduces an electrical conductivity in the reservoir, at least in the area surrounding the fluid guide and/or the conductor.
Enclosing the conductor at least in certain portions should be understood as meaning, inter alia, that the conductor and the fluid guide itself are arranged adjacently and, for example, are surrounded by a common insulation with respect to the ground, which has the identical and/or same perforation as the fluid guide or is at least partially permeable to fluids.
By reducing the electrical conductivity in the area surrounding the fluid guide, the current induced by the current-passing conductor in the area surrounding the fluid guide or the conductor is reduced. As a result, the inductively generated CA 02812711,2013-03-26 PCT/EP2011/066814 - 3a -heating output in the area surrounding the conductor or the fluid guide CA 02812711.2013-03-26 is reduced and the temperature of the conductor or of the fluid guide, in particular as a result of heat conduction of inductively generated heat in the directly surrounding area, is limited.
Water with a lower conductivity than the conductivity of water located in the reservoir may be introduced into the reservoir as the fluid. The amount of water introduced and/or the conductivity thereof should be determined on the basis of the value to which the temperature TL is intended to be limited, and in particular on the basis of the current intensity/voltage used for the induction through the conductor.
Alternatively or in addition, gas may be introduced into the reservoir as the fluid. In this case, air can be used particularly inexpensively and easily as the gas. However, carbon dioxide and/or nitrogen may also be used as the gas, or the gas may comprise carbon dioxide and/or nitrogen.
A solution of chemical substances, the chemical substances of which react to form a scarcely soluble salt in the reservoir and thereby lead to a precipitation of ions in the reservoir, may also be introduced into the reservoir as the fluid. In this case, it is of advantage if a chemical analysis is performed before the introduction of the solution into the reservoir. At least one fluid, in particular water, from the reservoir may be used in order to determine ions in the fluid removed from the reservoir and in order to select the chemical substances in the solution on the basis of the ions determined. Concentration determinations may also contribute to establishing the correct composition of the solution with which the temperature of the area directly surrounding the conductor, and consequently the conductor itself, can be kept to a predetermined value or below the limit value when a specific current is applied to the conductors. The concentration and species of the ions in the solution should have the effect that, with the solution, ions PCT/EP2011/066814 - 4a -are precipitated in the reservoir, for example in the form of a scarcely soluble salt, and so the overall ion concentration of the freely movable ions, which are charged and Consequently can be inductively moved via the current-passing conductor, is reduced to a value which, with a given structure of the conductor and application of current to it, leads to a predetermined temperature TL in the area directly surrounding it. By reducing the electrical conductivity in the reservoir, the inductive heating by means of the current-passing conductor is reduced.
The temperature T in the area directly or indirectly surrounding the conductor and/or the fluid guide may be restricted to a maximum value, in particular to a value less than 150 C. A previously described introduction of fluid into the reservoir or a combination of the previously described types of introduction of fluid may be used for this. The temperature may be restricted to a maximum value at which components of an apparatus for the "in situ" extraction of bitumen or ultraheavy oil from oil-sand deposits as a reservoir, in particular insulating materials of the conductor, dielectrics between conductor components and/or materials of the fluid guide, are thermally stable. At a temperature of less than 150 C, materials such as dielectrics and insulating materials, for example PFA, PTFE and/or PEEK, are generally thelmally stable and are not thermally degraded over time. As a result, damage to the conductor as a result of high temperatures in the area directly surrounding it is avoided by the temperatures being kept below a limit value.
The fluid may reduce the electrical conductivity in the area surrounding the fluid guide, in particular in the range of 3 m around the fluid guide. This may be sufficient to reduce heat transported to the conductor via the surrounding area by thermal conductivity even to the extent that the temperature TL
of the conductor is prevented from exceeding a critical limit value when the area surrounding the conductor undergoes inductive heating.

a .
PCT/EP2011/066814 - 5a -The electrical conductor may be passed through by an alternating current with a current intensity in the range of over 100 A, in particular 270 A, and/or with a frequency in the range from 10 kHz to =

100 kHz, in particular 75 kHz, whereby in particular the ground of the reservoir in the area surrounding the electrical conductor is heated up by induced currents in the ground. In this case, a heating output in the range of several MW can be generated, at voltages over the electrical conductor in the range of greater than 10 kV. Other values are also possible, in particular depending on the embodiment of the conductor, the nature of the soil, the ultraheavy oil or bitumen to be extracted and further parameters involved in oil extraction by means of inductive heating.
Preferred embodiments of the invention with advantageous developments according to the features of the dependent claims are explained in more detail below on the basis of the figures, without however being restricted thereto.
In the figures:
Figure 1 shows a section through an oil-sand reservoir 100 with an injection pipe 101 and an extraction pipe 102, Figure 2 shows a perspective detail taken from an oil-sand reservoir 1 with an electrical conductor loop 2 running horizontally in the reservoir, Figure 3 shows a perforated, tubular conductor 3 with integrated capacitors and a device for introducing electrolyte.
In Figures 1 and 2, an oil-sand deposit 100, referred to as a reservoir, is represented, a cuboidal unit 1 with the length 1, the width w and the height h always having been taken as a basis for the further observations. The length I may be, for example, up to several 500 m, the width w 60 to 100 m and the height h approximately 20 to 100 m. It should be taken into CA 02812711.2013-03-26 , .
PCT/EP2011/066814 - 6a -consideration that, as seen from the Earth's surface E, there may be an "overburden" of a thickness s of up to 500 m.

CA 02812711.2013-03-26 When implementing the SAGD process, according to Figure 1, an injection pipe 101 for steam or a water/steam mixture and an extraction pipe 102 for the liquefied bitumen or oil are present in a known way in the oil-sand reservoir 100 of the deposit.
In Figure 2, a known arrangement for inductive heating is represented. This may be formed by a long, i.e. several 100 m to 1.5 km, conductor loop 10 to 20 laid in the ground, the outgoing conductor 10 and the return conductor 20 being routed next to each other, that is to say at the same depth, and connected to each other at the end by means of an element 15 inside or partially outside the reservoir 100. At the beginning, the conductors 10 and 20 are routed down vertically, or at a shallow angle, and supplied with electrical power by an RF generator 60, which may be accommodated in an external housing. In particular, the conductors 10 and 20 run next to each other at the same depth, but if appropriate also one above the other.
Typical distances between the outgoing and return conductors 10, 20 are 5 to 60 m in the case of an outside diameter of the conductors of 10 to 50 cm.
A dual electrical line 10, 20 in Figure 2 with the aforementioned typical dimensions has a series inductance per unit length of 1.0 to 2.7 H/m. The transverse capacitance per unit length with the given dimensions is only 10 to 100 pF/m, so that the capacitive transverse currents can initially be ignored. At the same time, wave effects should be avoided. The wave velocity is given by the capacitance CA 02812711,2013-03-26 and inductance per unit length of the conductor arrangement.
The characteristic frequency of the arrangement is governed by the length of the loop and the wave propagation rate along the arrangement of the dual line 10, 20. The length of the loop should therefore be chosen to be so short that no interfering wave effects can occur here.
It can be shown that the simulated power loss density distribution in a plane perpendicular to the conductors - as formed when current is applied in phase opposition to the upper and lower conductors - decreases radially.
For an inductively introduced heating output of 1 kW per meter of dual line, at 50 kHz a current amplitude of approximately 350 A is required for low-resistance reservoirs with resistivities of 30 irIm and of approximately 950 A for high-resistance reservoirs with resistivities of 500 K1m. The required current amplitude for 1 kW/m falls by a power of two with the excitation frequency. In other words, at 100 kHz, the current amplitudes fall to 1/4 of the above values.
In the case of an average current amplitude of 500 A at 50 kHz and a typical inductance per unit length of 2 H/m, the inductive voltage drop is approximately 300 V/m.
In order to restrict the overall inductive voltage drop over a conductor loop 2 to values of less than 100 kV in total, and in order consequently to avoid insulation problems, the line inductance L is compensated portion by portion by series capacitances C of a discrete or continuous configuration. A
particular feature of compensation that is integrated in the line is that the frequency of the RF line generator must be made to match the resonant frequency of the current loop. This means that, for heating purposes, the dual line 10, 20 can only be operated expediently, i.e. with high current amplitudes, at this frequency.

CA 02812711,2013-03-26 As a result, an addition of the inductive voltages along the line is prevented. If in the case of the aforementioned example - that is to say 500 A, 2 H/m, 50 kHz and 300 V/m - for example a capacitor C, of 1 F capacitance is introduced every m into the outgoing conductor and the return conductor, the operation of this arrangement can take place resonantly at 50 kHz. In this way, the aggregate inductive, and correspondingly the capacitive, voltages are limited to 3 kV.
If the distance between adjacent capacitors C, is reduced, the capacitance values must increase in inverse proportion to the distance - given a voltage endurance requirement of the capacitors that is reduced in proportion to the distance - in order to obtain the same resonant frequency.
An advantageous embodiment that is known from the prior art and is represented in Figure 3, with capacitances integrated in the line 2, provides that the capacitance is formed by cylindrical capacitors C, between a tubular outer electrode 32 of a portion I and a tubular inner electrode 34 of the portion II, between which there is a dielectric 33. The adjacent capacitor between the portions II and III is formed in an entirely corresponding way.
Apart from a high voltage endurance, the dielectric of the capacitor C must also be required to have a high temperature resistance, since the conductor is located in the inductively heated reservoir 100, which can reach a temperature of for example 25000, and the resistive losses in the conductors 10, may lead to further heating up of the electrodes. The requirements for the dielectric 33 are met by many capacitor ceramics.

For example, the group of aluminum silicates, i.e. porcelains, have temperature resistances of several 100 C and dielectric strengths of > 20 kV/ram at permittivity values of 6. This.
allows the above cylindrical capacitors to be implemented with the required capacitance and to have an overall length of for example 1 to 2'm.
If the overall length happens to be shorter, a nesting of multiple coaxial electrodes should be provided. This is not represented in the figures for the sake of simplicity. Other customary types of capacitor may also be integrated in the line, as long as they have the required voltage and temperature resistance.
In Figure 3, the entire electrode is already surrounded by an insulation 31. The insulation from the surrounding ground is necessary in order to prevent resistive currents through the ground between the adjacent portions, in particular in the region of the capacitors. The insulation also prevents the resistive current flow between the outgoing conductor and the return conductor. The requirements for the insulation with respect to voltage endurance have been lowered, however, in comparison with the uncompensated line from 100 kV to in the above example slightly above 3 kV, and consequently can be met by many insulating materials. In the same way as the dielectric, the insulation of the capacitors must permanently withstand relatively high temperatures, ceramic insulating materials once again being suitable for this. At the same time, the thickness of the insulating layer must not be chosen too small, since otherwise capacitive leakage currents could flow away into the surrounding ground. Insulati,ng layer thicknesses greater than for example 2 mm are sufficient in the case of the above exemplary embodiment.
It is also possible for a number of tubular electrodes to be connected in parallel. The parallel connection of the PCT/EP2011/066814 - 10a -capacitors can be advantageously used to increase the capacitance or to increase their voltage endurance.
_ cp, 028127112013-03-26 In the case of an arrangement according to Figure 3, it is possible according to the prior art to introduce electrolyte portion by portion into the ground for selectively increasing the heating effect. For this purpose, the line 2 has apart from the compensated electrode an insulated inner tube 40 with insulated outlet openings 41, 42 and 43, which are also referred to hereinafter as perforated. This allows, for example, water or an electrically conductive aqueous salt solution or other electrolyte to be introduced into the reservoir, in order to increase the conductivity of the reservoir.
Furthermore, the water introduced can be used for cooling the conductor. If the outlet openings are replaced by valves, the changing of the conductivity can be selectively performed in terms of time and in terms of space portion by portion.
The increasing of the conductivity serves for increasing the inductive heating effect, without having to increase the current amplitude in the conductors.
In Figure 3, a compensation of the series inductance takes place by means of predominantly concentrated transverse capacitances. Instead of introducing a greater or lesser number of short capacitors into the line as concentrated elements, the capacitance per unit length that a two-wire line, such as for example a coaxial line, or multi-wire lines provide in any case over their overall length can also be used for compensating the series inductances. For this purpose, the inner and outer conductors are alternately interrupted at equal intervals and thus the current flow is forced via the distributed transverse capacitances. The advantage of the distributed capacitances lies in a reduced requirement for the dielectric strength of the dielectric.

CA 02812711,2013-03-26 PCT/EP2011/066814 - ha -It goes without saying that a compensated electrode with distributed capacitances can also be used in combination with a device for introducing electrolyte.

CA 02812711 µ2013-03-26 In the overburden through which the outgoing and return conductors are routed vertically to the reservoir 100, a heating effect is undesired: in the vertical region of the dual conductors 10, 20, which are not yet in the reservoir 100 but are being led down to it, the outgoing conductor 10 and the return conductor 20 may be spaced apart by a small distance, of for example 1 to 3 m, whereby their magnetic fields compensate for each other already at the smaller spacing of the dual line and the inductive heating effect is correspondingly reduced.
As an alternative, the outgoing conductor 10 and the return conductor 20 may be surrounded by a shielding of highly conductive material enclosing the two conductors, in order to avoid the inductive heating of the surrounding ground of the overburden.
In a further alternative, a coaxial conductor arrangement in the vertical region of the outgoing conductor and the return conductor is conceivable, having the effect that the magnetic fields are extinguished completely in the outer region, and consequently there is no inductive heating of the surrounding ground. The transverse capacitance per unit length that is increased as a result can be used for the configuration of a gyrator, which according to the prior art converts a voltage of a voltage-injecting power converter into an alternating current.
In the case of all three methods mentioned, compensation of the respective inductance per unit length of the line arrangement, including the possibly present shielding, is necessary.
The power generator 60 in Figure 2 is formed as a radio-frequency generator. It can generate power outputs of up to 2500 kW. Typically, frequencies between 5 and 20 kHz are used.
However, higher frequencies may also be used. The power generator 60 is of a three-phase construction and preferably PCT/EP2011/066814 - 12a -comprises a transformer-type coupling and power semiconductors as components. In particular, the circuit comprises a voltage-injecting inverter. A current injection with load-independent fundamental ak 02812711 2013-03-26 oscillation, which can be set by means of filter components, is obtained if the quadrupole matching network downstream of this inverter is suitably chosen. Depending on the topology of the quadrupole matching network, a differing current loading of the feeding inverter is obtained.
As already mentioned, in the case of such a generator, operation under resonance conditions is required for use as intended, in order to achieve reactive-power compensation. If appropriate, the driving frequency must be suitably adjusted during operation.
In the case of a conductor loop 10, 15, 20 according to Figure

2, which represents a two-pole inductor, a single-phase generator may also be used. Such generators, with for example 440 kW at 50 kHz, are commercially obtainable.
As described above and known from the prior art, a selective increase in the heating effect can take place by means of introducing electrolyte into the ground. For example, water or an electrically conductive aqueous salt solution or other electrolyte may be introduced into the reservoir in order to increase the conductivity of the reservoir.
As also in the case where electrolyte is not introduced, heating up of the conductor 3 or of the conductor loop 10, 20, 15 by thermal conduction from the ground to the conductor 3 is problematic here. As mentioned above, the materials such as the insulator and the dielectric are only stable up to certain temperatures, depending on the choice of material. In the case of high outputs, according to the invention it is therefore possible alternatively or additionally (at successive times) for the conductivity of the area surrounding the conductors 3 to be specifically reduced by means of introducing a fluid into the ground. Serving as fluids here are, inter alia, water, and/or gases such as air, nitrogen, carbon dioxide and/or PCT/EP2011/066814 - 13a -solutions of chemical substances, which react in the reservoir to form scarcely soluble ak 02812711 2013-03-26 salts and thereby lead to a precipitation of ions in the reservoir.
As a result, when there is inductive heating of the ground by means of the conductor 3, the heating output in the area directly surrounding the conductor 3 can be reduced. The conductivity in the surrounding area, for example up to 3 m around the conductor 3, can be reduced by the fluid. The decrease in the conductivity is particularly great in the area directly surrounding the conductor 3, where the most heating output by induction occurs. The induced ionic currents in the ground around the conductor 3 are reduced by the fluid or the reduction of the conductivity in the ground. In regions further away from the conductor 3, where the heating output by induction is less, there is less to no reduction of the conductivity by the fluid. Although it is introduced even into regions of the ground that are further away, for example by diffusion, this is to a much lesser extent than in the area directly surrounding the conductor 3. As a result, the lower heating output that occurs in regions of the ground further away from the conductor 3 is not reduced any further, or only slightly. The conductivity, and with it the induced heating output and consequently the amount of heating up, is reduced in the directly surrounding area, decreasing with distance from the conductor 3. The lower amount of heat in the area surrounding the conductor 3 leads to a lower heat conduction to the conductor 3, and consequently to less heating up of the conductor 3 itself. The temperature TL of the conductor 3 can thus be restricted to a maximum value, at which the individual materials of the conductor 3 are not thermally degraded and are stable in the long term.
By the process according to the invention described above, the heating output in the area surrounding the electrical conductor

3 is evened out. In the directly surrounding area, with high induced field strengths around the conductor 3, the heating CA 02812711,2013-03-26 PCT/EP2011/066814 - 14a -output is reduced by reducing the conductivity, while further away the conductivity is not changed, or only slightly, ak 02812711 2013-03-26 and consequently the heating output remains substantially the same. With the same electrical output for the induction by means of the conductor 3, the conductor 3 is heated up to a lesser degree, with the advantages described above. As a result, the power can be further increased for as long as the temperature at the conductor 3 does not reach the critical value, at which materials such as for example the insulation or the dielectric are degraded. It is thus achieved that better heating up of the ground takes place away from the conductor 3, by means of more induction, and consequently the ultraheavy oil or bitumen is liquefied or made flowable better. By means of reducing the conductivity in the area surrounding the conductor 3, at the same time less heating up is achieved in the area directly surrounding the conductor 3, and consequently there is less transport of heat to the conductor 3, which has the consequence of less heating up of the conductor 3 itself.
Consequently, with the process according to the invention, ultraheavy oil or bitumen can be liquefied in a greater area surrounding the conductor 3, and an amount extracted can be increased, without damaging the conductor 3.
The invention is not restricted to the exemplary embodiment of the process described above. Combinations of processes from the prior art with the process according to the invention are also possible. Thus, for example, an introduction of electrolyte to increase the conductivity, followed by an introduction of fluid to reduce the conductivity in the area surrounding the conductor 3 is possible at successive times. This allows for example a first extraction of ultraheavy oil and bitumen to be performed in the area directly surrounding the conductor 3 with lower induction and heating output. After introducing the fluid to reduce the conductivity, this is then followed by ultraheavy oil or bitumen further away from the line 3 being liquefied, and consequently extracted, with a higher output, without damaging the line 3.

s PCT/EP2011/066814 - 15a -A repeated, alternating introduction of electrolyte to increase the conductivity and of fluid to reduce the conductivity is also possible. As a result, from time to time CA 02812711 2013-03:26 =

a cooling of the line 3 can be achieved. A pulsed, repeated introduction only of fluid to reduce the conductivity is also possible.
An introduction of electrolyte to increase the conductivity, followed by an introduction of fluid to reduce the conductivity in the area surrounding the conductor 3 may also be of advantage if a good extraction of ultraheavy oil or bitumen is intended to be achieved in regions further away from the conductor 3. Thus, the electrolyte for increasing the conductivity may be introduced into regions further away, for example by high pressure and/or diffusion, and the subsequently introduced fluid for reducing the conductivity can displace the electrolyte for increasing the conductivity in the area directly surrounding the conductor 3. As a result, the induced heating output is increased in regions further away, while the heating up is reduced in the area directly surrounding the conductor 3 and at the conductor 3 itself. It may in this case specifically be of advantage that a liquid electrolyte conducts heat better than for example a gas. Thus, away from the conductor, the lower induction can be compensated by a better conductivity and, in the area directly surrounding the conductor 3, a gas may lead to a reduced transport of heat to the conductor 3.
The processes according to the invention described above in themselves or in combination lead to improved ultraheavy oil or bitumen extraction, as a result of high electrical power that can be used, and associated induction, with reduced risk of thermal degradation of the conductor 3 or of the materials of its components, such as for example the dielectric and/or insulation.

Claims

CLAIMS:

1. A process for the "in situ" extraction of bitumen or ultraheavy oil from oil-sand deposits as a reservoir, wherein the reservoir is inductively heated by means of at least one electrical current-passing conductor to reduce the viscosity of the bitumen or ultraheavy oil, and wherein at least one perforated fluid guide, which surrounds or encloses the at least one conductor at least in certain portions, is used to introduce a fluid into the reservoir via the perforation in the fluid guide, wherein the fluid reduces an electrical conductivity in the reservoir, at least in the area surrounding the fluid guide.

2. The process as claimed in claim 1, wherein water with a lower conductivity than the conductivity of water located in the reservoir is introduced into the reservoir as the fluid.

3. The process as claimed in claim 1 or 2, wherein gas is introduced into the reservoir as the fluid.

4. The process as claimed in claim 3, wherein air is used as the gas or the gas comprises air.

5. The process as claimed in claim 3, wherein carbon dioxide and/or nitrogen is used as the gas or the gas comprises carbon dioxide and/or nitrogen.

6. The process as claimed in any one of claims 1 to 5, wherein a solution of chemical substances, the chemical substances of which react to form a scarcely soluble salt in the reservoir and thereby lead to a precipitation of ions in the reservoir, is introduced into the reservoir as the fluid.

7. The process as claimed in claim 6, wherein a chemical analysis of at least one fluid from the reservoir is used in order to determine ions and the chemical substances in the solution are selected on the basis of the ions determined, in order then, with the solution, to precipitate ions in the reservoir.

8. The process as claimed in claim 7, wherein the at least one fluid is water.

9. The process as claimed in any one of claims 1 to 8, wherein, by reducing the electrical conductivity in the reservoir, the inductive heating by means of the current-passing conductor is reduced.

10. The process as claimed in claim 9, wherein the temperature T in the area directly or indirectly surrounding the conductor and/or the fluid guide is restricted to a maximum value.

11. The process as claimed in claim 9, wherein the temperature T in the area directly or indirectly surrounding the conductor and/or the fluid guide is restricted to a value of less than 250°C.

12. The process as claimed in claim 10 or 11, wherein the temperature T is restricted to a maximum value at which components of an apparatus for the "in situ" extraction of bitumen or ultraheavy oil from oil-sand deposits as a reservoir are thermally stable.

13. The process as claimed in claim 12, wherein the components of the apparatus are insulating materials of the conductor, dielectrics between conductor components and/or materials of the fluid guide.

14. The process as claimed in any one of claims 1 to 13, wherein the fluid reduces the electrical conductivity in the area surrounding the fluid guide.

15. The process as claimed in claim 14, wherein the fluid reduces the electrical conductivity in a range of 3 m around the fluid guide.

16. The process as claimed in any one of claims 1 to 15, wherein the electrical conductor is passed through by an alternating current with a current intensity in the range of over 100 A and/or with a frequency in the range from 10 kHz to 100 kHz.

17. The process of claim 16, wherein the current intensity is 270 A.

18. The process of claim 16 or 17, wherein the frequency is 75 kHz.

19. The process of any one of claims 16 to 18, wherein the ground of the reservoir in the area surrounding the electrical conductor is heated up by induced currents in the ground.

20. The process of claim 19, wherein the ground of the reservoir is heated with a heating output in the range of several MW with voltages over the electrical conductor in the range of greater than 10 kV.