Electric submersible pump motor and conveying device, especially for geothermal energy

Description

[0001] The invention relates to an electric submersible pump motor which, due to its small diameter, is suitable for installation in a borehole of a deep borehole, but which, in order to generate sufficient pumping capacity, must have a correspondingly large length for the respective required power, in a design which does not require a power supply to the rotor.

[0002] The invention further relates to a conveying device for geothermal energy but also for oil and water extraction with a submersible pump motor.

[0003] Electric submersible pump motors are used to pump a fluid through a deep borehole from a reservoir in the Earth's mantle. This can be, for example, crude oil, gas, or hot water. The latter is used in geothermal energy for energy generation. Since the high temperature required for this increases with depth, the borehole can be 3,000 m or more. For example, in the Upper Rhine Graben, at a depth of 3,000 m, the temperature is approximately 170°C. For cost reasons, the borehole diameter must be limited; this is usually 340 mm or less. To achieve high pumping performance with such a small diameter, the motors must sometimes be 40 m or more long. To handle such a length during transport and installation, several motors are often connected in series. Individual lengths of up to 12 m are manageable, which are then connected by couplings after being inserted into the borehole.

[0004] To achieve high performance, either high voltage or high current is needed. High voltages would require complex insulation, which the small diameter of the bores doesn't allow for. At high currents, the problem arises that heat is generated in the supply lines, which is compounded by the high temperatures at these depths and the heat loss generated by the submersible pump motor. This limits the motor power, which in turn limits the pumping capacity of the pumping device.

[0005] WO 2018 / 112399 A2 discloses a submersible pump system of the type mentioned above, in which the submersible pump motor consists of several coupled motors, each with a stator and rotor. This allows the motor to be installed in a narrow borehole, but since the motors are jointly supplied with power, the aforementioned power limitation occurs.

[0006] EP 3 306 798 B1 discloses a linear motor with multiple stators. Since these must be sequentially supplied with current to generate a linear motion, a completely different principle is used here, which also requires a pump that is not based on the principle of rotation.

[0007] The invention is based on the object of achieving an increase in performance in an electric submersible pump motor of the type mentioned above and in a conveying device, in particular for geothermal energy.

[0008] This is achieved by having at least two stators assigned to a rotor, which are equipped with separate power supplies, whereby the power supplies come from a power source on the earth's surface with the same current and the same voltage.

[0009] For a pumping device, especially for geothermal energy, this is achieved by equipping it with the aforementioned submersible pump motor.

[0010] The invention makes it possible to achieve high pump performance even though only the small diameter of the borehole is available for supplying electrical energy, which also largely serves to accommodate the production pipe, deep well pump, intake manifold, and volume compensation device. With the invention, the voltages are neither so high that excessive space is required for insulation, nor are the currents so high that large-diameter cables, which are difficult to accommodate, are necessary. Likewise, heat loss in the cables and motor is greatly reduced in an already hot environment. The entire energy supply is distributed across multiple power supplies for the individual stators, which can be arranged in the small space between the production pipe or other components of the production device and the borehole wall.

[0011] By limiting voltages, currents, and their waste heat, as well as more evenly distributing them through the arrangement of multiple cables, greater operational reliability is achieved. Heat loss is not concentrated in one cable and motor but is reduced through even distribution, and power can be increased by increasing the number of power supplies. For electric motors with the usual diameter-to-length ratio and separate power supplies, mechanical coupling would lead to synchronization problems unless appropriate control is provided to compensate for this.However, for electric motors with a small diameter relative to their length, such control is not necessary: ​​In these motors, the slip between the stator field and the rotor is above average, resulting in dynamic synchronization, so that multiple stators can drive a single rotor without additional synchronization control. It is particularly important for use in geothermal energy that no synchronization control is required, as sensors for recording the control variables cannot be installed on-site due to the high temperatures at depth.

[0012] The subclaims provide advantageous developments: The rotor can be provided with several sections along its longitudinal extension, each with an arrangement for generating a rotating field. The longitudinal extension of the rotor can consist of several sections connected by couplings. Such a section can then contain one or more of the aforementioned sections. In this way, for example, a 48 m long rotor can consist of four sections, which can still be transported and installed at 12 m. In this way, a rotor can also be extended almost indefinitely if this is necessary to achieve higher performance.

[0013] A further advantage of separate power supplies is that the individual stators can be switched on together or separately. This allows only some of the stators to be operated if lower power is desired, or the conveyor can continue to operate if one or more stators fail, albeit with a reduction in conveyor capacity. The same applies for repairs or if a stator must be deactivated for other reasons.

[0014] The submersible pump motor can be operated from the surface with a common power source or with several synchronized power sources.

[0015] The submersible pump motor can be a permanent magnet motor, an induction motor, or a reluctance motor. The latter two are particularly useful in geothermal applications, as permanent magnets made of rare earth elements are only partially heat-resistant.

[0016] The submersible pump motor according to the invention is intended for use in pumping devices, and is particularly suitable for geothermal energy, where the highest possible temperatures in usually very deep boreholes are desirable for high energy yield. However, it is precisely these high temperatures that make it necessary to avoid any further heating and, in particular, the formation of hot spots, for example, on cables and stators, caused by the energy supply.

[0017] The invention is explained below with reference to the drawing. Fig. 1a an embodiment of the invention, Fig. 1b the circuit of the windings of the stators of this embodiment, Fig. 2a an example of the state of the art, Fig. 2b the circuit of the windings of the stators of this example, Fig. 3a a conveying device for geothermal energy with a submersible pump motor according to the invention and Fig. 3b the arrangement of power supplies of the submersible pump motor according to the invention.

[0018] Fig. 1a shows a possible submersible pump motor 1 as an example for the implementation of the invention and the Fig. 1b the circuit of the windings 11, 11', ...11 n< of this submersible pump motor 1.

[0019] The submersible pump motor 1 consists of a plurality of stators 4, 4', ... 4 n< , whereby the interruption 13 and the designation of the last stator with 4 n< indicate that this number can be increased according to the desired pumping capacity. All stators 4, 4', ... 4 n< act with their rotating fields on a rotor 3, which consists of sections 9, 9', ... 9 n< connected by couplings 10. The reason for this is that a rotor 3 of 40 m or more would be impossible to transport or install due to this length. Each section 9, 9', ... 9 n< can be a rotor section 8 or, as shown here, consist of several rotor sections 8, 8', 8", 8‴, each of which has a stator arrangement for generating a rotating field.

[0020] The design can be any, for example, as a permanent magnet rotor, a squirrel-cage rotor, or a reluctance motor. The rotating field required for rotation is generated by the stators 4, 4', ... 4 n<, which extend along the rotor 3 and each of which has a power supply 5, 5', ... 5 n<, which Fig. 1a are shown as cables. These cables then contain several conductors, as in Fig. 1b There, they are connected to the windings 11, 11', ... 11 n< of the stators 4, 4', ... 4 n<, whose ends are joined in a known manner in a star connection 12 for three-phase operation. This is, of course, only an example, since any type of motor is possible, as long as the rotor 3 does not require a power supply.

[0021] It is essential for the invention that at least two stators 4, 4', ... 4 n< - but regularly a plurality - are supplied with power from the earth's surface 7 with a power source 6 or by means of synchronized power sources through their own power supply 5, 5', ... 5 n<.

[0022] However, these power supplies 5, 5', ... 5 n< are not as short as in Fig. 1a und 1b symbolically represented, but as in the Fig. 3a drawn in a length (which is also shown in abbreviated form in this illustration) which corresponds almost to the depth of borehole 2, which causes the problems of the state of the art mentioned at the beginning.

[0023] In order to make this understandable, the Fig. 2a und 2b Such a submersible pump motor 1 with power supply 5 and windings 11 according to the prior art is shown. Even though it also has a long rotor 3 assembled from individual parts, it has a stator 4 for the entire submersible pump motor 1. Even though this must of course also be assembled from parts due to transport and installation, electrically it is a stator 4, as is the case with the Fig. 2b A cable 5, for example with 3 conductors for the three-phase current, is laid through the entire borehole 2 (corresponding to Fig. 3a ) to the submersible pump motor 1 which, for example, with a length of 40 m, must flow through correspondingly long windings 11 of the (electrically speaking) single stator 4 to the star point 12, even if these are usually shorter windings 11 connected in series, which is also the case with multiple motors. This means that the entire current intensity, depending on the cable resistance, flows concentrated on the one supply line 5 and the length of the windings 11, thereby producing waste heat which cannot be optimally dissipated in the hot environment. However, a reduction in the cable resistance by means of very thick copper cables is limited by the small space available in the borehole 2 and is not possible at all with regard to the windings 11 due to the small motor diameter.

[0024] Fig. 3a shows another conveying device for geothermal energy with a submersible pump motor 1 according to the invention.

[0025] Starting from an above-ground fitting and pipe 22, the borehole 2—shown here in a very abbreviated form—leads into the ground 14. Within the borehole 2, enclosed by the well wall 15, is the delivery pipe 16 for transporting the hot well water to the earth's surface 7. Located at depth is a deep well pump 17, driven by the submersible pump motor 1, which pumps the well water drawn in through an intake port 18. A volume compensation device 19 compensates for volume fluctuations in the operating oil of the pumping device due to temperature fluctuations. Only a short section of the submersible pump motor 1 is symbolically shown, with two stators 4, 4'. However, the interruption 20 shows that the submersible pump motor 1 still has a considerable length with many stators 4, 4', ... 4 n<, at least enough to achieve the desired pumping capacity.Finally, at the end of the conveyor device there is a centering device 21 which stabilizes the entire arrangement.

[0026] Starting from a power source 6 on the earth's surface 7, as many power leads 5, 5', ... 5 n< run through the borehole 2 as the submersible pump motor 1 has stators 4, 4', ... 4 n<.

[0027] Fig. 3b shows how an annular space for the power supplies 5, 5', ... 5 n< remains between the well wall 15 and the above-mentioned components of the conveying device (conveying pipe 16, deep well pump 17, suction nozzle 18 and volume compensation device 19), which are arranged centrally within the well wall 15. Since the current intensity is different in relation to the single power supply 5 of the prior art ( Fig. 2a und 2b ) is distributed across a large number of power supplies 5, 5', ... 5 n< (three are shown here as an example), the current intensity is reduced accordingly (here to one-third). The heat loss from each power supply 5, 5', ... 5 n< is correspondingly reduced, and with multiple power supplies 5, 5', ..., 5 n<, this heat can be dissipated to the environment much more effectively than with a single power supply 5, which becomes a hot spot.

[0028] The illustrated embodiment can of course vary in many respects, in particular different types of electric motors can be equipped as submersible pump motor 1 with a rotor 3 and many stators 4, 4', ... 4 n<, which in the same way have a corresponding number of power supplies 5, 5', ... 5 n<. Bezugszeichenliste

[0029] 1Submersible pump motor 2Borehole 3Rotor 4, 4', 4 n< Stators 5, 5', ...5 n< Power supplies 6Power source 7Ground surface 8, 8', 8", 8‴Sections of the rotor 9, 9' ... 9 n< Sections of the rotor 10Couplings 11, 11', ...11 n< Stator windings 12Star connection for three-phase current 13Interruption to indicate additional stators 14Soil 15Well wall 16Delivery pipe 17Deep well pump 18Intake nozzle 19Volume compensation device 20Interruption to indicate additional stators of the submersible pump motor 21Centering device 22Above-ground fitting and line

Claims

1. Electric submersible pump motor (1) which, owing to a correspondingly small diameter, is suitable for arrangement in a borehole (2) of a deep well owing to a correspondingly small diameter but, in order to generate a sufficient delivery capacity, has to have a correspondingly long length for the respectively required performance, with a design that does not require power supply to the rotor (3), wherein a rotor (3) is assigned at least two stators (4, 4', ... 4n) which are equipped with separate power supplies (5, 5', ... 5n), wherein the power supplies (5, 5', ... 5n) are fed with the same current and the same voltage from a power source (6) on the Earth's surface (7).

2. Electric submersible pump motor according to Claim 1, characterized in that the rotor (3), in its longitudinal extent, has a plurality of portions (8, 8', 8", 8‴), each with a stator arrangement for generating a rotating field.

3. Electric submersible pump motor according to Claim 2, characterized in that the rotor (3), in its longitudinal extent, consists of pieces (9, 9', ... 9n) connected to couplings (10).

4. Electric submersible pump motor according to any of Claims 1 to 3, characterized in that the stators (4, 4', ... 4n) can be switched on together or separately by switches.

5. Electric submersible pump motor according to any of Claims 1 to 4, characterized in that a common power source (6) is provided.

6. Electric submersible pump motor according to any of Claims 1 to 4, characterized in that a plurality of synchronized power supply sources are provided for the stators (4, 4', ... 4n).

7. Electric submersible pump motor according to any of Claims 1 to 6, characterized in that it is an induction motor.

8. Electric submersible pump motor according to any of Claims 1 to 6, characterized in that it is a reluctance motor.

9. Electric submersible pump motor according to any of Claims 1 to 6, characterized in that it is a permanent-magnet motor.

10. Conveying device, in particular for geothermal applications, characterized in that it is equipped with a submersible pump motor (1) according to any of Claims 1 to 9.