BR112013011709B1 - REMOTE SENSOR SYSTEM AND METHOD - Google Patents

Abstract

system and method for remote sensor. a system, method and device can be used to monitor conditions in a borehole. the well tubing and casing tube act as a conductive pair to supply energy to one or more active well bottom sensors, on the surface, energy and signal are isolated so that the same conductive pair can act to transmit the sensor signals to the surface. in one embodiment, the sensor signals are RF signals, and the surface electronics demodulate the RF signals from the sensor energy.

Description

[0001] This application claims the benefit of Provisional Patent Application 61 / 413,179, filed on November 12, 2010, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention relates generally to remote reading and, more particularly, to the reading of pressures and temperatures in a downhole environment.

BACKGROUND OF THE INVENTION

[0003] In resource recovery, it can be useful to monitor various conditions in locations away from an observer. In particular, it may be useful to provide in-depth monitoring temperatures and pressures in a borehole that has been drilled for exploratory or production purposes. Because such boreholes can extend for several miles, it is not always practical to replace power supplies for sensors located in the borehole.

BRIEF DESCRIPTION

[0004] One aspect of an embodiment of the present invention includes an apparatus for monitoring conditions in a borehole. The well lining pipe and tube act as a conductive pair to supply energy to one or more active sensors at the bottom of the well. On the surface, energy and signal are isolated so that the same conductive pair can act to transmit the sensor signals to the surface.

[0005] One aspect of an embodiment of the present invention includes a system for measuring a condition in a downhole environment of a borehole under a surface, including a source, configured and arranged to transmit an energy signal, via a drilling column, into the borehole of a sensor module in electrical communication with the source, via the drilling column, the sensor module comprising an oscillator, having a resonant frequency that varies with changes in the background environment condition well, the sensor module being configured and arranged to receive energy from the source and to produce a sensor signal in response to the condition of the well bottom environment, and to transmit the signal, via the drill string, to the surface, and a detector in electrical communication with the sensor module, via the drilling column, and configured and arranged to receive the sensor signal.

[0006] One aspect of an embodiment of the present invention includes a system for monitoring conditions in a borehole. The well casing pipe and tube act as a conductive pair to supply energy to one or more active downhole sensors. On each surface and sensor, energy and sensor signals are isolated so that the same conductive pair can act to transmit the sensor signals to the surface.

[0007] Another aspect of an embodiment of the present invention includes a method of monitoring conditions in a borehole. An energy signal is transmitted, via the drill string, to one or more active downhole sensors. The sensor signal is transmitted, via the drill string, to the surface. On each surface and sensor, energy and sensor signals are isolated.

[0008] Aspects of embodiments of the present invention include tangible computer-readable means encoded with executable computer instructions for carrying out any of the foregoing methods and / or for controlling any of the foregoing devices or systems.

DESCRIPTION OF THE DRAWINGS

[0009] Other aspects described here will be more readily evident to those skilled in the art when reading the following detailed description in combination with the accompanying drawings, in which:

[0010] Figure 1 is a schematic illustration of a system for determining a downhole environment in a borehole under a surface, according to an embodiment of the present invention;

[0011] Figure 2 is an electrical schematic diagram illustrating a circuit configured to supply DC power to a sensor at a downhole location, and to admit the sensor input for transmission to the surface;

[0012] Figure 3 is a schematic diagram illustrating an alternating current embodiment of a power and signal transmission system for a remote sensor;

[0013] Figure 4 is a schematic diagram illustrating an embodiment of direct current from a power and signal transmission system to a remote sensor;

[0014] Figure 5 is a block diagram of a transformer coupling system, according to an embodiment of the present invention;

[0015] Figure 6 is a block diagram of a sensor module unit, according to an embodiment of the present invention;

[0016] Figure 7 is a block diagram of a sensor module interface, according to an embodiment of the present invention; and

[0017] Figure 8 is a block diagram of an isolated system, according to an embodiment of the present invention.

DETAILED DESCRIPTION

[0018] Figure 1 illustrates an example of an apparatus 100, for monitoring a condition in a subsurface borehole. Apparatus 100 includes an electromagnetically transmissive means, such as a conductive line 102, for conducting electromagnetic energy through the borehole. It will be observed, by those having common skill in the art, that the conductive line 102 can have different shapes or embodiments, depending on the state of the borehole. Thus, for example, conductive line 102 may comprise a production pipeline column in a finished borehole, or a drill column in a borehole under construction. Near the top of conductive line 102, a transformer 104 is provided to couple the conductive tube to an electromagnetic energy source. Alternative coupling methods for transformer 104 can be employed. For example, the transmission line can directly couple on a coaxial cable or any other suitable cable.

[0019] In the exemplary embodiment, as shown, transformer 104 includes a stack of ferrite rings 106 and a wire 108 wrapped around the rings. Wire 108 includes conductors 110 that can be coupled to a signal generator 112, which can be configured to produce a pulsed or continuous wave signal, when necessary or desirable. The wire 108 can also be coupled to a receiver 114. The receiver 114 can be incorporated as a computer, which includes a bus for receiving signals from the apparatus 100 for storage, processing and / or display. In this regard, computer 114 may be provided with a monitor 118, which may include, for example, a graphical user interface.

[0020] Computer 114 can be programmed to process the received sensor signals to provide a measurement of the measured characteristic. Computer 114 can perform any desired processing of the detected signal, including but not limited to statistical analysis (e.g., Fourier) of the signal, deconvolution of the signal, correlation with another signal, or the like. Commercial products are readily available and known to those skilled in the art, which can be used to perform any suitable frequency detection. Alternatively, the computer can be provided with a look-up table in memory or in accessible storage that correlates received modulated signals with conditions measured in the borehole.

[0021] In a typical drilling application, the borehole will be lined with a borehole lining tube 120, which is used to provide structural support to the borehole. This casing tube 120 is often made of a conductive material, such as steel, in which case it will cooperate with line 102 in order to form a coaxial transmission line, and it is not necessary to provide any additional conductive means. Where the casing tube is not conductive, a conductive sleeve (not shown) can be provided inside the casing tube in order to form the coaxial structure. In order to maintain a distance between the line 102 and the casing tube 102, the apparatus 100 may include dielectric rings 122 periodically disposed along the conductive line 102.

[0022] Spacers can, for example, be configured as isolated centralizers, which can be discs formed from any suitable material, including but not limited to nylon or polytetrafluoroethylene (PTFE). Although the illustrated embodiment makes use of a coaxial transmission line, it is considered that alternative embodiments of a transmission line can be employed, such as a single conductive line, conductive lines arranged in pairs, or a waveguide . For example, the sheath tube alone can act as a waveguide for certain frequencies of electromagnetic waves. In addition, coaxial cable lengths can be used for all or part of the line. Such a coaxial cable can be particularly useful when dielectric fluid cannot be used inside sheath tube 120 (for example, when salt water or other conductive fluid is present in sheath tube 120).

[0023] A part of the probe 124 is located close to the distal end of the apparatus 100. In principle, part of the probe can be located at any point along the length of the transmission line. In fact, such multiple probe parts can be placed at intervals along the length. In principle, wavelength multiplexing on the coaxial line could be used to allow multiple probes to use a single communication line without interference.

[0024] The probe part may include an opening 126, which is configured to transmit ambient pressures and / or temperatures of the fluid, present in the borehole, into the probe, where they can be measured by the sensor (not shown in Figure 1 ). Below the probe is shown a plug 128 and plug teeth 130.

[0025] Figure 2 is an electrical schematic illustrating a bottom part of an embodiment of the system according to the invention. An RC 200 terminator is designed to reduce or eliminate reflections on the line terminal. From the line terminal, the path of the power signal depends on whether it is a DC or AC signal. The applied DC will adopt the upper path 202, through the high inductance inductor 204 (which can be, for example, about 1mH), and will pass through diode 206, reaching the DC 208 power outlet to the right of the Figure. On the other hand, the applied AC will pass through the relatively lower inductance inductor 212 (which can be, for example, about 17 pH). AC power passes through a power transformer 214 and a bridge rectifier 216 to produce DC power from the same DC power output part of circuit 208. The sensors produce a signal (usually an RF signal), which is accepted at the RF sensor input part of circuit 218 and re-coupled to the conductive pair for transmission to the surface.

[0026] The inventors determined that an electrically insulated well tubing would make it possible to better match the impedance of the well tubing with respect to an RF signal being propagated. Additionally and concurrently, such an insulator would allow the transmission of AC and DC energy along the pipeline for deeper energy functions in the well. A passive energy switching method and apparatus allows the selective application of energy to the downhole circuits and loads.

[0027] The physical implementation of a well pipe insulator (DC) generally requires robust mechanical components, which, when combined within the unit, can reliably support up to 90.72 kg of well pipe tubes, withstand strong coupling torques , and withstand chemical and environmental abuse.

[0028] In theory, an insulator can be nothing more than a dielectric switch in a solid part of the pipe on the other side. In actual practice, such an insulator needs to fit into well casing tubes with sufficient clearance, exhibit low end-to-end capacitance, be able to keep many hundreds of volts of applied potential separate, and perhaps most importantly, be received by the administrators of the well site with the confidence that it will not fail. Aspects of integrated fail-safe design may also be useful or required for acceptance by users.

[0029] According to an embodiment of the invention, a technique for DC insulation includes a ceramic or other non-conductive insulator inserted in series with the well tubing. This can, for example, be integrated into a 121.92 cm section of tubes, commonly referred to as a “sub”.

[0030] The ceramic and tubing parts can be attached to each other and must be connected without electrically shorting the parts of the tubing together. An insulating coating can be applied to the internal and external surfaces of the unit to protect the electrical stop through the span.

[0031] In one embodiment, the RF (sensor signal) and the DC (energy) connection are produced for the pipeline through a common connection, with the signal separation handled electronically from outside the well.

[0032] Multiple mechanical topologies have been traced and built. Many exhibited very low electrical resistance values for practical use. In practice, insulation values of 2,000 ohms or greater have proven useful.

[0033] An example of an installation, according to an embodiment of the invention, is schematically illustrated in Figure 3. In the example of Figure 3, the energy signal generated on the surface is an AC signal supplied to input 300. The signal AC is coupled to a conductive pair, via energy cores 302, which can be of the ferrite transformer type described above in relation to Figure 1. Figure 4 illustrates an alternative approach in which the energy signal is a DC signal.

[0034] As can be seen by Figures 3 and 4, a primary difference is the use of a transformer, which can be, for example, a toroidal transformer produced with cores wrapped in tape in the well tubing tubes just below the head of well and above a set of RF 304 ferrite cores. In this approach, a small number of turns make up the primary winding of the transformer, with the well tubing making up the secondary winding of the transformer. In one example, it can be a secondary single-turn winding. The sensor module 310 and the arc spring centralizer 312, used to access the DC isolator, remain unchanged in such an AC application.

[0035] In this way, the energy signals generated by the power supply 318 are supplied to the sensor module 310 of the lower transformer 304. In the opposite direction, the sensor module 310 generates communication signals that are transmitted to the lower transformer 304. The communication lines are conducted to the pipe column of the upper transformer 302 and then transmitted to the receiver 320 of the surface system 500 (as illustrated in Figure 5). The electrical path is completed by grounding the tubing column on the unused sides of the upper and lower transformers, and grounding the surface system and sensor module 310. In practice, the casing tube is generally grounded. Thus, the pipe column, above the upper transformer, can be grounded by coupling the pipe column to the casing pipe through the wellhead. The tubing column, below the bottom transformer 304, can be grounded by connecting the tubing column to the casing tube, via the arc spring centralizer 312, for example.

[0036] In one embodiment, transformers are formed using the pipe column as one of the windings of each transformer. For example, in the upper transformer, the energy signal from the surface system is transmitted to the primary winding of a toroidal transformer positioned around the pipe column. The piping column itself is the secondary single-turn winding from the transformer to the power circuit. Similarly, the bottom transformer is another toroidal transformer surrounding the pipe column and includes, for the energy circuit, a primary winding, which is the pipe column itself, and a secondary winding, which is connected to the sensor module 310. In the circuit communication signals are transmitted using the same transformers, although (when compared to the power circuit) the primary and secondary winding rollers in each transformer are inverted.

[0037] In one embodiment, the AC insulation technique includes an insulator integrated into a short-circuited section of the steel pipe, incorporating magnetic AC and RF. The separation of AC and RF electrical connections (300, 314, respectively) can be done through a wellhead support 316. An adequate impedance for the RF signal can be established by selecting the RF magnetic material. A suitable impedance for the AC source can be established by selecting the characteristics of the AC transformer.

[0038] In this approach, the RF impedance, established by the RF magnets, is also affected by the presence of the AC magnets, which represent a very high impedance for RF. As such, it may be necessary to provide an electrical path around the magnetic AC for the wellhead of the RF currents running above the well tubing of the 310 sensor package. In this case, two different electrical connections for the wellhead would be required.

[0039] In practice, energy frequencies can be between 5kHz and 200kHz, for example. On the other hand, the RF frequencies of the data can be between 3MHz and 8MHz. In one embodiment, the energy is supplied in a range between 1 and 10kHz and the data is transmitted using a modulation scheme by manipulating frequency deviation in frequencies in the range between 15 and 30kHz. Energy frequencies above the RF range are, in theory, usable. The sensor data frequencies can also be selected from outside the previous ranges. Because the transmission frequencies of the energy and sensor signals are different, it is possible to separate them using filtering from the surface system 500 and / or the sensor module 310.

[0040] As a result of transformer-based energy and communication transmission, via the drill string, there may be no need to limit current or direct devices (that is, devices to ensure current flows above and below the pipeline). Because there is no need to direct energy and data transmission along the pipe column, it tends to be less susceptible to attenuation than it would be if current directing devices were required. This, in turn, allows the use of low-energy sensors (for example, less than <10V) in the sensor module. These low-energy sensors allow the system as a whole to tolerate significant attenuation between the power source and the downhole sensors.

[0041] Figure 6 is a block diagram of a sensor module unit 600 according to an embodiment of the present invention. As will be noted, the sensor module 600 is similar to the arrangement illustrated in Figure 2 and represents an alternative approach to illustrate similar concepts.

[0042] The sensor module 600 connects to the lower transformer through a 602 bus, which carries both the energy signal and the data signal from the sensor. A low-pass filter 604 passes the low-frequency energy signal to the power circuits of the sensor module, which consists of a transformer 606, a rectifier 608, and a voltage regulator 610. Power is supplied to a microprocessor 612 and for one or more 614 digital meters, each can be, for example, a Quartzdyne® meter, available from Quartzdyne, Inc. of Salt Lake City, UT. Such meters constitute a quartz resonator and are often packaged together with an accompanying oscillatory circuit and processor (eg, frequency display), and may include reference and temperature crystals along with their respective oscillatory circuits.

[0043] The 614 meter output is provided to the 612 processor, which processes the data and outputs a communication signal through a 616 frequency modulator. The communication signal is passed back to the pipe column via the 602 bus and the lower transformer. A low-pass filter 618 (which can be a capacitor), in combination with the low-pass filter 604, isolates the communication signal from the power path.

[0044] A part of the surface system 500, which acts as a meter interface module, is shown in the form of a block diagram in more detail in Figure 7. A bus 702 communicates with the upper transformer 302. One series input 704 draws power from a power supply, not shown. A 706 MPU controls input energy and emits energy through a 708 low-pass filter, digital attenuator 710, and 712 power amplifier. A 714 energy monitor measures the emitted energy and returns measured energy data to the MPU . A second low-pass filter 716, which in the illustrated embodiment is an inductor, passes the power signal to bus 702 and excludes the higher frequency data signals being returned from the sensor module. The data signals, in contrast, pass through a low-pass filter 718 to a demodulator 720 and from there to the MPU 706. The MPU output can be passed via an Ethernet connection 722, or another type of connection.

[0045] Figure 8 is a block diagram illustrating an arrangement similar to that illustrated in Figure 4 and represents an alternative approach to illustrate similar concepts. As described above, this approach makes use of insulated ceramic tubing subs in order to insulate a portion of the tubing. One insulation sub forms the upper insulator 319, while another forms the lower insulator 321. A portion of the intermediate pipeline 802 becomes the transmission line for signals and energy in the system. Similar to the transformer embodiment, the pipe column conducts energy signals from a connection point located just below the sub ceramic insulated piping sub (upper insulator 319) to a connection point located just above the sub piping sub lower ceramic (lower insulator 321). The energy signals are provided to a sensor / meter module unit 310 of the connection point located just above the lower insulator 321. In the opposite direction, the sensor module 310 generates communication signals that are transmitted to the connection point located just above the lower insulator 321. The communication signals are conducted above the pipe column to the connection point located just below the upper insulator 319, and then transmitted to the surface system 500. The electrical path is completed by grounding the piping above the upper ceramic insulated pipe sub and below the lower ceramic insulated pipe sub and grounding the surface system and sensor module. In practice, the casing is generally grounded. Thus, the pipe column above the sub ceramic insulated pipe sub can be grounded by coupling the pipe column to the casing tube through the wellhead. The tubing column, below the sub ceramic insulated tubing sub, can be grounded by connecting the tubing column to the casing tube, via an arc spring short circuit centralizer, for example.

[0046] In an experimental test, the inventors had up to 5181.6 m of coaxial cable that combined the losses of a field test (that is, they simulated the depth of a typical deep well). A remote full-wave AC power rectifier / filter was provided at the end of the cable to provide DC power to amplify the sensor signal.

[0047] A low frequency 60 hertz AC voltage was transmitted under the cable. It provided about 10 volts DC (outside the rectifier / filter) at the end of the cable. An amplified sensor signal (peak frequency) was received at the surface using an HF radio detector. This organization allowed receiving more than 120 readings per second on the surface.

[0048] In one embodiment, parameters, such as pressure or temperature, are measured (singularly or simultaneously) in great depth using the well piping hardware as well as the path for energizing the sensors (and other associated devices) , as well as to carry data signals from the sensors. As such, this technique uses the same conduction system for both electrical energy and the signal path of the parameter data. The applied energy can be DC and / or AC energy at various frequencies, to accommodate a multitude of uses of lower energized or upper energized remote functions, including artificial lifting systems (pumps).

[0049] This technique uses the well tubing and casing tube as a conductive pair (CP), to transport the energy below the devices of the energized or associated remote sensing group. This is done with a magnetic core AC coupler (similar to a transformer) or an insulated pipe member 319, just below the support of the pipe column (on the surface), and a similar insulated pipe member 321, near the terminal end of the piping column of a DC application. The piping is kept in the center of the casing-well tube with annular insulating spacers (“centralizers”), so that the conductive pair (tubing and casing tube) is not electrically shorted between them. From the end of the tubing column, below the bottom insulated tubing member, there must be a conductive “plug” or arc spring centralizer 312, or another mechanism for making contact with the casing tube to complete the circuit.

[0050] As will be noted, by electronic separation / isolation of the top of the energy well and signal, this same conductor pair can make such a path to the wellhead for processing the data of the sensor set. Those familiar with the art will understand the selective frequency filtering methods employed here to separate signal energy, and function from function. This process uses sensors that transfer the parameter of interest to a low energy Radio Frequency (RF) transmitter. The carrier of each transmitter is modulated to provide the embedded data for surface level instrumentation. The RF carrier is then demodulated into the surface electronics for use.

[0051] A second use of the CP arrangement of the well hardware described here is to energize an electric submersible pump (ESP) system for artificially elevating fluids in the production zones. The electrical energy sent to the ESP, via the pipe column, can be used to energize sensor systems fixed with the signals from these sensors using the same CP as the RF path back to surface instruments.

[0052] In one embodiment, the methods for controlling various downhole functions could be performed by selecting a specific force frequency that would perform several separate remote operations (i.e., multi-zone valve control, etc.) using resonant frequency selective networks at the remote valve location.

[0053] Those skilled in the art will note that the embodiments described here are by way of example only, and that numerous variations will exist. The invention is limited only by the claims, which encompass the embodiments described here as well as variants evident to those skilled in the art. In addition, it should be noted that structural aspects or steps of the method, shown or described in any of the embodiments here, can be used in other embodiments as well.

Claims (19)

1. System for measuring a condition in a downhole environment in a borehole below a surface, characterized by the fact that it comprises: a source (300), configured and arranged to transmit an energy signal, via a conductive line (102) in the borehole; a sensor module (310), in electrical communication with the source (300), via the conductive line (102), the sensor module (310) comprising an oscillator (614), having a resonant frequency that varies with changes in the environment condition downhole, the sensor module (310) being configured and arranged to receive the energy signal from the source (300) and to actively produce a sensor signal in response to the condition in the downhole environment and to transmit the signal, via the conductive line (102), to the surface; and a detector (320), in electrical communication with the sensor module (310), via the conductive line (102), and configured and arranged to receive the sensor signal. 2. System according to claim 1, characterized by the fact that it also comprises: an upper transformer (302), configured and arranged to receive the energy signal from the source, and to couple the energy signal with the conductive line of the column of drilling, and to receive the sensor signal from the conductive line of the drill string and to couple the sensor signal to the detector; and a lower transformer (304), configured and arranged to receive the energy signal from the conductive line of the drill string and to couple the energy signal to the sensor module, and to receive the sensor signal from the sensor module and to couple the signal sensor to the conductive line of the drill string. 3. System according to claim 1, characterized by the fact that it also comprises: a superior insulator (319), configured and arranged to electrically isolate a part of the conductive line of the surface drilling column; and a lower insulator (321), configured and arranged to electrically isolate the conductive line part of the drill column from a distal end of the conductive line of the drill column, the upper insulator (319) and lower insulator (321) defining the respective ends of a conductive part of the conductive line of the drill string, to transmit the energy signal and the sensor signal. 4. System according to claim 1, characterized by the fact that the sensor module also comprises a force conditioning circuit (606, 608, 610). 5. System according to claim 1, characterized by the fact that the sensor module further comprises a filter (604), built and arranged to separate the energy and data signals. 6. System according to claim 5, characterized by the fact that the filter comprises a low-pass filter (604), configured and arranged to pass the energy signal, via a force conditioning circuit (606, 608, 610 ), for the oscillator, and in which the sensor module further comprises: a frequency modulator, configured and arranged to modulate the sensor signal for transmission to the detector (320); and a high pass filter (618), configured and arranged to pass the modulated sensor signal, and to attenuate parts of the energy signal that would otherwise be transmitted to the detector. 7. System according to claim 1, characterized by the fact that the detector and the source together comprise a surface system and in which the surface system further comprises a filter (618), built and arranged to separate the energy signals and data. 8. System according to claim 7, characterized in that the filter comprises a low-pass filter (604), configured and arranged to pass the energy signal from the source to a power conditioning circuit (606, 608, 610), and the surface system detector further comprises: an additional low-pass filter (716), configured and arranged to pass the energy signal from the force conditioning circuit to the conductive line of the drill string, and to attenuate parts of the sensor signal that would otherwise be transmitted to the power conditioning circuit; a high pass filter (718), configured and arranged to attenuate the energy signal and to pass the sensor signal to a demodulator (720), the demodulator being configured and arranged to demodulate the sensor signal and to pass the signal from demodulated sensor for the detector. 9. System according to claim 1, characterized by the fact that it also comprises a short circuit positioned in the borehole, below the sensor module and connecting the conductive line of the drilling column to a borehole casing. 10. System according to claim 1, characterized by the fact that the conductive line comprises a drill string. 11. System according to claim 1, characterized by the fact that the conductive line comprises a production pipe. 12. Method of measuring a condition in a downhole environment in a borehole below a surface, characterized by the fact that it comprises: transmitting an energy signal, via a conductive line (102), inside the borehole ; receiving energy from the source in a sensor module (310) comprising an oscillator, having a resonant frequency that varies with changes in the condition of the downhole environment and positioned in the downhole environment; transmitting a sensor signal from the sensor module to the surface, via the conductive line of the drill string; detect the surface sensor signal; and splitting the energy signal and the sensor signal during reception and detection, while allowing the energy signal and the sensor signal to travel along a common path, via the conductive line of the drill string during transmission. 13. Method according to claim 12, characterized by the fact that the division of the energy signal and the sensor signal comprises filtering the signals based on frequency. Method according to claim 12, characterized by the fact that the division of the energy signal and the sensor signal comprises the low-pass filtering of a combined energy signal and sensor before the transmission of the energy signal. 15. Method according to claim 12, characterized by the fact that the division of the energy signal and the sensor signal comprises the high-pass filtering of a combined energy and sensor signal before the detection of the sensor signal on the surface. 16. Method according to claim 12, characterized in that it further comprises insulating a part of the conductive line used in the transmission with respective sub insulation units (319, 321) at a top of the part and a base of the part. 17. Method according to claim 12, characterized in that the energy and sensor signals are coupled to the conductive line by a pair of transformers (302, 304), a transformer (302) defining a top of a column part hole used in the transmission and the other transformer (304) defining a part base. 18. Method according to claim 12, characterized in that the conductive line comprises a drill string. 19. Method according to claim 12, characterized by the fact that the conductive line comprises a production pipe

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