WO2016024197A2 - Radio frequency (rf) system for the recovery of hydrocarbons - Google Patents

Radio frequency (rf) system for the recovery of hydrocarbons Download PDF

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Publication number
WO2016024197A2
WO2016024197A2 PCT/IB2015/056066 IB2015056066W WO2016024197A2 WO 2016024197 A2 WO2016024197 A2 WO 2016024197A2 IB 2015056066 W IB2015056066 W IB 2015056066W WO 2016024197 A2 WO2016024197 A2 WO 2016024197A2
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WO
WIPO (PCT)
Prior art keywords
transmission line
mode
coaxial transmission
converter
coaxial
Prior art date
Application number
PCT/IB2015/056066
Other languages
French (fr)
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WO2016024197A3 (en
Inventor
Michela DE SIMONI
Gilberto Toffolo
Alessandro CERUTTI
Original Assignee
Eni S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Eni S.P.A. filed Critical Eni S.P.A.
Priority to CN201580043470.9A priority Critical patent/CN106605037B/en
Priority to CA2957496A priority patent/CA2957496C/en
Priority to US15/502,923 priority patent/US10012060B2/en
Priority to RU2017104123A priority patent/RU2693972C2/en
Publication of WO2016024197A2 publication Critical patent/WO2016024197A2/en
Publication of WO2016024197A3 publication Critical patent/WO2016024197A3/en
Priority to SA517380869A priority patent/SA517380869B1/en

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Classifications

    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
    • E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
    • E21B43/2401—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection by means of electricity
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B36/00—Heating, cooling or insulating arrangements for boreholes or wells, e.g. for use in permafrost zones
    • E21B36/04—Heating, cooling or insulating arrangements for boreholes or wells, e.g. for use in permafrost zones using electrical heaters
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/04—Adaptation for subterranean or subaqueous use
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q13/00—Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
    • H01Q13/20—Non-resonant leaky-waveguide or transmission-line antennas; Equivalent structures causing radiation along the transmission path of a guided wave
    • H01Q13/203—Leaky coaxial lines
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0264—Arrangements for coupling to transmission lines
    • H04L25/0272—Arrangements for coupling to multiple lines, e.g. for differential transmission

Definitions

  • the present invention relates to a system for facilitating the extraction of hydrocarbons, in particular extraction by RF heating of high-viscosity hydrocarbons in situ by means of an antenna comprising a coaxial array of mode converters.
  • the present invention relates to a system for facilitating the extraction of hydrocarbons, in particular extraction by RF heating of high-viscosity hydrocarbons in situ by means of an antenna comprising a coaxial array of mode converters.
  • patent applications or already published patents disclose methods and systems for the application of RF heat within oil wells. These documents generally describe apparatus comprising generators of RF energy installed at the surface, transmission lines for transporting the RF signal to the base of the well and constructions
  • the resonant antennas of the concentrated type are not effective with horizontal wells having very long drains (for example having a length in the order of hundreds of metres). This is because resonant antennas cannot be effective in distributing radiation along the well, even if they have lengths typical of the drains concerned.
  • a dipole 1000 m long which is supplied from the centre and which irradiates within a dispersive medium (a typical range for the electrical conductivity of oil reservoirs is between 0.001 and 0.1 S/m) distributes an electrical field that is limited to a few metres around the supply point, regardless of the physical length of the dipole.
  • This performance is also characteristic of other types of resonant antenna, having geometric structures different from those of a dipole, such as helical, solenoid, or collinear with a coaxial sleeve dipole. Thus, it is not possible to utilise this class of antenna to distribute energy along the drain.
  • the radiating array configuration or design of the radiating array to be a function of the characteristics of the surrounding medium or of the desired distribution of energy along the drain.
  • the way RF power may be distributed uniformly along the drain is not defined.
  • triaxial antennas may be very bulky constructions, given the need for sleeve constructions surrounding the transmission line. This last aspect may constitute a disadvantage for incorporating antennas into oil wells.
  • Two-wire line antennas folded back on themselves to form elongated loops have other disadvantages, however.
  • the first of these arises from the fact that the two-wire line has high losses when transporting energy. This could result in a marked loss of energy inside the oil well, which is disadvantageous for the transfer of energy deep within the reservoir.
  • determining the radiant properties of the construction is the distance between the two conductors of the two-wire line, which is in any case limited to the section inside the well in which it is installed.
  • the proposed antennas having frequencies of 1 - 10 kHz have other disadvantages.
  • Antennas of this kind operate in frequency ranges in which the distribution of
  • the electromagnetic energy in the radial direction cannot be controlled by controlling the frequency. This is because in the range of 1 - 10 kHz, the skin depth (the depth at which the emf penetrates the medium, equal to
  • s electrical conductivity
  • ⁇ the angular frequency of the emf
  • ⁇ magnetic permeability
  • skin depth values are comparable with the heating ray (for example a skin depth of 1.5 - 5 m at frequencies of 10 - 1 MHz). This may be utilised to the benefit of thermal recovery, since it allows the distribution of energy deep in the medium (in the radial direction) to be regulated by the selection of frequency, which may thus be utilised to regulate the temperature range in the radial direction. Regulation of the temperature range may be utilised to maximise the mobility of the oil in the rock and to increase the well's productivity.
  • the object of the present patent application is to provide a technology that overcomes, at least in part, the disadvantages of the systems that are currently available.
  • the present invention relates to a system for heating high-viscosity hydrocarbons in a reservoir, including a drain with hydraulic connection, the system including: a radio frequency generator suitable for generating an electromagnetic signal; a coaxial transmission line connected to the generator and suitable for transmitting the signal along the well, the coaxial line including an external conductor and an internal conductor which are separated by a layer of dielectric material; at least one mode converter which is positioned along the coaxial transmission line, in which at least one mode converter interrupts the coaxial transmission line within the drain and includes a first and a second conductor, the first conductor of the converter providing an electrical connection between the external conductor of the transmission line upstream of the converter and the external conductor of the transmission line downstream of the converter, and the second conductor of the converter providing an electrical connection between the internal conductor of the transmission line upstream of the converter and the internal conductor of the transmission line downstream of the converter; the at least one mode converter being suitable for providing, in the presence of an RF signal along the coaxial transmission line, a disturbance of the differential mode
  • the system includes a plurality of mode converters distributed along the coaxial transmission line inside the drain.
  • the plurality of mode converters includes an array of mode converters placed at regular intervals along the coaxial transmission line. Each mode converter, by means of disturbance of the differential propagation mode, irradiates a proportion of the RF power that is propagated along the coaxial line, creating an irradiation that is distributed along the array of mode converters.
  • the mode converters may be of the capacitive or inductive type or indeed a combination of the two.
  • Inductive converters cause a disturbance of the differential mode of propagation of the signal along the coaxial transmission line by means of at least one inductive element.
  • Capacitive converters cause a disturbance of the differential mode of propagation of the signal along the coaxial transmission line by means of at least one capacitive element.
  • the system according to the present invention allows the RF irradiation to be distributed over long lengths of drain in horizontal, vertical or slant oil wells.
  • a system of this kind allows an effective increase in the productivity of wells for the recovery of high-viscosity hydrocarbons, in particular heavy oils, as a result of the ability to heat the reservoir uniformly and to moderate temperature over the entire length of the drain.
  • Heating the reservoir using RF energy by means of an antenna system located in a bore hole may be a valid alternative to traditional steam injection methods, in that it does not need to consume large quantities of water and may provide advantages such as the controlled distribution of energy, less dependence on the properties of the reservoir (in particular, the performance of steam injection methods depends to a large extent on the permeability of the reservoir and the continuity of the caprock), compact equipment, a limited expenditure of energy per barrel of oil produced as a result of the possibility of achieving a high level of efficiency in transporting energy to the base of the well and the possibility of controlling the distribution of energy inside the reservoir.
  • Radio frequency (RF) heating may thus be a valid alternative to steam injection for the thermal recovery of heavy oil, and may also be utilised to achieve moderate heating (in the order of just a few tens of degrees in a reservoir portion around the well in question) in cases where such heating is effective in reducing the viscosity of the oil to a significant extent and in increasing the productivity of the well.
  • Figure 1 shows a system for heating high-viscosity hydrocarbons in a drain according to a preferred embodiment of the present invention
  • Figure 2 shows the mechanism of electromagnetic mode conversion according to a preferred embodiment of the present invention
  • Figure 3 shows a mode converter according to an embodiment of the present invention
  • Figure 4 shows some alternative embodiments of a mode converter
  • Figure 5 shows possible embodiments for the end of the antenna that may be used in the system according to the present invention.
  • the system operates by applying power in the order of 100 - 1000 kW at frequencies in the range of 0.1 - 10 MHz.
  • An embodiment of the invention of this kind may be advantageous in achieving moderate heating along a drain in the order of several hundred metres in length, such as 1000 m or more.
  • An embodiment of this kind may increase the productivity of a heavy oil well to a significant extent, at the same time ensuring a limited expenditure of energy per barrel of oil produced.
  • the increase in temperature may be 50°C at the well, 28°C five metres away from the well in the radial direction, 13°C ten metres away and 10°C fifteen metres away.
  • the system operating at frequencies of between 0.1 and 10 MHz is used for the recovery of heavy oils.
  • the system to which the present invention relates may be suitable, by way of the design of the array parameters, for different reservoirs and for achieving the desired distribution of RF radiation along the well.
  • the system to which the present invention relates allows RF lines of limited section to be obtained, which is an advantageous aspect when installing the antenna directly in producing wells of standard dimensions without the need for additional, dedicated wells.
  • the system to which the present invention relates is thus characterised by the ability to irradiate along the drain at the frequencies concerned in controlled manner.
  • the system as illustrated in Figure 1 includes an RF generator 101 , a well perforator 103, a coaxial RF connector 105 and the coaxial array of mode converters 107 that comprise the antenna system 100.
  • the RF generator 101 is advantageously installed on the surface and operates within the range of frequencies of 0.1 - 10 MHz.
  • the transmitter may take the form of an array of solid state amplifiers, of vacuum tubes or of hybrid solutions combining the two.
  • the transmitter may also comprise an inverter.
  • the generator may also incorporate an impedance adapter unit which adapts the output from the transmitter to the load in order to maximise the transfer of power to the medium.
  • the generator output is connected to the well head by means of a coaxial cable.
  • the wellhead perforator 103 is the part of the system that enables the signal to be transmitted from the surface to the inside of the well by way of a construction integrated in the equipment at the well head.
  • the two ends of the perforator are connected to the coaxial cable coming from the generator and the coaxial cable installed inside the well for the transmission of power to the base of the well.
  • the wellhead perforator is coaxial in construction. In another embodiment, the perforator has a two-wire construction.
  • the coaxial transmission line 105 at the base of the well is the construction allowing the signal to be transported to the base of the well, or to the antenna input. Different types of construction may be used to form the coaxial cable.
  • the coaxial cable must ensure characteristics that are appropriate for the distance over which power is to be transferred, in respect of both peak power and average power, and low attenuation of the signal, in order to be able to transfer the desired power to the base of the well continuously and to supply a high level of energy efficiency.
  • the coaxial cable must be dimensioned with sections of external conductor (braid) and internal conductor (core) large enough to transfer the power over the desired distance.
  • the characteristics of the coaxial cable also depend on the dielectric material separating the internal conductor from the external one. The use of materials with low dielectric losses enables the distance over which the cable can transfer power and the efficiency to be increased. Materials that can be used to form a cable suitable for the application are for example PTFE (polytetrafluoroethylene) and expanded PTFE, which have low losses. Other types of dielectric materials may also advantageously be used to form the coaxial cable.
  • the antenna of the coaxial array of mode converters has a length compatible with that of the drian, or with a relevant proportion of the drain (e.g. 30%, 50% or 70%).
  • the length of the antenna thus depends on the length of the drain and may thus vary with the type of well and reservoir.
  • a typical drain length may be 1000 m.
  • Substantial lengths of bore hole may also be found in vertical or slant wells that intersect very thick reservoirs (for example drain lengths of 100 m).
  • the antenna of the array of mode converters may be designed and used to heat the reservoir over the entire extent of the drain of the vertical or slant well.
  • the mode converters 107 are electrical constructions which are connected to one another along the coaxial cable 105.
  • the particular construction of the mode converters has the function of disturbing the differential mode of propagation of the RF signal along the cable. Disturbance of the propagation mode sets up a common mode. This produces currents that flow outside the coaxial cable in a coaxial section that is centred on the point where the mode converter is installed. An emf is associated with such external currents in the surrounding area, and this heats the geological formation. This mechanism transfers a proportion of the power transported along the coaxial cable to the outside.
  • Figure 2 shows an illustration of the mechanism for converting the electromagnetic mode, which is the operating principle underlying the antenna. The figure shows how the discontinuity in the transmission line (resulting from the presence of the mode converter) changes the distribution of currents along the line itself and produces common-mode currents outside the line.
  • An array of interconnected mode converters on a coaxial line forms the antenna installed in the section of drain.
  • the mode converters have at least two conductors.
  • the first conductor connects the braid of the coaxial section upstream of the line to the braid of the coaxial section downstream of the line.
  • the second conductor connects the core of the coaxial section upstream of the line to the core of the coaxial section downstream of the line.
  • the geometry of the conductors in the mode converters is selected in order to create inductive and/or capacitive elements. Elements of this kind disturb the differential mode of propagation of the signal along the coaxial cable and allow a common mode to be set up. The latter induces currents in the external braid of the coaxial cable and an electromagnetic field in the surrounding area.
  • the electromagnetic field heats the surrounding medium by means of inductive or dielectric heating mechanisms or a combination of the two.
  • the mode converters are elements connected to a coaxial cable on both sides by means of appropriate connectors, which may be coaxial or two-wire in type.
  • the mode converters may be of the inductive type. Inductance may be brought about by the geometric structure of one of the two conductors or both the conductors. Inductance may be brought about by combining the geometric structure of the conductors with the use of materials of high magnetic susceptibility.
  • the converters may be of the capacitive type. Capacitance may be brought about by the geometric structure of one of the two conductors or both the conductors. Capacitance may be brought about by combining the geometric structure of the conductors with the use of materials of high dielectric permittivity.
  • the converters may be of the inductive-capacitive type. Converters of this kind are characterised by combinations of the constructions described above.
  • Figure 3 shows the general electrical layouts relating to the mode converters.
  • the figure shows that various combinations of inductive and capacitive elements are possible.
  • Either of the two conductors comprising the mode converter may include one or more inductive elements and/or one or more capacitive elements connected in series and/or in parallel.
  • Another possibility is for the internal conductor or the external conductor to form a direct connection.
  • Figure 4 shows specific embodiments of inductive, capacitive and inductive-capacitive mode converters.
  • Figure 4a shows a mode converter of the inductive- capacitive type in which the external conductor is wound to form a coil structure which creates an inductance parameter, and in which the internal conductor is interrupted by a pair of plates which create a capacitance parameter;
  • Figure 4b shows a mode converter of the inductive-capacitive type in which the external conductor is interrupted by a pair of plates which create a capacitance parameter, and the internal conductor is wound to form a coil structure which creates an inductance parameter.
  • Figure 4c shows a mode converter of the inductive type in which the external conductor is wound to form a coil structure which creates an inductance parameter, and the internal conductor forms a direct link from the core of the coaxial cable upstream to the core of the coaxial cable downstream.
  • Figure 4d shows a mode converter of the inductive type in which the external conductor is wound to form a coil structure which creates an inductance parameter, and the internal conductor, like the external one, is also wound to form a coil structure which creates an inductance parameter; finally, Figure 4e shows a mode converter of the inductive type in which the external conductor is wound to form a coil that is coaxial in relation to the internal conductor, unlike the structures above, in which coils are positioned laterally in relation to the internal conductor.
  • Positioning a mode converter on the coaxial line produces a discontinuity on the transmission line which causes a proportion of the power to be irradiated within the medium surrounding the antenna.
  • the electromagnetic behaviour of a mode converter may be described by way of two fundamental parameters: the efficiency of radiation (proportion of power irradiated in relation to the power input to the mode converter) and the return loss (proportion of power reflected in relation to the power input).
  • the values of such parameters in a specific mode converter depend on various variables, in particular the values of inductance and/or capacitance brought about by a mode converter, the frequency and the electromagnetic characteristics (dielectric permittivity and electrical conductivity) of the reservoir, the electromagnetic characteristics of the fluids inside the well, and any antenna coverings. It follows that the design of the array and the mode converters, or rather the selection of the distance between mode converters along the coaxial array, the constructional type of converter and the relative values of inductance and/or capacitance as a function of the frequency range and the electromagnetic characteristics of the surrounding medium, is one of the major aspects in constructing the system to which the present invention relates.
  • the mode converters used to form an array generally have constructional characteristics that differ from one another.
  • the mode converters positioned at the beginning of the array must be designed to supply low radiation efficiency, that is to say to irradiate a limited proportion of the power that is input, and allow a substantial proportion of the power to be transmitted downstream.
  • the mode converters positioned at the end of the array by contrast, must supply a high radiation efficiency to irradiate a substantial proportion of the remaining power.
  • the end of the antenna (corresponding to the base of the well) may be formed in various ways. It may be a short circuit or an open circuit to return the remaining, non-irradiated power from the mode converters and to allow it to be irradiated as it returns along the antenna, or an antenna of the resonant type, such as a coaxial monopole to irradiate the remaining non-irradiated power from the array of mode converters.
  • Figure 5 shows possible embodiments of the antenna end, in particular an open circuit, a short circuit and an antenna of the monopole type produced from the coaxial cable.
  • the well may be an open bore hole within the reservoir, or it may advantageously be lined with a tube of non-conductive material (material such as glass fibre, PTFE or other thermoplastic materials, ceramics or systems of non-conductive materials of another type) to allow irradiation from the antenna installed within it.
  • non-conductive material material such as glass fibre, PTFE or other thermoplastic materials, ceramics or systems of non-conductive materials of another type
  • the system to which the present invention relates may advantageously be formed by adapting the antenna to reservoirs having different properties or heterogeneous properties along the drain by the selection of the electrical parameters and the positioning of each mode converter along the array.
  • the individual mode converters may be designed to control the profile of irradiation along the drain.
  • a resistivity range within the reservoir of 50 - 200 ohm metres (a resistivity range which is typical of geological formations composed of rock matrices in which there is a high saturation of hydrocarbons and limited water saturation)
  • a range of radiation efficiencies of between 1% and 3% (which is required for the construction of an array of 100 elements and a total antenna length of 1000 m) with a frequency of 1 MHz
  • mode converters of the inductive type with a coil connecting the braid sections of the coaxial cable
  • inductance values may be obtained by forming coils of a diameter that is compatible with the installation in the well and having a number of turns of between 8 and 32.
  • Mode converters of this type may have a length in the order of 40 - 60 cm.
  • This exemplary embodiment shows the possibility of achieving distributed RF heating that gives high levels of performance.
  • electrical preconditions of this kind enable mode converters to be constructed whereof the section of the construction is limited to values compatible with their installation in drain of production wells.
  • a diameter of 6 cm may be compatible with installation in the production well. This is because a production well could have a bore hole diameter of 8.5 inches and a liner having an internal diameter in the order of 5 inches.
  • the exemplary embodiment allows the antenna to be installed in the well while leaving space for a possible antenna covering and for the flow of oil to the surface.
  • Installation of the RF system in the production well allows the effectiveness of thermal stimulation to be maximised while concentrating the heat close to the productive well and reducing the number of wells which have to be perforated in the production field.
  • the coaxial transport line most efficient transmission line in the range of frequencies concerned
  • the coaxial transport line most efficient transmission line in the range of frequencies concerned
  • This may be achieved by using a low-attenuation coaxial cable to form the array of mode converters, such as the coaxial cable used for the RF connection between the surface and the antenna input.
  • Measurements of reflection over a range of frequencies may be carried out on the RF line installed in the well by connecting the line to a spectrum analyser. Reflection
  • measurements at the surface are dependent on the return of the corresponding signal from each mode converter.
  • the information obtained from reflectometry may thus be utilised to monitor the radiation characteristics of the antenna and the surrounding medium and to optimise the operating frequency.
  • the system to which the present invention relates may advantageously be applied to the thermal recovery of an individual well or of separate wells (heater and producer) and may be combined with other advanced recovery methods (IOR/EOR, improved oil

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Abstract

The present invention relates to a system for facilitating the extraction of hydrocarbons, in particular extraction by RF heating of high-viscosity hydrocarbons in situ by means of an antenna comprising a coaxial array of mode converters.

Description

RADIO FREQUENCY (RF) SYSTEM FOR THE RECOVERY OF HYDROCARBONS Abstract
The present invention relates to a system for facilitating the extraction of hydrocarbons, in particular extraction by RF heating of high-viscosity hydrocarbons in situ by means of an antenna comprising a coaxial array of mode converters.
Description
Field of the invention
The present invention relates to a system for facilitating the extraction of hydrocarbons, in particular extraction by RF heating of high-viscosity hydrocarbons in situ by means of an antenna comprising a coaxial array of mode converters.
Prior art
Numerous methods and systems are known from the prior art for the extraction of hydrocarbons by means of heating the hydrocarbons themselves.
In particular, patent applications or already published patents disclose methods and systems for the application of RF heat within oil wells. These documents generally describe apparatus comprising generators of RF energy installed at the surface, transmission lines for transporting the RF signal to the base of the well and constructions
(antennas) for irradiating or applying RF energy to the geological formation.
Some patent reference documents describe possible methods for oil production which can be achieved by means of RF heating in situ, in particular:
• Reducing the viscosity of heavy oils (US 7,891 ,421 Method and apparatus for in- situ RF heating Kasevich (2011 ))
• Liquefaction of solid hydrocarbons in reservoir conditions (tar sands) US
2012/0090844 Simultaneous Conversion and recovery of bitumen using RF
Madison et al. 2012)) • Production of oil by high-temperature pyrolysis of kerogens (in oil shale) (US 4,485,869 Recovery of liquid hydrocarbons from oil shale by electromagnetic heating in situ Sresty et al. (1984))
• Production of organic products from oil shale (US 4,508, 168 RF applicator for in situ heating Heeren (1985))
• In-situ conversion (upgrading) by means of heating heavy oils to high temperature (with or without the introduction of materials, catalytic beds and/or other reactive substances) (US 2010/0219107 Radio Frequency Heating of petroleum ore by particle susceptors Parsche (2010); US 7,441 ,597 Method and apparatus for in-situ RF assisted gravity drainage of oil Kasevich (2008))
• Methods for injecting steam assisted by RF heating (US 2012/0061080 Inline RF heating for SAGD operations Sultenfuss et al. (2012); US 8,646,527 RF enhanced SAGD method for recovery of hydrocarbons Trautman et al. (2014))
Further, there are patent reference documents relating to different types of antennas or applicators for wells:
• Antennas, whether dipole, helical, solenoid or collinear (US 7,441 ,597 Method and apparatus for in-situ RF assisted gravity drainage of oil Kasevich (2008); US
2012/0061380 Apparatus and method for heating of hydrocarbon deposits by RF driven coaxial sleeve Parsche (2012));
• Electrode arrays (US 4,485,869 Recovery of liquid hydrocarbons from oil shale by electromagnetic heating in situ Sresty et al. (1984));
• Two-wire transmission lines folded back on themselves to form elongated loops (US 2012/0061383 Litz Heating Antenna Parsche (2012));
• Triaxial transmission lines and sleeves (US 8,453,739 Triaxial linear induction
antenna array for increased heavy oil recovery Parsche (2013); US 2013/0334205 Subterranean antenna including antenna element and coaxial line therein and related methods Wright et al. (2013)).
Some of these references (US 7,441 ,597; US 2012/0061380) describe wire antennas of the resonant type. These types of antenna are generally limited to a length of a few metres and allow a limited portion of the reservoir around the antenna to be heated to high temperature. Systems having antennas of this kind could provide effective solutions for oil sands. Antennas of this kind are obtained by installing within the well ad-hoc metal constructions, or in some cases making use of the completion elements themselves. Other systems (as described for example in US 4,485,869) are based on arrays of electrodes installed in holes in the ground for forming a condenser construction. In these systems, heating is achieved inside the volume of the ground delimited by the electrodes. These systems have been proposed for the recovery of hydrocarbons in oil shale outcrops.
Finally, other systems proposed for application to oil sands are based on triaxial or elongated loop constructions for installations inside horizontal wells (US 2013/0334205, US 8,453,739, US 2012/0061383). These antenna systems, which are supplied at relatively low frequency (in the range of 1 - 10 kHz) and power in the order of several MW, are proposed for heating that is distributed along a horizontal well to the high temperatures required for liquefaction of solid bitumen.
The systems of the prior art have limitations and practical disadvantages, as summarised below.
The resonant antennas of the concentrated type are not effective with horizontal wells having very long drains (for example having a length in the order of hundreds of metres). This is because resonant antennas cannot be effective in distributing radiation along the well, even if they have lengths typical of the drains concerned. For example, a dipole 1000 m long which is supplied from the centre and which irradiates within a dispersive medium (a typical range for the electrical conductivity of oil reservoirs is between 0.001 and 0.1 S/m) distributes an electrical field that is limited to a few metres around the supply point, regardless of the physical length of the dipole.
This performance is also characteristic of other types of resonant antenna, having geometric structures different from those of a dipole, such as helical, solenoid, or collinear with a coaxial sleeve dipole. Thus, it is not possible to utilise this class of antenna to distribute energy along the drain.
Distributed antennas, which are designed to work at frequencies of 1 - 10 kHz, have other disadvantages, however. The parameters of triaxial antennas do not allow the
configuration or design of the radiating array to be a function of the characteristics of the surrounding medium or of the desired distribution of energy along the drain. In particular, the way RF power may be distributed uniformly along the drain is not defined.
Furthermore, triaxial antennas may be very bulky constructions, given the need for sleeve constructions surrounding the transmission line. This last aspect may constitute a disadvantage for incorporating antennas into oil wells.
Two-wire line antennas folded back on themselves to form elongated loops have other disadvantages, however. The first of these arises from the fact that the two-wire line has high losses when transporting energy. This could result in a marked loss of energy inside the oil well, which is disadvantageous for the transfer of energy deep within the reservoir. Furthermore, and similarly to triaxial antennas, it is not clear how the distribution of power transferred to the medium may be controlled. It seems that the only parameter
determining the radiant properties of the construction is the distance between the two conductors of the two-wire line, which is in any case limited to the section inside the well in which it is installed. The proposed antennas having frequencies of 1 - 10 kHz have other disadvantages. Antennas of this kind operate in frequency ranges in which the distribution of
electromagnetic energy in the radial direction (relative to the axis of the well) cannot be controlled by controlling the frequency. This is because in the range of 1 - 10 kHz, the skin depth (the depth at which the emf penetrates the medium, equal to
Figure imgf000007_0001
where s is electrical conductivity, ω is the angular frequency of the emf, and μ is magnetic permeability) is much greater than the heating ray concerned (which could generally be in the order of 10 - 15 m). As s=0.01 S/m, the skin depth will in fact be in the order of 50 - 160 m for frequencies of between 10 and 1 kHz.
It follows that the heating range coincides with close range (r«d), in which the distribution of the emf in the radial direction does not depend on frequency.
At higher frequencies, however, skin depth values are comparable with the heating ray (for example a skin depth of 1.5 - 5 m at frequencies of 10 - 1 MHz). This may be utilised to the benefit of thermal recovery, since it allows the distribution of energy deep in the medium (in the radial direction) to be regulated by the selection of frequency, which may thus be utilised to regulate the temperature range in the radial direction. Regulation of the temperature range may be utilised to maximise the mobility of the oil in the rock and to increase the well's productivity.
Object of the present invention
The object of the present patent application is to provide a technology that overcomes, at least in part, the disadvantages of the systems that are currently available.
General statement of the invention
The present invention relates to a system for heating high-viscosity hydrocarbons in a reservoir, including a drain with hydraulic connection, the system including: a radio frequency generator suitable for generating an electromagnetic signal; a coaxial transmission line connected to the generator and suitable for transmitting the signal along the well, the coaxial line including an external conductor and an internal conductor which are separated by a layer of dielectric material; at least one mode converter which is positioned along the coaxial transmission line, in which at least one mode converter interrupts the coaxial transmission line within the drain and includes a first and a second conductor, the first conductor of the converter providing an electrical connection between the external conductor of the transmission line upstream of the converter and the external conductor of the transmission line downstream of the converter, and the second conductor of the converter providing an electrical connection between the internal conductor of the transmission line upstream of the converter and the internal conductor of the transmission line downstream of the converter; the at least one mode converter being suitable for providing, in the presence of an RF signal along the coaxial transmission line, a disturbance of the differential mode of propagation of the signal along the coaxial transmission line and inducing a current in the external conductor of the coaxial transmission line and an electromagnetic field in the surrounding area which causes the hydrocarbons inside the reservoir to heat up.
According to a preferred embodiment of the present invention, the system includes a plurality of mode converters distributed along the coaxial transmission line inside the drain. In a preferred embodiment, the plurality of mode converters includes an array of mode converters placed at regular intervals along the coaxial transmission line. Each mode converter, by means of disturbance of the differential propagation mode, irradiates a proportion of the RF power that is propagated along the coaxial line, creating an irradiation that is distributed along the array of mode converters.
The mode converters may be of the capacitive or inductive type or indeed a combination of the two. Inductive converters cause a disturbance of the differential mode of propagation of the signal along the coaxial transmission line by means of at least one inductive element. Capacitive converters cause a disturbance of the differential mode of propagation of the signal along the coaxial transmission line by means of at least one capacitive element.
The system according to the present invention allows the RF irradiation to be distributed over long lengths of drain in horizontal, vertical or slant oil wells.
A system of this kind allows an effective increase in the productivity of wells for the recovery of high-viscosity hydrocarbons, in particular heavy oils, as a result of the ability to heat the reservoir uniformly and to moderate temperature over the entire length of the drain.
The importance of high-viscosity hydrocarbons as an energy resource is growing continuously as a result of the development of advanced methods of recovering oil, such as thermal recovery.
Heating the reservoir using RF energy by means of an antenna system located in a bore hole may be a valid alternative to traditional steam injection methods, in that it does not need to consume large quantities of water and may provide advantages such as the controlled distribution of energy, less dependence on the properties of the reservoir (in particular, the performance of steam injection methods depends to a large extent on the permeability of the reservoir and the continuity of the caprock), compact equipment, a limited expenditure of energy per barrel of oil produced as a result of the possibility of achieving a high level of efficiency in transporting energy to the base of the well and the possibility of controlling the distribution of energy inside the reservoir.
Radio frequency (RF) heating may thus be a valid alternative to steam injection for the thermal recovery of heavy oil, and may also be utilised to achieve moderate heating (in the order of just a few tens of degrees in a reservoir portion around the well in question) in cases where such heating is effective in reducing the viscosity of the oil to a significant extent and in increasing the productivity of the well.
Brief description of the drawings
Reference will now be made to a series of drawings to facilitate the description of some preferred embodiments of the present invention:
Figure 1 shows a system for heating high-viscosity hydrocarbons in a drain according to a preferred embodiment of the present invention;
Figure 2 shows the mechanism of electromagnetic mode conversion according to a preferred embodiment of the present invention;
Figure 3 shows a mode converter according to an embodiment of the present invention;
Figure 4 shows some alternative embodiments of a mode converter;
Figure 5 shows possible embodiments for the end of the antenna that may be used in the system according to the present invention.
Detailed description of a preferred embodiment
In a preferred embodiment of the present invention, the system operates by applying power in the order of 100 - 1000 kW at frequencies in the range of 0.1 - 10 MHz. An embodiment of the invention of this kind may be advantageous in achieving moderate heating along a drain in the order of several hundred metres in length, such as 1000 m or more. An embodiment of this kind may increase the productivity of a heavy oil well to a significant extent, at the same time ensuring a limited expenditure of energy per barrel of oil produced. In an embodiment of this kind, the increase in temperature may be 50°C at the well, 28°C five metres away from the well in the radial direction, 13°C ten metres away and 10°C fifteen metres away.
In a further preferred embodiment of the present invention, the system operating at frequencies of between 0.1 and 10 MHz is used for the recovery of heavy oils. The system to which the present invention relates may be suitable, by way of the design of the array parameters, for different reservoirs and for achieving the desired distribution of RF radiation along the well.
Furthermore, the system to which the present invention relates allows RF lines of limited section to be obtained, which is an advantageous aspect when installing the antenna directly in producing wells of standard dimensions without the need for additional, dedicated wells.
The system to which the present invention relates is thus characterised by the ability to irradiate along the drain at the frequencies concerned in controlled manner.
Particularly advantageous is the configuration in which irradiation is uniform, or rather the power irradiated from each mode converter is constant along the drain.
According to a preferred embodiment of the present invention, the system as illustrated in Figure 1 includes an RF generator 101 , a well perforator 103, a coaxial RF connector 105 and the coaxial array of mode converters 107 that comprise the antenna system 100. The RF generator 101 is advantageously installed on the surface and operates within the range of frequencies of 0.1 - 10 MHz. In some embodiments, the generator may deliver power <= 1 MW to achieve moderate heating, if this is sufficient to reduce the viscosity of the heavy oils to a significant extent. In other embodiments, the power may be >= 1 MW, if there is a requirement to reach high temperatures over a distance of several metres from the well in order to mobilise the hydrocarbon.
There are various ways to construct a high-power RF generator in the range of frequencies concerned. The transmitter may take the form of an array of solid state amplifiers, of vacuum tubes or of hybrid solutions combining the two.
The transmitter may also comprise an inverter. The generator may also incorporate an impedance adapter unit which adapts the output from the transmitter to the load in order to maximise the transfer of power to the medium. The generator output is connected to the well head by means of a coaxial cable.
The wellhead perforator 103 is the part of the system that enables the signal to be transmitted from the surface to the inside of the well by way of a construction integrated in the equipment at the well head. The two ends of the perforator are connected to the coaxial cable coming from the generator and the coaxial cable installed inside the well for the transmission of power to the base of the well.
In an embodiment of the invention, the wellhead perforator is coaxial in construction. In another embodiment, the perforator has a two-wire construction.
Any electrical construction which gives limited insertion loss and return loss values may be used to form the perforator.
The coaxial transmission line 105 at the base of the well is the construction allowing the signal to be transported to the base of the well, or to the antenna input. Different types of construction may be used to form the coaxial cable.
The coaxial cable must ensure characteristics that are appropriate for the distance over which power is to be transferred, in respect of both peak power and average power, and low attenuation of the signal, in order to be able to transfer the desired power to the base of the well continuously and to supply a high level of energy efficiency.
These characteristics improve as the diameter of the cable increases. To this end, the coaxial cable must be dimensioned with sections of external conductor (braid) and internal conductor (core) large enough to transfer the power over the desired distance. The characteristics of the coaxial cable also depend on the dielectric material separating the internal conductor from the external one. The use of materials with low dielectric losses enables the distance over which the cable can transfer power and the efficiency to be increased. Materials that can be used to form a cable suitable for the application are for example PTFE (polytetrafluoroethylene) and expanded PTFE, which have low losses. Other types of dielectric materials may also advantageously be used to form the coaxial cable.
The antenna of the coaxial array of mode converters has a length compatible with that of the drian, or with a relevant proportion of the drain (e.g. 30%, 50% or 70%).
The length of the antenna thus depends on the length of the drain and may thus vary with the type of well and reservoir. For horizontal wells, a typical drain length may be 1000 m. Substantial lengths of bore hole may also be found in vertical or slant wells that intersect very thick reservoirs (for example drain lengths of 100 m).
In such contexts, the antenna of the array of mode converters may be designed and used to heat the reservoir over the entire extent of the drain of the vertical or slant well.
The mode converters 107 are electrical constructions which are connected to one another along the coaxial cable 105. The particular construction of the mode converters has the function of disturbing the differential mode of propagation of the RF signal along the cable. Disturbance of the propagation mode sets up a common mode. This produces currents that flow outside the coaxial cable in a coaxial section that is centred on the point where the mode converter is installed. An emf is associated with such external currents in the surrounding area, and this heats the geological formation. This mechanism transfers a proportion of the power transported along the coaxial cable to the outside.
The use of an array of mode converters positioned along the coaxial line allows a considerable proportion or all of the power supplied to the coaxial cable to be transferred. Figure 2 shows an illustration of the mechanism for converting the electromagnetic mode, which is the operating principle underlying the antenna. The figure shows how the discontinuity in the transmission line (resulting from the presence of the mode converter) changes the distribution of currents along the line itself and produces common-mode currents outside the line.
An array of interconnected mode converters on a coaxial line forms the antenna installed in the section of drain.
The mode converters have at least two conductors. The first conductor connects the braid of the coaxial section upstream of the line to the braid of the coaxial section downstream of the line. The second conductor connects the core of the coaxial section upstream of the line to the core of the coaxial section downstream of the line.
Favourably, the geometry of the conductors in the mode converters is selected in order to create inductive and/or capacitive elements. Elements of this kind disturb the differential mode of propagation of the signal along the coaxial cable and allow a common mode to be set up. The latter induces currents in the external braid of the coaxial cable and an electromagnetic field in the surrounding area.
The electromagnetic field, of frequency f, heats the surrounding medium by means of inductive or dielectric heating mechanisms or a combination of the two.
In an embodiment of the invention, the currents that flow in the external braid induce a magnetic field in the surrounding area and in particular inside the reservoir. Variation in the magnetic field over time in turn induces an electrical field inside the reservoir, which produces eddy currents of J=sE, where J is the current density, s is the electrical conductivity of the reservoir and E is the induced electrical current. The power dissipated per unit of volume inside the geological medium is q = 0.5 s E2. This procedure forms the basis for the RF heating by an antenna installed in the well.
The mode converters are elements connected to a coaxial cable on both sides by means of appropriate connectors, which may be coaxial or two-wire in type.
The mode converters may be of the inductive type. Inductance may be brought about by the geometric structure of one of the two conductors or both the conductors. Inductance may be brought about by combining the geometric structure of the conductors with the use of materials of high magnetic susceptibility.
The converters may be of the capacitive type. Capacitance may be brought about by the geometric structure of one of the two conductors or both the conductors. Capacitance may be brought about by combining the geometric structure of the conductors with the use of materials of high dielectric permittivity.
The converters may be of the inductive-capacitive type. Converters of this kind are characterised by combinations of the constructions described above.
Figure 3 shows the general electrical layouts relating to the mode converters. The figure shows that various combinations of inductive and capacitive elements are possible. Either of the two conductors comprising the mode converter (internal and external) may include one or more inductive elements and/or one or more capacitive elements connected in series and/or in parallel. Another possibility is for the internal conductor or the external conductor to form a direct connection.
Figure 4 shows specific embodiments of inductive, capacitive and inductive-capacitive mode converters. In particular, Figure 4a shows a mode converter of the inductive- capacitive type in which the external conductor is wound to form a coil structure which creates an inductance parameter, and in which the internal conductor is interrupted by a pair of plates which create a capacitance parameter; Figure 4b shows a mode converter of the inductive-capacitive type in which the external conductor is interrupted by a pair of plates which create a capacitance parameter, and the internal conductor is wound to form a coil structure which creates an inductance parameter. Figure 4c, by contrast, shows a mode converter of the inductive type in which the external conductor is wound to form a coil structure which creates an inductance parameter, and the internal conductor forms a direct link from the core of the coaxial cable upstream to the core of the coaxial cable downstream. Figure 4d, by contrast, shows a mode converter of the inductive type in which the external conductor is wound to form a coil structure which creates an inductance parameter, and the internal conductor, like the external one, is also wound to form a coil structure which creates an inductance parameter; finally, Figure 4e shows a mode converter of the inductive type in which the external conductor is wound to form a coil that is coaxial in relation to the internal conductor, unlike the structures above, in which coils are positioned laterally in relation to the internal conductor.
Positioning a mode converter on the coaxial line produces a discontinuity on the transmission line which causes a proportion of the power to be irradiated within the medium surrounding the antenna. The electromagnetic behaviour of a mode converter may be described by way of two fundamental parameters: the efficiency of radiation (proportion of power irradiated in relation to the power input to the mode converter) and the return loss (proportion of power reflected in relation to the power input).
The values of such parameters in a specific mode converter depend on various variables, in particular the values of inductance and/or capacitance brought about by a mode converter, the frequency and the electromagnetic characteristics (dielectric permittivity and electrical conductivity) of the reservoir, the electromagnetic characteristics of the fluids inside the well, and any antenna coverings. It follows that the design of the array and the mode converters, or rather the selection of the distance between mode converters along the coaxial array, the constructional type of converter and the relative values of inductance and/or capacitance as a function of the frequency range and the electromagnetic characteristics of the surrounding medium, is one of the major aspects in constructing the system to which the present invention relates.
In particular, the mode converters used to form an array generally have constructional characteristics that differ from one another. The mode converters positioned at the beginning of the array must be designed to supply low radiation efficiency, that is to say to irradiate a limited proportion of the power that is input, and allow a substantial proportion of the power to be transmitted downstream.
The mode converters positioned at the end of the array, by contrast, must supply a high radiation efficiency to irradiate a substantial proportion of the remaining power.
The end of the antenna (corresponding to the base of the well) may be formed in various ways. It may be a short circuit or an open circuit to return the remaining, non-irradiated power from the mode converters and to allow it to be irradiated as it returns along the antenna, or an antenna of the resonant type, such as a coaxial monopole to irradiate the remaining non-irradiated power from the array of mode converters.
Figure 5 shows possible embodiments of the antenna end, in particular an open circuit, a short circuit and an antenna of the monopole type produced from the coaxial cable. The well may be an open bore hole within the reservoir, or it may advantageously be lined with a tube of non-conductive material (material such as glass fibre, PTFE or other thermoplastic materials, ceramics or systems of non-conductive materials of another type) to allow irradiation from the antenna installed within it.
The system to which the present invention relates may advantageously be formed by adapting the antenna to reservoirs having different properties or heterogeneous properties along the drain by the selection of the electrical parameters and the positioning of each mode converter along the array.
In one aspect of the present invention, the individual mode converters may be designed to control the profile of irradiation along the drain.
For example, digital simulations carried out on electromagnetic antenna modelling instruments show that, by establishing inductance values in the range from a few tenths to a few tens of microhenrys, it is possible to obtain a range of radiation efficiencies to result in homogeneous heating over a drain 1000 m long. For example, in a resistivity range within the reservoir of 50 - 200 ohm metres (a resistivity range which is typical of geological formations composed of rock matrices in which there is a high saturation of hydrocarbons and limited water saturation), it is possible to achieve a range of radiation efficiencies of between 1% and 3% (which is required for the construction of an array of 100 elements and a total antenna length of 1000 m) with a frequency of 1 MHz using mode converters of the inductive type (with a coil connecting the braid sections of the coaxial cable) that are characterised by inductance values of between approximately 0.5 uH and 10 uH. Such inductance values may be obtained by forming coils of a diameter that is compatible with the installation in the well and having a number of turns of between 8 and 32. Mode converters of this type may have a length in the order of 40 - 60 cm.
Moreover, with inductance values of this kind, little power is returned from each mode converter (for the first converters in the array, with efficiencies in the order of 1%, the return loss is around -24 dB, and for converters at the end of the array, with efficiencies in the order of 30% or more, the return loss is -10 dB) and this allows a target in the order of -15 dB of total return loss for the antenna to be achieved, a value which is sufficient for the application (equivalent to a transfer of power to the formation of 97% and of power returned towards the generator of 3%).
This exemplary embodiment shows the possibility of achieving distributed RF heating that gives high levels of performance. Moreover, electrical preconditions of this kind enable mode converters to be constructed whereof the section of the construction is limited to values compatible with their installation in drain of production wells.
Purely by way of example, a diameter of 6 cm (equivalent to 2.4 inches) may be compatible with installation in the production well. This is because a production well could have a bore hole diameter of 8.5 inches and a liner having an internal diameter in the order of 5 inches. Thus, the exemplary embodiment allows the antenna to be installed in the well while leaving space for a possible antenna covering and for the flow of oil to the surface.
Installation of the RF system in the production well allows the effectiveness of thermal stimulation to be maximised while concentrating the heat close to the productive well and reducing the number of wells which have to be perforated in the production field.
In another aspect of the present invention, it is possible to minimise the ohmic losses along the drain by utilising the coaxial transport line (most efficient transmission line in the range of frequencies concerned) in the antenna section as well. This may be achieved by using a low-attenuation coaxial cable to form the array of mode converters, such as the coaxial cable used for the RF connection between the surface and the antenna input. Measurements of reflection over a range of frequencies may be carried out on the RF line installed in the well by connecting the line to a spectrum analyser. Reflection
measurements at the surface are dependent on the return of the corresponding signal from each mode converter. The information obtained from reflectometry may thus be utilised to monitor the radiation characteristics of the antenna and the surrounding medium and to optimise the operating frequency.
The system to which the present invention relates may advantageously be applied to the thermal recovery of an individual well or of separate wells (heater and producer) and may be combined with other advanced recovery methods (IOR/EOR, improved oil
recovery/enhanced oil recovery).

Claims

1. A system for heating high-viscosity hydrocarbons in a reservoir including at least one drain, the system including:
a radio frequency generator suitable for generating an electromagnetic signal; a coaxial transmission line connected to the generator and suitable for transmitting the signal along the drain, the coaxial line including an external conductor and an internal conductor which are separated by a layer of dielectric material;
at least one mode converter which is positioned along the coaxial transmission line inside the well, in which the at least one mode converter interrupts the coaxial transmission line and includes a first and a second conductor, the first conductor of the converter providing an electrical connection between the external conductor of the transmission line upstream of the converter and the external conductor of the transmission line downstream of the converter, and the second conductor of the mode converter providing an electrical connection between the internal conductor of the transmission line upstream of the mode converter and the internal conductor of the transmission line downstream of the mode converter;
the at least one mode converter being suitable for providing, in the presence of an RF signal along the coaxial transmission line, a disturbance of the differential mode of propagation of the signal along the coaxial transmission line and for inducing a current in the external conductor of the coaxial transmission line and an
electromagnetic field in the surrounding area which causes the hydrocarbons inside the reservoir to heat up.
2. An apparatus according to Claim 1 , including a plurality of mode converters distributed along the coaxial transmission line inside the well, in which each of the plurality of mode converters interrupts the coaxial transmission line.
An apparatus according to Claim 2, in which the plurality of mode converters includes an array of mode converters placed at regular intervals along the coaxial transmission line.
An apparatus according to one of the preceding claims, in which at least one of the plurality of mode converters is of the inductive type, in which the disturbance of the differential mode of propagation of the signal along the coaxial transmission line is caused by at least one inductive element.
An apparatus according to one of the preceding claims, in which at least one of the plurality of mode converters is of the capacitive type, in which the disturbance of the differential mode of propagation of the signal along the coaxial transmission line is caused by at least one capacitive element.
An apparatus according to one of the preceding claims, in which at least one of the plurality of mode converters is of the capacitive and inductive type, in which the disturbance of the differential mode of propagation of the signal along the coaxial transmission line is caused by at least one capacitive element and at least one inductive element.
An apparatus according to one of the preceding claims, in which the
electromagnetic signal generated by the RF generator has a frequency of between 0.1 and 10 MHz.
An apparatus according to Claim 7, in which the RF signal has a frequency of between 0.5 and 5 MHz.
A system according to one of the preceding claims, in which the mode converters are positioned along the array and dimensioned, from the electrical point of view, such that a distributed/controlled irradiation is obtained along the array itself. 10. A method for extracting hydrocarbons, including the step of heating the
hydrocarbons inside the reservoir and the drain by means of an apparatus according to one of the preceding claims.
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US20170226835A1 (en) 2017-08-10
CA2957496C (en) 2023-07-04
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CN106605037A (en) 2017-04-26
WO2016024197A3 (en) 2016-05-12
RU2017104123A (en) 2018-09-13
RU2693972C2 (en) 2019-07-08
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CA2957496A1 (en) 2016-02-18
US10012060B2 (en) 2018-07-03

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