KR102395017B1 - EMU impulse antenna for low frequency radio waves using large dielectric and ferrite materials - Google Patents

Abstract

An electromagnetic energy source that emits a pulse of electromagnetic energy includes a sonde assembly having a first section axially aligned with the second section and spaced apart from the second section. The energy storage capacitor includes electrodes mounted to each of the first and second sections of the sonde assembly and operable to generate an electric field. A capacitive charge storage medium is mounted to each of the first and second sections of the sonde assembly and surrounds each electrode, in which case the capacitive charge storage medium is a large dielectric and large permeability ferrite. A fast closing switch is positioned between the first and second sections of the sonde assembly.

Description

EMU impulse antenna for low frequency radio waves using large dielectric and ferrite materials

The present disclosure relates to imaging sub-surface structures, particularly hydrocarbon reservoirs and fluids within the hydrocarbon reservoirs, and more particularly to electromagnetic energy sources for electromagnetic surveying of sub-surface structures.

Some electromagnetic (EM) survey systems used in geophysics provide electromagnetic energy traveling through subterranean hydrocarbon reservoirs for electromagnetic imaging of subterranean hydrocarbon reservoirs. Multiple sources and receivers may be located in bores extending into the subterranean hydrocarbon reservoir or at the surface above the subterranean hydrocarbon reservoir. In this way, the direction, velocity and saturation of the injected fluid (such as during a water flood) can be monitored. The system can also be used to locate diverted oil and detect high conductivity zones (such as fracture corridors and super-k zones) to provide early warning of water break-througs. . Such action can help to optimize reservoir management and prevent oil bypass to improve volumetric sweep efficiency and production rate.

Many current low-speed antenna models target high-frequency (HF) or very high-frequency (VHF) electromagnetic waves in the range of 10 megahertz (MHz) to 300 MHz. In geophysics, some current EM systems include antennas that are too large to be able to generate reasonable low-frequency signals, such as applications with frequencies ranging from 10 kHz to 1 MHz from small antennas. The apparent 'aperture' of the antenna (the ratio of wavelength to antenna size) can be problematic. Some current EM systems cannot easily match the impedance of the system with the lipid matrix to increase the transmission efficiency. Some current EM systems use high-current cables to power the EM transmitter. However, such a system has been shown to have difficulties in transmitting sharp high-current pulses from the power supply to a low-loss cable and then matching the pulses to the antenna. Additionally, high-current cables also cannot transmit signals to make the resulting measurement unambiguous.

Embodiments of the present disclosure combine low-velocity antennas with energy storage and pulse-shaping elements to achieve high power, ideally suited for downhole electromagnetic interrogation techniques, such as electromagnetic imaging of subterranean hydrocarbon reservoirs. , to realize a small aperture transmission antenna. The systems and methods described in this disclosure provide a transmitter that is compact, has a high instantaneous power output, and generates a clear signal. As used herein, “high power” is considered to be power in the range of several kilowatts to several megawatts.

Embodiments of the present disclosure provide a dipole antenna that is shorter than some currently available antennas because the cladding material of the electromagnetic impulse antenna contains a large dielectric and a hybrid material called large permeability ferrite, thereby reducing the physical antenna length. allow, and as a result the antenna is manageable for downhaul use in the low frequency range, such as applications with frequencies in the 10 kHz - 1 MHz range. As used herein, “EMU” antenna is an abbreviation for antenna with electrical permittivity (E) and magnetic permeability (MU).

Additionally, the antenna elements of embodiments of the present disclosure are used as capacitive energy storage elements in which each half of the dipole is initially maintained at a high voltage relative to each other. The voltage may depend on the capacitance and impedance of the circuit, as well as the dimensions of the antenna, and may vary with the operating frequency of the antenna. The voltages of the dipole halves are equal and opposite voltages, so the outermost end of each half has the largest voltage magnitude. As used herein, the “high voltage” of each half of the dipole may be in the range of 1000 volts (V) or more relative to the other.

A fast closing switch, such as a triggered spark gap, is provided between a pair of such antennas to initiate pulse transmission. A pair of antennas can be biased by a large voltage so that the structure is discharged in a single large current pulse and emits a very high power transient radio frequency signal. The magnitude of the current will depend on the resistance and power and voltage of the antenna, which in turn depends on the frequency, but, as used herein, "mass current" is considered to be a current in the range of 100-1000 amps (A). can be Thus, the systems and methods of the present disclosure combine energy storage, pulse forming, and radiating elements into a single structure, eliminating the need for impedance matching between separate distribution components for their respective functions.

The systems and methods of the present disclosure eliminate the problem of load matching between a power supply, a cable or transmission line, and an antenna. Using switches inside the energy storage element and the transmit antenna element, cables between the two are eliminated, minimizing reflections and losses in the system.

In an embodiment of the present disclosure, an electromagnetic energy source emitting a pulse of electromagnetic energy includes a sonde assembly including a first section axially aligned with and spaced apart from the second section. The energy storage capacitor includes electrodes mounted to each of the first and second sections of the sonde assembly and operable to generate an electric field. A capacitive charge storage medium is mounted on each of the first and second sections of the sonde assembly and surrounds each electrode, in which case the capacitive charge storage medium is a large dielectric and large permeability ferrite. A fast closing switch is positioned between the first and second sections of the sonde assembly.

In an alternative embodiment, the electromagnetic energy source may further include a high voltage power supply coupled between the first section and the second section of the sonde assembly. A fast closing switch and a high voltage power supply may be connected between the electrodes. A current limiting resistor may be positioned between the high voltage power supply and the electrode.

In another alternative embodiment, the electromagnetic energy source may further comprise a plurality of electromagnetic energy sources that emit pulses of electromagnetic energy traveling through the subterranean hydrocarbon reservoir. The electromagnetic energy source can move from a well borehole to a continuous location to emit pulses of electromagnetic energy at a continuous location traveling through an underground hydrocarbon reservoir. The sonde assembly may have a conductor member serving as a first conductor and the electrode serving as a second conductor. A capacitive charge storage medium may be positioned between the conductor member and the electrode. The conductor member is electrically insulated from the electrode by a capacitive charge storage medium.

In an alternative embodiment of the present disclosure, a source for emitting pulses of electromagnetic energy traveling through a subterranean hydrocarbon reservoir for electromagnetic imaging of the subterranean hydrocarbon reservoir is a wireline for travel in a well borehole towards a depth of interest. ) with a sonde assembly attached to it and a fast closing switch.

In yet another alternative embodiment of the present disclosure, a system using pulses of electromagnetic energy for electromagnetic imaging of an underground hydrocarbon reservoir includes at least one electromagnetic energy source, each electromagnetic energy source oriented into a well directed to a depth of interest. and a sonde assembly attached to a wireline for movement in the borehole, the sonde assembly including a first section axially aligned with the second section and spaced apart from the second section. Energy storage capacitors are mounted to each of the first and second sections of the sonde assembly and are operable to generate an electric field and capacitive charge storage mounted to each of the first and second sections of the sonde assembly and surrounding each electrode. A medium comprising a medium, in which case the capacitive charge storage medium is a giant dielectric and a large permeability ferrite. A fast closing switch is positioned between the first and second sections of the sonde assembly. The plurality of electromagnetic sensors form a measurement of the resulting signal from the electromagnetic energy source.

In an alternative embodiment, the plurality of electromagnetic sensors may be mounted in a well tool that descends from a sensor bore in an underground hydrocarbon reservoir. The plurality of electromagnetic sensors may be located in an array on the surface above the subterranean hydrocarbon reservoir. The system control unit may be used to store information related to the result signal received by the plurality of electromagnetic sensors and to perform a computerized analysis of the result signal.

In yet another alternative embodiment of the present disclosure, a method of emitting pulses of electromagnetic energy to an electromagnetic energy source includes a sonde assembly comprising a first section axially aligned with a second section and spaced apart from the second section; providing an electromagnetic energy source. The energy storage capacitor comprises an electrode mounted to each of the first and second sections of the sonde assembly and a capacitive charge storage medium mounted to each of the first and second sections of the sonde assembly and surrounding the electrode, wherein the capacitance The star charge storage medium is a large dielectric and large permeability ferrite. A fast closing switch is positioned between the electrodes of the first section and the second section. The energy storage capacitor is charged such that the fast closing switch is closed and a pulse of electromagnetic energy is emitted from the electromagnetic energy source.

In an alternative embodiment, the electromagnetic energy source may further include a high voltage power supply coupled to the electrodes of the first section and the electrodes of the second section of the sonde assembly. The electromagnetic energy source may further include a high voltage power supply and a current limiting resistor positioned between both the electrode of the first section and the electrode of the second section. The method may further include lowering the electromagnetic energy source on the wireline at the well borehole in the subterranean hydrocarbon reservoir to a depth of interest. The electromagnetic energy source may be moved to a continuous location in the well borehole to emit pulses of electromagnetic energy at a continuous location traveling through the subterranean hydrocarbon reservoir.

In another alternative embodiment, the plurality of electromagnetic sensors may descend through the sensor bore in an underground hydrocarbon reservoir. The plurality of electromagnetic sensors may be located in an array on the surface above the subterranean hydrocarbon reservoir. Pulses of electromagnetic energy emitted from the electromagnetic energy source may be directed to travel through an underground hydrocarbon reservoir, and measurements of time-of-arrival data of the pulses of electromagnetic energy at the plurality of electromagnetic sensors may be formed, from the plurality of electromagnetic sensors. Measurements of the time-of-arrival data of can be analyzed to form a representation of the subsurface features of the subterranean hydrocarbon reservoir, and an image of the representation of the subterranean feature of the subterranean hydrocarbon reservoir can be formed.

In order that the recited features, aspects and advantages of the present disclosure, as well as others that will become apparent, may be achieved and understood in detail, a more specific description of embodiments of the present disclosure, briefly summarized above, are shown in the drawings, which form a part hereof: This can be done with reference to the embodiment. However, the appended drawings illustrate only certain embodiments of the present disclosure, and therefore should not be construed as limiting the scope of the present disclosure to the extent that the present disclosure admits other equally effective embodiments.
1 is a schematic cross-sectional view of a transmitter-receiver array for borehole-to-borehole electromagnetic surveying, in accordance with an embodiment of the present disclosure;
2 is a schematic cross-sectional view of an electromagnetic energy source and a storage capacitor, in accordance with an embodiment of the present disclosure;
FIG. 3 is a schematic cross-sectional view of the electromagnetic energy source of FIG. 2 ;
FIG. 4 is a schematic cross-sectional view of the electromagnetic energy source of FIG. 2 ;
5 is a schematic cross-sectional view of an electromagnetic energy source, in accordance with an embodiment of the present disclosure.
6 is a schematic cross-sectional view of the electromagnetic energy source of FIG. 5 ;
7 is a schematic cross-sectional view of an electromagnetic energy source, in accordance with an embodiment of the present disclosure.
FIG. 8 is a schematic cross-sectional view of the electromagnetic energy source of FIG. 7 ;
9 is a circuit diagram of the electromagnetic energy source of FIG. 7 ;
10 is a schematic cross-sectional view of an electromagnetic energy source and a storage capacitor, in accordance with an embodiment of the present disclosure.
11 is a schematic cross-sectional view that may be coaxial with the electromagnetic energy source of FIG. 10 ;
12 is a circuit diagram of the electromagnetic energy source of FIG. 10 ;
13 is a graph showing the relative magnetic permeability according to the frequency of large ferrite FeMn (ZnO).
14 is a graph showing the dielectric constant according to the frequency of large ferrite FeMn (ZnO).

1 , an exemplary arrangement of a transmitter-receiver array for borehole-to-borehole electromagnetic surveying is shown. The transmitter may be an electromagnetic energy source 10 . The electromagnetic energy source 10 may be located within the well bore hole 12 . A well bore hole 12 may extend through an underground hydrocarbon reservoir 14 . The electromagnetic energy source 10 may emit pulses of electromagnetic energy traveling through the subterranean hydrocarbon reservoir 14 for electromagnetic imaging of the subterranean hydrocarbon reservoir 14 .

Although one electromagnetic energy source 10 is shown in the example of FIG. 1 , in alternative embodiments, multiple electromagnetic energy sources 10 may be located within the well borehole 12 . Alternatively, the one or more sources of electromagnetic energy 10 may be located at the earth's surface 15 above the subterranean hydrocarbon reservoir. In the example of FIG. 1 , a series of electromagnetic sensors 16 are located in the sensor bore 18 . The sensor bore 18 may be a borehole that extends through the subterranean hydrocarbon reservoir 14 and is spaced apart from the well borehole 12 . In an alternative embodiment, the electromagnetic sensors 16 may be in an array on the ground surface 15 above the subterranean hydrocarbon reservoir 14 (not shown). When the electromagnetic energy source 10 is located in the well borehole 12 and the electromagnetic sensor 16 is located above the ground surface 15, the arrangement is known as a bore-to-surface array. Typically one or both of the electromagnetic energy source 10 and the electromagnetic sensor 16 are located within the borehole so that the EM signal passes through the subterranean hydrocarbon reservoir 14 as it travels from the electromagnetic energy source 10 to the electromagnetic sensor 16 . do. The electromagnetic sensor 16 may form a measure of the arrival time of a pulse emitted from the electromagnetic energy source 10 to the image subsurface hydrocarbon reservoir 14 .

As can be seen in FIG. 1 , a number of EM energy measurements were performed at a transmitter location 20 and a receiver location 22 , including an underground hydrocarbon reservoir 14 , to sample various portions of subsurface topographic features from different directions. can be performed with different combinations of Both the electromagnetic energy source 10 and the electromagnetic sensor 16 may be part of or located within a downhole tool and may be movable between successive positions, such as between a transmitter position 20 and a receiver position 22 . .

An electromagnetic energy source 10 may be attached to a source wireline 24 to travel from the well bore hole 12 to a depth of interest. In the example of FIG. 1 , the source wireline 24 extends from the vehicle 26 at the surface. A system control unit 28 may be associated with the vehicle 26 and may be used to control the pulses emitted by the electromagnetic energy source 10 . The second vehicle 30 is attached to the electromagnetic sensor 16 and may have a receiver wireline 32 for moving the electromagnetic sensor 16 within the sensor bore 18 . The electromagnetic energy source 10 may include a quarter wave dipole antenna.

2-3 , the electromagnetic energy source 10 includes a sonde assembly 34 . Sonde assembly 34 has two main sections: a first section 34a is axially aligned with a second section 34b and spaced apart from the second section. The electromagnetic energy source 10 also includes an energy storage capacitor 40 having a capacitive charge storage medium 44 .

The electrode 42 is mounted to each of the first section 34a and the second section 34b of the sonde assembly 34 . The first electrode 42a is located in the first section 34a and the second electrode 42b is located in the second section 34b. The electrode 42 may be an elongate member and may have a tubular shape. Electrode 42 may be formed of copper, and in alternative embodiments, may be formed of silver, aluminum, gold, or other material having sufficient conductivity, corrosion resistance, and hardness suitable for use as an electrode.

A capacitive charge storage medium 44 is mounted to each of the first section 34a and the second section 34b of the sonde assembly 34 . Capacitive charge storage medium 44 may include a large dielectric and large transmittance ferrite, the advantages of which are discussed in this disclosure. 2-3 , an electric field may radiate from each electrode 42 through a nearby capacitive charge storage medium 44 forming an energy storage capacitor 40 .

4, the electromagnetic energy source 10 may further include a fast closing switch 46 positioned between the first and second electrodes 42a, 42b of the first and second sections 34a, 34b, respectively. can The fast closing switch 46 may be, for example, a spark gap. When the fast closing switch is closed, such as when the spark gap is broken, the electromagnetic energy source 10 will generate an electromagnetic pulse. For example, an electrical spark may pass between the first and second electrodes 42a, 42b when the potential difference between the first and second electrodes 42a, 42b exceeds the breakdown voltage of the gas in the gap. In an alternative embodiment, the fast closing switch 46 may include avalanche transistors, thyratrons, igniters, silicon controlled rectifiers and in particular a triggered spark gap. The fast closing switch 46 may be selected to have performance metrics regarding peak current, peak voltage, number of useful shots, jitter, complexity and geometry suitable for the environment, conditions and performance criteria in which the electromagnetic energy source 10 will be used. can

The electromagnetic energy source 10 may also have a high voltage power supply 48 coupled between the first and second electrodes 42a, 42b. The high voltage power supply 48 may have a voltage of 1,500 volts or more, for example. Power may be provided to the high voltage power supply 48 from outside the electromagnetic energy source 10 having a pair of high resistivity leads. A high impedance direct current (DC) connection will reduce the amount of induced current that will be generated in connection by a high current pulse through electrode 42 when sonde assembly 34 is discharged.

In the exemplary embodiment of Figures 2-4, the capacitive charge storage medium 44 acts as a ground. In such an embodiment, the capacitive charge storage medium 44 proximate the electrode 42 will form the energy storage capacitor 40 , and the capacitive charge storage medium 44 proximate the outer diameter of the capacitive charge storage medium 44 . ) will act as a ground.

A current limiting resistor 50 may be positioned between the high voltage power supply 48 and both the first electrode 42a of the first section 34a and the second electrode 42b of the second section 34b. . Current limiting resistor 50 may block high current pulses from returning to the supply wire towards high voltage power supply 48 . This will isolate the antenna system from the high voltage power supply 48 while the electromagnetic pulses are being emitted.

In each exemplary embodiment, a high voltage power supply 48 is positioned between the same components as the fast closing switch 46, and any component not directly connected to the high voltage power supply 48 will act as ground. Note that you can

2-3 , each section 34a , 34b of sonde assembly 34 may include an elongate tubular member having a central bore centered about axis Ax. The electrode 42 is centered along the axis Ax of each of the first section 34a and the second section 34b of the sonde assembly 34 . The electrode 42 is covered within the capacitive charge storage medium 44 such that the capacitive charge storage medium 44 surrounds the electrode 42 . Energy storage capacitor 40 is formed by an electric field radiating from electrode 42 and through nearby capacitive charge storage medium 44 . The amount of energy stored will vary with the square of the electric field. If the electrode 42 has a small diameter, almost all of the field potential drop will occur inside the capacitive charge storage medium 44 .

5-6, the conductor member 33 of the sonde assembly 34 serves as the first conductor and the capacitive charge storage medium 44 includes the conductor member 33 and the electrode 42. located between The capacitive charge storage medium 44 electrically insulates the conductor member 33 from the electrode 42 . In such an embodiment, both the conductor member 33 and the electrode 42 are shown as elongate members, which may be solid rods or wires.

5-6, a fast closing switch 46 is connected between the first and second conductor members 33a, 33b and the high voltage power supply 48 is also connected between the first and second conductor members 33a and 33b. connected between the second conductor members 33a and 33b. In this exemplary embodiment, the first electrode 42a and the second electrode 42b act as a ground. The current limiting resistor 50 is to be positioned between the high voltage power supply 48 and both the first conductor member 33a of the first section 34a and the second conductor member 33b of the second section 34b. can

5-6 , the conductor member 33 may be a wire extending through each section 34a , 34b of the sonde assembly 34 . The conductor member 33 is encased in a capacitive charge storage medium 44 . Electrode 42 may also be a wire extending through each section 34a , 34b of sonde assembly 34 . Electrode 42 is also covered in capacitive charge storage medium 44 . The energy storage capacitor 40 is formed by a pair of wires, which are a conductor member 33 and an electrode 42 capable of having a large potential voltage between the wires. The capacitive charge storage medium 44 between the electrode 42 and the conductor member 33 increases the mutual capacitance of the electrode 42 and the conductor member 33 . Both the conductor member 33 and the electrode 42 serve as conductor elements of the energy storage capacitor 40 and as part of a transmission element of the electromagnetic energy source 10 for emitting electromagnetic pulses.

7-9, the conductor member 33 of the sonde assembly 34 serves as the first conductor, and the capacitive charge storage medium 44 includes the conductor member 33 and the electrode 42 ) is located between The capacitive charge storage medium 44 electrically insulates the conductor member 33 from the electrode 42 . In such an embodiment, the conductive member 33 is an outer body surrounding the capacitive charge storage medium 44 . Electrode 42 is shown as an elongate member, which may be a solid rod or wire. Each section 34a, 34b of sonde assembly 34 may have an end cap 39 formed of an insulating material. The capped distal ends of the first section 34a and the second section 34b may face towards each other. The electrode 42 may protrude through the distal end cap 39 of the sonde assembly 34 .

7-9 , a fast closing switch 46 is connected between the first and second conductor members 33a , 33b , and the high voltage power supply 48 is also connected to the first of the conductor members 33 . and the second conductor member 33a, 33b. In this exemplary embodiment, the first electrode 42a and the second electrode 42b act as a ground. A current limiting resistor 50 is to be positioned between the high voltage power supply 48 and both the first conductor member 33a of the first section 34a and the second conductor member 33b of the second section 34b. can

In the example of FIGS. 7-8 , the conductor member 33 may be the outer metal body of the sonde assembly 34 . Each section 34a , 34b of the sonde assembly 34 may have an elongate tubular member, such as a metal body, closed at one distal end and having a distal end cap 39 at the opposite distal end. Sonde assembly 34 may have a central bore centered about axis Ax. The electrode 42 is centered along the axis Ax of each of the first section 34a and the second section 34b of the sonde assembly 34 . The electrode 42 may be an elongate member and may be a solid rod. Both the conductor member 33 and the electrode 42 serve as conductor elements of the energy storage capacitor 40 and as part of a transmission element of the electromagnetic energy source 10 for emitting electromagnetic pulses.

10-12 , sonde assembly 34 includes a coaxial cable 52 wound around a core member 54 . The core member 54 may be, for example, polyvinyl chloride (PVC) pipe, or any other suitable core member available that provides sufficient support to the coaxial cable 52 without interfering with the performance of the sonde assembly 34 . If the coaxial cable 52 is sturdy and strong enough to stand on its own, no core member is required. The coaxial cable 52 includes an electrode 42 , which may be a wire extending within the coaxial cable 52 . A capacitive charge storage medium 44 of the coaxial cable 52 surrounds the electrode 42 .

10-12, a fast closing switch 46 is connected between the first and second electrodes 42a, 42b, and the high voltage power supply 48 is also connected to the first and second electrodes 42a, 42b; 42b) is connected between In this example, the capacitive charge storage medium 44 of the first section 34a and the second section 34b is connected in series. A current limiting resistor 50 may be positioned between the high voltage power supply 48 and both the first electrode 42a of the first section 34a and the second electrode 42b of the second section 34b. . A braid 56 of the coaxial cable 52 connects the first electrode 42a and the second electrode 42b together by a secondary resistor 58 . The secondary resistor 58 reflects the current so that when the capacitor discharges, the maximum voltage is directed to the spark gap 46 .

In the exemplary embodiment of FIGS. 10-12 , each of the first and second electrodes 42a , 42b may be a wire extending through a respective section 34a , 34b of the sonde assembly 34 . Each electrode 42 is covered within a capacitive charge storage medium 44 such that the capacitive charge storage medium 44 surrounds the electrode 42 . Energy storage capacitor 40 is formed by an electric field radiating from electrode 42 and through nearby capacitive charge storage medium 44 . By using a coiled coaxial cable, it is possible to set the capacitance of the antenna by winding the required length of coaxial cable around the core member 54 . In this way, the capacitance of the antenna can be adjusted without changing the overall length of the antenna.

In each exemplary embodiment, capacitive charge storage medium 44 may include a large dielectric and large permeability ferrite. Depending on the desired frequency, the use of a large dielectric and large magnetic permeability ferrite will allow the antenna length to be reduced to a length ranging from 0.10 meters (m) to 2 m for frequencies in the range from 10 kilohertz (kHz) to 1 MHz. can Large dielectric and large permeability ferrites are a special class of materials having a dielectric constant of 104-105 and ferrites having a relative magnetic permeability greater than 600 in the range of 10 kHz - 1 MHz. Cladding the EMU impulse antenna with this material allows the maximum height of the antenna's physical length to be reduced up to orders of magnitude compared to conventional high dielectric and magnetic permeability materials, eliminating the need for thickening of the cladding and , this is a common problem when constructing low-speed antennas.

A slow wave is referred to as the group velocity of an EM wave traveling along a structure. The group velocity can be made slower by changing the electromagnetic properties of the guiding structure, or specifically by changing the cladding around the guidewire according to the following formula:

where V = wave velocity, ε _r is the dielectric constant, and μ _r is the relative magnetic permeability.

The slower group velocity of EM waves can proportionally reduce the physical length of the antenna, which is particularly important for low frequency applications, such as applications with frequencies in the 10 kHz - 1 MHz range with very large wavelengths, e.g. not cladded. This is a case in which the length of the antenna, which corresponds to 1/4 of the resonant wavelength of the non-resonant antenna, is several hundred meters.

The height reduction factor (N) of a slow wave antenna is the ratio of the electrical length of the clad antenna to the electrical length of the unclad antenna. Therefore, the maximum height reduction factor is directly related to:

Or simply put, the slower the speed of the EM wave, the smaller the physical length of the dipole antenna can be.

For traditional high dielectric and ferrite materials, the cladding thickness increases with decreasing frequency. The equations governing cladding thickness at about 100 MHz show that the thickness volume is unrealistically large and non-uniform. For applications with wavelengths spanning hundreds of meters, such as in the 750 kHz - 1 MHz range, the use of these materials in pulsed dipole antennas may result in unrealistically thick cladding for downhole operations, resulting in unrealistically long antennas; or both.

Large dielectric materials include calcium copper titanate (CCTO), a family of A-Cu3Ti4O12 compounds (where A is trivalent rare earth or Bi), doped nickel oxide, doped cupric oxides, barium titanate, bismuth strontium titanate, and other materials including iron in combination with manganese, zinc and nickel-based compounds. Note that a doped metal is a metal that has an impurity intentionally to change the electrical properties of the metal.

As an example, FIG. 13 shows the relative permeability by frequency of large ferrite FeMn (ZnO). Referring to FIG. 13 , the spectrometer used in the laboratory test detected high frequencies in the range of 1 MHz - 1 (gigahertz) GHz. When the frequency is less than 10 MHz, the relative magnetic permeability increases exponentially. Extrapolation of such tests results in relative magnetic permeability near or above 1000 at 100 kHz. Referring to FIG. 14 , the dielectric constant of FeMn (ZnO), which is the same material, is plotted as a frequency. The antenna height reduction factor for this material at 100 Hz is 1000.

As used herein, the antenna height reduction factor ( n ) is defined as:

In this case, ε _r is the relative electrical permittivity (also known as the dielectric constant), and μ _r is the relative magnetic permeability of the antenna cladding material. Then, this height reduction coefficient value ( n ) is multiplied by the length of the virtual antenna using a material where ε _r and μ _r are both equal to 1 to determine how much the height of the antenna of the present disclosure increases by increasing the electrical and magnetic properties of the cladding. You can determine if it has been greatly reduced.

Referring to FIG. 1 , in an example of operation, an electromagnetic energy source 10 may be mounted to or part of a well tool to form an electromagnetic image of an underground hydrocarbon reservoir 14 , and a well bore hole 12 . It can be lowered to the depth of interest on the wireline at

A downhole tool associated with the electromagnetic energy source 10 may have an upper section having a mechanical connector attached to a wire line, a power connection, and a synchronization signal connection. Such upper sections and connections can be oriented like known current downhole wireline tools. A lower section of the downhole tool may house a sonde assembly 34 . The electromagnetic energy source 10 may be encased in a strong insulating polymer material to also allow transmission of electromagnetic signals while providing structural integrity.

As shown in the example of FIG. 1 , a single electromagnetic energy source 10 may be used. Alternatively, the plurality of electromagnetic energy sources 10 may descend from the well bore hole 12 . Pulses of electromagnetic energy may be emitted from a single electromagnetic energy source 10 or, if applicable, each of a plurality of electromagnetic energy sources 10 to travel through an underground hydrocarbon reservoir 14, and the resulting signal is transmitted to an electromagnetic sensor ( 16) can be received. Electromagnetic pulses with known properties are generated from a high power pulsed electromagnetic energy source 10 from a location at or near an underground hydrocarbon reservoir 14 . To generate the electromagnetic pulse, high voltage power supply 48 charges energy storage capacitor 40 through current limiting resistor 50 until fast closing switch 46 closes. In the closed state of the fast closing switch, the electromagnetic energy source 10 will emit a pulse of electromagnetic energy. After the electromagnetic pulse is emitted, the high voltage power supply 48 can recharge the energy storage capacitor 40 .

By combining the energy storage, pulse forming and radiating elements into a single structure, the impedance matching problem between the individual distribution components of the electromagnetic survey system required for each of these functions is eliminated. The system and method of the present disclosure thus eliminates the load matching problem between the power supply, cable or transmission line and the antenna. Both the energy storage element of the energy storage capacitor 40 and the fast closing switch 46 are inside the transmit antenna elements of the pair of disclosed self-driven impulse antennas, eliminating the need for cables between the power source and the transmitting elements; And reflections and losses in the system are minimized.

The plurality of electromagnetic sensors 16 may be mounted to or part of the well tool and may descend in a sensor bore 18 extending through the subterranean hydrocarbon reservoir 14 . Alternatively, the plurality of electromagnetic sensors 16 may be disposed in an array above the ground surface 15 on the subterranean hydrocarbon reservoir 14 . The emitted pulsed EM signal is transmitted through the subterranean hydrocarbon reservoir 14 and recorded to one or more electromagnetic sensors 16 after traveling through the well bore hole 12 and the subterranean formation surrounding the sensor bore 18 . The EM signal recorded by the electromagnetic sensor 16 is a source of electromagnetic energy ( 10) is different from the pulse signal emitted by

The electromagnetic energy source 10 moves between successive positions, such as a transmitter position 20 in a well bore hole 12 to emit a pulse of electromagnetic energy at such a position traveling through the subterranean hydrocarbon reservoir 14 . can Similarly, electromagnetic sensor 16 can move between successive positions, such as receiver position 22, to receive a resulting signal at such successive positions. In this way, a more complete electromagnetic image can be formed for the subterranean hydrocarbon reservoir 14 .

A recording and processing instrument associated with the system control unit 28 at the surface may receive and store information related to the resulting signal received by the electromagnetic sensor 16 . The system control unit 28 also performs additional functions, such as computerized analysis of the resultant signal, displays predetermined results derived from the resultant signal, and is placed on the computer for further processing and computerized analysis. The resulting signal and computerized analysis can be stored. The system control unit 28 may be used, for example, to form a measurement of the time of arrival of pulses emitted from the plurality of electromagnetic sensors and to analyze the measurement of the time of arrival data from the plurality of electromagnetic sensors. From this information, images of representations of subterranean features of the subterranean hydrocarbon reservoir and representations of subterranean features of the subterranean hydrocarbon reservoir can be formed.

As such, embodiments of the present disclosure generate information regarding the composition and spatial distribution of fluids in hydrocarbon reservoirs. For example, operations may be repeated periodically to determine the direction, velocity, and saturation of the injected fluid, such as water overflow, or to visualize the deformed reservoir volume as a function of time. This can help improve volumetric sweep efficiency and production rate by optimizing storage management and preventing oil bypass.

By using a large dielectric/ferrite material, an antenna transmitting at 100 kHz can be reduced from 3000 m for an antenna without a clad to approximately 30 m for an antenna with a conventional high dielectric constant ferrite material, with a large dielectric In the case of an antenna clad with ferrite material, it can be reduced to 0.25 m.

The embodiments of the present disclosure have been described sufficiently to enable those skilled in the art to reproduce and obtain the results mentioned in the present disclosure. Nevertheless, a person skilled in the art, the subject of this disclosure, can make variations not described in this disclosure and apply these variations to the determined structures or to their manufacturing processes, and the resulting structures are described in the present disclosure. included within the scope of the right of disclosure.

It should be noted and understood that improvements and modifications may be made to the embodiments described in detail in the present disclosure without departing from the scope of the present disclosure.

Claims (22)

An electromagnetic energy source for emitting pulses of electromagnetic energy traveling through an underground hydrocarbon reservoir for electromagnetic imaging of the subsurface hydrocarbon reservoir, the electromagnetic energy source comprising:
a sonde assembly comprising a first section axially aligned with the second section and spaced apart from the second section;
An energy storage capacitor, wherein the energy storage capacitor comprises:
an electrode mounted to each of the first and second sections of the sonde assembly and operable to generate an electric field; and
A capacitive charge storage medium mounted on each of the first section and the second section of the sonde assembly and surrounding each electrode - The capacitive charge storage medium comprises: calcium copper titanate (CCTO), an A-Cu3Ti4O12 compound (in this case, A is trivalent rare earth or Bi) family, doped nickel oxide, doped cupric oxides, barium titanate, bismuth strontium titanate, and iron in combination with manganese, zinc and nickel-based compounds. Including; large dielectric and large permeability ferrite selected from other materials; and
a fast closing switch selected from an avalanche transistor, a thyratron, an igniter, a silicon controlled rectifier and a triggered spark gap, the fast closing switch positioned between the first and second sections of the sonde assembly;
and the electromagnetic energy source is attached to a wireline for movement in the well borehole towards a depth of interest. The method according to claim 1,
and a high voltage power supply coupled between the first and second sections of the sonde assembly. 3. The method according to claim 2,
and the fast closing switch and the high voltage power supply are connected between the electrodes. 3. The method according to claim 2,
and a current limiting resistor positioned between the high voltage power supply and the electrode. The method according to claim 1,
wherein the electromagnetic energy source further comprises a plurality of electromagnetic energy sources emitting pulses of electromagnetic energy traveling through the subterranean hydrocarbon reservoir. The method according to claim 1,
wherein the electromagnetic energy source is moveable from a well borehole to the continuous location to emit pulses of electromagnetic energy at a continuous location traveling through an underground hydrocarbon reservoir. The method according to claim 1,
wherein the sonde assembly has a conductor member serving as a first conductor and the electrode serving as a second conductor. 8. The method of claim 7,
and the capacitive charge storage medium is positioned between the conductor member and the electrode. 8. The method of claim 7,
and the conductor member is electrically insulated from the electrode by the capacitive charge storage medium. delete A system for using pulses of electromagnetic energy for electromagnetic imaging of an underground hydrocarbon reservoir, the system comprising:
at least one electromagnetic energy pulse emitting electromagnetic energy source according to claim 1 ; and
a plurality of electromagnetic sensors that form measurements of resultant signals from the electromagnetic energy source. 12. The method of claim 11,
and the plurality of electromagnetic sensors are mounted to a well tool that descends from a sensor bore in the subterranean hydrocarbon reservoir. 12. The method of claim 11,
wherein the plurality of electromagnetic sensors are located in an array on a surface above the subterranean hydrocarbon reservoir. 13. The method of claim 12,
and a system control unit for storing information related to a result signal received by the plurality of electromagnetic sensors and performing a computerized analysis of the result signal. A method of emitting a pulse of electromagnetic energy with an electromagnetic energy source, comprising:
providing the electromagnetic energy source, wherein the electromagnetic energy source comprises:
a sonde assembly including a first section axially aligned with the second section and spaced apart from the second section;
an energy storage capacitor comprising an electrode mounted to each of the first and second sections of the sonde assembly and a capacitive charge storage medium mounted to each of the first and second sections of the sonde assembly and surrounding the electrode; The capacitive charge storage medium is CCTO (calcium copper titanate), a family of A-Cu3Ti4O12 compounds (where A is trivalent rare earth or Bi), doped nickel oxide, doped cupric oxide, barium titanate, bismuth strontium large dielectric and large magnetic permeability ferrites selected from titanates and other materials including iron in combination with manganese, zinc and nickel-based compounds; and
a fast closing switch selected from an avalanche transistor, a thyratron, an igniter, a silicon controlled rectifier, and a triggered spark gap, wherein the fast closing switch is positioned between the electrode of the first section and the electrode of the second section;
lowering an electromagnetic energy source on a wireline in a well borehole in an underground hydrocarbon reservoir to a depth of interest;
charging the energy storage capacitor such that the fast closing switch closes and a pulse of electromagnetic energy is emitted from the electromagnetic energy source;
directing a pulse of electromagnetic energy emitted from the electromagnetic energy source to travel through an underground hydrocarbon reservoir;
forming measurements of time-of-arrival data of pulses of electromagnetic energy at the plurality of electromagnetic sensors;
analyzing measurements of time-of-arrival data from the plurality of electromagnetic sensors to form a representation of subterranean features of the subterranean hydrocarbon reservoir; and
forming an image of a surface of a subterranean feature of the subterranean hydrocarbon reservoir; 16. The method of claim 15,
wherein the electromagnetic energy source further comprises a high voltage power supply coupled to the electrode of the first section and the electrode of the second section of the sonde assembly. 17. The method of claim 16,
wherein the electromagnetic energy source further comprises a current limiting resistor positioned between the high voltage power supply and both the electrode of the first section and the electrode of the second section. delete 16. The method of claim 15,
and moving the electromagnetic energy source from a well borehole to the continuous location to emit a pulse of electromagnetic energy at a continuous location traveling through the subterranean hydrocarbon reservoir. 16. The method of claim 15,
and unloading the plurality of electromagnetic sensors through the sensor bore in the subterranean hydrocarbon reservoir. 16. The method of claim 15,
and positioning the plurality of electromagnetic sensors in an array on a surface above the subterranean hydrocarbon reservoir. delete

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