• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    Neutron generators that employ direct ionization of ionizable fusion gas, well logging tools, and methods that utilize these neutron generators are disclosed. In various embodiments, the neutron generator includes a cylindrical field ionization structure distributed around the inner surface of a tubular housing (102), and a cylindrical ion acceleration grid (126) disposed around the longitudinal axis (101) concentrically with respect to the field ionization structure. The ions generated by the field ionization structure can accumulate within the ion acceleration gate (126), from which they can be axially extracted and accelerated to a fusion target. Additional tools, systems, and methods are disclosed.
    公开号:FR3035263A1
    申请号:FR1651789
    申请日:2016-03-03
    公开日:2016-10-21
    发明作者:Juan Navarro-Sorroche；Weijun Guo
    申请人:Halliburton Energy Services Inc；
    IPC主号:
    专利说明:

    [0001] 1 FIELD IONIZATION NEUTRON GENERATOR Background [0001] Pulsed neutron logging tools are routinely used in oil and gas well logging operations to evaluate the physical characteristics of subsurface formations penetrated by a borehole. These tools typically include a neutron generator that produces high energy neutron flushes, and one or more radiation detectors at selected distances from the neutron generator for measuring secondary radiation (eg, inelastic gamma rays, rays). capture gamma, epithermal neutrons, or thermal neutrons) resulting from interactions of high energy neutrons with materials in and surrounding the borehole. [0002] High energy neutrons can be generated in fusion reactions of hydrogen isotopes, deuterium and / or tritium. To cause fusion reactions, in turn, ionized deuterium and / or tritium gas can be accelerated by an ultra high voltage electric field to a target containing deuterium and / or tritium.
    [0002] Ions can be generated from neutral deuterium and / or tritium gas in various ways; the most classical pulsed neutron generators use high energy electron shock ionization. In a conventional Penning ion source, for example, a high voltage pulse (e.g., having an amplitude of a few kilovolts) is applied between a cathode and an anode to create an arc discharge that causes the emission of electrons 2 3035263 from the cathode and their acceleration to the anode, colliding with and thus ionizing gas molecules along the way. Alternative approaches for creating the required free electrons include thermal emission from heated cathodes in so-called "hot cathode" ion sources, or field emission, i.e. electron tunnel through a potential barrier lowered by a very powerful electric field. [0003] The indirect process of first creating electrons and then creating ions via electron collisions with neutral gas molecules generally results in a somewhat variable delay of a few microseconds. between the application of an electron-generating voltage pulse and the resulting neutron burst, making precise control over the timing of neutron pulses difficult. Other characteristics of the neutron pulses, such as their shape and total neutron output, may likewise be less predictable or controllable than desired for the logging operations provided. Additional disadvantages of various conventional pulsed neutron generators include limited neutron output (which may be due, for example, in Penning ion sources, to the fact that the majority of the ions are diatomic); high ionization voltages, which can subject the neutron generator to electrical stresses which decrease its reliability and / or lifetime; and a volume and complexity derived from additional ion source components (such as, in Penning ion sources, a magnet used to elongate electron trajectories to thereby increase collision efficiency. ). Brief Description of the Drawings [0004] Figs. 1A and 1B are schematic longitudinal sectional views of neutron generators employing field ionization according to various embodiments. [0005] Fig. 2 is a schematic cross-sectional view of the ion source of the neutron generator of Figs. 1A and 1B. Figure 3 is a diagram of an exemplary field ionization structure according to various embodiments. Figure 4 is a graph of the deuterium-tritium fusion cut as a function of core energy of the incident ion. [0008] Fig. 5 is a diagram of a pulsed neutron tool deployed in a borehole, according to various embodiments. Figure 6 is a flowchart of a method of using a pulsed neutron logging tool, in accordance with various embodiments.
    [0003] DETAILED DESCRIPTION [0010] Neutron generators that employ direct ionization of ionizable fusion gas are described herein. Also disclosed are pulsed neutron logging tools including these neutron generators, and methods of operating and using them. A neutron generator according to various embodiments comprises a tubular housing containing ionizable fusion gas (e.g., deuterium and / or tritium) and defining ion source and ion acceleration portions. . In the ion source portion, the neutron generator has a cylindrical field ionization structure distributed around the inner surface of the tubular housing. The field ionization structure may include a nanopoint field ionization array extending inwardly from a cylindrical substrate, and a cylindrical field ionization grid disposed concentrically with respect to the small distance (for example, ten micrometers or less) from it. The neutral melt gas can be ionized in the field ionization structure by applying a negative electrical potential (or voltage) suitable for the field ionization gate (relative to the nanopoint array). In accordance with various embodiments, the neutron generator further comprises a high-transparency cylindrical ion acceleration grid disposed about the longitudinal axis of the neutron generator concentrically with respect to the ionization structure of the neutron generator. field, and maintained at a negative electrical potential with respect to the field ionization gate. The ions generated by the field ionization structure accumulate within the ion acceleration gate, from which they can be axially extracted and accelerated, within the accelerating portion of the ion acceleration gate. ions of the neutron generator, towards a fusion target. The term "cylindrical", as used herein, refers to the general shape of the respective component (not taking into account the small surface elements), and does not require a perfect, but simply "substantially" cylindrical geometry.
    [0004] A structure is judged to be "substantially cylindrical" (here simply "cylindrical") if the radial distances from any point thereon relative to the cylinder axis vary by less than 20%. Variations with respect to the radius of the cylinder may arise for example from the approximation of a perfectly cylindrical shape with a plurality of segments or flat strips. [0011] Beneficially, using direct field ionization (as opposed to shock ionization), the "ion source initiation time", i.e., the delay. Between the application of a voltage pulse to the field ionization structure and the creation of a fusion neutron pulse can be reduced, in various embodiments, to less than a microsecond. The ability to control the neutron pulse characteristics can thus be considerably improved. Further, the ionization voltage (which, in ion source configurations in accordance therewith, corresponds to the voltage applied between the field ionization matrix and the field ionization gate) can be on the order of only a few hundred volts, which corresponds to a reduction in ionization voltage, compared with various conventional neutron generators (such as those using Penning ion sources), of approximately one magnitude. The reduced voltage can contribute to an increase in the reliability and the operational life of the neutron generator. Another advantage of the neutron generators in accordance with the invention is their ability to achieve, in various embodiments, ion populations with greater than 50% monoatomic ions. In comparison to diatomic ions, the monoatomic ions reach about twice the energy per core, which results in an associated melting section approximately five times higher. Thus, a predominantly monoatomic ion population can result in considerably higher neutron yields. Neutron generators according to some embodiments yield 109 melting neutrons per second or more - about an order of magnitude above the neutron efficiencies that can be achieved with many conventional neutron generators (such as using Penning ion sources). Higher neutron yields can contribute to an increase in the lifetime and reliability of the neutron generator, and provide better signal intensities for pulsed neutron measurements. In addition, they can provide sufficient numbers of 2.45 MeV neutrons from a deuterium-deuterium fusion to make feasible measurements based thereon; this is advantageous since 2.45 MeV neutrons are more suitable for the measurement of certain formation properties than the 14.1 MeV neutrons created during deuterium-tritium fusion reactions. [0013] Exemplary embodiments of field ionization neutron generators will now be described in more detail with reference to the accompanying drawings. As will be readily apparent to one skilled in the art having the benefit of this disclosure, various structural and operational changes to the specific embodiments discussed can be made without departing from the scope of this disclosure. [0014] FIG. 1A illustrates a neutron generator 100, in accordance with one embodiment, in a sectional view taken along a longitudinal axis 101 of the device. The neutron generator 100 has a closed (usually hermetically sealed) tubular housing 102 defining a vacuum chamber 5 for containing an ionizable fusion gas such as, for example, deuterium gas, gaseous tritium, or a mixture thereof. this. (The interior of the housing 102 is here called a "vacuum chamber" because the gas pressures therein are, in an operative device, generally substantially less than atmospheric pressure). The housing 102 may be made of a suitable metal or metal alloy, such as, for example, F15 (a nickel-cobalt-iron alloy) or an iron-nickel alloy. It can be (and for the purposes of the discussion that follows, it is supposed to be) grounded, that is, held at an electrical potential of zero volts. As illustrated, the housing 102 may comprise, along the longitudinal axis 101, a cylindrical section defining an ion source portion 104 of the neutron generator 100, 20 and a frustoconical section defining an ion acceleration portion 106 of the neutron generator 100. The two portions 104, 106 may be physically separated by an ion source cover 108 which defines an ion extraction port 110 centered at the longitudinal axis 101. In embodiments, the outer diameter of the housing 102 is less than about 1.5 "(for example, about 1.3" (3.302 cm) in accordance with certain industry standards). The small diameter facilitates the use of the neutron generator 100, in typical borehole environments, where the outer diameter of a tool, including its pressurized housing, can be limited to about 2 "(5.08 cm) or less (for example, about 1.7 "(4,318 cm) in some typical tool configurations). The length (i.e. the longitudinal dimension) of the housing 102 may be several inches (cm). The ion source portion 104 comprises a gas reservoir element 11 comprising a metal filament (or metal alloy) coated with a material (for example another metal) on which molecules are adsorbed. deuterium and / or tritium. For example, in some embodiments, the gas reservoir member 112 is a titanium coated tungsten filament. The gas reservoir member 112 may be heated by causing an electric current to flow through the filament. The current may be provided, for example, via a gas reservoir element control electrode 114 maintained at a positive or negative voltage with respect to the housing 102 (grounded), which may be in electrical contact with the gas reservoir member 112 to provide the second electrode. As the temperature of the gas reservoir member 112 increases, adsorbed deuterium / tritium gas is released into the vacuum chamber. Conversely, as the gas reservoir member 112 cools, the gaseous deuterium / tritium is (re) adsorbed by the filament coating. The equilibrium gas pressure established within the vacuum chamber is dependent on the temperature of the gas reservoir element 112, and can thus be regulated via the electric current supplied to the gas reservoir element. 112. The operating gas pressure used during the operation of the neutron generator 100 may be, for example, of the order of 30 mTorr (133 mPa) (i.e., considerably less than atmospheric pressure). ). The ion source portion 104 of the neutron generator 100 further includes a cylindrical field ionization structure arranged along an interior surface of the housing 102; In Figure 2, this structure is shown in cross-sectional view (i.e., a section taken perpendicular to the longitudinal axis 101 through the ion source portion 104). The field ionization structure comprises a field ionization matrix 120 - i.e., an array of inwardly directed nanopoints 10 disposed on a cylindrical electrically conductive substrate (shown in more detail in the figure). electrically inside and 3) - and a cylindrical conductive field ionization grid 122 disposed concentrically with the field ionization matrix 120. In some embodiments, the radial distance between the matrix 120 and the gate 122 is less than one micrometer, in some embodiments it is even less than five hundred nanometers. When applying a negative electric potential to the field ionization gate 122 (provided, for example via an ion source electrode 124, shown in FIG. 1A), with respect to the matrix of field ionization 120 (which can be grounded, for example via an electrical connection to housing 102), the gas molecules near the nanopoints are ionized. The rate at which the gas is ionized, and thus the ion currents generated by the ion source portion 104, is generally proportional to the area of the field ionization matrix 120. Beneficially, the The radial configuration of the cylindrical field ionization structures in accordance with the present invention increases the area of the field ionization matrix as compared to that of a linear arrangement (as conventionally used in the laboratory or in the laboratory). other contexts where the spatial limitations imposed by the well logging industry do not apply) including planar circular field ionization matrices and grids sized to fit into a tool suitable for applications well logging. For example, an ion source portion 104 with a diameter d and a length 1 can accommodate a cylindrical field ionization matrix having an area of at most Acyl = lud-1 or a field ionization matrix. circular plane (oriented perpendicular to the longitudinal axis) of at most Apian = It / 4.d. With examples of dimensions of 15 d = 1.25 "(3.175 cm) (which is suitable for fitting into a housing having an outside diameter of 1.5" (3.81 cm)) and 1 = 2.5 "(6.35 cm), the area of the cylindrical field ionization matrix exceeds that of the Acyi / Apian plane matrix = 4-1 / d 8. If a larger field ionisation matrix is Although it is desirable to produce higher ion currents, the length of the cylindrical matrix can be further increased.The size of a circular matrix, on the other hand, is usually much smaller because of the spatial limitations of the tool. As a result, the cylindrical geometry of the field ionization structures described herein can contribute to obtaining sufficiently high neutron yields for well logging operations, thus making it possible to generate direct field ionization neutron generation. [0018] Still referring to FIG. The ionized az can be accelerated to the radial center of the vacuum chamber by a cylindrical ion acceleration gate 126 disposed about the longitudinal axis 101 and maintained at a negative electrical potential with respect to the ionization grid. 122. In some embodiments, as shown in FIG. 1A, the acceleration gate 126 is connected to the same ion source electrode 124 which also provides a voltage to the field ionization gate 126. , but a bias resistor 127 connected in series to the field ionization gate creates a voltage difference (e.g., about 100 V) between the field ionization gate 122 and the acceleration gate of FIG. 126. In alternative embodiments, illustrated in FIG. 1B, a separate electrode 129 is used to connect the ion acceleration gate 126 independently of the field ionization gate 122. The throttle gate 126 is extremely transparent (occluding with its mesh, for example, only 10% or less of the cylindrical surface it defines), allowing the ions to oscillate through the vacuum chamber and finally accumulating in the defined cylindrical cavity, by the acceleration gate 126, forming an electrically charged plasma 128 therein. The ions can be extracted axially from this plasma region through the extraction port 110. The diameter of the acceleration gate 126 can be about a quarter of an inch; in some embodiments, it is consistent with the diameter of the aperture 110. [0019] The ion acceleration portion 106 of the neutron generator 100 includes, at the end opposite the source cap of 108 (and thus, distal to the ion source portion 3035263 of ions), the melting target 130, for example in the form of a layer of titanium (or other suitable metal) impregnated with deuterium and / or tritium (the "target atoms"), which is arranged on a target rod 132 (which may be made for example of copper). Together, the target rod 132 and the deuterium / tritium containing layer disposed thereon are referred to as the target cathode. An ultra-high negative voltage, for example of the order of (minus) 100 keV, is applied between the target cathode and the ion source (for example, the ion acceleration gate 126), creating a A strong axial electric field which extracts the positive ions from the cavity of the acceleration gate 126 and accelerates them towards the target 130. Upon an impact with the target 130, a portion of the ions undergo fusion reactions with the atoms deuterium and / or tritium in target 130, creating fast neutrons (e.g., 14.1 MeV neutrons from fusion of a deuterium nucleus with a tritium nucleus, or neutrons of 2, 45 MeV from the fusion of two deuterium nuclei) in the process. Suitable structural and operational parameters of the ion acceleration portion 106 of the neutron generator 100 (including dimensions, materials, and voltages) are well known to those skilled in the art. With reference to FIG. 3, examples of field ionization structures will now be described. In general, a field ionization structure according to the present invention comprises a substrate 120 and extending therefrom a plurality of nanotips 300, arranged for example in a regular matrix. In accordance with various embodiments, the term "nanotip" here refers to structures with the largest dimensions not exceeding one micrometer. In some embodiments, the largest dimension of the nanopoints does not exceed 500 nanometers; for example, the size of the nanopoints can range from about 200 nanometers to about 300 nanometers. The substrate 120 may be made of any of a variety of suitable semiconductor or conductor materials (eg, silicon, silicon oxide, aluminum oxide, gallium arsenide, nickel-based material, etc. .). The nanotips 300 may be made, for example and without limitation, of silicon, carbon, tungsten, molybdenum, chromium, aluminum nitride, or combinations thereof. For example, in some embodiments, the nanotips each have a tungsten-based tip attached to the substrate and a molecularly-shaped carbon tip on the tip of the tungsten tip. The nanotips 300 may be substantially tapered (as shown), or have any of a variety of other geometric shapes. For example, in some embodiments, the nanotips are substantially cylindrical carbon nanotubes. The matrix may comprise of the order of one million nanopoints per square centimeter. The size, aspect ratio, and density of the nanopoints may depend on the particular manufacturing process employed. The field ionization structure further comprises a field ionization gate 122 disposed above the nanopoint matrix. Openings 302 of grid 122 are generally aligned with nanotips 300. For example, as illustrated in FIG. 3, gate 122 may be formed of a matrix of grid electrodes 304 sandwiched between nanotips 300 and spaced from each other and isolated from the substrate by insulators 306. The height of the nanotips 300 may be slightly greater, equal to, or smaller than the distance between the substrate 120 and the field ionization gate 122, so that the 300 nanopoints enter the grid 122 or, alternatively, terminate at the plane or below the field ionization gate 122 (as shown). The spacing between the nanotips 300 and the gate electrodes 304 may be selected so that the ionization voltage pulses applied together (indicated at 310) serve to ionize the gas in the space surrounding the nanotips 300. [0022] The field ionization matrices and grids 120, 122 are structurally similar to the field emission gates, the main difference (or in some cases the only difference) being an inverted polarity between the matrix 120 and the gate. 122: while, in field emission structures, the gate 122 is held at a positive voltage relative to the nanotips 300 to cause tunneling of electrons from the nanotips 300 through the diminished potential barrier into the gate. In vacuo, the field ionization structures employ a negative voltage of gate 122 to cause tunneling of electrons from neutral particles (eg for example, gas molecules) near the tips 300 to the tips 300, thereby creating ions. The threshold nominal electric field strength (i.e., the threshold ratio between the applied voltage and the distance between the substrate 120 and the gate 122) required in the field ionization structure to generate a current The tip-sensitive ionic level 300 depends, among other things, on the geometry and material of the nanopoint 300, and can be about three to seven times higher than the required electric field strength. to generate the same electric current with electrons generated by field emission. (This is because the surface potential of typical materials is 2-5 eV, while the ionization potential of hydrogen is about 13.5 eV - about three to seven times higher) . For example, for carbon nanotubes, the field ionization thresholds may be between about 7.5 and 16 V / pm (compared to 0.75 to 1.6 V / pm for field emissions), while that for nanopoints of silicon, aluminum nitride, tungsten, and molybdenum, the field ionization thresholds may be between about 20 and about 40 or 50 V / μm. Note that the actual local field strengths near the nanopoints are much higher than the nominal field strength, because of the small dimensions of the nanopoints (especially at their upper free ends). The field ionization matrices and grids adapted for use in neutron generators as contemplated herein, and their methods of manufacture, are generally well known to those skilled in the art. However, in accordance with the present invention, the field ionization structure is cylindrical (and not, as in most conventional, planar structures). In some embodiments, a cylindrical field ionization structure (or a component thereof, such as the field ionization matrix) is assembled from a plurality of flat strips which are secured around the inner surface of the housing 102 parallel to the longitudinal axis 101. In other embodiments, a cylindrical field ionization structure (or its constituent components, such as the die 120 and the gate 122) is formed as a unit, for example in one piece with the housing 102 or as a separate self-contained structure insertable into the housing 102. The neutron generators according to the present invention can provide various performance characteristics. advantageous or other beneficial properties. For example, in some embodiments, the ion source of the neutron generator produces (following the use of direct field ionization) deuterium and / or tritium ions which are largely monoatomic ( for example, more than 50%, in some embodiments more than 75% or even more than 90%). Figure 4 shows the fusion sections for deuterium-tritium fusion reactions as a function of core energy of the incident ion. For an incident diatomic deuterium ion, core energy accounts for only half of the energy of a monoatomic deuterium ion (because the energy at which the diatomic ion is accelerated between the extraction port 110). and the melting target 130, which is the same as for a monoatomic ion, is split between the two nuclei). Thus, in an electric field in which monoatomic ions are accelerated to an energy of about 110 keV, where the melting section is at its highest point at about five barns (as shown in FIG. Individual diatomic ions reach energies of only about 55 keV, reducing their melting section to about 0.8 barn. As a result, the monoatomic ion fusion section is larger than the diatomic ion by a factor of five to six. Since the probability that melting occurs upon a shock of a deuterium or tritium ion on the target is proportional to the melting section, the higher melting section results, for a beam current. The ions incident on the target, in a proportionally higher number of fusion reactions and, thus, generated neutrons. Another contributing factor, in various embodiments, to the increase in neutron yields is the cylindrical configuration of the field ionization matrix, which results in a larger area (compared to ionization patterns). flat field) and thus higher electron beam currents. In some embodiments, the neutron generator achieves neutron yields for 14.1 MeV neutrons generated during the deuterium-tritium fusion of about 109 neutrons per second or more. By way of comparison, many conventional neutron generators used in well logging tools only reach about 108 neutrons per second. Since the neutron yield for deuterium-deuterium fusion is about two orders of magnitude lower than that of deuterium-tritium fusion, these conventional neutron generators generally do not generate in sufficient numbers the generated 2.45 MeV neutrons. from deuterium-deuterium so that they are useful for measurements. The considerably higher neutron yields provided by various embodiments of the disclosed neutron generator can, however, make feasible measurements using 2.45 MeV neutrons. This is beneficial because neutrons in the 2.45 MeV energy range provide a better interactive tool for measuring certain formation properties, such as hydrogen index and formation porosity. The neutron generators according to the present invention also have the advantage of having a considerably reduced ion source priming time. In many conventional neutron generators, the delay between the application of an ionization voltage and the generation of neutrons (the "activation" time), or between the elimination of the ionization voltage and the Neutron generation shutdown (the "off" time) is approximately ten microseconds. In contrast, the field ionization based neutron generators described herein may have ON / OFF times in the range of 20 nanoseconds (i.e., less than 1 ps). This is beneficial for Pulsed Neutron Logging Tools as it provides better control over and / or better knowledge of the timing and shape of neutron pulses (facilitating for example the creation of substantially square shaped neutron pulses). with short rise and fall times). [0026] Beneficial features of additional neutron generators in accordance with various embodiments include relatively low ionization voltages (e.g., a few hundred volts, rather than a few kilovolts used in Penning ion sources). 3035263 among others), and a certain structural simplicity in comparison to many conventional devices. For example, Penning ion sources generally use a magnetic field to elongate the electron trajectories in the ion source; which uses either a permanent magnet, which adds volume and causes manufacturing problems due to the fact that the intensity of the magnetic field tends to degrade at the high temperatures generally used to degas the vacuum chamber, ie a solenoid, with additional electrical connections and circuitry. The use of direct field ionization in accordance with the present invention eliminates the use of this type of permanent or electromagnetic magnet. The field ionization neutron generators described above can be used with appropriate radiation detectors and control and processing circuitry to provide pulsed neutron logging tools for use. in various well logging operations. Figure 5 illustrates a pulsed neutron logging tool 500 in accordance with various embodiments in a context in which it may be employed, namely, suspended from a wire rope 502 within a cased borehole 504 Although not illustrated, in alternate embodiments, the tool 500 may be downhole routed as part of a drill string, for example in a downhole assembly, during a drilling operation. Logging while drilling (LWD) or measurement while drilling (MWD). The well logging tool 500 may include a neutron generator 100 as described above, and one or more radiation detectors.
    [0005] For example, some tools use three gamma ray detectors 508, 510, 512 in a linear configuration. The well logging tool 500 may further include a control and processing circuitry 514 configured to control operation of the tool 500 and / or process data obtained therewith (such as radiation data). measured by the detectors). The control and processing circuitry 514 may be in communication via one or more telemetry systems with a data processing system 515 (including for example a processor and a memory) located above the surface, where measurements taken by the tool 500 may be further processed, displayed, and / or logged. The neutron generator 100 can be used to create high energy neutron pulses 516 (for example, with energies of 2.45 MeV or 14.1 MeV). These high-energy neutrons 516 generally penetrate the metal housing of the well logging tool 500 as well as the borehole casing 518, but are slowed down in the cement sheath 520 of the borehole or formation 522. surrounding the borehole by repeatedly dispersing and finally being captured by nuclei in these materials, creating gamma radiation 524 during the process. The gamma ray detectors 508, 510, 512 serve to detect and quantify gamma radiation, and thus capture information about the density and other properties of the materials. The use of multiple detectors at different distances from the neutron generator 100 can be used to probe different radial depths in the materials and / or to normalize certain quantities (for example, the total neutron count) by forming relationships between them. the readings of the different detectors. Alternatively or in addition to the gamma ray detectors, the well logging tool 500 may include one or more detectors for measuring secondary neutrons generated during melting neutron interactions with the borehole or formation. The control and processing circuitry 514 and / or the data processing system 515 can correlate the measured radiation pulses with the neutron pulses which cause them; improved neutron pulse synchronization control, achieved in accordance with various embodiments due to shorter ion source priming times, is beneficial for this purpose. To use the well logging tool 500 in a measurement operation while drilling, the neutron generator 100, the detectors 508, 510, 512 and the control and processing circuitry 514 can be mounted in the downhole assembly of a drill string, for example housed in or integrated with a drill collar section to form a separate reduction. Instead of being suspended from a wire rope, the tool 500 will then be moved into and out of the borehole together with the drill string. In this configuration, the linear arrangement of neutron generator 100 and detectors 508, 510, 512 shown in FIG. 5 may be retained. The tool 500 generally operates in the same manner, regardless of whether it is deployed in a wire rope probe (shown in FIG. 5) or as a measuring tool while drilling in a bottom set. of hole. FIG. 6 illustrates, in the form of a flowchart, a method 600 of using a well logging tool in accordance with the present invention. The method 600 comprises disposing a pulsed neutron well logging tool in accordance with the present disclosure (e.g., a tool 500 having a neutron generator 100) in a probe bore (step 602), for example going down the tool in the borehole on a wire rope (described in Figure 5) or as part of a drill string during a measurement operation while drilling. Once located at the desired depth in the borehole, the neutron generator can be operated in pulsed mode to generate flushes of neutrons (operation 604). Operation of the neutron generator generally involves applying a current to the gas reservoir element to create a desired service gas service pressure (operation 606); applying a pulsed voltage of the correct polarity to the field ionization structure and the acceleration gate (for example, by applying negative voltage pulses to the field ionization gate (via a bias resistor) and the acceleration gate and maintaining the field ionization array at zero volts (operation 608); and applying ultra-high voltage between the ion source (e.g., the acceleration gate) and the target cathode (operation 610). The method further includes measuring radiation from a neutron interaction with materials in or surrounding the borehole (step 612), the use of one or more appropriate radiation detectors of the well logging tool. The measured radiation data can then be processed together with neutron pulse data, taking into account the synchronization between the neutron pulses (as can be determined from the timing of the voltage pulses) and the detected radiation. to obtain borehole information and / or formation properties (operation 614). Many variations can be made to the structures and techniques described and illustrated herein without departing from the scope of the subject of the invention. Accordingly, the disclosed embodiments are not intended to limit the scope of the object of the invention. Rather, the scope of the subject matter of the invention is to be determined by the scope of the following claims and all the additional claims set forth herein, and all the equivalents of those claims. 24
    权利要求:
    Claims (21)
    [0001]
    REVENDICATIONS1. A neutron generator (100) comprising: a closed housing (102) containing an ionizable gas, the housing (102) defining first and second neutron generator portions (104, 106) along a longitudinal axis ( 101) thereof; a cylindrical field ionization structure arranged along an inner surface of the housing (102) in the first portion (104), the field ionization structure being configured to ionize the ionizable gas upon application of an electrical voltage to the structure; a cylindrical acceleration grid (126) disposed about the longitudinal axis (101) in the first portion (104), the acceleration gate (126) being configured, in use, to cause an accumulation of ions in the gate (126); and a target cathode disposed at an end of the second portion (106) which is distal to the first portion (104), the target cathode being maintained, in use, at a negative electrical potential with respect to the gate accelerator (126) for extracting ions from the gate (126) and accelerating them toward the target cathode to thereby cause fusion reactions between the ions and a portion of the target atoms contained in the target cathode to generate neutrons of high energy (516).
    [0002]
    The neutron generator (100) of claim 1, wherein the field ionization array (120) comprises a nanotip array disposed on a cylindrical substrate (120); and a field ionization gate (122) concentrically disposed within the cylindrical substrate (120) and aligned with the nanopoint array so that the nanotips (300) are located at apertures (302). ) of the grid (122).
    [0003]
    The neutron generator (100) according to claim 2, wherein a radial distance between the array (120) and the field ionization gate (122) is less than one micrometer.
    [0004]
    The neutron generator (100) according to claim 1, wherein the housing (102) has an outside diameter of less than 1.5 inches (2.54 cm).
    [0005]
    5. The neutron generator (100) according to claim 1, wherein the electrical potential applied to the target cathode enables the ions to be extracted and accelerated so as to cause fusion reactions reaching a neutron yield (516). ) of not less than 109 neutrons (516) per second. 25
    [0006]
    The neutron generator (100) according to claim 1, wherein the field ionization structure is configured to produce, in operation, an ionized gas having at least 50% monoatomic ions. 30
    [0007]
    The neutron generator (100) of claim 1, wherein applying a voltage pulse to the field ionization structure 2635263 creates a fusion neutron pulse in less than one microsecond after it .
    [0008]
    The neutron generator (100) according to claim 1, wherein the ionizable gas comprises at least one of deuterium and tritium.
    [0009]
    A well logging tool (500) comprising: a pulsed neutron generator (100) comprising, contained in a closed housing (102) defining first and second neutron generator portions (104, 106) along a longitudinal axis (101) thereof: a cylindrical field ionization structure arranged along an inner surface of the housing (102) in the first portion (104), the field ionization structure being configured for ionizing, when applying electrical voltage thereto, an ionizable gas contained in the housing (102); A cylindrical acceleration grid (126) placed around the longitudinal axis (101) in the first portion (104), the acceleration gate (126) being configured, in use, to cause ion accumulation in the grid (126); and a target cathode disposed at an end of the second portion (106) which is distal to the first portion (104), the target cathode being maintained, in use, at a negative electrical potential with respect to the acceleration gate (126) to thereby extract ions from the gate (126) and accelerate them to the target cathode, fusion reactions between the ions and a portion of the target atoms contained in the target cathode causing generation neutrons; and a radiation detector (508, 510, 512) configured to detect radiation (524) resulting from a neutron interaction with materials outside of the well logging tool (500).
    [0010]
    The tool (500) according to claim 9, further comprising circuitry configured to perform at least one of: regulating an operation of the neutron generator (100) or radiation detector (508, 510, 512) or processing data indicating the radiation (524) detected by the detector (508, 510, 512). 15
    [0011]
    The tool (500) of claim 9, wherein the field ionization matrix (120) of the pulsed neutron generator (100) comprises a nanotip array disposed on a cylindrical substrate (120); and a field ionization gate (122) concentrically disposed within the cylindrical substrate (120) and aligned with the nanopoint array so that the nanotips (300) are located at apertures (302). ) of the grid (122).
    [0012]
    The tool (500) of claim 9, wherein an outer diameter of the tool (500) is less than two inches (5.08 cm). 30
    [0013]
    The tool (500) of claim 12, wherein an outer diameter of the neutron generator housing (102) (100) is less than 1.5 inches (2.54 cm).
    [0014]
    The tool (500) according to claim 9, wherein the electrical potential applied to the target cathode enables the ions to be extracted and accelerated so as to cause fusion reactions reaching a neutron yield (516) of at least 109 neutrons (516) per second. 10
    [0015]
    The tool (500) according to claim 9, wherein the field ionization structure is configured to produce, in operation, an ionized gas having at least 50% monoatomic ions. 15
    [0016]
    The tool (500) according to claim 9, wherein the neutron generator (100) is configured to cause the creation of a fusion neutron pulse in less than one microsecond following the application of a voltage pulse to the field ionization structure.
    [0017]
    17. A method of using a logging tool comprising: disposing a tool (500) in a borehole, the tool comprising a neutron generator (100) comprising: a closed housing (102) containing an ionizable gas, the housing (102) defining first and second portions (104, 106) of a neutron generator (100) along a longitudinal axis (101) thereof; a cylindrical field ionization structure, arranged along an inner surface of the housing (102) in the first portion (104), for ionizing the ionizable gas upon application of an electrical voltage to this one; a cylindrical acceleration grid (126), disposed about the longitudinal axis (101) in the first portion (104), to cause an accumulation of ions in the grid (126); and a target cathode disposed at an end of the second portion (106) which is distal to the first portion (104) and maintained at a negative electrical potential with respect to the acceleration gate (126) , for extracting ions from the acceleration gate (126) and accelerating them toward the target cathode to thereby cause fusion reactions between the ions and a portion of the target atoms contained in the target cathode; and operating the neutron generator in pulsed mode to cause the generation of neutron pulses by melting the ionized gas with the target atoms.
    [0018]
    18. The method of claim 17, wherein operating the neutron generator (100) comprises applying a pulsed voltage to the cylindrical field ionization structure.
    [0019]
    19. The method of claim 17, further comprising measuring radiation (524) resulting from neutron interaction with materials in or surrounding the borehole. 3035263
    [0020]
    The method of claim 17, wherein the arrangement of the tool (500) in the borehole comprises suspending the tool from a wire rope. 5
    [0021]
    The method of claim 17, wherein the arrangement of the tool (500) in the borehole comprises disposing a drill string including the tool in the borehole.
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    同族专利:
    公开号 | 公开日
    DE112015006133T5|2017-11-02|
    GB2552746B|2020-08-26|
    US20180049305A1|2018-02-15|
    MX2017013279A|2018-01-26|
    GB2552746A|2018-02-07|
    US10455684B2|2019-10-22|
    BR112017019040A2|2018-04-17|
    MX367418B|2019-08-21|
    GB201714216D0|2017-10-18|
    WO2016167774A1|2016-10-20|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    FR2710782A1|1993-09-29|1995-04-07|Sodern|Neutron tube with magnetic confinement of electrons by permanent magnets and its manufacturing process.|
    KR20000052855A|1996-11-01|2000-08-25|죠지 에이치 밀레이|Spherical inertial electrostatic confinement device as a tunable X-ray source|
    JP2006300555A|2005-04-15|2006-11-02|Sanko Consultant Kk|Method and apparatus for logging all stratum|
    EP1925000A4|2005-06-29|2009-05-13|Univ Houston|Miniature neutron generator for active nuclear materials detection|
    US20150155127A1|2007-11-27|2015-06-04|Applied Nanotech Holdings, Inc.|Carbon nanotube-based ion source for particle generator|
    US9001956B2|2007-11-28|2015-04-07|Schlumberger Technology Corporation|Neutron generator|
    US7978804B2|2007-12-10|2011-07-12|Schlumberger Technology Corporation|Low power neutron generators|
    US7639770B2|2008-04-22|2009-12-29|The Regents Of The University Of California|Cylindrical neutron generator|
    US8319175B2|2010-08-31|2012-11-27|Schlumberger Technology Corporation|Nano-tips based gas ionization chamber for neutron detection|
    WO2012064801A2|2010-11-11|2012-05-18|Schlumberger Canada Limited|Particle accelerator with a heat pipe supporting components of a high voltage power supply|
    WO2012105937A1|2011-01-31|2012-08-09|Halliburton Energy Services Inc.|Neutron generator and method of use|
    US20130068941A1|2011-09-20|2013-03-21|Baker Hughes Incorporated|Boron liner for neutron dectectors for well logging applications|
    US9230772B2|2011-12-28|2016-01-05|Schlumberger Technology Corporation|Device and method for ion generation|
    EP2932508A4|2013-12-31|2015-12-23|Halliburton Energy Services Inc|Nano-emitter ion source neutron generator|
    WO2015102615A1|2013-12-31|2015-07-09|Halliburton Energy Services, Inc.|Tritium-tritium neutron generator and logging method|
    US10408968B2|2013-12-31|2019-09-10|Halliburton Energy Services, Inc.|Field emission ion source neutron generator|US10288763B2|2015-11-11|2019-05-14|Halliburton Energy Services, Inc.|Long-lifetime, high-yield, fast neutrons source|
    FR3087313B1|2018-10-16|2020-11-06|Sodern|NEUTRONIC GENERATOR|
    CN111741583B|2020-05-26|2021-09-28|中国原子能科学研究院|Integrated desktop type neutron generator|
    法律状态:
    2017-01-23| PLFP| Fee payment|Year of fee payment: 2 |
    2018-01-12| PLSC| Search report ready|Effective date: 20180112 |
    优先权:
    申请号 | 申请日 | 专利标题
    PCT/US2015/026193|WO2016167774A1|2015-04-16|2015-04-16|Field-ionization neutron generator|
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