Sub-surface gyrotron drill for deep microwave drilling

Abstract

A drill head (1) and corresponding method for drilling a borehole (2) into a sub-surface formation (3) comprises at least one drill housing (4) configured to be arranged sub-surface, and at least one gyrotron (5, 5a, …). The gyrotron (5, 5a, …) comprises an electron gun (6) configured to produce an electron beam, at least one magnet (7) configured to produce a magnetic field, and a cavity (8) configured to receive the electron beam and to generate microwaves by a resonance coupling between the electron beam and the magnetic field produced by the magnet (7). The microwaves are injectable into the sub-surface formation (3) for drilling the borehole (2). The gyrotron (5, 5a, …) is at least partially arranged in the drill housing (4) such, that the microwaves are generated sub-surface.

Description

[0001] F07426

[0002] 1

[0003] TITLE

[0004] SUB-SURFACE GYROTRON DRILL FOR DEEP MICROWAVE DRILLING

[0005] TECHNICAL FIELD

[0006] The present invention relates to a drill head for drilling a borehole into a sub-surface formation according to claim 1 , a drilling arrangement comprising such a drill head according to claim 13, a method of manufacturing such a drill head according to claim 14, and to a method of drilling boreholes with such a drill head according to claim 15.

[0007] PRIOR ART

[0008] Using high power microwaves to dig deep boreholes in sub-surface formations is well- known in the art, see US 8 393 410 B2. Yet, that approach calls for locating a gyrotron on the surface, then sending from kiliawatts to megawatts of power through a microwave transmission line from meters to kilometers below the surface. Microwave transmission lines are simply too lossy to result in sufficient power deep enough for efficient drilling. For example, in fusion tokamak experiments megawatts of 170 GHz power is transmitted only 100 meters above the surface in a highly engineering and precision aligned waveguide and quasi-optical system located in a clean laboratory setting. Here, the microwave loss is -10%. Assembling a waveguide on a drilling rig assembled with drill workers will result in yet higher losses per meter. Also, sub-surface drilling is rarely very straight, which further results in microwave losses. The expected power after even 1000 meters is not sufficient to bore holes into rock. In addition, the electron beam collectors of megawatt gyrotrons are currently too large and require too much water coolant in order to operate sub-surface effectively. Additoinally, the magnets required for >170 GHz gyrotrons are also too large to enable fitting gyrotrons down bore holes.

[0009] SUMMARY OF THE INVENTION F07426

[0010] 2

[0011] It is an object of the present invention to provide a drill head for drilling a borehole into a sub-surface formation that overcomes the drawbacks of the prior art. In particular, it is an object to provide a drill head that is configured to inject microwaves into sub-surface formations of high power and that at the same time has a compact design.

[0012] This object is achieved with a drill head according to claim 1. That is, a drill head for drilling a borehole into a sub-surface formation is provided. The drill head comprises at least one drill housing configured to be arranged sub-surface, and at least one gyrotron. The gyrotron comprises an electron gun configured to produce an electron beam, at least one magnet configured to produce a magnetic field, and a cavity configured to receive the electron beam and to generate microwaves by a resonance coupling between the electron beam and the magnetic field produced by the magnet. The microwaves are injectable into the sub-surface formation for drilling the borehole. The gyrotron is at least partially arranged in the drill housing, such, that the microwaves are generated sub-surface.

[0013] The gyrotron being at least partially arranged in the drill housing preferably means that the electron gun, the magnet and the cavity of the gyrotron are arranged in the drill housing.

[0014] That is, the drill head according to the invention is based on the insight that the provision of at least one gyrotron being small enough to fit down a borehole for drilling can act as a microwave drilling head, making it possible to generate megawatts of power even down to kilometers deep. In other words, the gyrotron is preferably configured to be located subsurface and inside the borehole.

[0015] Hence, the present invention solves the "microwave loss problem" of the known drill heads by locating the microwave generation within the borehole, i.e. by making the gyrotron a drill head. As such, the microwaves need only to travel a small distance, for instance less than a few meters to the sub-surface formation such as a target rock. That is, the drill head is preferably configured to penetrate sub-surface formations such as rock and other materials. As such, the drill head is preferably used to generate boreholes for use in geothermal energy extraction. Additionally or alternatively, the drill head could be used for the extraction of a natural resource such as ground water, brine, natural gas, helium, hydrogen, or petroleum, for the injection of a fluid from surface to a subsurface reservoir or for subsurface formations evaluation or monitoring, etc. Additionally or alternatively, the drill head could also be used for mining purposes, i.e. for creating holes for the deep or directional mining equipment, or for vaporizing the rock and ore deposits for the direct F07426

[0016] 3 purification and mining of valuable gases, minerals, metals and materials.

[0017] Since the gyrotron, in particular the electron gun, the magnet and the cavity, are at least partially and preferably entirely arranged in the drill housing of the drill head these components preferably have a small size compared to the known microwave generators that typically have large and expensive components. As such, the present invention preferably also provides gyrotron components that are smaller and simpler and that can be more easily mass-produced than those of the prior art.

[0018] Various electron guns are conceivable and are well-known in the art. For instance, the electron gun can be a triode gun. The electron gun preferably produces the electron beam that can be accelerated for instance by a high-voltage DC anode into the cavity as it is well- known in the art.

[0019] The cavity preferably has an elongated shape such as the shape of a cylinder, i.e., the cavity preferably extends along a longitudinal direction of the gyrotron. The cavity can comprise or consist of at least one metal compound and / or can comprise or consist of a metal coated dielectric.

[0020] The drill housing preferably has an elongated shape such as the shape of a cylinder as well, i.e. the drill housing preferably extends along a longitudinal direction of the drill head. The longitudinal direction of the drill head preferably runs parallel to the longitudinal direction of the gyrotron. The drill housing preferably serves the purpose of protecting the gyrotron for instance from high pressures and temperatures underground in the borehole. That is, the drill housing can be seen as a protective housing. The drill housing preferably comprises or consists of one or more metal compounds and / or mixtures therefor, for instance stainless steel or other strong metal(s). The drill housing is particularly preferably made from stainless steel to provide good structural strength which is chemically stable.

[0021] Moreover, it is preferred that the drill housing is configured for transmission of microwaves generated by the gyrotron towards an outside of the drill head. Additionally or alternatively, the drill housing preferably comprises one or more outlet windows configured to transmit the microwaves generated by the gyrotron towards an outside of the drill head. For instance, the at least one outlet window could comprise or consist of diamond, although other materials are likewise conceivable. F07426

[0022] 4

[0023] The drill head preferably comprises at least two, particularly preferably a plurality of gyrotrons.

[0024] Statements made with respect to one gyrotron preferably likewise apply to two or more gyrotrons and vice versa.

[0025] That is, each gyrotron preferably comprises an electron gun, at least one magnet, and a cavity.

[0026] Said at least two gyrotrons are preferably arranged at least partially and preferably entirely in the drill housing, i.e. in a common housing of the drill head.

[0027] The provision of two or more gyrotrons enables the generation of more microwave power, while also providing important redundancy, see also further below.

[0028] The gyrotrons are preferably configured to be controlled and / or operated independently from one another. Additionally or alternatively, the gyrotrons are preferably configured to be controlled and / or operated such as to steer the drill head and / or such that a temperature gradient is generated in the sub-surface formation.

[0029] That is, and as will be explained in greater detail further below, the one or more gyrotrons are preferably in connection with at least one power source. In particular, in the event of two or more gyrotrons it is preferred that they are in connection with a single power source.

[0030] Power from the power source is preferably supplied to the gyrotrons in parallel and via individual switches being provided for each gyrotron. For instance, one power supply line could be provided that extends from the power source towards the gyrotrons, and wherein the power supply line is then split off into branches, and wherein each branch is connected to a gyrotron, in particular to a switch of the gyrotron, in a parallel way.

[0031] However, two or more power sources are likewise conceivable, and wherein two or more gyrotrons can be connected to two or more power sources.

[0032] The one or more power sources are preferably arranged on the surface, i.e. not sub-surface.

[0033] The one or more power sources are preferably configured to supply different voltages, F07426

[0034] 5 alternating voltages, etc. to the gyrotron(s), in particular to the one or more components of the gyrotron(s) such as the electron gun or a collector, see also further below. In particular, the one or more power sources are preferably configured to supply different voltages, currents, and powers to a multi-stage depressed collector and also to the electron gun. The electron gun(s) are preferably also supplied with Alternating Current power to heat emitters, which ride on top of a direct current high voltage line. Different voltages can be supplied to the multistage depressed collector to increase the efficiency of the depressed collector.

[0035] The gyrotrons being configured to be controlled and / or operated independently from one another preferably means that each gyrotron can be selectively powered by the power source(s). In other words, each gyrotron is preferably selectively switched on and off. Said switching on and off is preferably enabled by at least one switch. Said switch preferably is an electrical component that can make or interrupt an electrical connection between the gyrotron and the at least one power source mentioned above. Said electrical connection is preferably provided by the power supply line mentioned earlier.

[0036] Depending on an operation state, i.e. whether a particular gyrotron is switched on or off, the drill head can be steered and / or a temperature gradient can be generated in the sub-surface formation. In fact, an operation state of the at least one gyrotron is preferably controlled such that a temperature gradient, as controlled by a gyrotron power, rate of progress of the drill heat, and other factors, result in the formation of the most stable rock-glass casing of the borehole. That is, the drill head according to the invention can be seen as comprising a microwave steering being provided by the selective operation of one or more gyrotrons. Conceivable steerings are a speed of penetration and / or a direction of penetration of the drill head through the subsurface formation.

[0037] Hence, whereas a single power supply line can be fed to the drill head, it is preferred that there are independent switches controlling the power feed to each gyrotron. This enables a quick shut off in the event of a gyrotron arc or failure, so that one gyrotron failure does not also render all other of the gyrotrons inoperable.

[0038] Additionally or alternatively, the selective operation of one or more gyrotrons can serve the purpose of generating a temperature gradient in the sub-surface formation, wherein the control of the temperature gradient can yield control over the cooling of the lava and glass formation. F07426

[0039] 6

[0040] That is, such a temperature gradient control enables the formation of a ceramic or glassy borehole wall which in turn improves the stability of the borehole. In fact, the injection of the microwaves into the sub-surface formation preferably melts the sub-surface formation such as rock and results in the formation of the aforementioned glassy or ceramic borehole wall. Said borehole wall can be seen as a casing that at least partially encases the drill head. Depending on a material of the sub-surface formation said borehole wall or casing can be so-called rock glass.

[0041] The drill head and / or the gyrotron(s) comprises and / or is in connection with at least one controller configured to control and / or operate the drill head and / or the gyrotron(s), respectively. Additionally or alternatively, said controller is preferably in connection with one or more further components such as the power source(s), cooling device(s), etc., see also further below.

[0042] To this end it is preferred that the gyrotron(s) are configured to be controlled and / or operated such that at least one temperature gradient along one axis, and preferably gradients along all three axes, i.e. the x, y and z-axis of an x,y,z-coordinate system, are generated in the sub-surface formation. For instance, the heat on an exposed surface will create more local heat than further down the rock / lava target.

[0043] It should be noted that such the drill head is preferably configured to generate such a temperature gradient with only one gyrotron. However, the temperature gradient or an associated cooling rate is better controlled if there are multiple gyrotrons. For instance, an x-y, or transverse, temperature gradient running orthogonal to a longitudinal direction of the borehole, or vertical direction of the borehole, can be much steeper with two or more gyrotrons. However, it is likewise conceivable that the temperature gradient is controlled with only one gyrotron. Especially in this case, it is preferred that the drill head comprises and / or is in connection with at least one controller being an interaction mode controller that is configured to control an interaction mode of the gyrotron.

[0044] In any case, it is preferred that the gyrotrons are configured to be controlled and / or operated such that the melted rock / lava or glass formation is cooled slowly in order to yield a stable rock / glass borehole wall or casing.

[0045] One or more of the gyrotrons are preferably arranged and / or configured such that their microwaves are injected into the borehole along a downward direction and / or an upward F07426

[0046] 7 direction and / or a radial direction of the borehole.

[0047] The downward direction and the upward direction of the borehole preferably run parallel to a vertical direction of the borehole. Furthermore, the upward direction preferably runs opposite to the downward direction. The radial direction of the borehole preferably runs parallel to a horizontal direction of the borehole. The vertical direction of the borehole preferably runs perpendicularly to the horizontal direction of the borehole.

[0048] As will be explained in greater detail below, each gyrotron preferably comprises at least one output window configured to output the generated microwaves from the gyrotron. To this end it is preferred that the gyrotrons are arranged and / or configured such that their microwaves can be outputted from the gyrotrons and thus injected into the borehole along a downward direction and / or an upward direction and / or a radial direction of the borehole.

[0049] In particular, one or more gyrotrons being arranged and / or configured such that its microwaves are injected into the borehole along a downward direction preferably serve the purpose of drilling the sub-surface formation.

[0050] One or more gyrotrons being arranged and / or configured such that its microwaves are injected into the borehole along a radial direction preferably serve the purpose of affecting a cooling rate to form a good rock / glass borehole wall or casing, see above.

[0051] One or more gyrotrons being arranged and / or configured such that its microwaves are injected into the borehole along an upward direction preferably serve the purpose of taking any drill out of the borehole so that is does not get stuck. In particular, hot glassy or ceramic material such as hot lava shall not touch the drill head. Or, if it does, it is preferred that a (fluid) cooled drill housing is provided that protects the drill head, see further below.

[0052] For instance, in case there is a borehole breakout, such an arrangement and / or configuration of the gyrotrons preferably together with the capability of individually controlling and / or operating the gyrotrons allows an activation or switching on of radial gyrotron outputs, as well as backwards facing gyrotron outputs in order to vaporize and clear out any rock from the borehole.

[0053] The gyrotrons preferably are arranged in a pattern. Additionally or alternatively, the gyrotrons preferably are arranged according to a horizontal arrangement with respect to a F07426

[0054] 8 horizontal direction of the drill head and / or according to a vertical arrangement with respect to a vertical direction of the drill head.

[0055] That is, various arrangements of the gyrotrons in the drill head are conceivable, such as arranged in a pattern, stacked vertically, arranged all in a same horizontal plane, or a combination of these two arrangements, also referred to as spiral arrangement. That is, the gyrotrons being arranged according to a horizontal and vertical arrangement can be seen as being arranged according to a spiral arrangement, or figuratively speaking, like a staircase. The vertical direction of the drill head preferably runs parallel to the vertical direction of the borehole. The horizontal direction of the drill head preferably runs parallel to the horizontal direction of the borehole. Said horizontal I vertical I spiral arrangement preferably relates to a spatial arrangement of the gyrotrons themselves. Advantages of these arrangements are, for instance, the provision of more space for the gyrotrons within the drill housing. For instance, a vertical stacking provides the most space allowing for bigger gyrotrons, and also less coupling of the magnetic fields of each magnet. The horizontal arrangement yields the most compact arrangements of gyrotrons, which might be the most power. A spiral arrangement is a compromise between the two.

[0056] The gyrotrons are preferably fixedly arranged in the drill head, in particular fixed to the drill housing such as bolted or welded in place, or otherwise secured to the drill housing of the drill head.

[0057] The drill head preferably further comprises at least one waveguide being in connection with the gyrotron and extending out of the drill housing. The waveguide preferably is configured to be inserted into the borehole and to guide the microwaves generated by the gyrotron into the borehole.

[0058] That is, the drill head can comprise at least one waveguide. In the event of two or more gyrotrons it is preferred that two or more waveguides are provided, namely at least one waveguide per gyrotron. Various arrangements of the waveguides are conceivable. For instance, one or more of the waveguides can be arranged straight or bent and / or so as to point along the downward direction or upward direction or radial direction of the borehole. For example, one or more waveguides can at least partially extend along the vertical direction of the borehole and / or along the horizontal direction of the borehole. Additionally or alternatively, one or more waveguides can at least partially extend at an angle to the vertical direction of the borehole and / or at an angle to the horizontal direction of the F07426

[0059] 9 borehole.

[0060] Various waveguides are conceivable. For instance, the waveguide can be overmoded and / or corrugated and / or comprising or consisting of at least one metal or a dielectric. Various lengths are conceivable. For instance, a length of the waveguide could be between 0.01 meter or more, such as 10 meter or more, for instance 100 meter or more or 1000 meter or more. Other lengths are likewise conceivable.

[0061] The one or more waveguides are preferably physically connected to the drill head, in particular to the drill housing of the drill head.

[0062] It is furthermore preferred that the waveguide(s) are aligned with the microwave beam, in particular with the output window(s) of the gyrotron.

[0063] Additionally or alternatively, the drill head can comprise at least one mirror system being configured and arranged to direct and / or focus and / or expand and / or transmit the microwaves into the borehole. To this end it is conceivable that no waveguide(s) are provided but just the at least one mirror system. The mirror system preferably is a quasi- optical arrangement comprising or consisting of one or more quasi-optical mirrors, for instance.

[0064] It is furthermore preferred that the mirror system(s), in particular the quasi-optical arrangement(s) is aligned with the microwave beams, in particular with the output window(s) of the gyrotron.

[0065] Hence, the microwaves generated by the gyrotron(s) can be injected into the borehole along different injection directions, wherein these different directions can result from the arrangement of the waveguide(s) and / or from the mirror system(s) and / or the spatial arrangement of the gyrotron(s) and / or outlet(s) of the microwaves from the gyrotron(s) for instance defined by the mirror system(s) that directs the microwaves through the outlet window(s) out of the gyrotron(s).

[0066] The gyrotron preferably comprises a gyrotron housing. The electron gun, the magnet, and the cavity are preferably at least partially arranged in the gyrotron housing. Additionally or alternatively, the gyrotron housing preferably is at least partially arranged in the drill housing. F07426

[0067] 10

[0068] That is, the at least one gyrotron preferably comprises a gyrotron housing that houses at least some and / or at least part of the components of the gyrotron, in particular the electron gun, the magnet, and the cavity.

[0069] If two or more gyrotrons are present it is preferred that each gyrotron comprises its own housing, wherein all of these gyrotron housings are in turn preferably at least partially arranged in the drill housing of the drill head. That is, the gyrotron housings can be seen as individual sub-housings for the gyrotrons that are arranged within a "common housing" provided by the drill housing of the drill head.

[0070] The gyrotron housings preferably have an elongated shape such as the shape of a cylinder as well, i.e. the gyrotron housings preferably extend along the longitudinal direction of respective gyrotron.

[0071] The gyrotron housing(s) are preferably physically connected to the drill housing, for instance welded, brazed, etc. To this end it is particularly preferred that a fixation of the gyrotrons to the drill housing is done with stainless steel bolts, or welding of stainless steel, to provide good mechanical connections.

[0072] Furthermore, the gyrotron housing(s) could comprise one or more interfaces for supplying power and / or for cooling such as with cryogenics or conduction, see also further below.

[0073] The gyrotron housing preferably houses the entire gyrotron and / or the components of the gyrotron such as the electron gun, the cavity, an output window, a collector, a vacuum pump such as a vacuum ion pump or cryo-pumping getter or the like, one or more cooling channels for the electron gun and / or collector, cooling of the magnet, insulation of the magnet (if cryogenic), insulation to maintain a quasi-ambient temperature down hole, an outside protective barrier to protect from the high pressure but also perhaps corrosive super heating vaporized rock, etc., and see also further below.

[0074] The gyrotron preferably further comprises a collector configured to collect a spent electron beam, the collector particularly preferably being a multi-stage depressed collector. Additionally or alternatively, the gyrotron preferably further comprises at least one output window configured to output the generated microwaves from the gyrotron. Additionally or alternatively, the gyrotron preferably further comprises a launcher configured to transform F07426

[0075] 11 a transverse electric mode of the microwaves generated in the cavity into a Gaussian mode.

[0076] That is, the one or more gyrotrons in each case preferably comprise a collector and / or an output window and / or a launcher. These components are preferably arranged in the drill head, in particular in the drill housing and, if present, also in the gyrotron housing of the gyrotron. Hence, these components are preferably configured to be arranged sub-surface as well.

[0077] The cavity can be seen as a resonator in which a high-frequency wave is generated by the resonance coupling of the electron beam performing a cyclotronic motion caused by the magnetic field generated by the magnet and the high-frequency electromagnetic field of a transverse electric mode of the cavity.

[0078] The electron beam preferably travels through the cavity in a strong axial magnetic field being generated by the magnet. In the cavity, a fraction of the transverse part of the electrons' kinetic energy is transformed into a high-frequency beam such as a high- frequency microwave beam as the electron beam resonates with a transverse electric (TE) cavity mode. That is, part of the velocity energy of the electrons is converted into high- frequency energy by a so-called cyclotron resonance maser interaction between the mode of the cavity and the electrons in cyclotron motion caused by the axial magnetic field generated by the magnet. The thus generated high-frequency beam is converted by the launcher, i.e. a mode converter, where the transverse electric mode is transformed to the fundamental Gaussian mode, and is reflected by one or more mirrors of the mirror system, which guides the high-frequency waves towards an outside of the gyrotron, in particular towards the output window that is preferably arranged in a wall of the gyrotron housing, preferably in a sidewall of the gyrotron housing, and for instance into the waveguide mentioned earlier.

[0079] The electron beam which has undergone the cyclotron resonance maser interaction in the cavity, i.e., the spent electron beam, can be collected by the collector which is configured to absorb the spent electron beam.

[0080] A preferred collector is a multi-stage depressed collector. A multi-stage collector preferably comprises multiple metal collector elements, each operating with a different electrical potential. This allows the electron beam to be separated into electrons with different energy, so that the remaining kinetic energy of the electrons can be harvested (this requires current F07426

[0081] 12 flow from each of the collector stages back to a power supply preferably on the surface) in order to improve the device’s electrical efficiency. The multi-stage depressed collector not only reduces the energy / power consumption of the gyrotrons, but also allows one to shrink the size of the collector. Moreover, the multi-stage depressed collector stages can be smaller than a conventional single stage collector because the electrons do not impact into the collector with as much kinetic energy, which turns into thermal energy (heat). Single stage collectors in megawatt gyrotrons are typically very large, more than 30 cm in diameters and require large amounts of water cooling supplied by water lines as big as a fire hose. Multi-stage depressed collectors can be much smaller, which makes them much easier to put downhole, but also require less water cooling, which also makes them more feasible downhole.

[0082] However, it is likewise conceivable that a single state compressor is used.

[0083] Various arrangements of the output window(s) are conceivable. For instance, the output windows could either be at one of the ends of the gyrotrons, for axial output of the microwaves, or along a side for transverse output of the microwaves.

[0084] The cavity is preferably connected to at least one of the electron gun, the output window, the launcher, mode converter mirrors, the vacuum pump, and the collector typically by welding, brazing, or conflat flanges. As mentioned earlier, these components are preferably arranged within the gyrotron housing. This entire gyrotron housing is then preferably mounted to the drill housing, for instance using bolts or welding.

[0085] These components can comprise or consist of various materials. For instance, barium impregnated tungsten with overcoating could be used to reduce any electronic work function for instance of the electron gun, and / or stainless steel could be used for instance for the tube body, electron gun, mounts for window, outside of collector, and / or copper could be used for the anode, the cavity, or the collector, and / or diamond could be used for the output window, and / or Kovar could be used as viewport to join the diamond to stainless steel.

[0086] Components being made out of copper have superior electrical and thermal conduction properties. Components can be made of steel for durability, strength, and ability to make better welding joints. Components being made of diamond to transmit microwaves and also provide high thermal conduction. The barium impregnated tungsten is one material which can be used in the emitter of the electron gun. If a cryo-pumping getter is used rather than F07426

[0087] 13 a vacuum ion pump to maintain high vacuum in the gyrotron or also in vacuum insulations such as a vacuum jacketed insulation within the gyrotron, of the drill housing, or of the superconducting cryo-cooled power transmission line running from the surface, for simplicity reasons and ease of use, the getter material is preferably charcoal, zeolites, or some other material with high surface area.

[0088] The magnet preferably is a superconducting magnet or a permanent magnet. Additionally or alternatively, the drill head preferably further comprises at least one adjusting magnet configured to generate a magnetic field that adjusts a magnetic field generated by the magnet.

[0089] The superconducting magnet preferably comprises or is made of at least one superconducting cable and / or at least one superconducting tape. That is, the superconducting magnet can be constructed using a superconducting tape such as a low- temperature superconductor (LTS) and / or a high-temperature superconductor (HTS) tape. Additionally or alternatively, the superconducting magnet can be constructed using a superconducting tape, preferably a low-temperature superconductor (LTS) and / or a high- temperature superconductor (HTS) tape. Additionally or alternatively, the superconducting magnet can have the shape of at least one coil, for instance a superconducting tape being wound into a coil. To this end the coil can be a single coil or a multi-coil such as a pancake coil. A superconductive magnet such as the superconductive cable or superconductive tape in the form of the coil has a very low electrical resistance, in particular in the order of nano-Ohm. Consequently, a high current can be supplied to generate high magnetic fields. The superconducting magnet can have a very small inner radius, for instance a few centimeters or a few millimeters, which significantly simplifies magnet fabrication, even for those generating extremely high magnetic fields. The superconducting tape or superconducting cable is preferably commercially available and / or well known in the art. For instance, the superconducting tape or superconducting cable can comprise or consist of a high-temperature superconducting material such as a rare earth barium copper oxide (REBCO), for instance GdBaCuO. Said superconducting material can be arranged, for instance deposited, on a substrate. The substrate can be non-magnetic and / or mechanically strong and / or corrosion resistant and / or temperature resistant. Additionally or alternatively, the substrate can be an alloy, in particular a nickel alloy such as a nickel alloy further comprising molybdenum, chromium, iron and mixtures thereof.

[0090] However, it is likewise conceivable that the magnet is not a superconducting magnet but a F07426

[0091] 14 permanent magnet.

[0092] The magnet, in particular the superconducting magnet or the permanent magnet, can be directly wound onto an outer surface of the cavity and / or the cavity can serve as a mandrel about which the magnet is wound. Alternatively, the magnet, in particular the superconducting magnet or the permanent magnet, can be indirectly arranged around the cavity. In this case it is preferred that at least one insulating element and / or vacuum insulation is arranged between the magnet, in particular the superconducting agent or the permanent magnet, and an outer surface of the cavity and / or that the magnet, in particular the superconducting magnet or the permanent magnet, and the cavity are arranged at a distance from one another.

[0093] The magnet being (directly or indirectly) wound around the cavity is preferably arranged coaxially to the cavity and / or at least partially along the longitudinal direction of the cavity and / or at least partially along a radial direction of the cavity.

[0094] The one or more gyrotrons in each case preferably comprises at least one further magnet, herein called the adjusting magnet. Such adjusting magnet is preferably configured to adjust a magnetic profile being generated by the magnet mentioned previously and being used to generate the microwaves by the resonance coupling with the electron beam. Said adjusting magnet can be a superconducting magnet or a permanent magnet. Additionally or alternatively, said adjusting magnet can be arranged, in particular wound directly or indirectly, around the launcher.

[0095] The drill head preferably further comprises at least one cooling device and / or is in connection with at least one cooling device that is configured to cool the drill head, in particular the drill housing, and / or to cool the gyrotron, in particular at least one of the gyrotron housing, the cavity, the magnet or the adjusting magnet.

[0096] The drill head being in connection with the at least one cooling device preferably means that the cooling device is a component being separate from the drill head and, for instance, being arranged on the surface, and wherein the drill head is in connection with said cooling device for instance via at least one cooling supply line such as a cryo-feedthrough, see also further below. The drill head comprising the cooling device preferably means that at least part of the cooling device is provided in the drill head and / or can be arranged sub-surface. F07426

[0097] 15

[0098] In any case it is conceivable that the cooling of the drill head and of the one or more gyrotrons is provided by a joint cooling device, i.e. that the drill head is in connection with a joint cooling device and / or comprises a joint cooling device that is configured to jointly cool the drill head, in particular the drill housing, and the one or more gyrotrons, in particular the gyrotron housing and / or the cavity and / or the magnet and / or the adjusting magnet of each gyrotron

[0099] Said joint cooling device can be a chamber such as a cryostat configured to receive at least one cooling fluid and / or configured to at least partially receive the drill head and / or the one or more gyrotrons, in particular the drill housing and / or the gyrotron housing and / or the cavity and / or the magnet and / or the adjusting magnet.

[0100] Alternatively, the joint cooling device can be cryogen-free and / or can be configured to conductively connect to the drill head and / or to the one or more gyrotrons, in particular to the drill housing and / or to the gyrotron housing and / or to the cavity and / or to the magnet of each gyrotron and to dissipate heat therefrom.

[0101] Moreover, it is conceivable that the magnet is cooled with a refrigerator, or other cooling device down hole, and that no liquid nitrogen (or helium, argon, or other cryogen) needs to be transferred downhole from the surface. It is also conceivable that the power supply line can be made of conventional metal conductors (like copper), and that a cryogenic cooled superconducting is not required for power delivery, se further below. It is also conceivable that room temperature, or higher temperature, superconductors are available in the future that supply power to the sub-surface gyrotron without the need of cryogens to maintain superconductivity. It is also conceivable that cooling refrigerators, or cooling devices, are mounted to the long HTS power supply line to cool the transmission line or reduce the required flow of liquid cryogen.

[0102] However, it is likewise conceivable that there is at least one gyrotron-cooling device and / or a drill-head cooling device in addition or in the alternative to the joint cooling device. The at least one gyrotron-cooling device is preferably configured to cool the gyrotron, in particular the gyrotron housing and / or the cavity and / or the magnet and / or the adjusting magnet. To this end it is conceivable that there is a single gyrotron-cooling device that is configured to jointly cool the gyrotrons in the event of two or more gyrotrons being present. However, it is likewise conceivable that there are two or more gyrotron-cooling devices that are configured to individually cool two or more gyrotrons. Statements made with respect to one gyrotron- F07426

[0103] 16 cooling device preferably likewise apply to two or more gyrotron-cooling devices and vice versa. Sections of the gyrotron that are preferably cooled, such as the electron gun, the cavity, and collector could preferably be cooled with the same cryogen which is used to cool the HTS power supply line, and cryogenic HTS magnet. Or it is conceivable that those sections of the gyrotron that are preferably cooled are cooled by water supplied from the surface, and that the water is afterwards used to flush the borehole and transport the vaporized rock to the surface. Similarly, it is conceivable that the cryogen cooling the HTS power supply line and magnet is used afterwards to flush the borehole and transport the rock debris (vaporized rock) to the surface.

[0104] Other components of the drill head and / or the gyrotrons can be cooled as well. For instance, the outlet windows can be cooled, any joints such as brazing joints could be cooled so they do not break, the vacuum pumps could be cooled, a local down hole controller configured to control an operation of the drill head and / or the gyrotrons could be cooled, the gyrotron housing and / or drill housing could be cooled.

[0105] If a drill-head cooling device and at least one gyrotron-cooling device are present, the gyrotron-cooling device is preferably configured to cool the at least one gyrotron independently of the drill-head cooling device cooling the drill head, in particular the drill housing, and vice versa. The gyrotron-cooling device can comprise at least one chamber being configured to thermally insulate the gyrotron housing and / or the magnet and / or the cavity from one another and / or being configured to receive at least one cooling fluid. Said chamber preferably is a cryostat. Additionally or alternatively, the gyrotron-cooling device can comprise one or more channels being in connection with or formed in an outer surface of the gyrotron housing and / or the cavity, and wherein said channels are configured to receive at least one cooling fluid being configured to cool the gyrotron housing and / or the cavity. Alternatively, the gyrotron-cooling device can be cryogen-free and / or can be configured to conductively connect to the gyrotron housing and / or the magnet and / or the cavity and to dissipate heat.

[0106] It should be noted that various cooling fluids are conceivable and well-known in the art. For instance, the cooling fluid can be liquid nitrogen, liquid helium or water.

[0107] The drill head preferably further comprises one or more power supply lines that connect the gyrotron, in particular at least one of the magnet, the electron gun, the collector, or the adjusting magnet to at least one power source. The power supply line preferably is a cryo- F07426

[0108] 17 feedthrough. Additionally or alternatively, the power source is preferably arranged on surface.

[0109] That is, and as mentioned earlier, the at least one gyrotron is preferably in connection with at least one power supply. To this end it is particularly preferred that the magnet, the electron gun, the collector, and the adjusting magnet are in each case in connection with at least one power supply. Said connection preferably is an electrical connection and is preferably established via one or more power supply lines. Preferably, one or more power supply lines for instance with multiple, different, or high voltages potentials run to the drill head, and then there are protecting switches so that the power flow to all of the gyrotrons will not be cut if one gyrotron arcs or fails. The high voltage power supply line for the electron guns also preferably has an alternating current riding on top of two high voltage lines; these two lines are then preferably connected to a heater under the emitter of the electron gun to heat the emitter during operation. Other high voltage power supply lines are preferably connected to the stages of the multistage depressed collector to bring power back up the borehole to the surface. Other power supply lines, for instance AC, could be also brought down the borehole to supply other elements of the drill head such as vacuum ion pumps or cryo-pumping getter or the like.

[0110] The power source is preferably arranged outside of the drill head and in particular on the surface. Said power source can be the power source mentioned earlier that is configured to supply power to the gyrotron, in particular to the switch, or an additional power source.

[0111] The at least one power supply line preferably is a so-called cryo-feedthrough. The cryofeedthrough is an electrical connector that is configured to transmit electrical currents or power through a cryogenic environment from the power source to the gyrotron, in particular to the magnet (if not running in persistent mode), the electron gun, the collector, and the adjusting magnet and optionally also to further components of the gyrotron(s). For instance, the cryo-feedthrough can be provided by a HTS cable or the like. To this end it is particularly preferred that the magnet is a superconducting magnet. The cryogenic environment is preferably provided by the at least one cooling device, in particular by the joint cooling device and / or the gyrotron-cooling device and / or the drill-head cooling device mentioned earlier.

[0112] Examples of conceivable cryo-feedthroughs and their connection to the components of the gyrotron(s) are given now for illustrative purposes. That is, it is conceivable that a 4-stage F07426

[0113] 18 depressed collector is operated by cryo-feedthroughs in the form of HTS cables such as 6- 7 HTS cables that are connected to one or more power supplies on the surface of the drill head. The electron gun can be operated by cryo-feedthroughs in the form of HTS cables as well, for instance 2-3 HTS cables. To this end it is particularly preferred that for the electron gun power supply an alternating current rides on top of a high voltage for heating of the emitter. Moreover, a HV potential preferably is the range of 10-70 kV, with an AC current preferably between two HV lines.

[0114] In addition, switches could be installed on the drill head to duty cycle, or control, the gyrotrons for instance to provide steering of the drill head, as well as heating of the cooled glassy or ceramic material and vertical debris clearing as previously described. The switches could be on the HV supplying the electron gun, on the anode controlling the gun electron beam accelerating voltage, etc.

[0115] The HTS cables can be cooled from the surface to the gyrotron to a temperature under its critical temperature, for instance to about 110° K. Various coolings are conceivable, for instance via the one or more cooling devices mentioned earlier and, for instance, using a cooling fluid such as liquid nitrogen. In fact, a vacuum insulation such as a vacuum jacketing could be implemented in the drill head to reduce thermal losses and nitrogen boil off of the cooling fluid such as nitrogen boil off. The vacuum jacketing preferably is at least one of a flexible, corrugated, or bellowed tubing, for instance with charcoal getting material on an inner surface to keep vacuum. The cooling liquid such as the liquid nitrogen can then be used a second time to cool the magnet(s) of the gyrotron(s), a third time to cool the cavity, a fourth time to cool the electron beam collector, a 5th time to cool all other elements of the drill head, and a 6th time (as vaporized gas) to remove vaporized rock debris to the surface. For instance, the cooling liquid could be transferred along these various components, for instance via feedthroughs such as cryo-feedthroughs that connect these components with one another. However, the feedthroughs do not need to be cryo- or vacuum jacketed after the cryogen is transferred away from the HTS magnet. The flow of the cryogens from one element to the next that is cooled can likewise be accomplished with stainless steel tubing, or 3D printing of metal, etc. Other cooling fluids such as liquid helium are of course likewise conceivable.

[0116] Moreover, the power supply line does not need to be a superconductor but could be a normal conductor instead. F07426

[0117] 19

[0118] The drill head and / or the gyrotron, in particular the drill housing and / or the gyrotron housing and / or the cavity and / or the magnet and / or the adjusting magnet, are preferably in connection with at least one vacuum pump that is configured to generate a vacuum within the drill head and / or the gyrotron.

[0119] That is, it is preferred that the drill head, in particular the drill housing, and / or the at least one gyrotron, in particular at least one of the gyrotron housing, the cavity, the magnet, or the adjusting magnet, is evacuated. Hence, it is preferred that the drill head, in particular the drill housing, and / or the at least one gyrotron, in particular at least one of the gyrotron housing, the cavity, the magnet, or the adjusting magnet, are in connection with at least one vacuum pump that is configured to generate a vacuum therein. If there are two or more gyrotrons, it is preferred that each gyrotron is individually in connection with at least one vacuum pump.

[0120] Various vacuum pumps are conceivable and are well-known in the art, for instance vacuum ion pumps or cryo-pumping getters.

[0121] The vacuum pump is configured to generate a vacuum in the drill head and / or the gyrotron, in particular in the drill housing and / or the gyrotron housing and / or the cavity and / or the agent and / or the adjusting magnet being, for instance, in the order of 10'6mbar or lower, such as about 10'9mbar.

[0122] To this end it is conceivable that the entire inside of the drill head is under vacuum. However, it is likewise conceivable that the drill head is not under vacuum but that there only parts or the drill head and / or the gyrotron are under vacuum, for instance components being provided within vacuum insulation components such as the vacuum jacketed insulation mentioned earlier.

[0123] In another aspect, a drilling arrangement comprising at least one drill head as described above is provided. The drilling arrangement further comprises at least one power source configured to power the drill head and / or the at least one gyrotron. Additionally or alternatively, the drilling arrangement further comprises at least one cooling device configured to cool the drill head and / or the at least one gyrotron.

[0124] Any statements made herein regarding the drill head as such preferably likewise apply to F07426

[0125] 20 the drilling arrangement comprising the drill head and vice versa.

[0126] Hence, it is conceivable that the drill head described above is part of a drilling arrangement and / or is configured to be connected to other components of a drilling arrangement. These other components can be, for instance, at least one power source that is configured to power the drill head and / or the at least one gyrotron. Said power source preferably corresponds to a power source as described previously. The drill head and / or the at least one gyrotron is preferably in connection with the at least one power source via the at least one power supply line described earlier. For example, the power source is preferably in connection with the vacuum pump.

[0127] Additionally or alternatively, the drill head and / or the gyrotron can be in connection with at least one cooling device. Said cooling device preferably corresponds to a cooling device described earlier as well, for instance the joint cooling device and / or the gyrotron-cooling device and / or a drill-head cooling device. The drill head and / or the gyrotron is preferably in connection with these one or more cooling devices via at least one cooling liquid supply line, for instance a cryo-feedthrough.

[0128] The at least one power source and / or the at least one cooling device are preferably arranged on the surface.

[0129] In another aspect, a method of manufacturing a drill head for drilling a borehole into a subsurface formation, preferably a drill head as described above, is provided. The method comprises the steps of i) providing at least one drill housing configured to be arranged subsurface, and ii) providing at least one gyrotron. The gyrotron comprises an electron gun configured to produce an electron beam, at least one magnet configured to produce a magnetic field, and a cavity configured to receive the electron beam and to generate microwaves by a resonance coupling between the electron beam and the magnetic field produced by the magnet. The microwaves are injectable into the sub-surface formation for drilling the borehole. The gyrotron is at least partially arranged in the drill housing, and wherein the microwaves are generatable sub-surface.

[0130] Any statements made herein regarding the drill head as such and the drilling arrangement comprising the drill head preferably likewise apply to the method of manufacturing the drill head and vice versa. F07426

[0131] 21

[0132] At least part of the drill housing and / or at least part of the gyrotron(s) are preferably 3D printed, such as in metal and / or ceramic.

[0133] In another aspect, a method of drilling boreholes into subsurface formations is provided. The method comprises the steps of i) providing at least one drill head as described above and / or as manufactured in the method as described above, and ii) drilling a borehole by injecting the microwaves generated the gyrotron into the sub-surface formation.

[0134] Any statements made herein with regard to the drill head as such, the drilling arrangement comprising the drill head, or the method of manufacturing the drill head preferably likewise apply to the method of drilling boreholes with the drill head and vice versa.

[0135] Hence, in summary it is noted that the drill head according to the invention is associated with several advantages, such as a delivery of more microwave power down hole because power is not lost in transmission lines or the like from the surface.

[0136] In addition, it the drill head and / or the at least one gyrotron is powered by a superconductor much more microwave power can be generated. The drill head can comprise two or more, in particular a plurality of gyrotrons, which enables a better steering of the drill head by the duty cycling of the plurality of gyrotrons.

[0137] Moreover, the drill head according to the invention offers a better cooling gradient control of the glassy or ceramic material such as the lava-glass which results in a better borehole integrity. In addition, it allows the clearing of debris in the borehole and a reformation of the glassy or ceramic material casing such as the lava glass casing in the case of a borehole breakout.

[0138] Overall, the drill head offer the ability to drill, in one go, from the surface down to many kilometers such as 20 kilometers without having to remove the drill head.

[0139] BRIEF DESCRIPTION OF THE DRAWINGS

[0140] Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings, Fig. 1 shows a schematical sectional view of a drilling arrangement comprising a drill head for drilling a borehole in a sub-surface formation by microwaves according to the invention, wherein the microwaves are generated by a plurality of gyrotrons being arranged in the drill head;

[0141] Fig. 2 shows a schematical sectional view of a gyrotron of the drill head according to figure 1 ;

[0142] Fig. 3 shows a schematical partial sectional view of another gyrotron of a drill head according to the invention;

[0143] Fig. 4 shows a schematical partial sectional view of another gyrotron of a drill head according to the invention.

[0144] DESCRIPTION OF PREFERRED EMBODIMENTS

[0145] Aspects of the drill head 1 according to the invention are now discussed with reference to the figures.

[0146] That is, figure 1 depicts a drilling arrangement 100 comprising a drill head 1 that drills a borehole 2 into a sub-surface formation 3. The drill head 1 comprises a drill housing 4 that is arranged sub-surface and a plurality of gyrotron 5, 5a, ... As best visible in figure 2, each gyrotron 5, 5a, ... comprises an electron gun 6 configured to produce an electron beam, at least one magnet 7 configured to produce a magnetic field, and a cavity 8 configured to receive the electron beam and to generate microwaves by a resonance coupling between the electron beam and the magnetic field produced by the magnet 7. The microwaves are injected into the sub-surface formation 3 for drilling the borehole 2. As directly follows from figure 1 , the gyrotrons 5, 5a, ... are entirely arranged in the drill housing 4 such, that the microwaves are generated sub-surface.

[0147] The cavity 8 has an elongated, cylindrical shape and extends along a longitudinal direction Lg of the gyrotron 5. The drill housing 4 has an elongated, cylindrical shape as well and extends along a longitudinal direction Ld of the drill head 1. The longitudinal direction of the drill head Ld runs parallel to the longitudinal direction Lg of the gyrotron 5.

[0148] The drill housing 4 is configured for transmission of microwaves generated by the gyrotrons 5, 5a, ... towards an outside of the drill head 1 and can comprise one or more windows configured to transmit the microwaves generated by the gyrotron towards an outside of the F07426

[0149] 23 drill head 1. For instance, figure 1 schematically indicates a microwave transmission via an arrow through a window or the like being arranged in a bottom end of the drill housing 4.

[0150] The gyrotrons 5, 5a, ... are arranged and configured such that their microwaves are injected into the borehole 2 along a downward direction D and / or an upward direction II and / or a radial direction R of the borehole 2. The downward direction D and the upward direction II of the borehole 2 run parallel to a vertical direction V of the borehole 2. Furthermore, the upward direction II runs opposite to the downward direction D. The radial direction R of the borehole 2 runs parallel to a horizontal direction H of the borehole 2. The vertical direction V of the borehole 2 runs perpendicularly to the horizontal direction H of the borehole 2.

[0151] As follows from figure 2, each gyrotron 5, 5a, ... comprises at least one output window 10 configured to output the generated microwaves from the gyrotron 5, 5a, .... To this end it is preferred that the gyrotrons 5, 5a, ... are arranged and configured such that their microwaves are outputted from the gyrotrons 5, 5a, ... and thus injected into the borehole 2 along the downward direction D and / or the upward direction II and / or the radial direction R of the borehole 2.

[0152] Moreover, the gyrotrons 5, 5a, ... are arranged in a pattern, in particular according to a horizontal arrangement with respect to a horizontal direction Hd of the drill head 1 and according to a vertical arrangement with respect to a vertical direction Vd of the drill head 1. The vertical direction Vd of the drill head 1 runs parallel to the vertical direction V of the borehole 2. The horizontal direction Hd of the drill head 1 runs parallel to the horizontal direction H of the borehole 2, see figure 1.

[0153] The drilling arrangement 100 comprises at least one cooling device 14. That is, the drill head 1 is in connection with at least one cooling device 14 configured to cool the drill head 1 , in particular the drill housing 4, and to cool the gyrotrons 5, 5a, ... . As follows from figure 1 , the drill head 1 and the gyrotrons 5, 5a, ... are in connection with said cooling device 14 via at least one cooling supply line 15.

[0154] The drilling arrangement 100 further comprises at least one power supply. That is, the drill head comprising one or more power supply lines 9, 9a, ... that connect the gyrotrons 5, 5a, ... , in particular at least the magnet 7, the electron gun 6, and a collector 11 , of each gyrotron 5, 5a, ... to at least one power source. In the depicted example, the power source is arranged on the surface. As follows from figure 1 , a plurality of power supply lines 9, 9a, ... F07426

[0155] 24 are provided that extend from the power source to the gyrotrons 5, 5a, , and wherein each power supply lines 9, 9a, ... is then individually connected to a gyrotron 5, 5a, ... , in particular to a switch of the gyrotrons 5, 5a, ....

[0156] Figure 2 depicts an individual gyrotron 5 of the drill head 1 . As follows from said figure, the gyrotron 5 comprises the mentioned electron gun 6, magnet 7, and cavity 8. The gyrotron 5 furthermore comprises a collector 11 configured to collect a spent electron beam, wherein the collector 11 is here a multi-stage depressed collector. The gyrotron 5 furthermore comprises an output window 10 configured to output the generated microwaves from the gyrotron 5, a launcher 12 configured to transform a transverse electric mode of the microwaves generated in the cavity into a Gaussian mode, as well as a mirror system 13.

[0157] The mirror system 13 corresponds here to a quasi-optical arrangement being configured and arranged to direct and / or focus and / or expand and / or transmit the microwaves into the borehole. The quasi-optical arrangement 13 consists here of quasi-optical mirrors. Moreover, the mirror system 13, in particular the quasi-optical arrangement, is aligned with the output window 10 of the gyrotron.

[0158] As follows from figures 3 and 4, the gyrotron 5 comprises a gyrotron housing 16 that houses the components of the gyrotron 5, in particular the electron gun 6, the magnet 7, the cavity 8, the collector 11 , the launcher 12, and the mirror system 13, and wherein the output window 10 is arranged in the gyrotron housing 16. Moreover, the gyrotron 5 is connected to a power source 18 via power supply lines 9, 9a, ... and is connected to cooling devices 14 via cooling supply lines 15, 15a, respectively. In particular, in the depicted examples, the gyrotron 5 comprises a first cooling supply line 15 that is configured to supply water as cooling fluid from the surface into the gyrotron housing 16 in order to cool components of the gyrotron 5 being arranged within the gyrotron housing 16. It furthermore comprises a second cooling supply line 15a that is configured to supply a cooling fluid such as liquid nitrogen into the gyrotron housing 16 and in particular to the magnet 7 that is preferably a superconducting magnet 7. In the depicted examples, the power supply lines 9 are preferably superconducting as well, in particular superconducting high voltage power lines. In addition, an insulation 19 in the form of a vacuum insulation is provided that insulates part of said cooling supply lines 15a and superconducting power supply lines 9, respectively. Moreover, the drill head 1 comprises a waveguide 17 being in connection with the gyrotron 5 and extending out of the drill housing 4. The waveguide 17 is aligned with the output window 10 of the gyrotron 5 and is configured to guide the microwaves generated F07426

[0159] 25 by the gyrotron 5 into the borehole 2.

[0160] 26

[0161] LIST OF REFERENCE SIGNS

[0162] 1 drill head

[0163] 2 borehole

[0164] 3 sub-surface formation

[0165] 4 drill housing

[0166] 5, 5a, ... gyrotron

[0167] 6 electron gun

[0168] 7 magnet

[0169] 8 cavity

[0170] 9, 9a, ... power supply line

[0171] 10 output window

[0172] 11 collector

[0173] 12 launcher

[0174] 13 mirror system

[0175] 14 cooling device

[0176] 15 cooling supply line

[0177] 16 gyrotron housing

[0178] 17 waveguide

[0179] 18 power source19 insulation

[0180] 100 drilling arrangement

[0181] Lg longitudinal direction of gyrotron

[0182] Ld longitudinal direction of drill head

[0183] D downward direction of borehole

[0184] II upward direction of borehole

[0185] R radial direction of borehole

[0186] V vertical direction of borehole

[0187] H horizontal direction of borehole

[0188] Hd horizontal direction of drill head

[0189] Vd vertical direction of drill head

Claims

1. F0742627CLAIMS1. A drill head (1) for drilling a borehole (2) into a sub-surface formation (3) comprising:- at least one drill housing (4) configured to be arranged sub-surface; and- at least one gyrotron (5, 5a, ...), wherein the gyrotron (5, 5a, ...) comprises an electron gun (6) configured to produce an electron beam, at least one magnet (7) configured to produce a magnetic field, and a cavity (8) configured to receive the electron beam and to generate microwaves by a resonance coupling between the electron beam and the magnetic field produced by the magnet (7), wherein the microwaves are injectable into the sub-surface formation (3) for drilling the borehole (2), characterized in that the gyrotron (5, 5a, ...) is at least partially arranged in the drill housing (4) such, that the microwaves are generated sub-surface.

2. The drill head (1) according to claim 1 , wherein the drill head (1) comprises at least two, preferably a plurality of gyrotrons (5, 5a, ...).

3. The drill head (1) according to claim 2, wherein the gyrotrons (5, 5a, ...) are configured to be controlled and / or operated independently from one another, and / or wherein the gyrotrons (5, 5a, ...) are configured to be controlled and / or operated such as to steer the drill head (1) and / or such that a temperature gradient is generated in the sub-surface formation (3).

4. The drill head (1) according to claim 2 or 3, wherein one or more of the gyrotrons (5, 5a, ...) are arranged and / or configured such that their microwaves are injectable into the borehole (2) along a downward direction (D) and / or an upward direction (U) and / or a radial direction (R) of the borehole (2).

5. The drill head (1) according to any one of claims 2 to 4, wherein the gyrotrons (5, 5a, ...) are at least one of:- arranged in a pattern; or- arranged according to a horizontal arrangement with respect to a horizontal direction (Hd) of the drill head (1) and / or according to a vertical arrangement with respect to a vertical direction (Vd) of the drill head (1).F07426286. The drill head (1) according to any one of the preceding claims, further comprising at least one waveguide (17) being in connection with the gyrotron (5, 5a, ...) and extending out of the drill housing (4), the waveguide (17) being configured to be inserted into the borehole (2) and to guide the microwaves generated by the gyrotron (5, 5a, ...) into the borehole (2), and / or further comprising at least one mirror system (13) being configured and arranged to at least one of direct, focus, expand or transmit the microwaves into the borehole (2).

7. The drill head (1) according to any one of the preceding claims, wherein the gyrotron (5, 5a, ...) comprises a gyrotron housing (16), wherein the electron gun (6), the magnet (7), and the cavity (8) are at least partially arranged in the gyrotron housing (16), and / or wherein the gyrotron housing (16) is at least partially arranged in the drill housing (4).

8. The drill head (1) according to any one of the preceding claims, wherein the gyrotron (5, 5a, ...) further comprises at least one of:- a collector (11) configured to collect a spent electron beam, the collector preferably being a multi-stage depressed collector,- an output window (10) configured to output the generated microwaves from the gyrotron (5, 5a, ...), or- a launcher (12) configured to transform a transverse electric mode of the microwaves generated in the cavity (8) into a Gaussian mode.

9. The drill head (1) according to any one of the preceding claims, wherein the magnet(7) is a superconducting magnet or a permanent magnet, and / or further comprising at least one adjusting magnet configured to generate a magnetic field that adjusts a magnetic field generated by the magnet (7).

10. The drill head (1) according to any one of the preceding claims, further comprising at least one cooling device (14) and / or being in connection with at least one cooling device (14) that is configured to cool the drill head (1), in particular the drill housing (4), and / or to cool the gyrotron (5, 5a, ...), in particular at least one of the gyrotron housing (16), the cavity(8), the magnet (7) or the adjusting magnet.F074262911. The drill head (1) according to any one of the preceding claims, further comprising one or more power supply lines (9, 9a, ...) that connect the gyrotron (5, 5a, ...), in particular at least one of the magnet (7), the electron gun (6), the collector (11), or the adjusting magnet, to at least one power source (18), and wherein the power supply line (9, 9a, ...) preferably is a cryo-feedthrough, and / or wherein the power source (18) is preferably arranged on surface.

12. The drill head (1) according to any one of the preceding claims, wherein the drill head (1) and / or the gyrotron (5, 5a, ...), in particular the drill housing (4) and / or the gyrotron housing (16) and / or the cavity (8) and / or the magnet (7) and / or the adjusting magnet, are in connection with at least one vacuum pump that is configured to generate a vacuum within the drill head (1) and / or the gyrotron (5, 5a, ...).

13. A drilling arrangement (100) comprising at least one drill head (1) as claimed in any one of the preceding claims and at least one of:- at least one power source (18) configured to power the drill head (1) and / or the at least one gyrotron (5, 5a, ...), or- at least one cooling device configured to cool the drill head (1) and / or the at least one gyrotron (5, 5a, ...).

14. A method of manufacturing a drill head (1) for drilling a borehole (2) into a subsurface formation (3), preferably a drill head (1) as claimed in any one of claims 1 to 12, the method comprising the steps of:- Providing at least one drill housing (4) configured to be arranged sub-surface; and- Providing at least one gyrotron (5, 5a, ...), wherein the gyrotron (5, 5a, ...) comprises an electron gun (6) configured to produce an electron beam, at least one magnet (7) configured to produce a magnetic field, and a cavity (8) configured to receive the electron beam and to generate microwaves by a resonance coupling between the electron beam and the magnetic field produced by the magnet (7), wherein the microwaves are injectable into the sub-surface formation (3) for drilling the borehole (2), characterized in that the gyrotron (5, 5a, ...) is at least partially arranged in the drill housing (4), and wherein the microwaves are generatable sub-surface.

15. A method of drilling boreholes (2) into sub-surface formations (3) comprising:F0742630Providing at least one drill head (1) as claimed in any one of claims 1 to 12 and / or as manufactured in the method according to claim 14, andDrilling a borehole (2) by injecting the microwaves generated by the gyrotron (5, 5a, ...) into the sub-surface formation (3).

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