Millimeter-wave boring systems

Abstract

A system for boring a borehole through rock, comprising a gyrotron, a gas supply and gas line, a drill string and a bottom hole assembly (BHA) at the distal part of the drill string; with the distal part advanceable through the borehole. The drill string comprises a waveguide to conduct millimeter wave (MMW) electromagnetic energy from the gyrotron toward the distal part, and, at the distal part, project the MMW energy at the bore front to melt the rock there. The gas line conducts a gas from the gas supply distally along the drill string. The BHA comprises a nozzle, mounted to face the bore front, and a jet operator to drive pulses of the gas through the nozzle in a manner that propels the molten rock away from the bore front, so the molten rock splashes against a sidewall of the borehole and rehardens on the sidewall.

Description

MILLIMETER-WAVE BORING SYSTEMSFIELD OF THE INVENTION

[0001] Some implementations of the present disclosure relate in general to boring systems. More specifically, some implementations of the present disclosure relate to boring systems that utilize millimeter-wave electromagnetic energy to bore into subsurface formations such as rock.BACKGROUND

[0002] Boreholes for geothermal power are a crucial element in the exploitation of geothermal energy, which is a renewable and sustainable energy source. The process involves drilling boreholes into the Earth's crustto access the heat stored in rocks and fluids in the Earth's interior. Drilling boreholes for geothermal power involves advanced and specialized techniques. These boreholes can be several kilometers deep and must withstand high temperatures and pressures.

[0003] Boreholes are also used for extracting subterranean resources, such as oil and gas.

[0004] Boring techniques are also implemented in the formation of tunnels for various purposes such as transportation, water distribution, drainage, utility corridors, and other infrastructure or civil engineering projects.SUMMARY OF THE INVENTION

[0005] This summary is meant to provide some examples and is not intended to be limiting of the scope of the invention in any way. For example, any feature included in an example of this summary is not required by the claims, unless the claims explicitly recite the features. Also, the features, components, steps, concepts, etc. described in examples in this summary and elsewhere in this disclosure can be combined in a variety of ways. Various features and steps as described elsewhere in this disclosure may be included in the examples summarized here.

[0006] There is therefore provided, in accordance with some implementations, a system for boring a borehole through rock, the system including a gyrotron; a gas supply; and / or a drill string. The drill string may include a bottom hole assembly (BHA) at a distal part of the drill string, the distal part of the drill string being advanceable through the borehole. The drill string may include a waveguide thatis configured to (i) conduct electromagnetic energy millimeter wave (MMW) energy from the gyrotron toward the distal part of the drill string, and / or (ii) at the distal part of the drill string, project the MMW energy at a bore front of the borehole to melt rock at the bore front into molten rock. In some implementations, the drill string includes a gas line that is arranged to conduct a gas from the gas supply distally along the drill string. In some implementations, the BHA includes (i) a nozzle, mounted to face the bore front, and / or a jet operator, configured to drive pulses of the gas through the nozzle in a manner that propels the molten rock away from the bore front.

[0007] In some implementations, the waveguide is circular in transverse crosssection.

[0008] In some implementations, the waveguide is configured to project the MMW energy as a circular beam directed at the bore front.

[0009] In some implementations, the waveguide is oblong in transverse crosssection.

[0010] In some implementations, the waveguide is configured to project the MMW energy as an oblong beam directed at the bore front.

[0011] In some implementations, the waveguide is annular in transverse crosssection.

[0012] In some implementations, the waveguide is configured to project the MMW energy as an annular beam directed at the bore front.

[0013] In some implementations, the nozzle is a gas jet.

[0014] In some implementations, the nozzle is a convergent nozzle.

[0015] In some implementations, the nozzle is mounted laterally from the waveguide.

[0016] In some implementations, the nozzle is mounted to extend circumferentially at least partway around the waveguide.

[0017] In some implementations, the gas is air, and the gas supply is a supply of air.

[0018] In some implementations, the gas is a noble gas, and the gas supply is a supply of the noble gas.

[0019] In some implementations, the gas supply includes a humidity controller, configured to control a humidity of the gas.

[0020] In some implementations, the gas supply includes a pump.

[0021] In some implementations, the gas su ply includes a container of the gas in a compressed state.

[0022] In some implementations, the gas supply includes a compressor.

[0023] In some implementations, the waveguide and the BHA are configured to cooperate to core a core of the rock at the bore front.

[0024] In some implementations, the waveguide is configured to facilitate the coring of the core by projecting the MMW energy as an annular beam directed at the bore front.

[0025] In some implementations, the system further includes a towline, the system being configured to secure the towline to the core, and to extract the core proximally out of the borehole by pulling on the towline.

[0026] In some implementations, the towline is configured to fasten to the core, and the system is configured to extract the core proximally out of the borehole by using the towline to draw the core proximally through the waveguide.

[0027] In some implementations, the drill string is configured to extract the core from the borehole by drawing the core proximally through the waveguide.

[0028] In some implementations, the system further includes a controller that includes a data-processing system, the controller being configured to operate the gyrotron to generate the MMW energy.

[0029] In some implementations, the controller is configured to operate the gyrotron to generate the MMW energy continually.

[0030] In some implementations, the controller is configured to operate the gyrotron to generate the MMW energy periodically.

[0031] In some implementations, the controller is configured to operate the gyrotron at a duty cycle of 30-70 percent.

[0032] In some implementations, the controller is configured to operate the gyrotron at a duty cycle of 30-50 percent.

[0033] In some implementations, the controller is configured to operate the gyrotron at a duty cycle of 50-70 percent.

[0034] In some implementations, the controller is configured to operate the gyrotron to generate the MMW energy during and between the pulses of the gas driven through the nozzle.

[0035] In some implementations, the controller is configured to operate the gyrotron to generate the MMW energy according to a predetermined temporal pattern.

[0036] In some implementations, the controller is further configured to actuate the jet operator to drive the pulses of the gas through the nozzle.

[0037] In some implementations, the controller is configured to actuate the jet operator to drive the pulses of the gas according to a predetermined temporal pattern.

[0038] In some implementations, the controller is configured to coordinate the operation of the gyrotron with the actuation of the jet operator.

[0039] In some implementations, the controller is configured to alternate the operation of the gyrotron with the actuation of the jet operator.

[0040] In some implementations, the controller is configured to provide intermissions during which the gyrotron does not generate the MMW energy, and to actuate the jet operator to drive a pulse of the gas during each of the intermissions.

[0041] In some implementations, the BHA includes a nozzle array, the nozzle being one of multiple nozzles of the nozzle array, and the jet operator being configured to drive the pulses of the gas through the multiple nozzles of the nozzle array.

[0042] In some implementations, the jet operator is configured to drive each pulse of the gas through the multiple nozzles of the nozzle array simultaneously.

[0043] In some implementations, the jet operator is configured to drive each pulse of the gas through the multiple nozzles of the nozzle array in a temporal pattern.

[0044] In some implementations, the jet operator is configured to drive each pulse of the gas through the multiple nozzles of the nozzle array successively.

[0045] In some implementations, (i) at the distal part of the drill string the waveguide defines a waveguide axis along which the waveguide projects the MMW energy at the bore front, and / or (ii) the nozzle is mounted laterally from the waveguide axis.

[0046] In some implementations, the nozzle is oriented such thatthe pulses of the gas are directed obliquely toward the waveguide axis.

[0047] In some implementations, the nozzle is mounted to extend circumferentially at least partway around the waveguide axis.

[0048] In some implementations, the nozzle is mounted to extend between 50 and 310 degrees around the waveguide axis.

[0049] In some implementations, the nozzle is mounted to extend between 60 and 240 degrees around the waveguide axis.

[0050] In some implementations, the nozzle is mounted to extend between 90 and 200 degrees around the waveguide axis.

[0051] In some implementations, the nozzle is mounted to extend between 120 and 180 degrees around the waveguide axis.

[0052] In some implementations, (i) at the distal part of the drill string the waveguide has an aperture out of which the waveguide projects the MMW energy at the bore front, and / or (ii) the nozzle is mounted laterally from the aperture.

[0053] In some implementations, the nozzle is mounted to extend circumferentially at least partway around the aperture.

[0054] There is further provided, in accordance with some implementations, a system for boring a borehole through rock, the system including a drill string that includes a bottom hole assembly (BHA) at the distal part of the drill string, and / or a waveguide. In some implementations, the waveguide has an aperture at a distal part of the drill string, and / or is configured to conduct electromagnetic energy millimeter wave (MMW) energy distally along the drill string, and / or project the MMW energy out of the aperture and at a bore front of the borehole to melt the rock at the bore front into molten rock. In some implementations, the BHA includes a nozzle, mounted to face the bore front.

[0055] The BHA may include a jet operator, configured to drive pulses of a gas through the nozzle in a manner that propels the molten rock away from the bore front.

[0056] There is further provided, in accordance with some implementations, a bottom hole assembly (BHA) for a drill string that includes a waveguide that is configured to conduct electromagnetic energy millimeter wave (MMW) energy along the drill string and to project the MMW energy at a bore front of a borehole to melt rock at the bore front into molten rock.

[0057] The BHA may include include (i) a nozzle, mounted to face the bore front, and / or (ii) a jet operator, configured to drive pulses of a gas through the nozzle in a manner that propels the molten rock away from the bore front.

[0058] There is further provided, in accordance with some implementations, a system for boring a borehole through rock, the system including a drill string. The drill string may include a waveguide having an aperture, and may be configured tocore a core from a bore front of the borehole at least in part by projecting electromagnetic energy millimeter wave (MMW) energy out of the aperture and at the bore front of the borehole. The system may be configured to extract the core from the borehole.

[0059] In some implementations, the system further includes a towline that is configured to fasten to the core, the system being configured to extract the core from the borehole by using the towline to draw the core proximally through the borehole.

[0060] In some implementations, the system is configured to extract the core from the borehole by drawing the core proximally through the waveguide.

[0061] In some implementations, the aperture is annular.

[0062] In some implementations, the waveguide is annular in transverse crosssection.

[0063] In some implementations, the waveguide is configured to project the MMW energy as an annular beam directed at the bore front.

[0064] There is further provided, in accordance with some implementations, a method for boring a borehole through rock, the method including iteratively: (i) melting rock at a bore front of the borehole into molten rock by directing electromagnetic energy millimeter wave (MMW) energy at the bore front; and / or (ii) propelling the molten rock away from the bore front by driving a pulse of a gas at the molten rock.

[0065] In some implementations, propelling the molten rock away from the bore front includes splashing the molten rock against a sidewall of the borehole such that the molten rock rehardens on the sidewall.

[0066] There is further provided, in accordance with some implementations, a method for boring a borehole through rock, the method including iteratively: (i) coring a core from a bore front of the borehole by directing electromagnetic energy millimeter wave (MMW) energy at the bore front; and / or (ii) extracting the core from the borehole.

[0067] In some implementations, the step of coring the core includes coring the core from the bore front by directing an annular beam of the MMW energy at the bore front.

[0068] There is further provided, in accordance with some implementations, a system for boring a borehole through rock, the system including a gyrotron; a gas supply; and / or a drill string that has a distal part that is advanceable through the borehole. The drill string may include a waveguide, configured to (i) conductelectromagnetic energy millimeter wave (MMW) energy from the gyrotron toward the distal part of the drill string, and / or (ii) at the distal part of the drill string, project the MMW energy at a bore front of the borehole to melt rock at the bore front into molten rock.

[0069] The drill string may include a gas line, arranged to conduct a gas from the gas supply distally along the drill string. The BHA may include a nozzle, mounted to face the bore front.

[0070] I n some implementations, the BHA includes a jet operator, configured to drive a jet of the gas through the nozzle in a manner that propels the molten rock away from the bore front.

[0071] There is further provided, in accordance with some implementations, a system for boring a borehole through rock, the system including a drill string that includes a waveguide and / or a bottom hole assembly (BHA). In some implementations, the waveguide has an aperture at a distal part of the drill string, and / or is configured to (i) conduct electromagnetic energy millimeter wave (MMW) energy distally along the drill string, and / or (ii) project the MMW energy out of the aperture and at a bore front of the borehole to melt the rock at the bore front into molten rock. In some implementations, the BHA is disposed at the distal part of the drill string and may include a nozzle, mounted to face the bore front. The BHA may include a jet operator, configured to drive a jet of a gas through the nozzle in a manner that propels the molten rock away from the bore front.

[0072] There is further provided, in accordance with some implementations, a bottom hole assembly (BHA) for a drill string that includes a waveguide that is configured to conduct electromagnetic energy millimeter wave (MMW) energy along the drill string and to project the MMW energy at a bore front of a borehole to melt rock at the bore front into molten rock, the BHA including: (i) a nozzle, mounted to face the bore front, and / or (ii) a jet operator, configured to drive a jet of a gas through the nozzle in a manner that propels the molten rock away from the bore front.

[0073] There is further provided, in accordance with some implementations, a method for boring a borehole through rock, the method including iteratively: (i) melting rock at a bore front of the borehole into molten rock by directing electromagnetic energy millimeter wave (MMW) energy at the bore front; and / or (ii) propelling the molten rock away from the bore front by driving a jet of a gas at the molten rock.

[0074] The present invention will be more fully understood from the following detailed description of applications thereof, taken together with the drawings, in which:BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figs. 1 and 2A-D are schematic illustrations of a boring system for boring a borehole through rock, in accordance with some implementations;

[0076] Figs. 3A-H are schematic illustrations of bottom hole assemblies for a boring system, in accordance with some implementations;

[0077] Figs. 4-6 are schematic transverse cross-sectional illustrations of boring system waveguides, in accordance with some implementations; and

[0078] Fig. 7 is a schematic illustration of a waveguide of a drill string of a boring system, in accordance with some implementations.DETAILED DESCRIPTION OF EMBODIMENTS

[0079] The present disclosure includes different variants of some elements. Variants of a given element typically have the same structure and / or function as each other except for any differences described. For any given element for which different variants are disclosed, the identical name is used for each variant, in order to denote that they are, in fact, variants the same given element. Unless stated otherwise, applications of the devices, systems, and techniques described herein may include any arrangement in which one variant of an element is substituted with another identically-named variant of that element. Furthermore, throughout the figures, suffixes are used to denote different variants of the same element. Unless stated otherwise, such variants may be substituted with each other, mutatis mutandis. That is, unless stated otherwise, any element having a given reference numeral may be substituted with any other element (i.e. any other variant of the element) having the same reference numeral, independent of any suffix.

[0080] In orderto avoid undue clutter from havingtoo many reference numbers and lead lines on a particular drawing, some elements are introduced via one or more drawings and not explicitly identified in every other drawing that contains that element.

[0081] Although the present disclosure is provided primarily in the context of boreholes for geothermal power, it is to be understood that the technologies disclosed herein mayalso be applicable, mutatis mutandis, to boreholes for other purposes. For example, the technologies described herein may be used for boring of boreholes forthe extraction of subterranean resources such as oil or gas, and / or for forming tunnels - e.g. for transportation, water distribution, drainage, utilitycorridors, or other infrastructure or civil engineering projects. Similarly, although the present disclosure is provided in the context of vertical boreholes, it is to be understood that the technologies disclosed herein may also be applicable, mutatis mutandis, to horizontal and sloped boreholes.

[0082] Reference is made to Figs. 1 , and 2A-D, which are schematic illustrations of a boring system 100 for boring a borehole 10 through rock 5, in accordance with some implementations. It is to be noted that the term "rock" is used broadly herein (including in the specification and the claims) and, unless stated otherwise, is not intended to be restricted to a single rock or a particular type of rock. For example, "rock" may be understood to refer to subsurface formations in general.

[0083] Boring system 100 comprises a drill string 110 that comprises a bottom hole assembly (BHA) 200 at a distal part of the drill string. Fig. 1 is an overview of boring system 100 boring borehole 10, and Figs. 2A-D show BHA 200 at a bore front 12 of the borehole - e.g. at the site indicated by box 2 in Fig. 1. The BHA of conventional boring apparatus has a mechanical drill bit, and the drill string of conventional boring apparatus transmits torque to the mechanical drill bit in order to mechanically drill the rock at the bore front of the borehole. In contrast, drill string 110 comprises a waveguide 120 that conducts electromagnetic energy millimeter wave (MMW) energy (i.e. electromagnetic energy having a frequency of 30-300 GHz) from a gyrotron 50 toward the distal part of the drill string, and to project the MMW energy at the bore front 12 - e.g. by projecting the MMW energy distally out of an aperture 122 of the waveguide while the aperture is facing the bore front. In some implementations, this aspect of boring system 100 may be achieved using apparatus and / or techniques similar to those described in one or more of the following publications, each of which is incorporated by reference:US Patent 8,393,410 to Woskov et al.Inti. Patent Application Publication WO 2023 / 122371 to WoskovInti. Patent Application Publication WO 2023 / 122372 to Woskov

[0084] Furthermore, aspects of the generation and transmission of the MMW energy, and componentry therefor (e.g. above-surface components), may be achieved using apparatus and / or techniques similar to those described in one or more of the above-referenced publications. The above-referenced publications describe boring via vaporization of the rock at the bore front and flow-like evacuation of the vaporized rock out of the borehole. In contrast, and as detailed hereinbelow, boring system 100 bores via meltingof the rock at the bore front and propelling the molten rock away (i.e. dispelling the molten rock) from the bore front - e.g. splashing or spattering the molten rock against the sidewall 14 of theborehole, where the molten rock deposited on the sidewall rehardens. Boring system 100 may thereby advantageously require less MMW energy to be applied to the rock, and may not require such evacuation of material from the borehole. For example, the resolidified rock may have a higher density than the original rock, and therefore takes up less volume than the original rock, resulting in a borehole without evacuation of the rock material. This may occur, for example, when the original rock is of low density - e.g. is porous and / or contains many voids. Nonetheless, the technologies described herein may be advantageous even for implementations (e.g. rocks) in which the resolidified rock does not have a higher density than the original rock.

[0085] In some implementations, in orderto implement such propulsion of the molten rock away from the bore front, BHA200 comprises at least one nozzle 210, mounted to face bore front 12, such that a gas (or, optionally, another fluid) 64 driven through the nozzle is directed at the bore front. That is, drill string 110 (e.g. BHA 200 thereof) is configured such that, while aperture 122 is facing the bore front, nozzle 210 also faces the bore front. BHA 200 typically further comprises at least one jet operator 220 configured to drive a jet of the gas (or other fluid) th rough the nozzle (and, therefore, at the bore front) in a manner that propels (e.g. splashes or spatters) the molten rock away from bore front 12.

[0086] In some implementations, the jet is driven as one or more pulses - i.e. jet operator 220 is configured to drive one or more pulses of the gas (or other fluid) through the nozzle (and, therefore, at the bore front) in a mannerthat propels (e.g. splashes or spatters) the molten rock away from bore front 12. In such implementations, jet operator 220 may therefore be referred to as a pulse operator. In some such implementations, each pulse has a duration of greater than 0.05 s (e.g. greater than 0.1 s, such as greater than 0.5 s) and / or less than 5 s (e.g. less than 3 s, such as less than 1 s).

[0087] In other implementations, the jet is substantially continuous. Nonetheless, such a continuous jet is sufficiently forceful and directed to propel the molten rock and, therefore, is distinct from a stream of flushing gas that may be pumped into the borehole in orderto pressurize orflush / exhaust vaporized rock from the borehole.

[0088] Fig. 2A shows the distal part of drill string 110, including BHA 200, within borehole 10, such that aperture 122 and nozzle 210 are facing bore front 12.

[0089] Fig. 2B shows, while aperture 122 is facing bore front 12, MMW energy 52 beingtransmitted from gyrotron 50, guided alongwaveguide 120, and projected out of aperture 122 at bore front 12, thereby melting rock 5 at the bore front into molten rock 20. During this process, aperture 122 and / or nozzle 210 may be, forexample, greater than 1 cm (e.g. greater than 10 cm) and / or less than 2 m (e.g. less than 1 m) from bore front 12. At least at the distal part of the drill stri ng, waveguide 120 defines a waveguide axis ax1 along which the waveguide projects the MMW energy at the bore front. Axis ax1 may be a central longitudinal axis of waveguide 120 - e.g. passing through the respective centers of axially-sequential transverse cross-sections of the waveguide.

[0090] Fig. 2C shows a pulse of gas 64 being driven through nozzle 210 at molten rock 20, thereby propelling the molten rock away from bore front 12. In the example shown, molten rock 20 is propelled (e.g. splashed or spattered) against sidewall 14 of borehole 10, such that, when it rehardens into rehardened rock 22, it does so on the sidewall - e.g. lining and / or reinforcing the sidewall. The steps shown in Figs. 2B-C thereby advance bore front 12, elongating borehole 10. Fig. 2D shows drill string 110 being advanced further into borehole 10, such that aperture 122 and BHA 200 approach bore front 12 again, for another round of melting and propelling. Thus, Figs. 2A-D may be considered to represent steps that are performed iteratively by boring system 100 in order to progressively bore a borehole through rock.

[0091] In some implementations, the driving of the pulse of gas is both performed while BHA 200 remains in the same position from which the MMW energy was applied. In some implementations, BHA 200 is moved (e.g. distally) after MMW energy is applied and prior to driving of the pulse of gas.

[0092] Gas 64 may be provided to BHA 200 (e.g. to jet operator 220 and / or nozzle 210) via a gas line 62. Gas line 62 may be a component of drill string 110 — e.g. running alongside or within waveguide 120. Boring system 100 may comprise a gas supply 60 that supplies gas 64 via gas line 62. Gas supply 60 may comprise gas canisters, a pump, a compressor, a filter, and / or a humidity controller.

[0093] Boring system 100 may comprise a controller 70, configured to control (e.g. operate) gyrotron 50 to generate MMW energy 52. Such control is represented as a connection 72. Controller 70 may comprise at least one data-processing system (DPS), and may be networked and / or remotely connected to other data- processing systems.

[0094] Fig. 1 shows gyrotron 50, gas supply 60, and controller 70 situated above a surface 6 of rock 5. However, one or more of these components may be situated below the surface - e.g. within a subsurface chamber. As distinct from BHA 200, these components may be collectively referred to as a top hole assembly (THA) 40 of boring system 100.

[0095] In some implementations, controller 70 operates gyrotron 50 to generate and / or transmit the MMW energy continually. In some implementations,controller 70 operates gyrotron 50 to generate and / or transmit the MMW energy periodically and / or according to a predetermined temporal pattern (e.g. order and / or cadence). In some implementations, controller 70 operates gyrotron 50 at a duty cycle of 30-70 percent (e.g. 30-50 percent, or 50-70 percent).

[0096] In some implementations, controller 70 is configured to operate gyrotron 50 to generate the MMW energy during and between the pulses of the gas driven through the nozzle. In some implementations, controller 70 is configured to operate gyrotron 50 to generate the MMW energy only between the pulses of the gas driven through the nozzle - e.g. responsively to a signal from BHA 200 that is indicative of pulse timing.

[0097] Controller 70 may also be configured to control (e.g. actuate) jet operator 220 to drive the pulses of gas 64 through nozzle 210. Such control is represented by a connection 74. (Alternatively, boring system 100 may comprise a dedicated pulse controller that controls (e.g. actuates) jet operator 220.)

[0098] In some implementations, controller 70 is configured to actuate the jet operator to drive the pulses of the gas according to a predetermined temporal pattern. In some implementations, controller 70 is configured to coordinate the operation of gyrotron 50 with the actuation of jet operator 220. For example, controller 70 may alternate the operation of gyrotron 50 with the actuation of jet operator 220. Similarly, controller 70 may provide intermissions during which gyrotron 50 does not generate the MMW energy, and may actuate jet operator 220 to drive a pulse of gas 64 during each intermission.

[0099] In some implementations, BHA 200 comprises a sensor 222 that senses a state of bore front 12. For such applications, jet operator 220 may operate nozzle 210 at least in part responsively to the state sensed by sensor 222. For example, jet operator 220 may drive a pulse of gas responsively to sensor 222 sensing that the rock at bore front 12 is molten (or that a threshold quantity of molten rock 20 exists at the bore front). Alternatively or additionally, BHA 200 may feed back the sensed state to controller 70 (e.g. via connection 72) - e.g. in order to pause generation and / or transmission of the MMW energy, such as for / during a pulse of the gas.

[0100] Alternatively or additionally to BHA 200, THA 40 may sense the state of bore front 12. For example, THA 40 may sense (e.g. via electromagnetic changes and / or feedback) that a plasma has formed at bore front 12. For example, the plasma may create or change a backward wave that can be sensed by THA 40. Responsively, generation and / or transmission of the MMW energy may be paused -e.g. fora pulse of the gas to be driven, or merely to allow the plasma to dissipate.

[0101] In some implementations, nozzle 210 is a gas jet. In some implementations, nozzle 210 is a liquid (e.g. water) jet. In some implementations, nozzle 210 is a convergent nozzle. In some implementations, nozzle 210 is a divergent nozzle. In some implementations, nozzle 210 is a convergent-divergent nozzle (e.g. a de Laval nozzle).

[0102] As described hereinabove, molten rock 20 may be propelled (e.g. splashed or spattered) against sidewall 14 of borehole 10 such that, when it rehardens into rehardened rock 22, it does so on the sidewall - e.g. lining and / or reinforcing the sidewall. However, the scope of the present disclosure includes other effects on, and / or outcomes for the propelled molten rock. For example, in some implementations, the propulsion of molten rock 20 may form the molten rock into droplets that rapidly cool and reharden into solid particulate matter (e.g. granules, dust, an aerosol, or similar) which does not adhere to the sidewall. This particulate matter can be removed from the borehole using a flushing gas or conveyor system.

[0103] In some implementations, gas 64 is air. In some implementations, gas 64 is a noble gas in order to avoid changes to the chemistry and / or properties of molten rock 20.

[0104] In some implementations, gas 64 is reactive with molten rock 20, in order to induce changes in the chemistry and / or properties of molten rock 20. In some such implementations, gas 64 is selected to enhance the formation of molten rock 20 into an effective lining of the borehole. In other such implementations, gas 64 is selected to enhance the formation of molten rock into solid particulate matter that can be removed from the borehole.

[0105] Reference is now made to Figs. 3A-H, which are schematic illustrations of variants of BHA 200, each of which has a respective variant of nozzle(s) 210, in accordance with some implementations. For simplicity, these figures do not show jet operator 220.

[0106] Fig. 3A shows a BHA 200a (i.e. a variant of BHA 200), which has a single nozzle 210a (i.e. a variant of nozzle 210), mounted laterally from axis ax1. For example, and as shown, nozzle 210a may be mounted laterally from waveguide 120 - e.g. laterally from the lumen 121 of the waveguide. In some implementations, and as shown, nozzle 210a is angled to point obliquely toward axis ax1 . In some such implementations, this angle is such that the nozzle directs the pulses of gas obliquely toward the center of molten rock 20 - e.g. in order to propel the molten rock evenly a round sidewall 14. In some such implementations, this angle is such that the nozzle directs the pulses of gas to propel the molten rock substantially toward the opposite side of borehole 10 from the nozzle - e.g.such that resolidified rock 22 becomes deposited disproportionately on one side of the borehole.

[0107] In some implementations, the nozzle may be configured to propel the molten rock such that resolidified rock 22 becomes deposited in a collection chamber (e.g. of a conveyor system) that extracts the resolidified rock from the borehole.

[0108] Nozzle 210a may be fed by a feed line 212a, which itself may be in fluid communication with jet operator 220 - e.g. the jet operator drives the pulses of gas via the feed line to the nozzle. Figs. 2A-D omit such a feed line - e.g. schematically showing jet operator 220 connected directly to nozzle 210. Both types of fluid connection (direct connection and connection via feed line) are feasible for each BHA described herein. As shown, feed line 212a may run alongside waveguide 120 - e.g. may be parallel with axis ax1 .

[0109] Fig. 3B shows a BHA 200b, whose nozzle 210b is annular and circumscribes waveguide 120. For example, and as shown, nozzle 210b may circumscribe aperture 122. In some implementations, and as shown, nozzle 210b is angled to point obliquely toward axis ax1 . In some such implementations, this angle is such that the nozzle directs the pulses of gas toward the center of molten rock 20 - e.g. in orderto propel the molten rock evenly around sidewall 14.

[0110] Nozzle 210b may be fed by a feed line 212b. As shown, feed line 212b may be annular and / or may run coaxially with waveguide 120 - e.g. may be coaxial with axis ax1 .

[0111] Fig. 3C shows a BHA 200c, whose nozzle 210c is annular and circumscribes waveguide 120. For example, and as shown, nozzle 210c may circumscribe aperture 122. Thus, nozzle 210c may be similar to nozzle 210b, except that nozzle 210c is flared (e.g. may be a divergent nozzle or a convergent- divergent nozzle). In some implementations, and as shown, nozzle 210c is flared toward axis ax1 (e.g. medially). In some such implementations, this angle is such that the nozzle directs the pulses of gas toward the center of molten rock 20 - e.g. in order to propel the molten rock evenly around sidewall 14.

[0112] Nozzle 210c may be fed by a feed line 212c. As shown, feed line 212c may be annular and / or may run coaxially with waveguide 120 - e.g. may be coaxial with axis ax1 .

[0113] Fig. 3D shows a BHA 200d, whose nozzle 210d is arc-shaped, and partially circumscribes axis ax1 (e.g. partially circumscribes waveguide 120). For example, and as shown, nozzle 210d may partially circumscribe aperture 122. Nozzle 21 Od may be flared (e.g. may be a diverging nozzle). Thus, nozzle 21 Od maybe similar to nozzle 210c, except that nozzle 21 Od only partially circumscribes waveguide 120. Nozzle 21 Od may be configured to direct the pulses of gas to propel the molten rock substantially toward the opposite side of borehole 10 from the nozzle - e.g. such that resolidified rock 22 becomes deposited disproportionately on one side of the borehole.

[0114] In the example shown, nozzle 210d extends halfway (i.e. 180 degrees) around axis ax1 (e.g. around waveguide 120). However, it is to be understood that the nozzle may extend less or more around axis ax1 (e.g. around waveguide 120) - e.g. 50-310 degrees, e.g. 60-240 degrees, e.g. 90-200 degrees, such as 120-180 degrees around the axis (e.g. around the waveguide).

[0115] For some implementations, nozzle 210d is flared toward axis ax1. For some implementations, and as shown, nozzle 21 Od is flared both medially and laterally - e.g. not specifically toward axis ax1 .

[0116] Nozzle 210d may be fed by a feed line 212d. In some implementations, feed line 212d is partially annular (i.e. has an arc-shaped cross section), such as semi-annular. Feel line 212d may run alongside and / or coaxially with waveguide 120 - e.g. may be coaxial with axis ax1 .

[0117] Fig. 3E shows a BHA 200e, whose nozzle 21 Oe is similar to nozzle 210b and / or nozzle 210c, except that it is fed by multiple feed lines 212e that are distributed circumferentially around axis ax1 (e.g. circumferentially around waveguide 120). Thus, at their distal ends, feed lines 212e may merge into nozzle 210c. In some implementations, and as shown, this merging may be such that the feed lines contribute to the shape of nozzle 21 Oe - e.g. such that the nozzle is wider at the circumferential positions of the feed lines, and narrower between such circumferential positions. BHA 200e may have 2-20 sub-nozzles 212, e.g. 3- 16 sub-nozzles, such as 3-9 sub-nozzles (e.g. 3, 4, 6, 8, or 9 sub-nozzles) or 6-15 sub-nozzles (e.g. 12 subnozzles). As shown, each feed line 212e may run alongside waveguide 120 - e.g. may be parallel with axis ax1 and / or with the other feed lines.

[0118] In some implementations, nozzle 210e is flared (e.g. may be a divergent nozzle or a convergent-divergent nozzle). In some such implementations, and as shown, nozzle 21 Oe is flared toward axis ax1 .

[0119] Fig. 3F shows a BHA 200f, which has a nozzle 21 Of that is annular and similar to nozzle 210b exceptthatitis set back from aperture 122 - i.e. the aperture is distal from the nozzle.

[0120] Whereas nozzles 21 Oa-e are shown as beingsubstantiallyaxiallyaligned with aperture 122, it is to be understood that any of the nozzles described hereinmay be modified to be set back similarly to nozzle 21 Of. Furthermore, any of the nozzles described herein may alternatively be set forward - meaning that they are distal to the aperture of their corresponding waveguide.

[0121] BHA 200f may comprise (i) a first tube 214f that (or whose inner surface) serves as waveguide 120, and (ii) a second tube 216f that is disposed coaxially over the first tube, such that a space between the two tubes serves as feed line 212f, and the distal end of the space serves as nozzle 21 Of. In some implementations, tube 214f and / or tube 216f have beveled distal ends. In the example shown, both tubes have beveled distal ends. In the example shown, the bevel of tube 214f is shown as beginning at or distal to nozzle 21 Of. However, in some implementations, the bevel of tube 214f begins further proximally, such that it partly defines nozzle 21 Of and shapes the nozzle to flare toward axis ax1 . It is to be understood that any of the annular nozzles and / orfeed lines described herein may be similarly defined by coaxial tubes, mutatis mutandis.

[0122] Figs. 3G-H show BHAs 200g and 200h, each of which has multiple nozzles - i.e. a nozzle array. In the examples shown, BHA 200g has eight nozzles, and BHA 200h has three. However, it is to be understood that such nozzle arrays may have many different numbers of nozzles. Purely for example, they may have 2-20 nozzles, e.g. 3-16 nozzles, such as 3-9 nozzles (e.g. 3, 4, 6, 8, or 9 nozzles) or 6-15 nozzles (e.g. 12 nozzles). Each nozzle may have its own feed line (not shown) that may run alongside waveguide 120 - e.g. may be parallel with axis ax1 and / or with the otherfeed lines.

[0123] In the examples shown, the nozzles of each array are distributed uniformly around axis ax1 - e.g. around waveguide 120, and at a uniform distance from aperture 122 (e.g. from its rim) and from axis ax1 . However, the scope of the present disclosure includes variants in which the nozzles of the array are distributed unevenly around axis ax1 (e.g. are arranged in clusters). Similarly, the scope of the present disclosure includes variants in which some nozzles of the array are further than others from the aperture (e.g. from its rim) - e.g. arranged in multiple rings or rows around the aperture.

[0124] For BHAs that comprise a nozzle array, the BHA may comprise a single jet operator that operates all of the nozzles, or multiple jet operators that each operates a corresponding one or more of the nozzles. In some implementations, the one or more BHAs are configured to drive each pulse of the gas through the multiple nozzles of the array simultaneously. In some implementations, the one or more BHAs are configured to drive each pulse of the gas through the multiple nozzles of the array differentially - e.g. successively and / or in a temporal pattern (i.e. with the pulse exiting some nozzles before others), such as in a sweeping pattern from one side of the BHA to the other, or in a swirling pattern around axisax1. This may be achieved by differential timing of the jet operators, or by differential configuration of the feed lines.

[0125] In some implementations, the BHA is configured such that the force of each pulse is uniform through each nozzle of the array. In some implementations, the BHA is configured such that the force of each pulse is greater through some nozzles of the array than through other nozzles of the array.

[0126] Reference is now made to Figs. 4-6, which are schematic transverse cross-sectional illustrations of boring system waveguides within the distal region of their boreholes, in accordance with some implementations. Each of these waveguides may be considered to be a variant of waveguide 120, described hereinabove. Similarly, any of the BHAs described hereinabove may be modified for use with, and / or to accommodate, any of these waveguides. For simplicity, no BHA is shown in Figs. 4-6.

[0127] Foreach example described with reference to Figs. 4-6 (and with respect to Fig. 7), the cross-sectional shape represents that of at least the distal aperture of the waveguide. Forexample, in some implementations thewaveguide may have the described cross-sectional shape only at (or close to) the BHA. For example, the waveguide may have, along most of its length, a shape and / or other characteristics that are optimized for conducting (i.e. transmitting) MMW energy over long distances (e.g. may have a circular cross-sectional shape). That is, the waveguide may have a transmission segment that extends from the gyrotron toward the BHA (and which may account for most of the length of the waveguide), and a beam-shaping segment at the BHA. For such implementations, drill string (e.g. thewaveguide) may comprise an adapter (e.g. comprising a mode converter) between the transmission segment and the beam-shaping segment. Such an approach may be particularly important for reducing transmission loss in implementations in which the waveguide is kilometers long. Alternatively, the waveguide may have the described cross-sectional shape along most, or all, of its length.

[0128] Fig. 4 shows a waveguide 120a, which has a circular transverse crosssection, as does its lumen 121a. That is, waveguide 120a comprises a wall 124a that (or whose inner surface) is circular in transverse cross-section, and that (or whose inner surface) defines lumen 121a as circular. Waveguide 120a may project the MMWenergy as a circular beam. Consequently, the borehole 10a that it bores may be substantially circular in transverse cross-section (herein a "circular borehole").

[0129] Figs. 5-6 show waveguides 120b and 120c, each of which has an oblong transverse cross-section, as do their respective lumens 121 b and 121 c.Waveguide 120b and lumen 121 b are noncircular elliptical in transverse crosssection. That is, waveguide 120b comprises a wall 124b that (or whose inner surface) is noncircular elliptical in transverse cross-section, and that (or whose inner surface) defines lumen 121 b as noncircular elliptical. Waveguide 120b may project the MMW energy as a noncircular elliptical beam. Waveguide 120c and lumen 121 c are rectangular in transverse cross-section. That is, waveguide 120c comprises a wall 124c that (or whose inner surface) is rectangular in transverse cross-section, and that (or whose inner surface) defines lumen 121c as rectangular. Waveguide 120c may project the MMW energy as a rectangular beam. Consequently, the boreholes 10b and 10c that are bored by boring systems that comprise these waveguides are substantially oblong (e.g. noncircular elliptical or rectangular) in transverse cross-section (herein "oblong boreholes"). This may, in some implementations, confer advantages over a boring system that utilizes a circular waveguide and that bores a circular borehole.

[0130] One such advantage, which is particular to boring system 100 (and variants thereof) stems from the surface area of the sidewall of a borehole relative to the volume of the borehole (herein "relative surface area") being greater for an oblong borehole compared with a circular borehole. In the transverse crosssections of Figs. 4-6, this corresponds to the perimeter of the sidewall relative to the cross-sectional area of the borehole being greater for an oblong borehole compared with a circular borehole. For example, if elliptical borehole 120b were to have the same cross-sectional area as circular borehole 120a, but having a major diameter 2.5 times its minor diameter, the circumference of its sidewall 14b would be more than 10 percent greater than that of sidewall 14a. This effect increases with increased eccentricity. As described hereinabove, boring system 100 bores by propelling molten rock away from the bore front - e.g. such that it resolidifies on the sidewall of the borehole. Due to its increased relative surface area, the sidewall of an oblong borehole has a higher relative capacity for the resolidified rock. That is, for a given borehole volume (or cross-sectional area) through a given type of rock, the layer of rehardened rock deposited on the sidewall can be thinner for an oblong borehole than for a circular borehole. This advantage may be amplified when boringthrough a rockof low density (e.g. that is porous and / or contains many voids) - e.g. due to the resulting resolidified rock deposited on the sidewall beingdenser, as described hereinabove.

[0131] Another such advantage may be particularto implementations in which the borehole is for a geothermal power station: The above-described larger relative surface area of an oblong borehole may provide for greater heat transfer from the rock (or other subsurface structure) to the working fluid (e.g. water).

[0132] Furthermore, for implementations in which multiple pipes are to be placed alongside each otherthrough the borehole, an oblongshape may facilitate more efficient use of the borehole cross-section. For example, for implementations in which two pipes are to be placed side by side (e.g. an input pipe and an output pipe of a geothermal power station), the pipes may be placed side by side on the long axis of the oblong cross-section, allowing both pipes to be more than half as wide as the short axis of the oblong cross-section.

[0133] It is to be understood that, also included within the scope of the present disclosure, a re waveguide variants havingotheroblongtransverse cross-sectional shapes such as, but not limited to, oval, stadium, and teardrop shaped.

[0134] Reference is now made to Fig. 7, which is a schematic illustration of a waveguide 120d of a drill string 110d of a boring system, in accordance with some implementations. The series of phases i-iv illustrate the function of a boring system that utilizes drill string 110d, and the insets are transverse cross-sectional illustrations of waveguide 120d within the distal region of a borehole 10d (e.g. comparable to Figs. 4-6).

[0135] In transverse cross-section, waveguide 120d is annular, having an annular lumen 121 d. That is, waveguide 120d comprises (ii) a wall 124d (i.e. an outer wall) that (or whose inner surface) is circular in transverse cross-section, and (ii) an inner wall 126d that (or whose outer surface) is circular in transverse cross-section and that is coaxial with wall 124d, such that lumen 121 d is disposed coaxially between these walls. Inner wall 126d circumscribes an inner region 128 that, although surrounded by lumen 121 d, is in fact external to the waveguide -i.e. is outside of lumen of the waveguide. Waveguide 120d may project the MMW energy as an annular beam.

[0136] A boring system that utilizes waveguide 120d comprises a complementary BHA that cooperates (e.g. whose nozzle(s) cooperate) with the waveguide to melt an annular bore front into rock 5, coring a core 6 of the rock (phase ii). Thus, for such a drill string, the molten rock is propelled and deposited against both the sidewall 14d (e.g. similarly to as described hereinabove), as well as against core 6 - e.g. against a temporary medial wall 16d of the borehole. In some implementations, and as shown, during this phase the drill string (e.g. its BHA) may be advanced over core 6 -e.g. such that the core enters the inner region of waveguide 120d. In other implementations, the drill string remains proximal from core 6 at this stage.

[0137] Core 6 is then extracted from the borehole (phases iii-iv). Thus, the distal region of borehole 10d, which was temporarily annular (inset of phase ii), becomes circular (inset of phase iv).

[0138] In some implementations, a towline 130 is used to draw the core proximally through and out of the borehole. In some implementations, and as shown, towline 130 is secured to core 6 after the core has been cored. Alternatively, towline 130 may be secured to the rock (e.g. to the bore front) prior to coring - e.g. the drill string advances the annular bore front distally such that the part of the rock to which the towline is secured becomes core 6.

[0139] Towline 130 may be secured tothe core / rock (e.g. the towline mayfasten to the core / rock) via drilling (e.g. as represented in the figures), grasping, hooking, and / or any other suitable means.

[0140] In some implementations, and as shown, core 6 is extracted via drill string 110d - e.g. by drawing the core proximally through inner region 128 of waveguide 120d. In some such implementations, such drawing of the core is performed using towline 130 - in which case the towline may be, or may be considered to be, a component of drill string 110d.

[0141] In some implementations, the drill string (or a part thereof, such as the waveguide) is removed from the bore hole prior to extraction of the core.

[0142] Phases i-vare repeated iteratively in order to advance the bore front and extend bore hole 10d into the rock.

[0143] It is to be understood that the annular shape of waveguide 120d is only an example of a waveguide for a coring drill string, and that the scope of the present disclosure includes drill strings that have other outline shapes, and / or that project MMW energy in other outline shapes, in a manner that cores rock to form cores that can be mechanically extracted. For example, such a drill string may be configured to core the rock to form oblong cores that can be mechanically extracted.

[0144] Such an approach, by which a borehole is formed by iteratively (i) coring using MMW energy and (ii) mechanically removing the resulting core, may advantageously require less energy than a comparable approach in which all of the rock that is moved to form from the borehole is modified (e.g. melted) using MMW energy. Thus, the scope of the present disclosure also includes boring systems and techniques that form boreholes using variants of this iterative boring approach in which the MMW-effected coring is achieved using MMW-based vaporization of rock - i.e. in which the vaporized rock is extracted from the borehole using a stream of gas. Therefore, the scope of the present disclosure includes versions of the systems and techniques described in one or more of the following references, modified to use their MMW energy to core the rock into mechanically-extractable cores:US Patent 8,393,410 to Woskov et al.US Patent 11 ,028,648 to Araque et al.Inti. Patent Application Publication WO 2023 / 122371 to WoskovInti. Patent Application Publication WO 2023 / 122372 to WoskovInti. Patent Application Publication WO 2023283167A1 to Phan et al.

[0145] In the example shown, the thickness d1 of the annular bore front (e.g. the distance between sidewall 14d and temporary medial wall 16d, and / or the difference between the total diameter d3 of the bore front and the core diameter d2 of core 6) is approximately half of the core diameter d2 of core 6, and thereby approximately one quarter of the total diameter d3 of the bore front (and the eventual borehole 10d). However, it is to be understood that this is merely for illustrative purposes. However, it is to be noted that d1 may be even smaller relative to d2. For example, thickness d1 may be less than 10 percent, e.g. less than 1 percent, e.g. less than 0.1 percent, such as less than 0.01 percent of core diameter d2. Such reduction in thickness d1 relative to core diameter d2 may further increase the efficiency of the technique described with reference to Fig. 7. This approach may be particularly suited to wide-bore boring such as, but not limited to, that used in the formation of transport tunnels. For example, a tunnel having a diameter d3 of several (e.g. greater than 3 (e.g. greater than 5) and / or less than 20) meters may be bored using an annular waveguide that produces an annular bore front that has a thickness d1 of only a few (e.g. less than 10 and / or more than 0.5) centimeters.

[0146] Reference is again made to Figs. 1-7. Connection 74 is described as a means of communication between the THA and the BHA. Connection 74 may comprise a discrete electronic connection (e.g. a wire) that extends along the drill string - e.g. within a dedicated side-lumen. Alternatively, connection 74 may be provided by conductivity of the drill string itself - e.g. electronic signals may be transmitted (e.g. conducted) along the wall of the waveguide, along an outer wall of the drill string that surrounds the waveguide, and / or along any other metallic component that extends along the drill string. In some implementations, connection 74 is an electromagnetic connection. For example, electromagnetic signals between the THA and the BHA may be transmitted through the waveguide itself. For example, the signals may be modulated onto the MMW energy.

[0147] Reference is again made to Figs. 1-7. Although gas is used as the primary example of the fluid driven through the nozzle of the BHA in order to propel molten rock away from the bore front, it is to be understood that, for someimplementations, the fluid may be a liquid, or may be a gas that contains droplets of a fluid.

[0148] Reference is again made to Figs. 1-7. The scope of the present disclosure includes boring systems. However, any of the drill strings disclosed herein may be provided independently - e.g. for use in a boring system. Furthermore, any of the waveguides or BHAs disclosed herein may be provided independently - e.g. for use in a boring system (e.g. as part of a drill string).

[0149] The described systems, apparatuses, devices, methods, etc. should not be construed as limiting in any way. Instead, the present disclosure is directed toward all novel and nonobvious features and aspects of the various disclosed implementations and applications, alone and in various combinations and subcombinations with one another. The disclosed systems, apparatuses, devices, methods, etc. are not limited to any specific aspect, feature, or combination thereof, nor do the disclosed systems, apparatuses, devices, methods, etc. require that any one or more specific advantages be present or problems be solved.

[0150] In the present disclosure, the term data-processing system may referto, be part of, or include an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor (shared, dedicated, group) that executes code; memory (shared, dedicated, or group) that stores code executed by a processor; other suitable hardware components, such as optical, magnetic, or solid state drives, that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip. The term code, as used above, may include software, firmware, and / or microcode, and may refer to programs, routines, algorithms, functions, classes, and / or objects. The term shared processor encompasses a single processor that executes some or all code from multiple modules. The term group processor encompasses a processor that, in combination with additional circuitry (e.g. processors), executes some or all code from one or more modules. The term shared memory encompasses a single memory that stores some or all code from multiple modules. The term group memory encompasses a memory that, in combination with additional memories, stores some or all code from one or more modules. The term memory may be subset of the term computer-readable medium. The term computer-readable medium does not encompass transitory electrical and electromagnetic signals propagating through a medium, and may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory tangible computerreadable medium include nonvolatile memory, volatile memory, magnetic storage, and optical storage.

[0151] Example Implementations (some non-limiting examples of the concepts herein are recited below):

[0152] Example 1. A system for boring a borehole through rock, the system comprising: a gyrotron; a gas supply; and / or a drill string, having a distal part that is advanceable through the borehole, the drill string comprising: a waveguide, configured to: conduct electromagnetic energy millimeter wave (MMW) energy from the gyrotron toward the distal part of the drill string, and / or at the distal part of the drill string, project the MMW energy at a bore front of the borehole to melt rock at the bore front into molten rock; a gas line, arranged to conduct a gas from the gas supply distally along the drill string; and / or a bottom hole assembly (BHA) at the distal part of the drill string, the BHA comprising: a nozzle, mounted to face the bore front, and / or a jet operator, configured to drive pulses of the gas through the nozzle in a manner that propels the molten rock away from the bore front.

[0153] Example 2. The system according to example 1 , wherein the waveguide is circular in transverse cross-section.

[0154] Example 3. The system according to example 1 , wherein the waveguide is configured to project the MMW energy as a circular beam directed at the bore front.

[0155] Example 4. The system according to example 1 , wherein the waveguide is oblong in transverse cross-section.

[0156] Example 5. The system according to example 1 , wherein the waveguide is configured to project the MMW energy as an oblong beam directed at the bore front.

[0157] Example 6. The system according to example 1 , wherein the waveguide is annular in transverse cross-section.

[0158] Example 7. The system according to example 1 , wherein the waveguide is configured to project the MMW energy as an annular beam directed at the bore front.

[0159] Example 8. The system according to any one of examples 1-7, wherein the nozzle is a gas jet.

[0160] Example 9. The system according to any one of examples 1-7, wherein the nozzle is a convergent nozzle.

[0161] Example 10. The system accordingto anyone of examples 1-9, wherein the nozzle is mounted laterally from the waveguide.

[0162] Example 11 . The system accordingto anyone of examples 1-10, wherein the nozzle is mounted to extend circumferentially at least partway around the waveguide.

[0163] Example 12. The system accordingto anyone of examples 1-11 , wherein the gas is air, and the gas supply is a supply of air.

[0164] Example 13. The system accordingto anyone of examples 1-11 , wherein the gas is a noble gas, and the gas supply is a supply of the noble gas.

[0165] Example 14. The system accordingto anyone of examples 1-13, wherein the gas supply comprises a humidity controller, configured to control a humidity of the gas.

[0166] Example 15. The system accordingto anyone of examples 1-14, wherein the gas supply comprises a pump.

[0167] Example 16. The system accordingto anyone of examples 1-15, wherein the gas supply comprises a container of the gas in a compressed state.

[0168] Example 17. The system accordingto anyone of examples 1-16, wherein the gas supply comprises a compressor.

[0169] Example 18. The system accordingto anyone of examples 1-17, wherein the waveguide and the BHA are configured to cooperate to core a core of the rock at the bore front.

[0170] Example 19. The system according to example 18, wherein the waveguide is configured to facilitate the coring of the core by projecting the MMW energy as an annular beam directed at the bore front.

[0171] Example 20. The system according to example 18, further comprising a towline, the system being configured to secure the towline to the core, and to extract the core proximally out of the borehole by pulling on the towline.

[0172] Example 21 . The system according to example 20, wherein the towline is configured to fasten to the core, and the system is configured to extract the core proximally out of the borehole by using the towline to draw the core proximally through the waveguide.

[0173] Example 22. The system according to example 18, wherein the drill string is configured to extract the core from the borehole by drawing the core proximally through the waveguide.

[0174] Example 23. The system accordingto any one of examples 1-22, further comprising a controller that comprises a data-processing system, the controller being configured to operate the gyrotron to generate the MMW energy.

[0175] Example 24. The system accordingto example 23, wherein the controller is configured to operate the gyrotron to generate the MMW energy continually.

[0176] Example 25. The system accordingto example 23, wherein the controller is configured to operate the gyrotron to generate the MMW energy periodically.

[0177] Example 26. The system accordingto example 23, wherein the controller is configured to operate the gyrotron at a duty cycle of 30-70 percent.

[0178] Example 27. The system accordingto example 23, wherein the controller is configured to operate the gyrotron at a duty cycle of 30-50 percent.

[0179] Example 28. The system accordingto example 23, wherein the controller is configured to operate the gyrotron at a duty cycle of 50-70 percent.

[0180] Example 29. The system accordingto example 23, wherein the controller is configured to operate the gyrotron to generate the MMW energy during and between the pulses of the gas driven through the nozzle.

[0181] Example 30. The system accordingto example 23, wherein the controller is configured to operate the gyrotron to generate the MMW energy according to a predetermined temporal pattern.

[0182] Example 31 . The system accordingto example 23, wherein the controller is further configured to actuate the jet operator to drive the pulses of the gas through the nozzle.

[0183] Example 32. The system accordingto example 31 , wherein the controller is configured to actuate the jet operator to drive the pulses of the gas accordingto a predetermined temporal pattern.

[0184] Example 33. The system accordingto example 31 , wherein the controller is configured to coordinate the operation of the gyrotron with the actuation of the jet operator.

[0185] Example 34. The system accordingto example 33, wherein the controller is configured to alternate the operation of the gyrotron with the actuation of the jet operator.

[0186] Example 35. The system accordingto example 33, wherein the controller is configured to provide intermissions duringwhich the gyrotron does not generate the MMW energy, and to actuate the jet operator to drive a pulse of the gas during each of the intermissions.

[0187] Example 36. The system accordingto any one of examples 1-35, wherein the BHA comprises a nozzle array, the nozzle being one of multiple nozzles of the nozzle array, and the jet operator being configured to drive the pulses of the gas through the multiple nozzles of the nozzle array.

[0188] Example 37. The system according to example 36, wherein the jet operator is configured to drive each pulse of the gas through the multiple nozzles of the nozzle array simultaneously.

[0189] Example 38. The system according to example 36, wherein the jet operator is configured to drive each pulse of the gas through the multiple nozzles of the nozzle array in a temporal pattern.

[0190] Example 39. The system according to example 36, wherein the jet operator is configured to drive each pulse of the gas through the multiple nozzles of the nozzle array successively.

[0191] Example 40. The system according to any one of examples 1-39, wherein: at the distal part of the drill string the waveguide defines a waveguide axis along which the waveguide projects the MMW energy at the bore front, and / or the nozzle is mounted laterally from the waveguide axis.

[0192] Example 41 . The system accordingto example 40, wherein the nozzle is oriented such that the pulses of the gas are directed obliquely toward the waveguide axis.

[0193] Example 42. The system accordingto example 40, wherein the nozzle is mounted to extend circumferentially at least partway around the waveguide axis.

[0194] Example 43. The system accordingto example 42, wherein the nozzle is mounted to extend between 50 and 310 degrees around the waveguide axis.

[0195] Example 44. The system according to example 43, wherein the nozzle is mounted to extend between 60 and 240 degrees around the waveguide axis.

[0196] Example 45. The system according to example 44, wherein the nozzle is mounted to extend between 90 and 200 degrees around the waveguide axis.

[0197] Example 46. The system according to example 45, wherein the nozzle is mounted to extend between 120 and 180 degrees around the waveguide axis.

[0198] Example 47. The system according to any one of examples 1-46, wherein: at the distal part of the drill string the waveguide has an aperture out of which the waveguide projects the MMW energy at the bore front, and / or the nozzle is mounted laterallyfrom the aperture.

[0199] Example 48. The system according to example 47, wherein the nozzle is mounted to extend circumferentially at least partway around the aperture.

[0200] Example 49. A system for boring a borehole through rock, the system comprising a drill string that comprises: a waveguide, having an aperture at a distal part of the drill string, and configured to: conduct electromagnetic energy millimeter wave (MMW) energy distally along the drill string, and / or project the MMW energy out of the aperture and at a bore front of the borehole to melt the rock at the bore front into molten rock; and / or a bottom hole assembly (BHA) at the distal part of the drill string, the BHA comprising: a nozzle, mounted to face the bore front, and / or a jet operator, configured to drive pulses of a gas through the nozzle in a mannerthat propels the molten rock awayfrom the bore front.

[0201] Example 50. A bottom hole assembly (BHA) for a drill string that comprises a waveguide that is configured to conduct electromagnetic energy millimeter wave (MMW) energy along the drill string and to project the MMW energy at a bore front of a borehole to melt rock at the bore front into molten rock, the BHA comprising: a nozzle, mounted to face the bore front, and / ora jet operator, configured to drive pulses of a gas through the nozzle in a manner that propels the molten rock away from the bore front.

[0202] Example 51. A system for boring a borehole through rock, the system comprising a drill string, wherein: the drill string comprises a waveguide having an aperture, the drill string configured to core a core from a bore front of the borehole at least in part by projecting electromagnetic energy millimeter wave (MMW) energy out of the aperture and at the bore front of the borehole; and / or the system is configured to extract the core from the borehole.

[0203] Example 52. The system according to example 51 , further comprising a towline that is configured to fasten to the core, the system being configured to extract the core from the borehole by using the towline to draw the core proximally through the borehole.

[0204] Example 53. The system according to any one of examples 51-52, wherein the system is configured to extract the core from the borehole by drawing the core proximally through the waveguide.

[0205] Example 54. The system according to any one of examples 51-53, wherein the aperture is annular.

[0206] Example 55. The system accordingto any one of examples 51-54, wherein the waveguide is annular in transverse cross-section.

[0207] Example 56. The system according to any one of examples 51-55, wherein the waveguide is configured to project the MMW energy as an annular beam directed at the bore front.

[0208] Example 57. A method for boring a borehole through rock, the method comprising iteratively: melting rock at a bore front of the borehole into molten rock by directing electromagnetic energy millimeter wave (MMW) energy at the bore front; and / or propelling the molten rock away from the bore front by driving a pulse of a gas at the molten rock.

[0209] Example 58. The method according to example 57, wherein propelling the molten rock away from the bore front comprises splashing the molten rock against a sidewall of the borehole such that the molten rock rehardens on the sidewall.

[0210] Example 59. A method for boring a borehole through rock, the method comprising iteratively:coring a core from a bore front of the borehole by directing electromagnetic energy millimeter wave (MMW) energy atthe bore front; and / or extracting the core from the borehole.

[0211] Example 60. The method according to example 59, wherein the step of coring the core comprises coring the core from the bore front by directing an annular beam of the MMW energy at the bore front.

[0212] Example 61. A system for boring a borehole through rock, the system comprising: a gyrotron; a gas supply; and / or a drill string, havinga distal partthat is advanceable through the borehole, the drill string comprising: a waveguide, configured to: conduct electromagnetic energy millimeter wave (MMW) energy from the gyrotron toward the distal part of the drill string, and / or at the distal part of the drill string, project the MMW energy at a bore front of the borehole to melt rock at the bore front into molten rock; a gas line, arranged to conduct a gas from the gas supply distally along the drill string; and / or a bottom hole assembly (BHA) at the distal part of the drill string, the BHA comprising: a nozzle, mounted to face the bore front, and / or a jet operator, configured to drive a jet of the gas through the nozzle in a manner that propels the molten rock away from the bore front.

[0213] Example 62. A system for boring a borehole through rock, the system comprising a drill string that comprises: a waveguide, having an aperture at a distal part of the drill string, and configured to: conduct electromagnetic energy millimeter wave (MMW) energy distally along the drill string, and / orproject the MMW energy out of the aperture and at a bore front of the borehole to melt the rock at the bore front into molten rock; and / or a bottom hole assembly (BHA) at the distal part of the drill string, the BHA comprising: a nozzle, mounted to face the bore front, and / or a jet operator, configured to drive a jet of a gas through the nozzle in a manner that propels the molten rock away from the bore front.

[0214] Example 63. A bottom hole assembly (BHA) for a drill string that comprises a waveguide that is configured to conduct electromagnetic energy millimeter wave (MMW) energy along the drill string and to project the MMW energy at a bore front of a borehole to melt rock at the bore front into molten rock, the BHA comprising: a nozzle, mounted to face the bore front, and / or a jet operator, configured to drive a jet of a gas through the nozzle in a manner that propels the molten rock away from the bore front.

[0215] Example 64. A method for boring a borehole through rock, the method comprising iteratively: melting rock at a bore front of the borehole into molten rock by directing electromagnetic energy millimeter wave (MMW) energy at the bore front; and / or propelling the molten rock away from the bore front by driving a jet of a gas at the molten rock.

[0216] Although the operations of some of the disclosed methods are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language set forth herein. For example, operations described sequentially can in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed systems, apparatuses, devices, methods, etc. can be used in conjunction with other systems, apparatuses, devices, methods, etc.

[0217] The present invention is not limited to the examples that have been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.

Claims

CLAIMS1 . A system for boring a borehole through rock, the system comprising: a gyrotron; a gas supply; and a drill string, having a distal part that is advanceable through the borehole, the drill string comprising: a waveguide, configured to: conduct electromagnetic energy millimeter wave (MMW) energy from the gyrotron toward the distal part of the drill string, and at the distal part of the drill string, project the MMW energy at a bore front of the borehole to melt rock at the bore front into molten rock; a gas line, arranged to conduct a gas from the gas supply distally along the drill string; and a bottom hole assembly (BHA) at the distal part of the drill string, the BHA comprising: a nozzle, mounted to face the bore front, and a jet operator, configured to drive pulses of the gas through the nozzle in a manner that propels the molten rock away from the bore front, such that the molten rock splashes against a sidewall of the borehole and rehardens on the sidewall.

2. The system according to claim 1 , wherein the waveguide is circular in transverse cross-section.

3. The system according to claim 1 , wherein the waveguide is configured to project the MMW energy as a circular beam directed at the bore front.

4. The system according to claim 1 , wherein the waveguide is oblong in transverse cross-section.

5. The system according to claim 1 , wherein the waveguide is configured to project the MMW energy as an oblong beam directed at the bore front.

6. The system according to claim 1 , wherein the waveguide is annular in transverse cross-section.

7. The system according to claim 1 , wherein the waveguide is configured to project the MMW energy as an annular beam directed at the bore front.

8. The system according to anyone of claims 1-7, wherein the nozzle is a gas jet.

9. The system according to any one of claims 1-7, wherein the nozzle is a convergent nozzle.

10. The system according to anyone of claims 1-9, wherein the nozzle is mounted laterally from the waveguide.

11. The system according to any one of claims 1-10, wherein the nozzle is mounted to extend circumferentially at least partway around the waveguide.

12. The system according to any one of claims 1-11 , further comprising a controller that comprises a data-processing system, the controller being configured to operate the gyrotron to generate the MMW energy.

13. The system according to claim 12, wherein the controller is configured to operate the gyrotron to generate the MMW energy continually.

14. The system according to claim 12, wherein the controller is configured to operate the gyrotron to generate the MMW energy periodically.

15. The system according to claim 12, wherein the controller is configured to operate the gyrotron at a duty cycle of 30-70 percent.

16. The system according to claim 12, wherein the controller is configured to operate the gyrotron to generate the MMW energy during and between the pulses of the gas driven through the nozzle.

17. The system according to claim 12, wherein the controller is configured to actuate the jet operator to drive the pulses of the gas according to a predetermined temporal pattern.

18. The system according to claim 12, wherein the controller is configured to alternate the operation of the gyrotron with the actuation of the jet operator.

19. The system according to claim 12, wherein the controller is configured to provide intermissions during which the gyrotron does not generate the MMW energy, and to actuate the jet operator to drive a pulse of the gas during each of the intermissions.

20. The system according to any one of claims 1-19, wherein the BHA comprises a nozzle array, the nozzle beingone of multiple nozzles of the nozzle array, and the jet operator being configured to drive the pulses of the gas through the multiple nozzles of the nozzle array.21 . The system accordingto anyone of claims 1-20, wherein:at the distal part of the drill string the waveguide defines a waveguide axis along which the waveguide projects the MMW energy at the bore front, and the nozzle is mounted laterally from the waveguide axis.

22. The system according to claim 21 , wherein the nozzle is oriented such that the pulses of the gas are directed obliquely toward the waveguide axis.

23. The system according to claim 21 , wherein the nozzle is mounted to extend circumferentially at least partway around the waveguide axis.

24. The system according to claim 23, wherein the nozzle is mounted to extend between 50 and 310 degrees around the waveguide axis.

25. The system according to claim 24, wherein the nozzle is mounted to extend between 60 and 240 degrees around the waveguide axis.

26. The system according to claim 25, wherein the nozzle is mounted to extend between 90 and 200 degrees around the waveguide axis.

27. The system according to claim 26, wherein the nozzle is mounted to extend between 120 and 180 degrees around the waveguide axis.

28. The system accordingto anyone of claims 1-27, wherein: at the distal part of the drill string the waveguide has an aperture out of which the waveguide projects the MMW energy at the bore front, and the nozzle is mounted laterallyfrom the aperture.

29. The system according to claim 28, wherein the nozzle is mounted to extend circumferentially at least partway around the aperture.

30. A system for boring a borehole through rock, the system comprising a drill string that comprises: a waveguide, having an aperture at a distal part of the drill string, and configured to: conduct electromagnetic energy millimeter wave (MMW) energy distally along the drill string, and project the MMW energy out of the aperture and at a bore front of the borehole to melt the rock at the bore front into molten rock; and a bottom hole assembly (BHA) at the distal part of the drill string, the BHA comprising: a nozzle, mounted to face the bore front, anda jet operator, configured to drive pulses of a gas through the nozzle in a manner that propels the molten rock away from the bore front, such that the molten rock splashes against a sidewall of the borehole and rehardens on the sidewall.31 . A bottom hole assembly (BHA) for a drill string that comprises a waveguide that is configured to conduct electromagnetic energy millimeter wave (MMW) energy along the drill string and to project the MMW energy at a bore front of a borehole to melt rock at the bore front into molten rock, the BHA comprising: a nozzle, mounted to face the bore front, and a jet operator, configured to drive pulses of a gas through the nozzle in a manner that propels the molten rock away from the bore front, such that the molten rock splashes against a sidewall of the borehole and rehardens on the sidewall.

32. A method for boring a borehole through rock, the method comprising iteratively: melting rock at a bore front of the borehole into molten rock by directing electromagnetic energy millimeter wave (MMW) energy at the bore front; and by driving a pulse of a gas at the molten rock, splashingthe molten rock away from the bore front and against a sidewall of the borehole, such that the molten rock rehardens on the sidewall.

33. A system for boring a borehole through rock, the system comprising: a gyrotron; a gas supply; and a drill string, having a distal part that is advanceable through the borehole, the drill string comprising: a waveguide, configured to: conduct electromagnetic energy millimeter wave (MMW) energy from the gyrotron toward the distal part of the drill string, and at the distal part of the drill string, project the MMW energy at a bore front of the borehole to melt rock at the bore front into molten rock; a gas line, arranged to conduct a gas from the gas supply distally along the drill string; and a bottom hole assembly (BHA) at the distal part of the drill string, the BHA comprising:a nozzle, mounted to face the bore front, and a jet operator, configured to drive a jet of the gas through the nozzle in a mannerthat propels the molten rock away from the bore front, such that the molten rock splashes against a sidewall of the borehole and rehardens on the sidewall.

34. A system for boring a borehole through rock, the system comprising a drill string that comprises: a waveguide, having an aperture at a distal part of the drill string, and configured to: conduct electromagnetic energy millimeter wave (MMW) energy distally along the drill string, and project the MMW energy out of the aperture and at a bore front of the borehole to melt the rock at the bore front into molten rock; and a bottom hole assembly (BHA) at the distal part of the drill string, the BHA comprising: a nozzle, mounted to face the bore front, and a jet operator, configured to drive a jet of a gas through the nozzle in a manner that propels the molten rock away from the bore front, such that the molten rock splashes against a sidewall of the borehole and rehardens on the sidewall.

35. A bottom hole assembly (BHA) for a drill string that comprises a waveguide that is configured to conduct electromagnetic energy millimeter wave (MMW) energy along the drill string and to project the MMW energy at a bore front of a borehole to melt rock at the bore front into molten rock, the BHA comprising: a nozzle, mounted to face the bore front, and a jet operator, configured to drive a jet of a gas through the nozzle in a manner that propels the molten rock away from the bore front, such that the molten rock splashes against a sidewall of the borehole and rehardens on the sidewall.

36. A method for boring a borehole through rock, the method comprising iteratively: melting rock at a bore front of the borehole into molten rock by directing electromagnetic energy millimeter wave (MMW) energy at the bore front; andpropelling the molten rock away from the bore front by driving a jet of a gas at the molten rock, such that the molten rock splashes against a sidewall of the borehole and rehardens on the sidewall.

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