Crushing drill head and related methods

Abstract

The fracturing drill head (100) comprises a drill head body (102) with a main surface (104) facing substantially in a primary drilling direction (106) along a longitudinal axis of the drill head body. A liquid inlet may be present on the drill head body (102). The liquid inlet may be connected or connectable to a liquid supply line (110). An internal liquid connection (112) may open into the drill head body (102) and be liquid connected to the liquid inlet. A plurality of liquid jets (114) may be arranged oppositely on the main surface (104) of the drill head (100). The liquid jets (114) may be supplied with liquid from the liquid inlet through the internal liquid connection (112). The fluid jets may be associated with flow controllers (116) that control fluid delivery by the fluid jets, and the flow rates of at least two of the fluid jets (114) may be independently controllable.

Description

Background Art

[0001] To extract the energy stored in the earth's crust from hydrocarbons to thermal energy, it is usually necessary to drill a boring well in some form. The thermal energy in the earth's crust is virtually an inexhaustible carbon-free energy source and is used for power generation, building heating and cooling, desalination, hydrogen fuel production, and other human energy needs. However, it is difficult to reliably develop a storage site with the desired thermal energy density or a huge volume of the earth's crust, which is the bottleneck for current geothermal energy-based power generation (e.g., geothermal power generation). Economically, it is most feasible to locate the geothermal power generation system at a high-elevation crustal heat source, such as an unrealistic location like volcanic intrusion, which is highly fractured and permeable, covered by water-saturated or steam-saturated rock masses, and constantly replenished with water by injected water. Due to the geological complexity and current technical limitations, it is often difficult to extract sufficient geothermal energy for economical and reliable power generation. The main cause of the constraints is that the drilling depth range is limited for many of the current drilling methods.

[0002] Improving the efficiency and economic predictability of geothermal energy extraction is beneficial from several perspectives. Geothermal energy is a renewable power source with adjustable output, and its sufficient baseload capacity contributes to the stability of the power grid. The use of geothermal energy also has the potential to mitigate climate change concerns because its extraction process does not generate carbon dioxide. In the process of geothermal energy extraction, also known as "heat mining," a liquid is often heated and infiltrates through a network of permeable cracks in hot rock. The heated liquid then reappears on the surface through boreholes for liquid / steam recovery. Where there is no network of permeable cracks, hydraulic fracturing and thermal shock fracturing can create a network of cracks within "hot dry rock" (HDR). These boreholes and the created crack network in HDR are called "geothermal energy enhancement systems" (EGS). Current EGS systems have several problems stemming from hydraulic fracturing, including (1) the possibility of stimulating existing faults and inducing large seismic activity (applicable to all geothermal storage systems), (2) the difficulty in controlling the shape of the crack network created to increase heat production, and (3) the possibility of relatively large cracks forming that can serve as escape routes for high-flow liquids, leading to the rapid dissipation of heat that should be recovered.

[0003] Another major limitation of EGS is that as ambient temperature rises, the ductility of the rock body increases, suppressing the formation of cracks necessary for the mechanical drilling process. Combined with other technical difficulties, drilling becomes more difficult at greater depths. Above all, almost all current attempts using EGS technology rely on drilling multiple boreholes from the surface individually for both injection and production wells, increasing drilling costs and the uncertainty of creating a crack network connecting the injection and production wells. While progress has been made in EGS and other geothermal technologies, attempts to recover heat and generate electricity from geothermal reservoirs, which are more cost-effective and reliable, continue. Furthermore, the efficiency of many types of turbine generators depends heavily on the temperature of the liquid / steam recovered from the reservoir. This efficiency could be greatly increased if extraction with supercritical liquids becomes feasible, making deep crust an optimal target. Geothermal power generation has the potential to advance if heat sources in the deep crust can be reliably accessed anywhere. [Overview of the project]

[0004] This disclosure describes a fracturing drill head and methods of using it, which can be used for drilling boreholes for various purposes. The physical basis of the drilling and fracturing processes employed here is to generate stress for crack formation by rapidly changing the temperature of a small amount of rock using a jet of liquid, thereby converting thermal energy into mechanical energy. This fracturing drill head can be used for both cryogenic and hot fracturing. Cryogenic fracturing is a process that uses a low-temperature liquid to create micro-cracks in rock that is hotter. Cryogenic fracturing can potentially increase access to ultra-high temperature geothermal reservoirs, which are typically defined as being above 450°C. Hot fracturing, on the other hand, is a process that uses a high-temperature liquid to create micro-cracks in rock that is colder. The fracturing drill head described here will influence the process in various operating modes, including drilling for thermal extraction and other purposes, as well as creating micro-cracks to increase the permeability of liquid flow. These fracturing drill heads can help alleviate or remove current limitations on access to ultra-high temperature geothermal reservoirs.

[0005] In one example, the crushing drill head may include a drill head body. This drill head body may have a main surface substantially facing the primary drilling direction along its long axis. A liquid inlet may be provided on this drill head body. This liquid inlet may be connected to or connectable to a liquid supply line. Within the drill head body, an internal liquid connection section may open and be connected to the liquid inlet. Multiple liquid injection sections may be arranged opposite each other on the main surface of the drill head. Liquid may be supplied to these liquid injection sections from the liquid inlet through the internal liquid connection section. Flow rate control devices may be provided on these liquid injection sections to control liquid delivery. The flow velocities of at least two of these liquid injection sections may be independently controllable. This may allow the crushing drill head to be operated by changing the amount of liquid passing through different liquid injection sections.

[0006] In some cases, the drill head may not be equipped with a mechanical drill head for drilling in the primary drilling direction. In such cases, the drill head can perform drilling in the primary drilling direction by non-contact cryogenic fracturing. However, it may be possible to enhance or reinforce rock removal by primary fracturing by using one or more alternative elements to inflict mechanical damage on the rock surface during drilling.

[0007] In some cases, the crushing drill head may include a plurality of liquid injection sections. These liquid injection sections may be arranged in a row on the main surface of the drill head. For example, the first portion of these liquid injection sections may be oriented in a different direction from the second portion of these liquid injection sections. In yet another example, valves may be provided to which the liquid flow to these liquid injection sections oriented in different directions can be independently controlled, and the drill head may be controlled by flowing more liquid to the liquid injection section oriented in the desired direction. These valves may be liquid-connected to a single liquid injection section or to a small group of these liquid injection sections. This allows for completely independent operation of individual injection sections or divided operation of multiple zones of these injection sections, depending on the performance balance and complexity.

[0008] In yet another example, these liquid injection units may be divided into at least four groups. Each of these groups of liquid injection units is spatially separated from the others. The flow velocity to each group can be controlled independently. Valves may be connected to each of these groups of liquid injection units, allowing the liquid flow to each group to be controlled independently. This makes it possible to control the drill head by supplying at least one group of liquid injection units with at least one more liquid than another.

[0009] As an optional example, the liquid inlet of the crushing drill head described above can be used as the sole inlet for the liquid injected towards the rock body, allowing only one type of liquid to be injected through the drill head.

[0010] In another example, the flow control device for a crushing drill head may include a valve that generates a pulsed flow through these liquid injection sections. For example, this valve can be configured to stop the liquid flow through each liquid injection section, thereby promoting temperature equilibrium within the rock surrounding the drill head.

[0011] The above-described crushing drill head may, in some cases, be equipped with a liquid pump for pressurizing a liquid. This liquid pump can be liquid-connected to at least one liquid injection unit of the crushing drill head. The liquid can pressurize the jet stream ejected from at least one liquid injection unit. As an example, this liquid pump can be built into the drill head body.

[0012] The above-mentioned crushing drill head may, in some cases, be equipped with a chiller. This chiller can be built into the drill head body and, in conjunction with the internal liquid connection, can cool the liquid supplied to each liquid injection section. This chiller may, in some cases, be a thermoelectric chiller. When the crushing drill head is used for high-temperature crushing, the crushing drill head may be equipped with a heater. This heater can be built into the drill head body and, in conjunction with the internal liquid connection, can heat the liquid supplied to each liquid injection section. As an example, this heater may be an electric heater.

[0013] In further examples, the crushing drill head may be equipped with a slurry recovery port. This slurry recovery port may be provided on the front upper surface of the drill head body. A slurry outlet may also be provided on the rear upper surface of the drill head body, thereby allowing the slurry to be discharged outside the borehole. This slurry outlet may be connected to the slurry recovery port by an internal slurry connection within the drill head body. This slurry outlet may be connected to or be connectable to a slurry line. In yet another example, the crushing drill head may be equipped with a slurry pump attached to the internal slurry connection. This slurry pump can pump a slurry mixture of liquid and rock fragments to the slurry line. In one example, this slurry recovery port may be provided on the side of the drill head body.

[0014] The crushing drill head may be provided with an actuated sealing element on the drill head body between the slurry recovery port and the slurry outlet, which can be operated to temporarily isolate a portion of the borehole behind it from a portion of the borehole in front of it. In one example, the sealing element may be an inflatable packer provided on the side of the drill head body. When inflated, this inflatable packer can seal the space between the side of the drill head body and the inner wall surface of the borehole, forming a seal between the outer surface of the drill head body and the inner rock surface of the borehole. In one example, the drill head body may be cylindrical, and the inflatable packer may be formed as an annular tube encircling the drill head body. In yet another example, the crushing drill head may include a second inflatable packer formed as an annular tube encircling the drill head body and positioned alongside the first inflatable packer.

[0015] In some cases, the crushing drill head may be equipped with wheels or other mechanisms for positioning the device at the center of the borehole and for controlling the movement of the drill head body on its sides. These wheels or other mechanisms extend from the drill head body outward toward the inner wall of the borehole and can propel the drill head within the borehole at a desired speed, as well as fix the drill head in place. These wheels can also improve the lateral stability of the crushing drill head during use to some extent.

[0016] In yet another example, the crushing drill head may be provided with at least one lateral liquid injection nozzle directed toward the side of the drill head body. In yet another example, this at least one lateral liquid injection nozzle may be provided with lateral liquid injection nozzles arranged radially and longitudinally in a single line on the side of the drill head body. These lateral liquid injection nozzles can be used to facilitate debris removal, widen the drill well, and / or create a microcrack damage zone by facilitating heat exchange between the liquid and the rock.

[0017] In various examples, the crushing drill head may be a primary drill head, a secondary drill head extended from the primary drill head, a secondary drill head extended from a non-drill head base unit, or a tertiary drill head extended from the secondary drill head.

[0018] In another example, the crushing drill head may comprise a drill head body having a main surface substantially facing the primary drilling direction along its long axis. A liquid inlet on this drill head body is connected to, or may be connected to, a liquid supply line. An internal liquid connection is oriented within the drill head body and may be connected to the liquid inlet. At least one liquid injection unit may be oriented on the main surface of the drill head. This at least one liquid injection unit receives liquid from the liquid inlet through the internal liquid connection unit. A flow control device may be associated with the at least one liquid injection unit and may control the liquid delivery by the at least one liquid injection unit. The drill head body may have a slurry recovery port on its front upper surface. The drill head body may also have a slurry outlet on its rear upper surface. This slurry outlet may be connected to the slurry recovery port by an internal slurry connection unit within the drill head body. An actuated sealing element may be provided on the drill head body between the slurry recovery port and the slurry outlet. This sealing element can be operated to temporarily isolate a portion of the borehole in front of the sealing element from a portion of the borehole in the rear of the sealing element.

[0019] In one example, the actuated sealing element may include an inflatable packer on the side of the drill head body. When inflated, the inflatable packer can seal the space between the side of the drill head body and the inner wall of the borehole. The drill head body may have a cylindrical shape, and the inflatable packer may be formed as an annular tube encircling the drill head body. In another example, the drill head may be accompanied by an internal slurry connection and include a slurry pump that pumps a slurry mixture of liquid and rock fragments to the slurry line. Furthermore, the slurry recovery port may be provided on the side of the drill head body.

[0020] This disclosure also provides a method for fracture drilling. High-temperature fracture proceeds by activating the thermoelasticity of the rock mass to convert thermal energy into mechanical energy. When a thermal shock is applied to the surface of a high-temperature rock mass with a low-temperature liquid, a strong thermal gradient is created over a certain distance oblique to the surface of the rock mass. Along this gradient, the rock mass contracts, generating local tensile stress and causing microcracks in a shallow area of ​​the rock mass. Such a layer of fractured rock can be called a "fractured layer." The thickness of this layer is determined by heat transfer from the rock mass to the liquid through multiple mechanisms, which involve fracture processes dependent on thermoelastic coupling or nonlinear effects resulting from the dependence of thermal, mechanical, and transport properties on the density and shape of locally changing cracks. Heat transfer within this layer is achieved by conduction within the solid and by heat transfer from the crack surface to the liquid that permeates and convects within the cracks. Under extreme thermal imbalances, various heat transfer modes are possible, such as microliquid processes and, in some cases, radiative transfer between the liquid and the rock mass. The water pressure from the liquid also propels the cracks further into the rock body. Furthermore, this internal pressure (or mean stress) generates a steep pressure gradient near the excavated rock face, generally ranging from lithostatic pressure to near hydrostatic pressure, with a length range that is different from but related to the thermal gradient. This process is most effective in generating countless microcracks that ultimately lead to fracturing, or the suspension of the resulting rock fragments from the rock surface into the liquid. This process can be inhibited if the fragments do not detach from the rock surface even after the cracks penetrate the rock body. To achieve effective fracturing, a relatively hot surface beneath the fracturing layer is exposed and this becomes a new fracturing layer. In each method described herein, a steep thermal gradient can be maintained, and the resulting internal stress gradient can be used as the driving force for microcrack formation and fracturing. In particularly favorable examples, this method can maintain a steep temperature and stress gradient and control sufficient degrees of freedom to remove excavated rock debris (slurry) from the rock face. These subprocesses (thermal diffusion, radiative heat transfer from rock to liquid, heat and hydraulic propagation through cracks, and liquid flow for slurry removal) can be controlled using a multi-timescale method.

[0021] In one example of a crushing drilling method, a crushing drill head can be installed inside the borehole. This crushing drill head may be equipped with multiple liquid injection nozzles. In this method, liquid can be further injected from the liquid injection nozzles towards the rock body in the borehole. The temperature difference between the temperature of this liquid and the temperature of the rock body is sufficient to cause thermal fracture in the rock body from the drilling surface to a certain depth due to the liquid injection, causing fracture within the rock body, and thereby forming loose rock fragments within the rock body through a combination of thermal fracture and hydraulic pressure. By independently controlling the flow rate of at least one liquid injection nozzle from at least one other liquid injection nozzle, different flow rates of liquid can be ejected from each of these independently controlled nozzles. This allows for different amounts of fracture to be caused in different parts of the rock body. These liquid and loose rock fragments can be removed from the borehole in the form of a slurry, exposing a higher temperature layer with less fracture toward the liquid injection nozzles. Hydraulic pressure also pushes the liquid into the cracks, acting as a driving force for further crack propagation.

[0022] In some cases, the liquid can be injected as a pulsed flow with sufficient time intervals, thereby reheating the cooled rock surface to a sufficient temperature, which is then fractured by a subsequent blow of a cooler liquid. The cracking rate is controlled by the momentum (mass × velocity) of the liquid striking the rock surface and the temperature difference between the liquid and the rock. This method may include time-dependent control of the liquid's mass flow rate and some degree of temperature control. The liquid injection may be maintained at a constant mass flow rate, switched on and off, or controlled by pulses or vibrations based on desired duration and pauses with zero or reduced flow rate. The selection of these determines the thermal shock to the fracture interface and the thermal gradient from this interface into the rock body. If the interface cools excessively and cracking stops, the liquid injection can be stopped for a period of time sufficient for the rock surface to warm up again. The time between these different phases can range from a few seconds to several days, depending on natural thermal energy, rock characteristics, and other factors. Controlling and maintaining such thermal / mechanical gradients is possible through equipment design.

[0023] The temperature difference between the liquid and the rock mass during injection is about 50°C to 800°C, and it may also be 200°C to 500°C. There are also examples where the liquid during injection can be cooler than the rock mass. For example, the temperature of the liquid during injection is about 0°C to about 100°C, and in some cases about 20°C to about 90°C.

[0024] Each of the above liquid injection parts may be able to pulse the liquid flowing through it using a valve.

[0025] In yet another example, the liquid can be cooled before injection. As a notable example, this cooling can be performed within the drill head using electrothermal cooling or a heat exchanger filled with another low-temperature operating liquid.

[0026] As an example, the above drill head can perform excavation in the above primary excavation direction by non-contact cryogenic crushing, that is, without contacting the rock mass to be excavated by the drill head.

[0027] This method can include the step of operating the drill head to form a curved boring well.

[0028] In a further example, the plurality of liquid injection parts may be provided on the main surface of the drill head. This main surface may face substantially in the primary excavation direction. In some cases, at least some of the liquid injection parts may be oriented in a different direction from other liquid injection parts. The drill head can be maneuvered to rotate little by little by flowing more liquid through the liquid injection parts oriented in the desired direction, thereby enabling direction change within the boring well.

[0029] The liquid injected from the above liquid injection part may be pressurized using a dedicated liquid delivery pump. In another example, the liquid injection part may be pressurized using hydraulic pressure.

[0030] In a further example, the above slurry may be removed through a slurry recovery port on the drill head.

[0031] The pressure of the above-mentioned liquid can be controlled by sealing the borehole with an actuated sealing element on the drill head body after it has been injected into the rock mass. Here, the sealing element can be actuated to temporarily isolate a portion of the borehole in front of the sealing element from a portion of the borehole behind it. In one example, this sealing element may consist of a torus-shaped (like the inner tube of a tire) inflatable packer that acts between the side wall of the drill head and the inner wall of the borehole (for example, one used in hydraulic fracturing, but adapted for high-temperature conditions). Using this system of packers and valves, the space containing the liquid injected into the rock mass can be isolated. In one case, the method may also include a step of inflating a second inflatable packer that acts between the side wall of the drill head and the inner wall of the borehole. Alternatively, a sealing element may be used that protrudes so as to be sufficiently pressed against the rock wall of the borehole to form a seal, or that significantly restricts the liquid flow.

[0032] In one example, the liquid may be ejected from at least one lateral liquid injection unit in a lateral direction that is substantially perpendicular to the primary drilling direction.

[0033] In various examples, the drill head may be a primary drill head, a secondary drill head extended from a primary drill head, a secondary drill head extended from a non-drill head base unit, or a tertiary drill head extended from a secondary drill head. Drilling can be performed laterally. For example, the borehole may be a secondary borehole extending laterally from a vertical primary borehole.

[0034] To aid in understanding the detailed description of the invention described below and to ensure a correct recognition of its significance in the relevant art, we have provided a fairly broad overview of the important features of the invention. Other features of the invention will become more apparent from the detailed description below, the accompanying drawings and claims, or can be learned from the practice of the invention. [Brief explanation of the drawing]

[0035] [Figure 1] This is a schematic diagram of an exemplary crushing drill head according to one embodiment of the present invention. [Figure 2] This is a perspective view of an exemplary crushing drill head according to one embodiment of the present invention. [Figure 3] This is another schematic diagram of an exemplary crushing drill head according to one embodiment of the present invention. [Figure 4] This is another schematic diagram of an exemplary crushing drill head according to one embodiment of the present invention. [Figure 5] This is another perspective view of an exemplary crushing drill head according to one embodiment of the present invention. [Figure 6] This is another perspective view of an exemplary crushing drill head according to one embodiment of the present invention. [Figure 7] This is yet another schematic diagram of an exemplary crushing drill head according to one embodiment of the present invention. [Figure 8A8B] This is a schematic diagram of a crushing drill head with an extension. [Figure 9A] This is a vertical cross-sectional view showing an exemplary curved borehole and a crushing drill head inside the borehole according to one embodiment of the present invention. [Figure 9B] This is another vertical cross-sectional view showing an exemplary curved bore well and a crushing drill head within the bore well, according to one embodiment of the present invention. [Figure 10A] This is a cutaway diagram of an exemplary crushing drill head according to one embodiment of the present invention. [Figure 10B] Figure 10A is an enlarged cutaway view showing the control mechanism in the example shown. [Figure 10C10D] Figure 10B is a vertical cross-sectional view of the control valve within the control mechanism shown. [Figure 10E] Figure 10A is a cross-sectional view showing the control mechanism from below, along with the control valves in various open and closed states. [Figure 11A]This is a vertical cross-sectional view showing an exemplary primary borehole having a secondary borehole and a drilling drill within the secondary borehole, according to one embodiment of the present invention. [Figure 11B] This is an enlarged view showing a secondary boring well and a crushing drill head inside the secondary boring well, according to one embodiment of the present invention. [Figure 11C] This is an enlarged view of a crushing drill head that forms a loop-shaped secondary boring well according to one embodiment of the present invention. [Figure 11D] This is a perspective view of the primary and secondary boreholes. [Figure 12] This is a schematic diagram showing an exemplary non-drilling base unit and secondary drill head according to one embodiment of the present invention. [Figure 13A] This is an enlarged view of an exemplary crushing drill head that forms a damaged area on the wall surface of a horizontal boring well, according to one embodiment of the present invention. [Figure 13B] This is an enlarged view of another exemplary crushing drill head that forms a damaged area on the wall of a horizontal boring well, according to one embodiment of the present invention. [Figure 14A] This is a close-up view of an exemplary high-temperature fracturing drill head used to break up rock formations. [Figure 14B] This is a close-up view of an exemplary cryogenic fracturing drill head used for breaking up rock formations.

[0036] These drawings are intended to illustrate various aspects of the present invention and are not intended to limit any dimensions, materials, configuration, arrangement, or proportions unless specifically provided for in the claims. [Modes for carrying out the invention]

[0037] The following description of exemplary embodiments will enable those skilled in the art to easily implement the present invention. However, it should be understood that other embodiments may be realized, or various modifications may be made, as long as they do not depart from the spirit and scope of the present invention. Therefore, the following more detailed description of embodiments of the present invention is not intended to limit the scope of the present invention as described in the claims, but merely to describe the features and properties of the present invention without limiting them, describing the best embodiment of the present invention and enabling those skilled in the art to fully implement the present invention. Accordingly, the scope of the present invention is defined solely by the claims.

[0038] Definitions In describing the present invention and making claims, the following terms shall be used.

[0039] The term "geothermal energy" refers to all thermal energy present beneath the Earth's surface. Geothermal energy is stored within rock bodies across a wide range of temperatures and pressures and can exist at a wide depth range from the surface.

[0040] As used herein, “geothermal reservoir” refers to a region below the Earth’s surface that produces useful thermal energy and has a temperature (or thermal energy density) sufficient for extraction. Typically, geothermal reservoirs are naturally heated regions, in other words, they contain thermal energy flowing from deep within the Earth toward the surface, and are not introduced from surface heat sources.

[0041] Geothermal reservoirs include those that hold liquid within cracks and / or other forms of voids in the rock mass, and those that do not have such voids (referred to as "wet" and "dry," respectively). For example, wet geothermal reservoirs include subterranean hydrothermal systems or hot, wet rock masses (HWRs) that are hot enough to produce thermal energy. On the other hand, dry geothermal reservoirs include hot, dry rock masses (HDRs) that contain little or no liquid. These systems are referred to simply as HWRs or HDRs in this specification. Embodiments using lateral boreholes can be flexibly applied to either HWR or HDR heat sources (or mixed heat sources where permeability and liquid content vary over time and space). In either case, the system is applicable over a wide temperature range, but is particularly intended for geothermal reservoirs with high target temperatures (above 350°C), or "ultra-high temperature" conditions. While this system is particularly useful for power generation, other applications without limitations include energy storage through the production of hydrogen fuel (e.g., by electrolysis), direct steam production, direct heating, and the extraction of metals such as lithium dissolved in hot water (known as "direct lithium mining").

[0042] As used herein, "thermal contact" refers to a functional contact between two objects or liquids that transfers heat generated from one object or liquid to the other. Thermal contact can also be achieved through direct physical contact. For example, water injected directly into a crack in a hot rock layer is in thermal contact with the hot rock because heat is transferred from the rock to the water while the water is in direct physical contact with the rock. There are also cases where thermal contact is achieved without direct physical contact, in which case an intermediate medium capable of conducting heat is interposed. For example, water can be sealed in a pipe and brought into physical contact with a hot rock. This water can be said to be in thermal contact with the hot rock. Heat is transferred from the hot rock to the water through the pipe wall, but at this time, the water and the hot rock are not in direct physical contact.

[0043] As used herein, "liquid-connected" means that liquids, liquid lines, or liquid containers are connected in such a way that mass transfer of the liquid can occur from one to the other. Similarly, "liquid-isolated" means that liquids, liquid lines, or liquid containers are isolated in such a way that mass transfer of the liquid cannot occur from one to the other.

[0044] As used herein, “fracturing” refers to the process of separating rock fragments from a rock mass. Fracturing includes thermal fracturing, which uses thermal expansion or contraction to break a rock mass (or other solid such as concrete or metal) and separate rock fragments from the rock layer. “Hot fracturing” can be achieved by heating the rock surface with a flame, plasma, or laser. When a liquid is used to heat or cool the rock mass, this process is called “hydrothermal fracturing.” “Cold hydrothermal fracturing,” or “low-temperature fracturing,” has the temperature difference relationship reversed, with a cold liquid in contact with a hot rock mass. In these cases, the thermal shock causes the rock mass to expand or contract, respectively, generating compressive or tensile stress within the rock mass, respectively, resulting in microcracks in the rock layer. In some cases, low-temperature fracturing may be particularly useful in geothermal rock layers. The low-temperature fracturing process can be carried out by rapidly cooling the temperature of the hot rock mass, which causes rapid thermal contraction that results in microcracks or fractures within the rock layer, penetrating shallow parts from the surface of the rock mass. In some cases, a low-temperature liquid can be sprayed onto the rock mass to induce such a rapid temperature decrease. The rock fragments can be separated and removed by fracture due to rapid contraction and a combination of liquid pressure and kinetic force. Fragmentation is a phenomenon in which thermal energy is rapidly converted into mechanical energy to a level sufficient to produce localized cracking and removal of the fractured rock mass.

[0045] As used herein, a “flow control device” is a mechanism or device that manages the controlled transfer of liquid from one storage tank to another, and is part of a system that controls the flow velocity and pressure of the liquid. Such storage tanks may also constitute part of a crushing drill head. In some cases, these flow control devices may include a single valve, multiple valves, a single pump, multiple pumps, or a combination thereof. The controlled transfer may include steady flow, pulsed flow, intermittent flow, etc. The properties of pulsed flow can be changed; for example, the liquid can be pulsed by repeatedly increasing or decreasing the flow velocity of the liquid transferred from the crushing drill head. As an example, the liquid flow can be completely stopped between pulses, or in another example, the flow rate can simply be reduced between pulses with a high flow rate.

[0046] In this specification, when referring to any property that can be distributed between different levels, such as temperature distribution or pore size distribution, the property being referred to shall be the average value of the distribution unless otherwise specified.

[0047] In this specification and in the claims, singular nouns refer to multiple objects unless otherwise specified in the context. For example, “(one) layer” refers to one or more layers, “(one) particle” refers to one or more particles, and “to produce” refers to one or more steps.

[0048] In this specification, the terms “approximately” and “roughly” are used with flexibility; for example, a numerical value given within a certain range may be “slightly above” or “slightly below” its end. The degree of flexibility with respect to a particular variable can be easily determined from the context by those skilled in the art. However, unless otherwise specified, the flexibility of the term “approximately” is implicitly understood to be less than 2%, less than 1% in some cases, and less than 0.1% in others.

[0049] In this specification, the term “substantially” indicates that the degree of an action, characteristic, nature, state, structure, item, or result is complete or nearly complete. The degree of deviation from strict completeness may depend on the specific context. However, being nearly complete means achieving a result that is roughly the same as if strict completeness had been achieved. “Substantially” means that the degree of deviation from a particular characteristic or situation is small enough to be undetectable. The exact range of acceptable deviation may depend on the specific context. The term “substantially” can also be applied to negative contexts where a characteristic, nature, state, structure, item, or result is completely or nearly completely absent.

[0050] In this specification, “adjacent” means that two structures or elements are in close proximity. In particular, elements considered “adjacent” may be touching or connected. Such elements may be near or very close to each other, but do not necessarily have to be in contact. The exact degree of proximity may depend on the particular context. Therefore, adjacent structures or elements may be separated by additional structures or elements interposed between them.

[0051] In this specification, multiple items, structural elements, components, and / or materials are grouped together in common lists for convenience. However, these lists are intended to allow each member included in the list to be identified as an individual member. Therefore, unless otherwise indicated based solely on the nature of each member within the common group, no individual member included in such a list should be construed as being factually equivalent to any other member in the same list.

[0052] Numerical data such as concentrations, quantities, and other values ​​described herein are presented in range format. This range format is intended solely for simplicity and conciseness, and is interpreted to include not only the values ​​explicitly stated as upper and lower limits, but also all or part ranges of the individual values ​​within that range, as if they were individually stated. For example, a numerical range of approximately 1 to approximately 4.5 includes not only the values ​​of 1 and 4.5 explicitly stated as upper and lower limits, but also individual values ​​such as 2, 3, 4, and part ranges such as 1 to 3, 2 to 4, etc. The same principle applies to single notices; for example, "less than approximately 4.5" is interpreted to include all of the above values ​​and ranges. Furthermore, such interpretation applies regardless of the width or characteristics of the range being discussed.

[0053] Any method or any step referred to in a method claim may be performed in any order, and is not limited to the order described in the claims. The provisions of means-plus-function and step-plus-function apply only if a particular claim includes both the following: a) an explicit statement of “means for” or “steps for” and b) an explicit statement of the corresponding function. The structure, materials, and operation underlying means-plus-function are explicitly stated herein. Accordingly, the scope of the invention shall be defined solely by the claims and their legal equivalents, and not by the descriptions and examples herein.

[0054] The following describes specific embodiments using designated terminology, but this is not intended to limit the scope of the present invention. Other features and advantages of the present invention will become apparent from the following detailed description and accompanying drawings, which collaboratively illustrate the features of the present invention based on examples.

[0055] While general principles were stated in the "Summary of the Invention" above, when a system, or related apparatus or method, is described in this disclosure, every individual or specific description is understood to apply to all of them, regardless of whether they are explicitly discussed in the context of a particular example or embodiment. For example, when discussing an apparatus itself, the discussion includes other embodiments of apparatus, systems, and / or methods, and vice versa.

[0056] Furthermore, since various modifications and combinations may be derived from this disclosure and description, the following drawings should not be considered limiting.

[0057] Crushing drill head This disclosure describes a fracturing drill head that can be used to drill boreholes into rock bodies. This fracturing drill head is particularly useful for drilling boreholes into geothermal rock layers. At high temperatures, the ductility of rock bodies increases, and the temperature range in which the transition occurs depends on the composition and microstructure (properties such as grain size distribution) of the rock body, as well as the deformation rate. The more ductile the rock body becomes, the less effective mechanical drilling becomes. Also, the temperature of the rock body often increases as the borehole depth increases. For example, when a borehole penetrates a target geothermal reservoir and the rock body at the target depth exhibits significant ductility, methods such as mechanical fracturing and high-temperature fracturing become ineffective. For example, when the temperature of a rock body reaches about 50% to 70% of its melting point, the rock body enters a so-called "semi-brittle" state and undergoes a brittle-ductile transition. The temperature at which significant ductility appears in a rock body can vary depending on many factors, such as the rock body composition, pressure, water and other liquid content, microstructure characteristics such as grain size, and deformation rate. For example, granite coexisting with a small amount of water melts at approximately 650-700°C in the 5-10 km depth range, and its brittle-ductile transition begins at approximately 325°C. However, above this brittle-ductile transition temperature, cryogenic fracturing becomes particularly effective. The yield stress of the rock mass is lower under tension than under compression, and cryogenic fracturing acts to induce thermal contraction, so it proceeds easily. Cryogenic fracturing is initiated at a temperature range high enough to produce a rapid temperature drop, at which point the rock mass comes into contact with a cold liquid, generating thermal stress and reaching a critical stress for crack initiation. This temperature can be considerably lower than the brittle-ductile transition temperature. Therefore, the ranges in which mechanical drilling and hydrothermal drilling are effective can overlap considerably. A borehole can be drilled from the surface by mechanical or other means to a depth where cryogenic hydrothermal drilling is likely to begin.

[0058] A cryogenic fracturing drill head may be equipped with a nozzle that injects a low-temperature liquid, such as water, towards a geothermal rock mass. When cold water is injected towards a high-temperature rock mass, a thin layer of the rock mass is cooled and contracts very rapidly, causing small-scale fractures within the rock mass.

[0059] These fractures may result in the detachment of rock particles. For example, a cryogenic liquid may be significantly pressurized, allowing it to penetrate cracks and propagate them, thereby enhancing the fracturing process. These fragments and particles may be removed from the borehole through a slurry line. In yet another example, cryogenic liquid injection may be used in combination with mechanical force. For instance, after injecting a cryogenic liquid into the rock mass to form cracks, the drill head can use its rotational motion and impact force to break the cracked rock mass, or mechanical force can be used to inflict minor damage on the rock mass before applying thermal shock, creating more nucleation points in preparation for subsequent hydrothermal fracturing.

[0060] The cryogenic liquid injection unit can be pulse-driven or cyclic-driven. By controlling the liquid flux over time, an optimal or near-optimal heat / stress gradient can be maintained within the fracturing layer, and if necessary, further cracking can be induced to discharge the slurry. If the drilling target becomes too cold, the liquid injection is stopped, and the rock body is allowed to reheat through heat conduction. Once the necessary thermomechanical gradient is restored through reheating, fracturing drilling can be resumed.

[0061] The liquid may be pulsed while gradually increasing its pressure. Alternatively, the frequency of the pulsed drive of the liquid injection unit can be increased so that the rock mass below the shallow layer cannot be cooled in that time. The shallow layer of the rock mass that comes into contact with the cold liquid will crack, and this cracked rock mass will be removed, and the next pulse of the cold liquid will be injected before enough time has passed for the underlying hot rock mass to cool. Thus, the cold liquid can be continuously injected toward the hot rock mass to create a temperature difference sufficient to form cracks in the hot rock mass. The temperature and pressure of the part of the borehole below the drill head where fracturing is taking place (hereinafter referred to as the "fracturing chamber") are also controlled by the discharge rate of the liquid from the fracturing chamber, and these can be determined using a slurry outlet valve and a slurry outlet pump.

[0062] Another example is the use of high-temperature hydrothermal fracturing. For example, a pressurized liquid hotter than the rock mass can be used. For instance, the initial shallow portion of a rock mass may be relatively cold, in which case high-temperature hydrothermal fracturing may be useful until the temperature rises sufficiently for low-temperature fracturing to be more effective. This pressurized liquid widens and propagates through cracks, connecting with neighboring cracks as they grow, thereby causing fine rock fragments to break off, removing the fractured fragments in the form of a slurry, and exposing the new surface of the rock mass. This high-temperature fracturing mode may be useful for drilling through relatively shallow, low-temperature crustal regions before reaching hotter geothermal areas.

[0063] Both the cryogenic fracturing and high-temperature fracturing drilling methods described herein can utilize the injection of a liquid (at a lower or higher temperature than adjacent rock bodies) directed towards a rock mass. These methods may, in some cases, involve the injection of a single type of liquid. In other words, these methods do not involve the injection of multiple types of liquids towards a rock mass at different locations and at different times. Alternatively, a single type of liquid may be injected towards the rock mass in various injection patterns, such as pulsed or continuous patterns. In some cases, the injected liquid may be a mixture of multiple components in order to achieve certain physical properties, such as viscosity, heat capacity, or freezing point. For example, this liquid may be water, alcohol, propylene, or ethylene glycol, or an aqueous solution.

[0064] The fracturing drill head may be configured to be maneuverable. In some cases, the fracturing drill head may have multiple fluid jets oriented in different directions relative to the axis of the borehole. To maneuver the drill head, one can use the fluid jets oriented in the desired direction, thereby preferentially removing rock in that particular direction. This allows the drill head to be maneuvered and the drilling direction of the borehole to be changed. Although there is variation in the rate of change of direction and the resulting radius of curvature, in most cases such changes of direction are tens to hundreds of meters or yards.

[0065] As an example, the crushing drill head described herein is used in a geothermal drilling machine as described in U.S. Patent No. 11,029,062, the details of which are incorporated herein by reference. This geothermal drilling machine may be equipped with a primary drill head for drilling primary boreholes, and / or a secondary drill head for drilling secondary boreholes, and / or a tertiary drill head for drilling tertiary boreholes. The crushing drill head described herein may be useful as any of the primary, secondary, or tertiary drill heads used in conjunction with these geothermal drilling machines. Furthermore, these crushing drill heads can be used in primary boreholes, secondary boreholes branching from the primary boreholes, and / or tertiary boreholes branching from the secondary boreholes, even without being used in conjunction with these specific geothermal drilling machines.

[0066] With this general principle in mind, Figure 1 shows a schematic cross-sectional view of an example of a crushing drill head 100 according to this disclosure. This crushing drill head comprises a drill head body 102, which has a main surface 104 substantially facing the primary drilling direction 106 along its long axis. In Figure 1, the primary drilling direction is towards the bottom of the drawing. This direction is the direction in which the drill head advances as it drills through the rock, and can therefore also be called the forward direction. Thus, in the figure, the main surface of the drill head body is the bottom surface. The crushing drill head also includes a liquid inlet 108 on the drill head body. In this example, this liquid inlet is on the upper surface of the drill head body opposite to the main surface. This upper surface is opposite to the direction in which the drill head advances as it drills through the rock, and can therefore also be called the rear surface. The liquid inlet is connected to a liquid supply line 110. The liquid inlet is also connected to an internal liquid connection part 112 inside the drill head body. Multiple liquid injection units 114 are oriented on the main surface of the drill head. Liquid is supplied to these liquid injection units from the liquid inlet through the internal liquid connection section. A flow rate control device 116 is provided inside the drill head body, attached to the liquid injection units. This flow rate control device can selectively control the liquid flow, such as by pulsing the liquid delivery from the multiple liquid injection units. As described above, such flow rate control may be performed in common for all injection units, individually for each injection unit, or separately for several groups of injection units (e.g., multiple independent control zones). The exemplary crushing drill head shown in Figure 1 is used for cryogenic crushing drilling or high-temperature crushing drilling. Although some of the examples described herein are intended for cryogenic crushing drilling, the examples and features described for cryogenic crushing drill heads are all applicable to or can be applied to high-temperature crushing drill heads.

[0067] Figure 2 shows an example in which a crushing drill head 100 is installed in a borehole 150. This drill head 100 may be connected to a cryogenic liquid supply line 110. This cryogenic liquid supply line extends up the borehole to the surface. A cryogenic liquid valve is located above ground, which can control the flow of the cryogenic liquid down the supply line to the drill head. In one example, since the drill head is located deep below the surface (e.g., several hundred meters to several kilometers underground), the liquid in the cryogenic liquid supply line can naturally be subjected to high hydrostatic pressure. This high-pressure liquid causes cracks in the rock mass around the drill head, forming a slurry of the liquid and rock fragments. This slurry either crawls up between the side of the drill head and the wall of the borehole to reach the surface, or is pumped to the surface. In yet another example, a cryogenic liquid pump can be used to further pressurize the cryogenic liquid, increasing the pressure of the liquid ejected from the liquid injection nozzle. Figure 2 also illustrates a slurry line 130 extending from the crushing drill head to the ground surface. A slurry pump can also be installed on the ground side to assist in pumping up the slurry, which is a mixture of liquid and rock fragments, through the slurry line.

[0068] Figure 3 is a schematic diagram of a similar crushing drill head 100. This example includes a cryogenic liquid supply line 110 ("downstream pipe") from the ground surface to the drill head. When a cryogenic liquid valve 140 installed on the ground side is opened, the cryogenic liquid flows down through the cryogenic liquid supply line. The drill head has a built-in flow control device 116. In this example, this flow control device is a valve. When this valve is opened, the liquid can flow to the outside of the liquid injection section of the drill head. The storage section below the liquid injection section is the crushing chamber 152. The liquid injected from the injection section can crack the rock in the borehole and form a slurry. This slurry crawls up the space between the drill head and the wall of the borehole and reaches the slurry line 130 ("upstream pipe"). In the figure, three separate storage sections are shown, each having pressures P1, P2, and P3. In this example, the pressure in the cryogenic liquid supply line is higher than the pressure in the crushing chamber and also higher than the pressure in the slurry line.

[0069] Various types of liquids can be ejected from the liquid ejection device of the crushing drill head. In some cases, the liquid may be water. Therefore, the cryogenic liquid supply line may be able to supply cryogenic water. Water is particularly effective and readily available, but higher density liquids are also useful in increasing momentum at certain velocities and thereby increasing the crushing rate. Using liquids with a higher heat capacity is also useful in cooling the rock mass more efficiently. In some cases, fine particles can be suspended as solid reinforcing particles to increase the viscosity and heat capacity of the liquid. Generally, additives may be used in combination depending on the application. Suitable additives include, but are not limited to, scale inhibitors, foaming agents, tracers, reinforcing particles, and propane. Furthermore, the liquid may be an ordinary liquid or a supercritical liquid.

[0070] Figure 4 is a cross-sectional view of another example of the crushing drill head 200. Several components are added to this example. Similar to Figure 1, this example includes a drill head body 202, a liquid inlet 208, a liquid supply line 210, an internal cryogenic liquid connection 212, a plurality of liquid injection units 214, and a flow rate control device. In the example shown in Figure 4, the flow rate control device comprises a combination of valves. A main valve 218 is located above the internal cryogenic liquid connection and regulates the flow of cryogenic liquid throughout the entire drill head. A control valve 220 connected to the liquid injection units is also shown. This control valve can direct liquid to each group of individually controlled liquid injection units. Furthermore, any of these valves can be used to pulse the liquid flow. In the example shown in Figure 4, a chiller 222 is connected in series with the internal cryogenic liquid connection. The chiller may in some cases be a thermoelectric chiller. This chiller can cool the liquid sufficiently before it is injected towards the hot rock body to cause cracking. However, in some cases the temperature of the liquid may be higher than the freezing point of water.

[0071] In the example shown in Figure 4, the added components are a number of slurry recovery ports 224 located on the side of the drill head body. These slurry recovery ports are connected to an internal slurry connection section 226 that leads to a slurry outlet 228 on the drill head body. A slurry line 230 is connected to the slurry outlet, through which the slurry is sent to the surface. These slurry recovery ports are used to collect the slurry generated during drilling, which is a mixture of liquid and crushed rock fragments. In this example, a slurry pump 234 is also provided on the internal slurry connection section, which pumps the slurry through the slurry line.

[0072] Figure 4 also illustrates wheels 236 mounted on the side of the drill head body. These wheels perform one or all of the following functions: (1) centering the drill head in the borehole, (2) locking the drill head in place in the borehole, and (3) propelling and steering the drill head. Each wheel extends outward from the drill head body toward the inner wall of the borehole. Each wheel is mounted in a spring and functions as a borehole centering device. Alternatively, a standard spring-type "borehole centering" method can be used. As an example, these wheels can be hydraulically driven using the energy of a liquid flowing through a cryogenic liquid supply line. An energy conversion mechanism such as a turbine can be used to drive the wheels using the energy of the flowing liquid. As another example, these wheels can be driven by an electric motor or by other means. As yet another example, these wheels can be driven without any driving, and the drill head can be propelled in the depth direction using gravity acting on it. Alternatively, the drill head can be connected to the ground with a rigid wire, and the drill head can be pushed downward from the ground by pushing the rigid wire from the ground. Another example is that these wheels can be equipped with a braking mechanism to lock them in place, thereby holding the drill head in place as needed. Yet another example is that a mechanism for locking the drill head in place may be provided, such as a retractable rod or spike. Holding the drill head in place may be effective when the liquid injection unit is in operation, as this can contain the pressure generated by the liquid injection unit below the drill head without causing the drill head to float.

[0073] The example shown in Figure 4 also includes an inflatable packer 238. This inflatable packer may have the shape of an air-inflatable annular ring or torus that encircles the drill head body. The inflatable packer may also extend parallel to the length of the drill head. The inflatable packer inflates upon air injection, sealing the space between the drill head body and the inner wall of the borehole. When the packer expands in this manner, it can work in cooperation with the borehole to form a seal. This seal makes it easier to contain the pressure generated by the liquid injection section and the expansion due to the temperature rise of the working fluid, keeping the working fluid in a supercritical state. Thus, the pressure in the fracturing chamber 152, or the volume of the borehole below the drill head, can be controlled. As a general guideline, the pressure in the fracturing chamber is 5-10% less than the hydrostatic pressure, transiently less than 50% or more than 100% of the hydrostatic pressure, but lower than the lithostatic pressure. For example, at a depth of 10 km, the rock-static pressure is approximately 265 MPa and the hydrostatic pressure is approximately 100 MPa, while at a depth of 20 km, the rock-static pressure is approximately 530 MPa and the hydrostatic pressure is approximately 200 MPa.

[0074] In some cases, a second inflatable packer can be added next to the first inflatable packer to enhance the seal. In other cases, the inflatable packer may contain an inflatable inner tube that inflates with a fluid such as air or liquid. In some cases, the packer may be inflated using a liquid supplied through a cryogenic liquid supply line. In yet another example, the inner tube may be protected by an outer layer made of abrasion-resistant material. For example, the inner tube may be protected by passing it through a Kevlar fiber or carbon fiber sleeve. In yet another example, a rigid seal may be placed on top of the inner tube. This rigid seal may be made of rubber, silicone, plastic, metal or other material that can withstand a sufficiently wide temperature range, pressure and abrasion, and can expand its diameter from the diameter of the drill head body to the diameter of the borehole. When these packers inflate, the rigid seal presses against the inner wall of the borehole, sealing the borehole. The seals formed by these inflatable packers can prevent any liquid from passing through them, although some leakage is often permissible as long as the target pressure is maintained within the annular sealing area. For example, the maximum target pressure is 20% lower than the hydrostatic pressure, and transiently may exceed 100%, but the pressure at the bottom of the inlet pipe to the device coincides with the above peak range. In some cases, the drill head can be locked in place in the borehole before the packer expands. As mentioned above, the drill head can be locked in place using brakes or other mechanisms. These packers can be deflated before the drill head is unlocked, allowing the drill head to move further into the borehole.

[0075] Figure 5 is a front perspective view of the crushing drill head 200. Multiple liquid injection ports 214 are depicted as multiple holes on the main surface of this crushing drill head. As described above, liquid is supplied to all of these arranged liquid injection ports from the cryogenic liquid supply line 210 through the internal cryogenic liquid connection ports. Because the main surface of the drill head body has curvature, each liquid injection port is oriented in a different direction.

[0076] Figure 5 also shows a plurality of slurry recovery ports 224 on the side of the drill head body 202, arranged slightly behind the main surface. When rock fragments are broken up in the liquid injection section, a slurry of liquid and rock fragments is pumped out of the borehole through these slurry recovery ports. The slurry is pumped up through the slurry line 230, which is shown in Figure 5 as an upward line inside the borehole next to the liquid supply line 210. The inflatable packer 238 is also shown immediately behind these slurry recovery ports. This packer can inflate to seal the borehole where liquid is injected towards the rock and slurry is collected. The figure also shows a plurality of wheels 236 on the side of the drill head body. These wheels extend toward the inner wall of the borehole and, as described above, can propel the drill head inside the borehole.

[0077] In some cases, the main surface of the drill head body may be equipped with a component that inflicts mechanical damage on the rock in the borehole. After cracking the rock by thermal fracturing, it may be effective to use the mechanical component on the drill head body to scrape away the cracked rock and thoroughly remove rock fragments from the cracked area. In some cases, this mechanical damage component may consist of protrusions arranged in a cross-shaped area between the groups of liquid injection nozzles shown in Figure 5. These protrusions may be scraping plates made of metal, diamond, carbide, or ceramic, pointed spikes, or other components. The main surface of the drill head may also be rotatable by being equipped with a "rotating union". In some cases, each liquid injection nozzle on the main surface can be angled relative to the main surface to generate torque that gives rotational motion to the main surface. In other cases, a rotary drill, impact drill, or other mechanical drill may be provided on the main surface. Alternatively, or in addition to this, multiple grooves can be provided on the main surface of the drill head body to guide the liquid flow toward the edge of the main surface and to a discharge channel for the liquid or slurry.

[0078] Another similar example is shown in Figure 6. This figure is a side view of a crushing drill head 200 installed in a borehole 250. The drill head is connected to a cryogenic liquid supply line 210 and a slurry line 230. This example also includes multiple wheels 236 on the side of the drill head. Multiple inflatable packers 238 are also provided on the side of the drill head to seal the space between the drill head and the wall of the borehole. As the drill head forms a crushing slurry, this slurry flows out through a slurry recovery port 224 on the side of the drill head.

[0079] Figure 7 shows a schematic diagram of the liquid control system for an exemplary crushing drill head 100. In this figure, four separate liquid reservoirs are shown as “reservations” having pressures P1, P2, P3, and P4, respectively. Each reservoir is: (1) the liquid in the cryogenic liquid supply line 210 (labeled “downward pipe”), (2) the cryogenic liquid in the internal cryogenic liquid connection section 212 (labeled “cooling chamber”) where the chiller 222 is located, (3) the liquid injected from the liquid injection section and occupying the space outside the drill head body and the space inside the slurry recovery port (labeled “crushing chamber” 252), and (4) the slurry being pumped up towards the ground through the slurry line 230 (labeled “upward pipe”). The temperatures of these four types of reservoirs may differ individually. Also, the pressure of these reservoirs may decrease from P1 to P4 in some cases. The figure also shows a cryogenic liquid valve 240 installed on the ground and another valve 218 that controls the flow of cryogenic liquid towards the cooling chamber within the drill head. Two valves 220 control the liquid flow toward two groups of liquid injection sections. Furthermore, a slurry valve 232 is installed below the slurry pump 234. This slurry pump pumps slurry through the slurry line, and another slurry pump installed on the ground may be responsible for further pumping of the slurry.

[0080] These valves and pumps can all be considered as components of a flow control system. In some cases, this flow control system can control the pressure of each reservoir shown in Figure 7. The flow control system may also incorporate or be able to communicate with various sensors. These sensors can monitor the characteristics of the drill head, borehole, and surrounding rock formations. In some cases, these sensors may be temperature sensors, hydraulic sensors, acoustic sensors, proximity sensors, and others. For example, data from acoustic and thermal sensors can be combined to make a decision to pause fracturing and wait for the exposed rock surface to reheat if the fracturing rate falls below a desired threshold. Hydraulic sensors can also provide data to the flow control system's control system, which can maintain or change the liquid in different chambers to control the rate of cracking and fracturing. Since the type and properties of the rock and the thermodynamic conditions change as the drilling equipment advances, in-situ tests / experiments can be performed to capture the cracking rate as a function of temperature difference and pressure / mass flow velocity.

[0081] In one example, the flow control device can be used to operate multiple valves and pumps in a specific sequence. For example, the flow control device can open a valve that controls the liquid injection section, allowing the liquid to be injected towards the rock. Simultaneously, the flow control device can close valves on the slurry line to confine pressure in the space outside the liquid injection section and protect the slurry pump from high pressure. This is called pulsed driving of the liquid injection section. After a predetermined time, the valves controlling these liquid injection sections are closed, stopping the liquid flow from the liquid injection section. Subsequently, the slurry valve is opened, and the slurry pump is started, allowing the slurry, a mixture of liquid and rock fragments, to be pumped out from the space below the main surface of the drill head. Alternatively, in another example, the slurry pump can be kept running continuously while liquid is being injected from the liquid injection section. This allows for continuous injection towards the rock, and the liquid can be continuously pumped out through the slurry line. Therefore, depending on the specific application, each pump and valve can be operated in "start / stop" mode or continuous mode.

[0082] Furthermore, the movement of the crushing drill head itself can be configured to be either start-stop type in some cases or continuous type in others. In one example, the crushing drill head can advance to a certain point in the borehole and stop there. The inflatable packer is inflated to hold the crushing drill head in place, and during this time, the liquid injection part is used to crack the rock and remove the rock from the bottom of the borehole. After removing the desired amount of rock, the inflatable packer is deflated or retracted to advance the crushing drill head further in the borehole. In another example, the crushing drill head may move continuously as the borehole extends. In one example, the inflatable packer can be configured to slide along the wall of the borehole while maintaining a complete or partial seal against the wall of the borehole.

[0083] In one example, the drill head may be equipped with a telescopic front section that can advance toward the depths of the borehole while its main body is locked in place. This telescopic section comprises a main surface of the drill head and multiple liquid injection nozzles. Depending on the circumstances, this telescopic section may be able to slide freely or be detachable from other parts of the drill head body and operate independently. This allows drilling to continue to a depth greater than that of the drill head body, within the reach of the telescopic section, while the drill head body remains locked in place. This is useful for keeping the main surface of the drill head at a substantially constant distance from the rock layer in which the cracks are progressing. Therefore, this telescopic section can descend into the borehole at the same rate at which the rock mass is being removed by fracturing. In examples equipped with multiple inflatable packers, it is preferable to reduce the frequency of their expansion and contraction to reduce wear and damage to the inflatable packers. By keeping the inflatable packer in place while the telescopic section of the drill head is extended, a significant amount of rock can be removed before the inflatable packer deflates and the entire drill head body descends into the borehole. This extends the life of the packer (or other sealing element) and speeds up the drilling process. In yet another example, the telescopic section can extend in the depth direction until it physically contacts the rock body below the drill head. This telescopic section may be equipped with mechanical damage-inflicting means that can mechanically damage the rock body, such as projections protruding from the main surface. The telescopic section may be designed to rotate so that the mechanical damage-inflicting means scrapes off rock fragments through rotation. Alternatively, the telescopic section may strike the rock body like a hammer to inflict mechanical damage. This mechanical damage enhances the fracturing of the rock body through thermal fracturing.

[0084] Figure 8A shows a portion of an exemplary crushing drill head, including a drill head body 202 with an extension section 204. This extension section is located at the front end of the drill head and has a primary drilling surface. This example also includes a sliding connector 213 on an internal liquid connector that supplies liquid to the liquid injection section. Figure 8A shows the extension section in the retracted position, and Figure 8B shows it in the extended position. By extending the drill head in this way, the main surface of the drill head descends as the rock layer is removed below the drill head, while the remaining drill head body remains stationary. The inflatable packer 238 is inflated as shown. By keeping the drill head stationary for an extended period, the drill head can operate for a longer time before the inflatable packer is inflated and deflated. This example also includes mechanical damage-inducing means 282 on the primary drilling surface. In this particular example, the mechanical damage-inducing means are a number of bumps on the primary drilling surface that promote cracking and help remove rock fragments. The telescopic section described above can be designed to rotate as the mechanical damage-inducing means contacts and rotates the rock body, generating the force necessary for mechanical scraping and grinding. Alternatively, the telescopic section may be designed to strike the rock body with a striking motion, thereby inflicting mechanical damage upon it.

[0085] Figure 9A shows, as an example, how a crushing drill head 200 forms a curved borehole 250 through maneuvering. Depending on the circumstances, each liquid injection unit can be controlled to inject a larger amount of liquid on one side of the borehole and a smaller amount on the opposite side. This causes more cracks in the rock mass on one side than on the other. As a number of rock layers are cracked and removed in this way, the borehole becomes more likely to curve in that direction. Figure 9B is a magnified view of the crushing drill head after it has descended. In this example, a larger amount of rock mass has been removed on the left side of the borehole, causing the borehole to curve to the right. Depending on the circumstances, to curve the borehole, a larger amount of liquid can be injected on the opposite side of the direction in which the borehole is to bend. For example, if the borehole is to bend to the left, a larger amount of liquid can be injected on the right side of the borehole. Alternatively, a larger amount of liquid can be injected on the same side as the direction in which the borehole is to bend. Furthermore, when operating the drill head, it may be possible to use only some of these liquid injection sections while excluding others, or to inject a larger volume of water from some sections than from others. In some cases, each liquid injection section may be individually controllable, and thus the amount of liquid injected from each section can be adjusted to be greater or less. In other cases, these liquid injection sections can be grouped into groups or zones. Each group of injection sections can be independently controlled. In some examples, these liquid injection sections can be divided into 2, 4, 8, or other convenient numbers of groups. Each group can be controlled by a flow control device, with each liquid injection section individually equipped with a valve that can adjust the liquid flow to its respective group. Because the fluid dynamics in the space in front of the drill bit are very complex, it can be difficult to predict the effect of adjusting each liquid injection section. Therefore, experimental studies may be conducted to determine an appropriate control system for each liquid injection section to achieve the desired curvature of the borehole. When a borehole curves, the fracture drill head changes direction gradually. In some cases, the radius of curvature of the borehole formed by the crushing drill head may be approximately 100m to 500m.

[0086] Figure 10A is a cutaway view of an exemplary crushing drill head 200 equipped with multiple groups 206 of liquid injection nozzles 214. In this example, these liquid injection nozzles are divided into four groups, each group located in one of the four quadrants of the main surface of the drill head. The liquid flow through each group of these liquid injection nozzles is controlled by individual valves 220 within the drill head. A main valve 218 is also connected to a cryogenic liquid connection 212 and all the liquid injection nozzles and can be used to adjust the overall flow velocity of all these liquid injection nozzles. This main valve, and / or individual control valves, can also be used to pulse the liquid flow through these liquid injection nozzles. Individual control valves can be used to manipulate the drill head by causing larger cracks in the rock mass on either side of the borehole 250. As seen in the previous example, the drill head is equipped with a plurality of wheels 236, which may be used for propelling the drill head, assisting in steering, centering the drill head in the borehole, and / or locking the drill head in a predetermined position in the borehole.

[0087] Figure 10B is an enlarged cutaway view of the control mechanism used in the example shown in Figure 10A. Multiple control valves 220 are arranged around the cryogenic liquid connection section 212. Each control valve can control or shut off the liquid flow from one quadrant of the mechanism. Each quadrant is connected to four groups 206 of the liquid injection section 214. Figures 10C and 10D are cross-sectional views of the control valves in the open and closed positions, respectively. In Figure 10C, showing the open position, the control valve comprises a wedge portion 270 and a screw-type actuator 272 which can be hydraulically or electrically driven. The wedge portion is hinged and can rotate in and out of the flow path. When the control valve is open, the force of the liquid descending inside the valve keeps the wedge portion outside the flow path. The screw-type actuator may be a threaded screw and can move up and down by rotation. In Figure 10D, showing the closed position, the screw-type actuator rises to push the wedge portion upward, and the wedge portion moves into the flow path. The wedge moves across the flow path, completely closing the valve. The walls or barriers separating the four quadrants of the pipe may have openings above the valve locations, so that when a valve is closed, for example, liquid from the closed quadrant is diverted to the open quadrant. Figure 10E is a cross-sectional view of the control valves as seen from the upstream side of the liquid flow. In the first example, all four control valves are fully open. In the second example, two of these valves are open and two are closed to steer the drill head westward (with the top of the plane of the vertical borehole facing north). In the third example, for steering northward, a pair of another drill head is open and another pair is closed. In some cases, the drill head can also be steered in the opposite direction to the two open valves. This is because the open valves eject liquid through the liquid injection section, resulting in more rock fracturing on the side of the drill head where the valves are open.

[0088] Figures 11A and 11B show an example of a crushing drill head 300 drilling a lateral secondary borehole 350 obliquely to a central borehole 250. In this example, a base unit 370 is installed inside the primary borehole. This base unit deploys a smaller crushing drill head from its side to drill the lateral secondary borehole. The secondary borehole is almost perpendicular to the primary borehole. Drilling lateral secondary boreholes in this manner is considered effective in various situations. For example, when producing energy from a geothermal layer, a network of lateral boreholes can be formed and used for heat transfer. In this case, the base unit does not have any drill heads or drilling mechanisms other than the deployable lateral drill head. Figure 11C shows yet another example. In this figure, the crushing drill head is operated to form a loop-shaped secondary borehole. This loop-shaped secondary borehole can be completed by maneuvering the fracturing drill head toward the primary borehole, thereby creating a complete loop. Such a loop-shaped secondary borehole can be used, for example, to pump a heat transfer liquid through it to produce geothermal energy. Figure 11D shows a primary borehole and a secondary borehole that curves away from the primary borehole, where the secondary borehole is formed as a partial loop that looks back toward the primary borehole. In some cases, the base unit that feeds the secondary fracturing drill head may be a geothermal drilling machine as described in U.S. Patent No. 11,029,062, which is incorporated herein by reference. In other examples, the base unit may feed a lateral secondary fracturing drill head and guide a cryogenic liquid supply line and a slurry line from the surface to the secondary fracturing drill head.

[0089] Figure 12 shows another example of a base unit 370 that deploys a secondary drill head 300. This base unit includes a liquid supply line 210 that runs from the ground to the base unit. The liquid flows through this liquid supply line to a cryogenic liquid pump 242 in the base unit. This cryogenic liquid pump can pressurize the liquid before sending it to the secondary drill head. The base unit also includes a slurry pump 234 that returns slurry to the ground through a slurry line 230. Below the cryogenic liquid pump and slurry pump, both the liquid supply line and the slurry line may be housed in a hose 244. This hose may be coiled 246 within the base unit. The other end of the hose may be at or near the location of the secondary drill head. Thus, as the secondary drill head drills further away from the primary borehole, the hose unwinds and extends from the base unit, maintaining the connection between the drill head and the liquid supply line and slurry line. The coil of this hose is wound around a rotating drum 248, and a rotating union is provided as its base 258.

[0090] Figure 13A shows an example of a crushing drill head 300 for forming a horizontal borehole 350. This example further includes several liquid injection nozzles 380 on the side of the drill head body. These liquid injection nozzles are used to form a network of microcracks 354 in the wall of the horizontal or vertical borehole, depending on the drilling direction. The crushing drill head shown here also includes two inflatable packers 338. One inflatable packer is located near the front end of the drill head body, and the other is located near the rear end of the drill head body. Several lateral liquid injection nozzles are positioned on the side of the drill head body, between these two inflatable packers. When both inflatable packers inflate, the space between the side of the drill head body and the wall of the borehole is isolated. This allows the lateral liquid injection nozzles to inflict more microcrack damage on the wall of the borehole. Damaging the walls of a borehole in this way is useful, for example, in increasing heat transfer from the rock body when the borehole is used for geothermal production. Maintaining pressure or adding propane to the injected liquid also helps to reduce or prevent self-heating of microcracks that tend to occur as the temperature rises.

[0091] Figure 13B shows an example of a crushing drill head 300 for forming a horizontal borehole 350. The drill head body is equipped with multiple liquid injection nozzles 380 on its side to damage the wall of the borehole. However, in this example, the liquid injection nozzles are positioned in specific areas to form localized damage zones 356 that penetrate deeper into the rock. This is different from the example shown in Figure 13A. In the example in Figure 13A, the liquid injection nozzles are spaced apart across the entire side of the drill head body, causing widespread damage across the entire wall of the borehole. On the other hand, the example shown in Figure 13B can form localized damage zones that penetrate deeper into the rock of the borehole wall. The crushing drill head in this example also is equipped with multiple lateral mechanical damage heads 382 near the front end of the drill head body. These lateral mechanical damage heads may be small rotary drill heads or small impact drill heads. In one example, the crushing drill head shown in Figure 13B can be positioned at a desired location within the borehole, and multiple inflatable packers 338 can be inflated to seal the space between the drill head body and the borehole wall, while also holding the drill head in place. This lateral mechanical damage head can then be used to form a localized damage area on the borehole wall. Subsequently, the inflatable packers can be deflated, allowing the crushing drill head to advance slightly until the localized damage area aligns with the first set of lateral liquid injection nozzles on the side of the drill head body. The inflatable packers can then be inflated again, spraying liquid from the first set of liquid injection nozzles towards the rock mass, generating more microcracks in the rock mass. These microcracks grow using the already damaged areas as nuclei, thus forming a network of deeper microcracks at those locations. Simultaneously, the lateral mechanical damage head can also be used to form other sets of localized damage areas. Next, the fracture drill head can be advanced again until the microcrack network aligns with a second set of lateral liquid jets. This second set of lateral liquid jets can inject liquid into the rock mass, increasing the depth of the microcrack network.In this way, a deep damage zone can be formed on the wall of the borehole. Note that the example shown in Figure 13B has one set of mechanical damage heads and two sets of lateral liquid injection units, but there can be any number of mechanical damage heads and lateral liquid injection units.

[0092] Cryogenic fracturing and drilling method This disclosure also describes a cryogenic fracturing drilling method. In one example, the cryogenic fracturing drilling method may include the steps of: installing a cryogenic fracturing drill head equipped with at least one liquid injection unit in a borehole; injecting liquid from at least one liquid injection unit toward the rock body of the borehole, thereby creating a temperature difference between the temperature of the liquid and the temperature of the rock body sufficient to cause the rock body to contract due to the liquid injection, thereby cracking the rock body and forming loose rock fragments by a combination of thermal fracture and hydraulic pressure; and removing the liquid and the loose rock fragments from the borehole in the form of a slurry.

[0093] Depending on the circumstances, the step of installing a cryogenic fracturing drill head in a borehole may include the step of forming the borehole using the cryogenic fracturing drill head. In one example, the drill can be used as a high-temperature fracturing drill head for a while after drilling the borehole from the surface side where the rock body temperature is relatively low. Then, when the drill head reaches the higher temperature rock body underground, the operating mode can be switched to cryogenic fracturing. In another example, the initial part of the borehole can be drilled from the surface with a mechanical drill head such as a rotary drill head or an impact drill head. This mechanical drill head can be used up to a depth where the rock body temperature becomes high, for example, above 100°C, above 200°C, above 300°C, above 400°C, or above 500°C. The rock body may become more brittle as the temperature increases, which reduces the effectiveness of the mechanical drill head. At this point, the mechanical drill head can be withdrawn and the cryogenic fracturing drill head can be lowered into the borehole. From now on, this low-temperature fracturing drill head can be used for drilling high-temperature rock bodies.

[0094] The cryogenic fracturing drilling method described here can also be described as a method of drilling secondary or tertiary boreholes using a cryogenic fracturing drill head. The secondary or tertiary boreholes may branch off from other boreholes.

[0095] The liquid injection unit described above may be pulse-driven. This means that the liquid flow from the injection unit increases and decreases repeatedly over the control period. In some cases, the liquid flow may be completely interrupted during the time between pulses, and in other cases, the liquid flow may continue but be reduced during the time between pulses. In some cases, the pulse drive may be an oscillatory drive such that the time variation of the pressure follows a sinusoidal pattern. The pulse length and pulse interval may depend on practical factors such as the temperature difference between the liquid and the rock, the thermal expansion of the rock, and the time the drill head is advanced within the pulse interval, as well as various other factors. The pulse duration can vary from 0.1 seconds to several days. Similarly, the pulse interval can also vary from 0.1 seconds to several days.

[0096] In some cases, the crushing drill head can form a damage zone in the wall of the borehole, as shown in Figures 13A and 13B. If the borehole is used for geothermal extraction, this damage zone can facilitate heat transfer between the rock mass and the liquid that can flow through the borehole, which may be effective in extracting heat. Depending on the circumstances, if the temperature of the rock mass is sufficiently high, microcracks in the high-temperature rock mass may naturally repair themselves over time. Therefore, in some cases, it may be effective to fill the borehole with a coolant to prevent the repair of microcracks.

[0097] Each of the crushing drill heads described and illustrated herein is intended for carrying out the method described herein, but any other apparatus may be used in this method. For example, a geothermal drilling machine may be used, which may be equipped with a drilling drill as a primary drill bit, a secondary drill bit, a tertiary drill bit, or a combination thereof. Furthermore, a base unit may be lowered into the primary borehole, and a crushing drill bit may be deployed from this base unit to drill a lateral secondary borehole.

[0098] Figure 14A shows a side view of an example of a fracturing drill head 100 used in high-temperature fracturing drilling, along with several additional drawings illustrating the high-temperature fracturing process. The enlarged view of the fracturing chamber 101 shown here corresponds to a dashed frame enclosing a small area of ​​the primary drilling surface of the drill head and the rock mass undergoing cracking. In this figure, the high-temperature liquid is injected from the liquid injection nozzle toward the wall of the borehole. This high-temperature liquid heats the uppermost layer of the rock mass, causing it to expand along a temperature gradient perpendicular to the liquid-rock boundary. This expansion creates small cracks within the uppermost layer of the rock mass, which are then removed by the liquid stream ejected from the injection nozzle. An enlarged view of the rock mass 103 is also shown. In this figure, the thermal expansion of the rock mass is indicated by outward-pointing arrows within individual fragments. The stress resulting from this thermal expansion causes cracks in the rock mass, which then break into smaller fragments. Thermal expansion increases as the temperature of the rock mass approaches the temperature of the hot liquid being ejected, as shown by the temperature gradient. The degree of thermal stress (and the resulting crack shape) depends on various factors such as the anisotropy of thermal stress (expressed as the relative magnitude of arrows perpendicular to the directions parallel and perpendicular to the lattice plane within each crystal grain), the degree of inter-grain orientation difference, the shape and properties of grain boundaries, and the boundary conditions of rock masses of any size. Figure 14A also shows a series of graphs of properties including temperature 10⁵, pressure 10⁷, and cracking rate 10⁹. These properties change with the rock layer during fracture and the height of the liquid in the fracture chamber. Liquid temperature T f This is the initial temperature of the high-temperature liquid before it is ejected from the drill head. Once ejected from the liquid ejection nozzle, the liquid becomes turbulent, and its temperature undergoes significant spatial fluctuations within the turbulence. These temperature fluctuations are shown by the broad line in the temperature graph. The temperature decreases as it approaches the rock mass. There are also some temperature fluctuations in the rock layer during fracture, and the temperature T within the rock mass... r The lower temperature T of the bulk rock mass that has not yet cracked 0 r The pressure decreases in the depth direction until it reaches a certain point. The pressure graph shows the liquid pressure P f The pressure P of the rock body rThe graph shows that it is lower than the given value, and broad lines represent local pressure fluctuations within the turbulence and fracture layers. In the same graph, the curve labeled |σ'| represents the magnitude of the stress difference within the rock body. This stress increases within the fracture layer as the rock body heats and expands, but drops sharply to zero when the rock fragments break apart. The magnitude of the stress depends on local temperature changes, but also on the temperature gradient. The graph of cracking rate shows that the cracking rate increases from the bottom to the top of the fracture layer, and drops sharply to zero when the rock body cracks and breaks into fragments. These values ​​fluctuate both over time and spatially, and in ideal steady-state fracture drilling, they propagate together as a coherent front within the rock body.

[0099] Figure 14B shows a side view of an example of a fracturing drill head 100 used in cryogenic fracturing drilling, along with several additional drawings illustrating the cryogenic fracturing process. The enlarged view of the fracturing chamber 101 shown here corresponds to a dashed frame enclosing a small area of ​​the primary drilling surface of the drill head and the rock mass undergoing cracking. In this example, the cryogenic liquid is injected into the hot rock mass within the borehole. The rock layer is cooled, and thermal contraction causes the rock mass to crack and break into fragments. The enlarged view shows how the rock mass is broken into fine fragments, which are removed by turbulent liquid flow within the fracturing chamber space below the drill head. An enlarged view of the rock mass 103 is also shown. In this figure, the thermal contraction of the rock mass is indicated by inward-pointing arrows within the individual fragments. This thermal contraction causes the rock mass to crack and break into fragments. Thermal contraction increases as the temperature of the rock mass approaches the temperature of the injected cryogenic liquid. Figure 14B also shows a series of graphs of properties including temperature 105, pressure 107, and cracking rate 109. The signs are as previously described. These properties vary depending on the rock layer undergoing fracture and the depth of the liquid in the fracture chamber. The liquid temperature is the initial temperature of the low-temperature liquid before it is ejected from the drill head. Once ejected from the liquid injection nozzle, the liquid becomes turbulent, and the temperature of this liquid undergoes large spatial variations within the turbulence. These temperature variations are shown by the broad line in the temperature graph. The temperature increases as it approaches the rock mass. There are also some temperature variations in the rock layer undergoing fracture, and the temperature in the rock mass increases in depth until it reaches the temperature of the bulk rock mass that has not yet cracked. The pressure graph shows the liquid pressure P.f The pressure P of the rock body r The graph shows that it is lower than the given value, and the local pressure fluctuations within the turbulence and fracture layers are shown by broad lines. In the same graph, the curve labeled |σ'| represents the magnitude of the stress difference within the rock body. This stress increases within the fracture layer as the rock body cools and shrinks, but drops sharply to zero when the rock fragments break down after cooling. The graph of cracking rate shows that the cracking rate increases from the bottom to the top of the fracture layer, and drops sharply to zero when the rock body cracks and breaks into fragments.

[0100] The design intent of this embodiment, which includes a fracturing chamber, is to control the liquid flow inside and outside the fracturing chamber, thereby precisely adjusting the temperature and pressure changes within the chamber, as well as the temperature gradient and stress in the fracturing layer, in order to maximize the drilling speed while discharging the slurry. By defining several operating mode conditions and combining them sequentially as needed, the optimal thermal gradient and cracking rate can be maintained. "Primary sealing" is the condition in which both the inlet and outlet valves are closed, and the liquid and rock in the fracturing chamber reach thermal equilibrium. In the case of low-temperature fracturing, both the temperature and pressure of the liquid rise. In "steady flow," the inlet and outlet are kept at the same rate, and the temperature on the surface side is always kept the lowest. In the "active pressure control" condition, the liquid pressure inside the fracturing chamber decreases or increases. Lowering the hydraulic pressure makes it easier for cracks to grow due to a decrease in local vertical stress, causing the liquid to vaporize within the cracks and widening the pressure difference between the pressure inside the rock body due to lithostatic pressure and the local pressure inside the chamber. This is achieved by decreasing the flow velocity inside the chamber and increasing the flow velocity outside the chamber. On the other hand, increasing the hydraulic pressure increases the water pressure inside the cracks, causing the cracks to propagate forward (i.e., small-scale hydraulic fracture). This is achieved by decreasing the flow velocity outside the chamber and increasing the flow velocity inside the chamber. All of the above conditions, as well as those not described herein, can be achieved by combining the packer, slurry discharge channel, jet liquid flow, and the liquid injection unit of the present invention, which are central elements of this design and control of the thermal imbalance between the rock body and the liquid.

[0101] The exemplary crushing drill heads and systems described so far, specifically for cryogenic crushing drilling, can also be applied to high-temperature crushing. To use each of the above drill heads for high-temperature crushing drilling, high-temperature liquids can be used instead of cryogenic liquids. Therefore, the "cryogenic liquid supply line" or "cryogenic fluid supply line" can be replaced with a high-temperature liquid supply line. Similarly, the "cryogenic liquid connection" or "cryogenic fluid connection" can be replaced with a high-temperature liquid connection, and so on. In further examples, the crushing drill head can incorporate a heater instead of a chiller. Thus, each of the above crushing drill heads can be adapted for high-temperature crushing drilling.

[0102] All electronic and hydraulic equipment built into the device to maintain its operating temperature can also be used under high ambient temperature conditions. Although not shown in the diagram, such temperature control elements can utilize the cryogenic liquid flowing into the device, as well as thermoelectric and other cooling mechanisms.

[0103] The features, structures, and characteristics described above may be appropriately combined in any way in one or more examples. Specific details have been explained so far through various configuration examples to ensure a thorough understanding of each example of the present invention. However, those skilled in the art will realize that the present invention can be implemented even without one or more of the above specific details, or by using other methods, components, or apparatus. In other examples, known structures and operations are not illustrated or described in order to avoid ambiguity regarding aspects of the present invention.

[0104] The present invention has been described in detail above with specific embodiments as examples. However, various modifications and changes are possible without departing from the scope of the present invention as described in the attached claims. The above detailed description and attached drawings are merely illustrative and not limiting in any way. Even if modifications or changes are made, they will all fall within the scope of the invention as described herein.

Claims

1. A drill head body having a main surface facing the primary drilling direction along the long axis, A liquid inlet is provided at a location on the drill head body opposite to the main surface in the primary drilling direction, and is connected to or can be connected to a liquid supply line, An internal liquid connection part is oriented within the drill head body and connected to the liquid inlet, The drill head body is arranged opposite to the main surface, and a plurality of liquid injection units are supplied with liquid from the liquid inlet through the internal liquid connection part, A crushing drill head comprising, for controlling the delivery of liquid by these liquid injection units, a flow rate control device attached to each liquid injection unit, which is capable of independently controlling the flow velocity of at least two liquid injection units, so as to maintain a steep temperature gradient between the liquid and the rock surface that is sufficient to promote crushing by microcracks in the rock surface caused by a combination of thermal stress and hydraulic stress.

2. The crushing drill head according to claim 1, wherein the crushing drill head does not have a mechanical drill head that performs drilling in the primary drilling direction, and performs non-contact low-temperature crushing in the primary drilling direction.

3. The plurality of liquid injection units include at least two groups of liquid injection units. The crushing drill head according to claim 1, further comprising valves connected to each group of liquid injection units, wherein these valves independently control the liquid injection units to each group, and the crushing drill head can be operated by making the amount of liquid supplied to at least one group at least greater than that of at least one other group.

4. The crushing drill head according to claim 1, wherein the liquid inlet is the sole inlet for the liquid to be delivered, and only one type of liquid is delivered through the crushing drill head.

5. The crushing drill head according to claim 1, wherein the flow rate control device comprises a valve that generates a pulsed flow within the liquid injection section.

6. The crushing drill head according to claim 1, further comprising a cryogenic liquid pump connected to the plurality of liquid injection units and pressurizing the liquid ejected from the plurality of liquid injection units.

7. The crushing drill head according to claim 1, further comprising a chiller attached to the internal liquid connection part within the drill head body for cooling the liquid supplied to the plurality of liquid injection parts.

8. When the portion of the drill head body on which the main surface is located is defined as the front, The crushing drill head according to claim 1, further comprising a slurry recovery port provided on the circumferential surface of the drill head body near the front, and a slurry outlet provided on the drill head body at a location opposite to the main surface in the primary drilling direction, wherein the slurry outlet is connected to the slurry recovery port within the drill head body by an internal slurry connection, and the slurry outlet is connected to or can be connected to a slurry line.

9. A slurry pump attached to the internal slurry connection section for pressurizing a slurry mixture of liquid and rock fragments to the slurry line, and An inflatable packer is provided on the side of the drill head body, and when it expands, it fills and seals the space between the side of the drill head body and the inner wall surface of the borehole well. The crushing drill head according to claim 8, further comprising at least one of the above.

10. The crushing drill head according to claim 1, further comprising wheels on the circumferential surface of the drill head body, wherein each wheel extends outward from the drill head body toward the inner wall surface of the boring well.

11. The crushing drill head according to claim 1, further comprising at least one liquid injection unit facing the circumferential surface of the drill head body.

12. The crushing drill head according to claim 1, further comprising a cryogenic liquid supply line connected to the liquid inlet, which is capable of extending the borehole to the surface while maintaining a steep temperature gradient.

13. The crushing drill head according to claim 1, suitable for use in high-temperature environments of 300°C or higher.

14. The crushing drill head according to claim 1, wherein the flow rate control device is configured to control the liquid flux over time, and the flow velocity is periodically or pulsed in order to maintain a steep temperature gradient sufficient to cause microcracks due to crushing by reheating the rock surface.

15. The crushing drill head according to claim 14, further comprising sensors including one or more of a temperature sensor, a hydraulic sensor, an acoustic sensor, and a proximity sensor, which are used as a feedback signal for adjusting the time control of the liquid flux.

16. A drill head body having a main surface facing the primary drilling direction along the long axis, with the portion where the main surface is located being the front and the portion located opposite the main surface being the rear, A liquid inlet is provided on the drill head body and is connected to or can be connected to a liquid supply line, An internal liquid connection part is oriented within the drill head body and connected to the liquid inlet, The drill head body comprises at least one liquid injection unit facing the main surface, from which liquid is supplied from the liquid inlet through the internal liquid connection portion, A flow rate control device attached to the at least one liquid injection unit controls the delivery of liquid by the at least one liquid injection unit, A slurry collection port is provided on the circumferential surface near the front of the drill head body, A slurry outlet is provided at the rear of the drill head body and is connected to the slurry collection port by an internal slurry connection part within the drill head body, An actuated sealing element provided on the circumferential surface of the drill head body between the slurry recovery port and the slurry outlet, the actuated sealing element operates to temporarily block a portion of the boring well behind the actuated sealing element from a portion of the boring well in front of the actuated sealing element, Equipped with, The actuated sealing element is provided across the circumferential surface of the drill head body, filling and sealing the space between the circumferential surface of the drill head body and the inner wall surface of the boring well, in a crushing drill head.

17. The crushing drill head according to claim 16, wherein the actuated sealing element is provided across the circumferential surface of the drill head body and comprises an inflatable packer that, when expanded, fills and seals the space between the circumferential surface of the drill head body and the inner wall surface of the boring well.

18. The crushing drill head according to claim 17, wherein the drill head body has a cylindrical shape, and the inflatable packer is formed in the shape of an annular tube that encircles the drill head body.

19. The crushing drill head according to claim 16, further comprising a slurry pump attached to the internal slurry connection section for pressurizing a slurry mixture of liquid and rock fragments to the slurry line.

20. The crushing drill head according to claim 16, wherein the slurry collection port is provided on the circumferential surface of the drill head body.

21. The process involves installing a crushing drill head equipped with multiple liquid injection nozzles inside a boring well, The process involves injecting liquid from a liquid injection unit toward the rock body of the borehole, and at that time, creating a temperature difference between the temperature of the liquid and the temperature of the rock body sufficient to cause thermal fracture of the rock body along the primary drilling direction by the liquid injection, thereby forming loose rock fragments through a combination of thermal fracture and liquid pressure. A process in which the flow rate of at least one liquid injection unit is controlled independently of the flow rate of at least one other liquid injection unit, thereby causing different flow rates of liquid to be ejected from each of these independently controlled liquid injection units, resulting in different amounts of destruction. A step of removing the liquid and the floating rock fragments from the borehole in the form of a slurry, A crushing and excavation method comprising the following:

22. At least one of the following conditions, namely, The temperature difference between the ejected liquid and the rock body is approximately 50°C to approximately 800°C; The liquid being ejected is at a lower temperature than the rock body; The temperature of the sprayed liquid is approximately 0°C to approximately 100°C; The process further includes cooling the liquid before it is sprayed. The method according to claim 21, which satisfies the requirements.

23. The method according to claim 21, wherein the crushing drill head performs the drilling in the primary drilling direction by non-contact low-temperature crushing.

24. The method according to claim 21, further comprising the step of operating the crushing drill head to form a curved borehole.

25. A step of filling and sealing the space between the circumferential surface of the crushing drill head and the inner wall surface of the boring well by an actuated sealing element provided over the circumferential surface of the crushing drill head, the actuated sealing element comprising an inflatable packer provided over the circumferential surface of the crushing drill head, A step of increasing the pressure of the liquid after it has been injected toward the rock by inflating the inflatable packer between the circumferential surface of the crushing drill head and the inner wall surface of the borehole, thereby isolating the space containing the liquid injected toward the rock body, The method according to claim 21, further comprising:

26. The method according to claim 25, further comprising the step of inflating a second inflatable packer between the circumferential surface of the crushing drill head and the inner wall surface of the boring well.

27. The method according to claim 21, further comprising the step of injecting a liquid from at least one lateral liquid injection unit in a lateral manner substantially perpendicular to the primary drilling direction.

28. The method according to claim 21, wherein the excavation is performed in the lateral direction.

29. The method according to claim 28, wherein the borehole is a secondary borehole extending laterally from a vertical primary borehole.

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