阅读说明：本技术 用于钻孔的声导航的系统 (System for acoustic navigation of a borehole ) 是由 H·埃尔巴达维 M·C·拉塞尔 C·T·拉塞尔 T·J·艾德 M·布顿 于 2018-01-16 设计创作，主要内容包括：产生用于生成地热能或其他目的的钻孔的方法包括通过使弹丸加速与地质材料接触来形成所述钻孔。所述弹丸与所述地质材料之间的相互作用生成声信号,诸如地层内的振动,所述声信号使用沿着钻井导管、在表面处或在单独钻孔内的声传感器来检测。可以基于所述声信号的特性来确定所述地质材料的特性,诸如硬度、孔隙率或裂缝的存在。可以基于所述地质材料的所述特性来修改所述钻孔延伸的方向,诸如以产生与一个或多个裂缝相交的钻孔,以用于生成地热能。(A method of producing a borehole for the generation of geothermal energy or other purposes comprises forming the borehole by accelerating a projectile into contact with a geological material. The interaction between the projectile and the geological material generates an acoustic signal, such as vibrations within the formation, which is detected using acoustic sensors along the drill pipe, at the surface, or within a separate borehole. A characteristic of the geological material, such as hardness, porosity or the presence of fractures, may be determined based on a characteristic of the acoustic signal. The direction in which the borehole extends may be modified based on the characteristics of the geological material, such as to create a borehole intersecting one or more fractures for generating geothermal energy.)

1. A method for generating power using a borehole, comprising:

accelerating a first projectile through a conduit, wherein the first projectile interacts with a geological material at a first location to form at least a portion of a borehole;

circulating a first material associated with an interaction between the first projectile and the geological material away from the first location;

determining that a first temperature of the first material exceeds a threshold temperature; and

providing a fluid having a second temperature less than the first temperature into the borehole based on the first temperature exceeding the threshold temperature.

2. The method of claim 1, further comprising:

generating electricity using a thermoelectric element, wherein:

the fluid having the second temperature is located on a first side of the thermoelectric element,

a geological material is located on a second side of the thermoelectric element; and

the thermoelectric element generates the electrical power based at least in part on a temperature difference between the second temperature and a third temperature of the geological material.

3. The method of claim 1, further comprising:

receiving user input indicative of one or more of an amount of thermal energy or an amount of electrical power;

determining the threshold temperature based on one or more of the amount of thermal energy or the amount of electrical power;

determining a borehole depth corresponding to the threshold temperature; and

extending the borehole to the borehole depth.

4. The method of claim 1, further comprising:

determining an acoustic signal related to an interaction between the first projectile and the geological material at the first location;

determining, based on the acoustic signals, an ability of the geological material to one or more of retain heat or transfer heat;

determining one or more of the threshold temperature, a characteristic of the fluid, or a characteristic of one or more thermoelectric elements used to generate electricity based at least in part on the capability of the geological material;

wherein the fluid having the second temperature less than the first temperature is provided into the borehole further based on the capability of the geological material.

5. A method for generating power using a borehole, comprising:

accelerating the first projectile to interact with the geological material at a first location of the first borehole;

determining that a first temperature of a first material associated with an interaction between the first projectile and the geological material is greater than a threshold temperature; and

providing a fluid having a second temperature less than the first temperature into the first borehole based on the first temperature exceeding the threshold temperature.

6. The method of claim 5, further comprising:

circulating the fluid through one or more of a lateral hole or at least one fracture between the first borehole and a second borehole, wherein heating the fluid to a third temperature greater than the second temperature by one or more of the first borehole, the second borehole, or the one or more of the lateral hole or the at least one fracture; and

generating electricity using heat from the fluid having the third temperature.

7. The method of claim 5, further comprising:

circulating the fluid into the first borehole through a first conduit in the first borehole; and

circulating the fluid out of the first borehole through a second conduit in the first borehole.

8. The method of claim 5, further comprising:

generating electrical power using a thermoelectric element, wherein the fluid having the second temperature and a portion of the first borehole having a third temperature are positioned relative to the thermoelectric element, and the thermoelectric element generates the electrical power in response to a temperature difference between the second temperature and the third temperature.

9. The method of claim 5, further comprising:

determining an acoustic signal related to an interaction between the first projectile and the geological material at the first location;

determining, based on the acoustic signals, an ability of the geological material to one or more of retain heat or transfer heat; and

determining one or more of the threshold temperature, a characteristic of the fluid, or a characteristic of a thermoelectric element used to generate electricity based at least in part on the capability of the geological material.

10. A system for generating power using a borehole, comprising:

a first conduit in a borehole, the first conduit having a first end proximate geological material in the borehole;

a first projectile in the first conduit, wherein the first projectile exits the first conduit to interact with the geological material;

a temperature sensor that determines a first temperature of a first material related to an interaction between the first projectile and the geological material; and

one or more hardware processors executing computer-executable instructions to:

determining the first temperature of the first material; and

circulating a fluid having a second temperature less than the first temperature through the first conduit based on the first temperature.

11. The system of claim 10, further comprising:

an acoustic sensor that detects an acoustic signal generated by an interaction between the first projectile and the geological material; and

computer-executable instructions for:

determining, based on the acoustic signals, an ability of the geological material to one or more of retain heat or transfer heat;

determining a threshold temperature based at least in part on the capability of the geological material; and

determining that the first temperature is greater than the threshold temperature, wherein the fluid is circulated through the first conduit based on the first temperature being greater than the threshold temperature.

12. The system of claim 10, further comprising:

an acoustic sensor that detects an acoustic signal generated by the interaction between the first projectile and the geological material; and

computer-executable instructions for:

determining, based on the acoustic signals, an ability of the geological material to one or more of retain heat or transfer heat;

determining, based at least in part on the capabilities, one or more of:

a property of the fluid; or

Characteristics of a thermoelectric element for generating electricity.

Background

Conventional drilling and excavation methods, such as those used to form wells for the production of hydrocarbon, water or geothermal energy, utilize drill bits to form holes in the earth's surface. Conventional drilling methods can be expensive, material intensive, and time consuming, requiring time varying from minutes to hours or days to remove the geological material and enlarge the depth of the hole by longitudinal scale, depending on the cross-sectional area and characteristics of the material being moved. Additionally, effective location and navigation of conventional boreholes toward geological features may be limited to features that can be easily detected using signals from the surface or by using devices within the drill string.

Drawings

Certain embodiments and implementations will now be described more fully hereinafter with reference to the accompanying drawings, in which various aspects are shown. However, the various aspects may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. The drawings are not necessarily to scale and the relative proportions of the indicated objects may have been modified for ease of illustration rather than by limitation. Like numbers refer to like elements throughout.

FIG. 1 depicts an embodiment of a system for determining a property of a formation using acoustic signals generated by interaction between a projectile and a geological material.

Figure 2 shows a first part of a method for forming a borehole in a geological material by accelerating the interaction of a projectile with the formation ahead of the drill bit.

Figure 3 illustrates a second part of a method for forming a borehole in a geological material by accelerating the interaction of a projectile with the formation ahead of the drill bit.

FIG. 4 illustrates a third portion of a method for forming a borehole in a geological material by accelerating the interaction of a projectile with the formation ahead of the drill bit.

FIG. 5 depicts an embodiment of a system for generating geothermal energy using a borehole.

FIG. 6 depicts an embodiment of a system for generating geothermal energy using a borehole by circulating a fluid in a downhole environment.

Fig. 7 is a diagram depicting an embodiment of a conduit configured to house a thermoelectric element.

FIG. 8 is a flow chart illustrating a method for producing a borehole using data determined from acoustic signals.

FIG. 9 is a flow chart illustrating a method for producing a borehole based on user constraints and data determined from acoustic signals.

Detailed Description

Conventional drilling and excavation techniques for penetrating materials typically rely on a mechanical drill bit for cutting or grinding on a working surface. Tool wear and tear associated with mechanical drill bits may slow these operations, thereby increasing costs. Furthermore, the low schedule in cutting through wear resistant materials such as hard rock can be prohibitively expensive due to the time and cost required. Additionally, the environmental impact of conventional drilling techniques may be significant. For example, conventional drilling techniques may require a large supply of water, which may not be readily available in some areas. As a result, resource mining can be extremely expensive, time consuming, or both. Drilling a well through a geographic formation may be used to create water wells, oil wells, gas wells, underground pipes, geothermal wells, and the like.

For example, geothermal energy may be generated by drilling a borehole into the earth's surface to a depth where the geological formation has a temperature significantly higher than the temperature at the earth's surface. The ambient temperature of rock or other geological material within the borehole increases proportionally based on the depth of the borehole. Heat from the geological material may be conducted to the surface for generating energy, such as by providing cold fluid into the borehole, where the heat from the formation is transferred to the fluid, which is then returned to the surface. For example, fluid may be provided into a first borehole and then circulated out through a second borehole connected to the first borehole. As another example, fluid may be provided to a first drill string or annulus in a single borehole and then circulated outwardly through a second drill string or annulus. In other embodiments, the thermoelectric material may be provided into a borehole formed in the earth's surface. The thermoelectric material can generate electricity, such as an electric current when exposed to a temperature gradient. To create the temperature gradient, a fluid that is cooler than the surrounding geological material may be injected into the borehole, such as within a pipe, conduit, or other type of conduit, and then circulated toward the surface. Fluids within the conduit that are cooler than the geological material outside the conduit create a temperature gradient that can cause thermoelectric materials associated with the conduit to generate an electrical current. One example System for utilizing Geothermal Energy from abandoned oil and gas wells is described in published U.S. patent application 2010/0180593 entitled "System for Closed-Loop Large Scale thermal Energy Harvesting" filed on 21.1.2009, which is incorporated herein by reference in its entirety.

In many cases, it is not economical to form a borehole that extends to a depth sufficient to generate significant amounts of geothermal energy. For example, forming a borehole may require a significant amount of time, equipment, and materials, may incur significant costs, and may create significant environmental impacts. Although human demand for energy continues to increase, the value of geothermal energy available from within a borehole may not offset the significant costs to form the borehole. However, geothermal energy is advantageously not affected by geographical location or climate in such a way that solar energy, wind energy, hydroelectric energy or other renewable energy sources may be affected. Additionally, geothermal energy is not limited in supply or causes significant environmental impact commonly associated with non-renewable hydrocarbon-based energy sources such as coal, oil, and natural gas. Natural radioactive decay within the earth is generally consistent across all geographical locations and provides 85% to 95% of the heat generated, with the remaining heat of the planet being latent heat from planet formation and acceleration.

Described in this disclosure are methods and systems for efficiently producing boreholes for the generation of geothermal energy that may be more economical than conventional methods that utilize geothermal energy. Embodiments may include a scalable, closed-loop system in which the working fluid provided into the system does not contact the geological material, and may not require the use of fracturing techniques (e.g., "hydraulic fracturing"). In other embodiments, artificial or natural stimulation of geological formations may be used to improve the recovery of geothermal energy.

In some embodiments, the borehole may be formed in the earth's surface at least in part by using accelerated projectiles. For example, U.S. patent applications 15/340,753 and 15/698,549, previously incorporated by reference, describe systems and methods in which the progress of a rotary drill bit may be facilitated by accelerating the projectile into the geological material ahead of the drill bit. The accelerated projectiles may be moved through a drill string or other type of conduit by using movement of pressurized materials, combustible materials, drilling fluids or other materials, and the like. In some embodiments, the drill pipe used to form the borehole may comprise coiled tubing, thereby reducing the above-ground drilling infrastructure required to form the borehole when compared to other techniques utilizing other types of drill pipes. For example, a Bottom Hole Assembly (BHA) configured to accelerate the projectiles, such as the BHA described with respect to U.S. patent application 15/340,753, and a drill bit having one or more orifices configured to permit passage of the accelerated projectiles may be secured to the end of a section of coiled tubing. Upon contact with the geological material, the accelerated shot may displace at least a portion of the material and weaken at least a portion of the material to facilitate the ability of the drill bit to displace the weakened material. In some embodiments, to avoid the need to provide shot into a string of continuous tubes that may have a limited diameter, mud or other types of fluids may be used to form the shot, such as drilling fluid, uncured concrete, barite concrete, and the like. A container for receiving mud or other fluid may be positioned downhole and, once filled with material, the container may be accelerated to impact the geological material. In some embodiments, the container for receiving the material may include a resin or other curable material that may be provided downhole as a liquid and then cured, such as by using ultraviolet light, chemicals, or other types of energy.

In some cases, the borehole may be formed using a projectile accelerated with a ram accelerator assembly. For example, U.S. patent application 62/253,228, previously incorporated by reference; 13/841,236, respectively; 15/292,011, respectively; 61/922,830, respectively; 14/708,932, respectively; 15/246,414, respectively; 62/067,923, respectively; 14/919,657, respectively; 62/150,836, respectively; and 15/135,452 describe the use of accelerated projectiles to form holes in various materials. In other embodiments, the borehole may be formed at least partially in the earth's surface by using detonated materials, which may be used to facilitate progression of the drill bit in some cases. For example, U.S. patent application 15/348,796, previously incorporated by reference, describes a system and method for creating a hole using a projectile that, in some embodiments, includes a detonable material.

The use of accelerated projectiles to form a borehole may allow the borehole to be formed and extended to significant depths suitable for the generation of geothermal energy in a downhole environment at less time and cost than conventional drilling techniques, which may result in the economics of geothermal energy production within the downhole environment. In some embodiments, such as described in U.S. patent application 15/698,549, previously incorporated by reference, the direction in which the borehole extends may be controlled at least in part by the direction in which the projectile accelerates relative to the longitudinal axis of the drill string, drill bit, or BHA. The direction in which the borehole extends may be selected based at least in part on the location of the geological feature suitable for generating geothermal energy.

For example, at least a portion of the interaction between the accelerated projectile and the geological formation may generate a detectable acoustic signal, such as vibration conducted outward through the formation from the point of impact between the projectile and the formation. These acoustic signals may be detected using one or more sensors at the earth's surface, within the drill string, or within other boreholes near the borehole extended using accelerated projectiles. For example, the sensor may be positioned within a length of fiber optic cable disposed within the borehole. By processing the acoustic signals, characteristics of the formation through which the acoustic signals travel may be determined. The characteristics of the formation may be used to determine a location suitable for generating geothermal energy. For example, the acoustic signals may be analyzed to determine the hardness and porosity of the geological material at a depth having a temperature suitable for generating geothermal energy and the location of natural fractures of the geological formation. Thus, the acoustic signal can be used to judiciously steer the direction in which the borehole is created to optimize the rate at which the borehole extends, such as by steering the drill bit away from hard stones or toward more porous geological material. Additionally, the acoustic signal may be used to extend the borehole in a direction that may more efficiently generate thermal energy, such as by steering the drill bit toward a region in the formation that includes the natural fracture. The presence of natural fractures of at least a threshold size may increase the amount of natural heat that may be extracted from the formation. Additionally, in some cases, the presence of natural fractures may increase the efficiency of hydraulic fracturing or other stimulation operations to extend or widen existing fractures or increase the number of fractures present. Based on the location of the natural fracture or other desired characteristics of the geological material, the borehole may be navigated toward a selected location, such as by using the techniques described in U.S. patent application 15/698,549.

In some embodiments, the properties of the formation determined using the acoustic signals may be used to determine properties of projectiles, drill bits, combustible materials, explosive materials, and the like that may be used to optimize formation of the borehole and the direction in which the borehole is formed. For example, a projectile configured to accelerate material in a lateral direction toward a detected feature may be used when the drill bit is near a location with a natural fracture such that interaction between the accelerated material and the formation may enhance the fracture. The enhancement of the area including the fracture may extend or widen the existing fracture, create additional fractures in the formation, and the like.

Each successive interaction between the projectile and the formation may generate additional acoustic signals that may be used to further determine the properties of the formation as the borehole extends. Additionally, as drilling mud or other fluids are circulated within the borehole, the temperature of the fluid circulated to the surface may be measured to determine the potential for generating thermal energy at the current depth of the borehole. Furthermore, in addition to using acoustic signals to manipulate the direction in which the borehole extends, acoustic signals may be used to determine the position of the drill bit or other component of the drill string. For example, the position of the drill bit or other portion of the drill string in the earth may be determined based on characteristics of the acoustic signal generated by the interaction between the formation and the accelerated projectile, the time at which the projectile is accelerated, the time at which the acoustic signal is received by a particular acoustic sensor, and so forth. The use of acoustic signals to position the drill bit may be used to place Measurement While Drilling (MWD) equipment or similar positioning equipment used in BHA, thereby reducing the complexity, expense and weight associated with drilling operations.

After a depth suitable for efficient or economical generation of geothermal energy has been reached, heat from the geological formation may be transferred towards the surface by providing a fluid in the borehole that is cooler in temperature than the formation. Within the borehole, the formation may heat the fluid, and the heated fluid may be circulated to the surface, where the heat may be used to generate electrical energy. In some cases, the fluid may circulate into one or more boreholes and exit from one or more different boreholes. For example, multiple boreholes may be connected by lateral drilling techniques or by using existing natural fractures in the formation. In other cases, the fluid may circulate into and out of the same borehole. For example, the borehole may include an inner conduit, such as a section of coiled tubing, another type of drill conduit, or a separate conduit may be provided in the borehole after removal of the coiled tubing drill conduit. The borehole may also include an outer conduit, such as casing, that provides a barrier between the geological material and the borehole to define an annulus. A fluid may be provided into the inner conduit that is cooler than the geological material. The fluid may exit the inner conduit at its lower end or through one or more other openings formed in the inner conduit to enter the annulus and flow toward the surface. In other embodiments, the fluid may flow into the annulus and be retrieved through the inner conduit. In still other embodiments, a plurality of conduits may be included within the borehole, wherein one or more conduits may be used to flow fluid into the borehole and wherein one or more conduits may be used to flow fluid toward the surface.

In some embodiments, the bore may be formed using an outer catheter, while an inner catheter having a smaller diameter than the outer catheter may be inserted into the outer catheter and secured to a sizing (counter) catheter, such as by using extrusion, welding, or one or more plugs. The inner conduit may then be used to provide cement or other completion materials into the borehole to enable completion of the borehole (e.g., with a cement liner) to be performed simultaneously or in close temporal proximity to formation of the borehole.

In some embodiments, electrical power (such as electrical current) may be generated within the borehole for transmission to the surface. For example, a thermoelectric material, such as a Thermophotovoltaic (TPV) energy conversion element, may be positioned along at least a portion of the exterior of the inner conduit, at least a portion of the interior of the outer conduit, or on both the inner and outer conduits. Placing the thermoelectric material within the annulus between the inner conduit and the outer conduit (such as along the interior of the outer conduit proximate the geological material) may help create a thermal gradient across the thermoelectric material. For example, a geological material that may have an elevated temperature compared to the earth's surface based on the depth of the borehole may be adjacent a first side of the thermoelectric material while the interior of the borehole is positioned on a second side of the thermoelectric material. Thus, the fluid may flow adjacent to and through the second side of the thermoelectric material, thereby creating a thermal gradient in conjunction with warmer geological material located adjacent to the first side of the thermoelectric material. In some cases, the coiled tubing unit may provide the dual purpose of using the tubing for inner tubing (cold water) completions. In some embodiments, the BHA may have a thermoelectric element, electrical connections, and fluid connections attached at the time of use, thereby enabling drilling and completion to be completed in a single step. For example, a single hole may be drilled to enable completion without requiring repeated trips of the completion process. In some embodiments, the properties of the formation determined by using the acoustic signals may be used to determine the amount, placement, and type of thermoelectric elements within or at the surface of the drill pipe in real time, which may optimize the use of the borehole to generate thermal energy.

In some embodiments, an external annulus may exist between the geological material and the exterior of the outer conduit within the borehole. For example, U.S. provisional patent application 62/393,631 and U.S. patent application 15/698,549, previously incorporated by reference, describe methods by which a drill bit may be manipulated and the shape of the borehole may be controlled by accelerating the projectile in a non-parallel direction relative to the longitudinal axis of the drill bit. Selective acceleration of the projectile in a particular direction may be used to provide drilling to areas of different diameter, such as areas of greater diameter than the diameter of the casing. Additionally, the directional use of the shot may enable drilling to be provided to areas having unique cross-sectional shapes (such as hexagonal shapes). Where an outer annulus is formed between the outer conduit and the geological material, the fluid or other material within the outer annulus may be warmer than the fluid provided into the inner conduit. In some embodiments, a plug, valve, seal, or other type of closure element may be positioned in the outer annulus to prevent circulation of warm fluid or other material from the downhole environment toward the surface via the outer annulus. Placement of the closure element or use of one or more downhole devices (such as pumps or turbines) may enable circulation of fluids or other materials within the outer annulus to distribute and maintain heat proximate the exterior of the outer conduit. The circulation of fluid in the outer annulus may also transfer heat from the lower portion of the borehole toward the upper portion.

Embodiments described herein may also include a method of forming a borehole for generating geothermal energy based on user input. For example, a user accessing an application or other type of user interface may indicate a geological location, a desired price or cost of energy (e.g., expressed in units of currency per unit of energy, such as U.S. dollars per kilowatt-hour), a desired date or range of dates on which energy is needed, and so forth. Additional information such as interest rates, discounts on time value and cost due to currency, etc. may also be entered or derived based on geological, economic, political, or other factors. Based on the input and the derived information, a chart or other output relating temperature to depth of the geological location may be determined. Based on the requested amount or price of electricity, the amount of energy storage available, the load served by the energy, and so forth, the total power demand of the system for producing geothermal energy may be determined, such as depth, temperature, amount of thermoelectric materials, placement of thermoelectric materials, and so forth. Formation properties determined by analyzing the acoustic signals and the temperature of the material circulating within the borehole may be used to determine the volume of the borehole for generating geothermal energy. In some cases, the economic characteristics of using the borehole to generate geothermal energy may be determined and updated as the borehole extends.

Fig. 1 depicts an embodiment of a system 100 for determining a property of a formation 102 using an acoustic signal 104 generated by interaction between a projectile 106 and a geological material. As previously described and described in more detail with respect to fig. 2-4, one or more boreholes 108 may be formed in the formation 102 at least in part by accelerating the shot 106 through a portion of the drill string 110 that is in contact with the formation 102. For example, the interaction between the shot 106 and a portion of the formation 102 near the drill bit may weaken the formation 102 near the drill bit and facilitate advancement of the drill bit through the formation 102. As each projectile 106 impacts the formation 102 near the drill bit, the interaction between the projectile 106 and the impacted location of the formation 102 may generate one or more acoustic signals 104. For example, the acoustic signal 104 may include vibrations of rock, soil, or other geological material within the formation 102. In some embodiments, the projectile 106 may be accelerated using a ram accelerator assembly 112, which may be positioned in the drill string 110 at or near its lower end, at or near its upper end, or at another location along the length of the drill string. With respect to U.S. patent application 13/841,236 previously incorporated by reference; 15/292,011, respectively; 14/708,932, respectively; 15/246,414, respectively; 14/919,657, respectively; 15/135,452 and 15/698,549 describe example systems and methods for accelerating the projectile 106 using the ram accelerator assembly 112.

The acoustic signal 104 generated by the interaction between the projectile 106 and the formation 102 may be detected using one or more acoustic sensors 114. The acoustic sensors 114 may include, for example, geophones, accelerometers, Distributed Acoustic Sensing (DAS) systems that use fiber optics to detect signals, and so forth. For example, the DAS system may propagate an optical pulse signal along the fiber optic cable and measure the strain experienced by the cable due to the acoustic signal 104 based on the manner in which the optical pulse signal is affected by interaction with the acoustic signal 104. The acoustic sensor 114 may be positioned in various locations to detect the acoustic signal 104. For example, fig. 4 depicts a first set of acoustic sensors 114(1) positioned at the earth's surface 116, such as within one or more facilities configured to provide material into or receive material from the borehole 108. Continuing with the example, the facilities at the surface 116 may be used to provide cold fluid into the borehole 108 for heating by the formation 102, and then receive warm fluid from within the borehole for generating geothermal energy. As another example, facilities at the surface 116 may provide drilling fluid into the borehole 108 to facilitate operation of the drill bit, measure the temperature of drilling fluid or debris flowing from the borehole 108, raise and lower the drill string 110, and so forth. Acoustic sensors 114(1) may also be positioned outside of the facility, buried within geological material at or near surface 116, at a location above surface 116, within a body of water at surface 116, and so forth. Fig. 1 depicts a second set of acoustic sensors 114(2) positioned along drill string 110 within first borehole 108 (1). For example, one or more conduits or other elements within drill string 110 may house one or more acoustic sensors 114 (2). In some embodiments, acoustic sensor 114(2) may be included in a fiber optic cable or similar flexible elongate member. In other embodiments, one or more acoustic sensors 114(2) may be associated with a BHA used to accelerate the projectile 106 into contact with the geological material (such as near an upper or lower end of the BHA). In still other embodiments, acoustic sensor 114(3) may be within one or more other boreholes 108 in the vicinity of first borehole 108 (1). For example, fig. 1 depicts a third set of acoustic sensors 114(3) within a second borehole 108(2) near the first borehole 108 (1). Continuing with the example, a length of fiber optic cable or similar element associated with one or more acoustic sensors 114(3) may be lowered within borehole 108(2), wherein acoustic signals 104 associated with another borehole 108(1) may be detected.

The detected acoustic signals 104 may be analyzed, such as at one or more facilities at the surface 116 of the borehole 108, to determine the position of the drill bit or other portion of the drill string 110. For example, the location of the end of the drill string 110 within the formation 102 may be determined based on the time that the shot 106 accelerates into contact with the formation 102, the location of the various acoustic sensors 114, and the time that the acoustic signal 104 is received by the acoustic sensors 114. Thus, the drill bit or other component of the drill string 110 may be positioned, and the extension of the borehole 108 may be manipulated, without requiring the use of MWD equipment or other means for positioning the drill bit or drill string 110. By avoiding the use of MWD equipment or other devices for positioning the drill bit or drill string 110, costs associated with forming the borehole 108 may be reduced, reliability may be improved, and the like.

Additionally, the acoustic signals 104 may be analyzed to determine characteristics of the formation 102 at various depths and locations. For example, the characteristics of the vibration through a region of the formation 102 between a first location where the shot 106 contacts the formation 102 and a second location where the acoustic sensor 114 is located may be indicative of the hardness or porosity of the geological material within the region. Continuing with the example, the acoustic signal 104 may be used to determine the presence of hard rock or softer geological material, which in turn may be used to steer the drill string 110 in a direction conducive to faster lengthening of the borehole 108(1), such as by steering the drill string 110 toward more porous or softer material or away from more hard or less porous material. Other characteristics of the formation 102 that may be detected using the acoustic signal 104 may include the density of a region of the formation 102, the presence of water (e.g., aquifers), the presence of salt (e.g., salt domes), the presence of natural formation fractures 118 ("fractures"), and so forth. Locations within the formation 102 that include the fracture 118 may be more conducive to generating heat, and thus, fluid may be provided within the borehole 108 near the fracture 118. In some cases, specialized projectiles 106 may be used to impact or enlarge the fracture 118 to increase the amount of heat that may be used within the borehole 108 (1). In other cases, the fracture 118 may serve as a lateral conduit between multiple boreholes 108. In still other cases, the fracture 118 may indicate a weakened region of the formation 102 through which the drill bit may be easily navigated in a lateral direction, such as by steering the drill bit. For example, a borehole through a region of the formation 102 that includes the fracture 118 may facilitate forming a connection between the plurality of boreholes 108. In this case, the fluid provided into the first bore 108 may be circulated and retrieved through the second bore 108. In some embodiments, the direction of elongation of the borehole 108(1) may be controlled by controlling the direction in which the projectile 106 accelerates away from the drill string 110 relative to the longitudinal axis of the drill string, such as described in U.S. patent application 15/698,549, previously incorporated by reference.

Fig. 2 illustrates a first portion 200 of a method for forming a borehole in a geological material by accelerating the interaction of a projectile 106 with the formation 102 ahead of a drill bit 202. As noted, for example, in U.S. patent application 15/698,549, previously incorporated by reference, the launch tube 204 may be used to direct an accelerated projectile through an aperture in the drill bit 202 and into the geological formation 102. The upstream end of the launch tube 204 may terminate at a combustion chamber 206 within the BHA, while the downstream end of the launch tube 204 terminates at an orifice in the drill bit 202. In use, the pressure generated using the propellant within the combustion chamber 206 may accelerate the shot 106 positioned within the launch tube 204 in a downstream direction toward the drill bit 202, where the shot 106 may exit the orifice to impact the geological formation ahead of the drill bit 202. Subsequent operation of the drill bit 202 may cause the drill bit 202 to penetrate portions of the formation 102 weakened by interaction with the shot 106.

At block 208, a plunger 210, which may be housed in a tube, conduit, or other type of housing located upstream of the launch tube 204, may extend in a downstream direction toward the drill bit 202. The plunger 210 may carry the projectile 106 and an end cap 212 positioned in the combustion chamber 206 or launch tube 204 at a downstream end thereof toward the drill bit 202. For example, the projectiles 106 adjacent the combustion chamber 206 and the end cap 212 within the projectile chamber 214 may enter the combustion chamber 206 or the launch tube 204 before the plunger 210 extends toward the drill bit 202. As the plunger 210, the shot 106, and the end cap 212 advance in the downstream direction, this motion may push drilling fluid, formation fluid, debris, or other types of ejecta out of the launch tube 204, such as by forcing the ejecta through an orifice or another opening in the drill bit 202 or the launch tube 204.

At block 216, the plunger 210 may seat the end cap 212 at or near the downstream end of the launch tube 204. The end cap 212 may seal the launch tube 204 to prevent the ingress of drilling fluid, formation fluids, debris, or other ejecta from the borehole 108. Additionally, placing the end cap 212 may enable evacuation of the launch tube 204 to facilitate acceleration of the projectile 106 toward the drill bit 202. For example, as the plunger 210 and projectile 106 are withdrawn in the upstream direction, this motion may evacuate the launch tube 204. In some embodiments, at least a portion of the launch tube 204 may be evacuated to a pressure of 25 torr or less.

At block 218, the plunger 210 may be withdrawn from the launch tube 204, thereby seating the projectile 106 at the upstream end of the launch tube 204. In some embodiments, a valve 220 or other type of closure mechanism located between the launch tube 204 and the combustion chamber 206 may close when the plunger 210 is withdrawn, such that the projectile 106 is seated at the upstream end of the launch tube 204, near the combustion chamber 206, through the valve 220.

Fig. 3 depicts a second portion 300 of the method for forming a borehole 108 in a geological material by accelerating the interaction of a projectile 106 with the formation 102 ahead of a drill bit 202. As described with respect to fig. 2, a plunger 210 or similar mechanism may be used to place an end cap 212 at or near the downstream end of launch tube 204 to seal launch tube 204 and prevent debris 302 from entering. Downstream movement of the plunger 210 and end cap 212 may push or wipe debris 302, such as formation material, drilling fluid, ejecta, etc., from the launch tube 204, while upstream movement of the plunger 210 and projectile 106 may evacuate the launch tube 204 after placement of the end cap 212. The shot 106 may be placed at or near the upstream end of the launch tube 204, such as near the combustion chamber 206, on the opposite side of the valve 220 that separates the combustion chamber 206 from the launch tube 204.

At block 304, the combustion chamber 206 may be at least partially filled with a propellant 306. Propellant 306 may include any manner of combustible material, pressurized material, or other type of reactant or motive force source that may be applied to projectile 106. For example, the propellant 306 may include one or more combustible gases that may be ignited. In some embodiments, compressing the propellant 306 via movement of the projectile 106 or the plunger 210 upstream may ignite or pressurize the propellant 306. In other embodiments, other types of ignition may be used, such as a separate ignition mechanism. Pressure from the combustion reaction or other type of reaction associated with the propellant 306 may accelerate the projectile 106 through the launch tube 204 and toward the drill bit 202. With the valve 220 or other closure mechanism separating the combustion chamber 206 from the launch tube 204, the pressure from the propellant 306 may cause the valve 220 to open or otherwise permit pressure from the propellant 306 into the launch tube 204. In some embodiments, evacuation of launch tube 204 caused by upstream movement of plunger 210 and projectile 106 as described with respect to fig. 2 may further increase the pressure differential between launch tube 204 and combustion chamber 206, which may help accelerate projectile 106 through launch tube 204.

At block 308, the projectile 106 may penetrate the end cap 212 and exit the launch tube 204 at the face of the drill bit 202, such as by passing through an aperture in the drill bit 202. The accelerated projectile 106 may then impact the geological formation 102 ahead of the drill bit 202. The interaction between the projectile 106 and the formation 102 may weaken the formation 102, enabling the drill bit 202 to penetrate the weakened formation 102 more effectively than the drill bit 202 would penetrate the formation 102 in the absence of the interaction between the formation 102 and the projectile 106. The interaction between the projectile 106 and the formation 102 may damage at least a portion of the projectile 106 and the formation 102, and in some embodiments, at least a portion of the end cap 212. In other embodiments, a gate, valve, diaphragm, or other closure mechanism may instead be used in place of the end cap 212, and passage of the projectile 106 may open the closure mechanism. Debris 302 resulting from these interactions may be carried toward the surface 116, such as by the flow of drilling fluid in an upstream direction. In some embodiments, byproducts, waste, or debris 302 generated by the combustion or discharge of propellant 306 may also exit launch tube 204. For example, byproducts of propellant 306 combustion may exit orifices in the drill bit 202. In other embodiments, one or more vents or other openings in the launch tube 204, drill bit 202, or combustion chamber 206 may be used to permit byproduct flow into the annulus. In some cases, the byproduct of the propellant 306 exiting the aperture in the drill bit 202 or another portion of the drill string 110 may help to transport the debris 302 in the upstream direction.

At block 310, after the shot 106 exits the launch tube 204, the valve 220 at the upstream end of the launch tube 204 may be closed, and another shot 106 and the end cap 212 may be positioned in the launch tube 204 or the combustion chamber 206 to enable the process described with respect to fig. 2 and 3 to be repeated. For example, after the acceleration of the previous shot 106, the shot 106 from the shot chamber 214 and the end cap 212 may enter the combustion chamber 206 due to the pressure differential between the shot chamber 214 and the combustion chamber 206. As the drill bit 202 advances through the formation 102, the launch tube 204 will be filled with drilling fluid, jet, or other debris 302. For example, after the accelerated projectile 106 breaks the end cap 212, the debris 302 may enter an aperture in the drill bit 202. Debris 302 entering the launch tube 204 may be cleared by the movement of the plunger 210 for setting the subsequent end cap 212, as described with respect to fig. 2.

Fig. 4 depicts a third portion 400 of a method for forming a borehole in a geological material by accelerating the interaction of a projectile 106 with the formation 102 ahead of the drill bit 202. As described with respect to fig. 2 and 3, the launch tube 204, the combustion chamber 206, the one or more propellant 306 materials, the plunger 210, and the projectile chamber 214 containing the one or more projectiles 106 and the end cap 212 may be housed within a bottom hole assembly 402 of a drill string. The acceleration of the projectile 106 toward the formation 102 may cause the projectile 106 to interact with at least a portion of the formation 102 proximate the drill bit 202, which may facilitate penetration of the drill bit 202 into the formation 102 as compared to penetration of the drill bit 202 in the absence of interaction between the projectile 106 and the formation 102.

At block 404, the accelerated projectile 106 may exit an aperture in the drill bit 202, impact the geological formation 102, and penetrate at least a short distance into the formation 102. For example, the shot 106 may accelerate to a super high velocity and may interact with the formation 102 after impact, as a fluid-fluid interaction, to form a hole having a generally cylindrical shape. As another example, the shot 106 accelerated to a non-super-high velocity may interact with the formation 102, as a solid-solid interaction, which may fracture or fracture a portion of the formation 102, forming a hole that may be cylindrical, a crater with a conical profile, or another shape. Independent of the velocity of the shot 106, the interaction between the accelerated shot 106 and the formation 102 may displace, compress, remove, fracture, or otherwise weaken the geological material of the formation 102 at or near the point where the shot 106 impacts the formation 102.

At block 406, the interaction between the shot 106 and the formation 102 may crush or otherwise degrade at least a portion of the shot 106 and weaken at least a portion of the formation 102 ahead of the drill bit 202. The generated debris 302 may flow upstream, such as via the annulus. In some embodiments, the debris 302 may include portions of the end cap 212 penetrated by the projectile 106, the propellant 306 used to accelerate the projectile 106, byproducts of combustion or reaction from the propellant 306, and the like. In some cases, the debris 302 may flow into the drill bit 202 or the launch tube 204, such as through an aperture in the drill bit 202. However, when the latter end cap 212 is placed at or near the drill bit 202 (such as by moving the plunger 210 carrying the end cap 212), the debris 302 may then be removed from the launch tube 204, as described with respect to fig. 2.

At block 408, the drill bit 202 may advance through a weakened formation 410 formed by interaction with the projectile 106. For example, the weakened formation 410 may include a conical crater formed via impact between the shot 106 and the formation 102. Continuing with the example, the interaction between the formation 102 and the shot 106 may break up the shot 106 and the portion of the formation 102 occupying the crater. The crushed debris 302 may flow upstream from the crater, and the rotation and lowering of the drill bit 202 may cause the drill bit 202 to penetrate the weakened formation 410. At or near the point where the drill bit 202 traverses the weakened formation 410, the subsequent projectile 106 may be accelerated into the formation 102 to weaken the subsequent portion of the formation 102, thereby further facilitating advancement of the drill bit 202.

Fig. 5 depicts an embodiment of a system 500 for generating geothermal energy using the borehole 108. As previously discussed, the borehole 108 may be formed within a geological material of the formation 102, such as the surface 116 of the earth or another planet. Geological materials may include rock, soil, sand, ice, and the like. The temperature of the geological material may increase based on the depth of the borehole 108. For example, below 300 feet in depth on earth, the temperature of the geological material surrounding the borehole 108 typically increases by one degree celsius per 30 meters of depth. A typical rock body may have a density of about 2700 kilograms per cubic meter and a nominal temperature gradient in the range of 20 degrees celsius to 30 degrees celsius per kilometer. In some embodiments, thermal gradients within the geological material may be tested during the drilling process. For example, during drilling of the borehole 108, the temperature of the debris 302 or other fluid circulated out of the borehole 108 may be measured. In some embodiments, a fluid having a temperature lower than the geological material may flow through the drill string 110, and over time, the temperature at one or more locations within the borehole 108 may be measured based on the temperature of the fluid. Based on such measurements, the elasticity (e.g., heat flux and thermal coefficient) of the temperature of the geological material may be determined. The measurements may be used to determine a target depth of the borehole 108 and placement of material within the borehole 108. In some implementations, the properties of the geological material determined based on the analysis of the acoustic signals 104 may be used to determine a target depth of the borehole 108 and the type or amount of material to be placed in the borehole 108. For example, based on the porosity of the geological material or the presence of natural fractures 118, the thermal properties of the geological material may be determined.

The bore 108 may include one or more conduits therein. For example, the outer conduit 502 may separate the geological material from the interior of the borehole 108. The inner catheter 504 may be positioned within the outer catheter 502. Although in some embodiments, the inner conduit 504 and the outer conduit 502 may comprise concentrically disposed cylindrical conduits, in other embodiments, the inner conduit 504 and the outer conduit 502 may comprise any cross-sectional shape, and the inner conduit 504 may be disposed at any location within the interior of the outer conduit 502. In still other embodiments, the inner catheter 504 and the outer catheter 502 may instead comprise a plurality of catheters that are not placed within each other. In some embodiments, the inner conduit 504 may comprise a drill conduit, such as coiled tubing or drill pipe, used to form the borehole 108. In other embodiments, the outer conduit 502 may comprise a conduit used to form the bore 108. For example, the borehole 108 may be drilled, such as using the methods described with respect to fig. 1-4, using a catheter having a substantially constant diameter selected as a target or optimal diameter for the borehole 108. In still other embodiments, the inner conduit 504 may be positioned within the borehole 108 after the borehole 108 is formed using the outer conduit 502 or another drilling conduit. In some embodiments, the outer conduit 502 may include casing, cement, bushings, and another type of barrier that may be positioned in the borehole 108 during or shortly after formation of the borehole, e.g., to prevent geological material from entering the borehole 108. In still other embodiments, the outer catheter 502 may be omitted. For example, certain types of geologic materials may have a desired density, porosity, hardness, or other material properties that avoid a barrier between the geologic material and the borehole 108.

As shown in fig. 5, placement of the inner conduit 504 and the outer conduit 502 within the borehole 108 may subdivide the borehole 108 into an inner bore 506 within the inner conduit 504 and an annulus 508 positioned outside of the inner bore 506. In some embodiments, the inner bore 506 may be in fluid communication with the annulus 508 via an open lower end 510 of the inner conduit 504. In other embodiments, the inner conduit 504 may include one or more openings (not shown) formed in a sidewall thereof through which fluid may enter or exit the annulus 508.

To generate geothermal energy using the borehole 108, a fluid 512 having a cooler temperature than the formation 102 at a target depth within the borehole 108 may be provided into the borehole 108, such as via the inner bore 506. While within the borehole 108, the formation 102 may transfer heat to the fluid 512, which may then be circulated in an upstream direction to the surface 116, such as via the annulus 508. In some implementations, the properties determined based on the acoustic signals 104 may be used to determine properties of the formation 102. For example, changes in the acoustic signal 104 as it travels through a region of the formation 102 may indicate the hardness, porosity, density, or other material properties of the formation 102, such as the presence of fractures 118, rock, salt, water, and so forth. The properties of the formation 102 may indicate the ability of the formation 102 to retain and transfer heat. These characteristics may be used to determine the type of fluid 512 provided in the borehole 108 and the rate at which the fluid 512 is delivered. For example, the fluid 512 may include brine, metal fluids, ammonia, water, brine, molten salts, or other types of fluids, each of which may receive heat from the formation 102, retain heat, and dissipate heat at different rates based on the characteristics of the fluid. Based on the depth of the borehole 108 and the characteristics of the formation 102, the fluid 512 may be selected to optimize the heat received from the formation 102 and minimize the dissipation of heat as the fluid 512 flows toward the surface 116. At the surface 116, one or more turbines or other types of devices may be used to convert heat from the heated fluid 512 into electricity (e.g., electrical current). In some cases, the type and amount of equipment used to generate power using the heated fluid 512 may be determined based in part on the characteristics of the formation 102 determined using the acoustic signal 104. In other embodiments, the fluid 512 may be provided into the borehole 108 via the annulus 508 and circulated uphole via the inner bore 506. In still other embodiments, the fluid 512 may be provided into the first borehole 108 via one or more conduits, circulated to the second borehole 108, such as via one or more lateral holes or existing formation fractures 118, and then circulated uphole via the second borehole 108. In still other embodiments, the fluid 512 may be provided into any number of conduits or boreholes 108 and circulated up using any number of other conduits or boreholes 108.

In some embodiments, the current may be generated within the borehole 108 itself. For example, one or more thermoelectric elements 514 may be placed within the borehole 108 to generate an electrical current based on a thermal gradient between the geologic material and the fluid 512 within the borehole 108 or between the fluid 512 that has been heated within the borehole 108 and the fluid 512 that has not been heated. Continuing with the example, one or more thermoelectric elements 514 may be positioned within annulus 508 along an inner surface of outer conduit 502. Fig. 5 depicts the thermoelectric elements 514 positioned along the outer conduit 502 near the lower end 510 of the inner conduit 504, however, the thermoelectric elements 514 may be placed at any location along the length of the outer conduit 502. In other embodiments, the thermoelectric elements 514 may be placed along an outer surface of the outer conduit 502 (e.g., proximate to or in contact with the geologic material), along an outer surface of the inner conduit 504 (e.g., within the annulus 508), or along an inner surface of the inner conduit 504 (e.g., within the inner bore 506). In still other embodiments, the thermoelectric elements 514 may be positioned at selected locations within the borehole 108 along the geological material itself, if the outer conduit 502 is not used. The type of thermoelectric elements 514 used and the amount and placement of thermoelectric elements 514 may be determined based at least in part on characteristics of the formation 102, such as density, porosity, heat flux, etc., which may be determined based on analysis of the acoustic signal 104 propagating through the formation 102. In some cases, a conduit carrying a selected type and amount of thermoelectric elements 514 may be inserted into the borehole 108 in real time based on the characteristics of the formation 102 determined by analyzing the acoustic signals 104. For example, the inner conduit 504 with one hundred TPV elements secured to its outer surface may be lowered into the borehole 108 based on a determined temperature difference between the interior of the borehole 108 and the surrounding formation 102.

Thermoelectric element 514 may include any manner of thermoelectric generation material, thermocouple, or thermionic device. For example, thermoelectric element 514 may include a doped silicon-based semiconductor (e.g., tellurium-gallium, Si) that converts the temperature difference to an electrical potential using a peltier or seebeck process for generating electricity. In other embodiments, thermoelectric element 514 may comprise a TPV element that may generate photons in response to a geological material. For example, a TPV element may include an emitter configured to generate photons in response to a particular temperature or temperature difference and a receiver to capture at least a portion of the photons. The frequency of the generated tube may be affected by a particular temperature, and in some cases, the frequency of the photons captured by the receiver electrode may be coordinated based on the expected temperature within the borehole 108. Electrons associated with the photons can be collected by a photocell to generate an electrical current. In some embodiments, thermoelectric elements 514 may comprise square or rectangular sections of thermoelectric material, such as rectangular material having a length and width in the range of 30 to 50 millimeters and a thickness of 10 millimeters or less. In other embodiments, the thermoelectric elements 514 may have other shapes that are integral with the structure of the conduit to which they are bonded. For example, the thermoelectric elements 514 may be formed as cylindrical or hexagonal tubes.

The thermoelectric element 514 may generate an electrical current in response to a temperature difference between the geological material and the interior of the borehole 108. For example, when a fluid 512 having a temperature lower than the temperature of the geological material passes over the thermoelectric element 514, a temperature differential may be created across the thermoelectric element 514. Continuing with the example, a cooling fluid 514, such as brine, a metallic fluid, ammonia, water, brine, molten salt, etc., may be provided from the surface 116 (e.g., via a pump) and then circulated toward the surface 116 for capture or recirculation. In some embodiments, the system 500 may include a closed loop system in which the borehole 108 is not in fluid communication with the geological material, such that the fluid 512 does not contact the geological material and the geological material does not enter the borehole 108.

Electrically conductive material within one or more of the inner conduit 504, the outer conduit 502, the thermoelectric element 514, or the fluid 512 may be used to conduct the generated current toward the surface 116. In some embodiments, thermoelectric element 514, or one or more other portions of system 500, may include a power converter, power regulator, or other element that modifies the current.

Fig. 6 depicts an embodiment of a system 600 for generating geothermal energy using a borehole 108 by circulating a fluid 512 in a downhole environment. As described with respect to fig. 1-4, the accelerated shot 106 may be used, at least in part, to displace or weaken geological material of the formation 102 to form a borehole 108 within the formation 102. Conduits used to form and isolate the borehole 108 (such as drilling conduits and outer casing) may subdivide the borehole 108 into a hole and annulus that may be used to flow the fluid 512 in uphole and downhole directions.

As described with respect to fig. 5, the inner conduit 504 and the outer conduit 502 may be positioned within the borehole 108, with the inner conduit 504 positioned within the outer conduit 502. In some implementations, the borehole 108 may have a diameter greater than the diameter of the outer conduit 502, such as by using accelerated projectiles 106 projected from the drilling conduit at an angle relative thereto or projectiles 106 configured to generate a force in a lateral direction relative to the drilling conduit. Thus, the inner conduit 504 may separate the inner bore 506 of the bore 108 from an inner annulus 602 positioned between the inner conduit 504 and the outer conduit 502. The outer conduit 502 and the borehole wall 604 positioned outside the outer conduit 502 may define an outer annulus 606.

In some embodiments, the outer annulus 606 may be filled with a warm fluid 608, such as conductive or convective mud. For example, after the borehole 108 has been extended to a target depth, graphite mud or another type of fluid may be injected beyond the lower end of the outer conduit 502 or through one or more openings in the outer conduit 502 into the outer annulus 606. The warm fluid 608 may contact the geological material of the formation 102 and conduct or convect heat from the geological material toward the outer conduit 502 to facilitate heat transfer toward the inner annulus 602. In some embodiments, the warm fluid 608 may be circulated, such as by using a pump, turbine, drill bit, or other fluid moving device (not shown in fig. 6) that may be positioned at or near the end of the outer conduit 502. The circulation of warm fluid 608 may help to evenly distribute heat along the exterior of outer conduit 502. For example, circulation of the warm fluid 608 may cause the warm fluid 608 to transfer heat or material from deeper within the borehole 108 to a portion of the outer annulus 606 that is located farther uphole. In some embodiments, one or more isolation elements 610 (such as concrete plugs, seals, valves, or other types of barriers or closure mechanisms) may be positioned within outer annulus 606 to restrict warm fluid 608 from flowing to selected areas of outer annulus 606.

Cold fluid 612 (e.g., having a temperature less than the temperature of warm fluid 608) may be provided into bore 108 via one of inner bore 506 or inner annulus 602, and circulated toward surface 116 via the other of inner bore 506 or inner annulus 602. The cold fluid 612 may be heated by the proximity of the warm fluid 608. For example, heat from the warm fluid 608 may be conducted across the outer conduit 502 to the cold fluid 612. The heated cold fluid 612 can be returned to the surface 116, where heat from the cold fluid 612 can be used to generate an electrical current. In some embodiments, thermoelectric elements 514 may be positioned within borehole 108 such that cold fluid 612 and warm fluid 608 create a thermal gradient across thermoelectric elements 514. For example, the thermoelectric element 514 may be positioned on a portion of the outer catheter 502.

Fig. 7 is a diagram 700 depicting an embodiment of a conduit 702 configured to house a thermoelectric element 514. As previously discussed, the borehole 108 may have any cross-sectional shape, including non-circular shapes, due to the ability to accelerate the projectile 106 into the geological material at various angles relative to the axis of the drill pipe. Thus, the conduit 702 used to form or insert the bore 108 may not necessarily have a circular cross-sectional shape. For example, fig. 7 depicts a conduit 702 having a pentagonal cross-sectional shape defined by five walls 704, which in turn define an aperture 706 extending through the conduit 702. In some cases, the shape of the conduit 702 relative to the shape of the borehole 108 may facilitate circulation of fluid within the annulus 508 between the borehole 108 and the conduit 702. For example, placing a conduit 702 having an angled surface within the circular bore 108 may affect the manner in which fluid within the annulus 508 moves relative to the conduit 702. In some implementations, one or more of the walls 704 can include an electronics frame 708 associated therewith. For example, the wall 704 may be formed from or otherwise integral with the electronics frame 708, or the electronics frame 708 may be attached to the wall 704.

The electronics frame 708 may be formed from an electrically conductive material and configured to conduct electrical current generated by the thermoelectric elements 514 toward the surface 116. In some implementations, the electronics framework 708 may also include or be in electrical communication with electrical conditioning components. The electronics frame 708 may be configured to retain the thermoelectric elements 514 in a desired position. For example, one embodiment of the electronics frame 708 may include a rectangular plane formed by interlocking linear elements to define a grid shape having one or more spaces 710 therein. Each space 710 may be configured to engage or otherwise retain a rectangular thermoelectric element 514. In other embodiments, the mono-sub frame 708 may have other shapes corresponding to the conduits 702 having other cross-sectional shapes. For example, the electronics frame 708 and the thermoelectric element 514 may have a curvature that corresponds to the curvature of the cylindrical conduit 702. In some implementations, one or more electronics frames 708 can be connected together in series or in parallel. The use of the electronics frame 708 may enable the addition, removal, or replacement of particular thermoelectric elements 514 or particular electronics frames 708 in a modular fashion, such as at the time when one or more thermoelectric elements 514 or one or more electronics frames 708 become damaged.

The electronics frame 708 may be formed using a thermally insulating material, and in some embodiments, each space 710 may include electrical connections, such as sockets, for engaging the thermoelectric elements 514. The electronics frame 708 may also include a bus connecting adjacent thermoelectric elements 514 or connecting thermoelectric elements 514 to a power transfer element. For example, in one or more of the spaces 710, a power conditioning unit or a power converter may be placed. Continuing with the example, the power conditioning unit may convert the direct current generated by the thermoelectric elements 514 into alternating current, or may otherwise modify the power generated by the thermoelectric elements 514. In embodiments using TPV elements, a first portion of space 710 may include a thermal emitter and a second portion of space 710 may include a photovoltaic cell.

Fig. 8 is a flow chart 800 illustrating a method for generating a borehole 108 using data determined from the acoustic signal 104. At 802, one or more projectiles 106 may be accelerated through a conduit and into contact with a geological material to form a borehole 108. For example, the methods described with respect to fig. 2-4 may be used to accelerate the contact of the shot 106 with the geological material to at least partially weaken the material, while the drill bit 202 may be used to drill through the weakened material.

At 804, one or more acoustic signals 104 caused by the interaction between the projectile 106 and the geological material may be detected. For example, as described with respect to fig. 1, the interaction between the projectile 106 and the geological material may cause vibrations within the geological material that may be detected using the one or more acoustic sensors 114. The acoustic sensor 114 may be positioned within the borehole 108 where the projectile 106 is accelerated, within another borehole 108, or at the surface 116.

At 806, based on the acoustic signal 104, one or more characteristics of a portion of the geological material may be determined. For example, the projectile 106 may impact geological material at a first location, which may cause one or more acoustic signals 104 to be projected outward from the first location. The acoustic sensor 114 at the second location may detect the acoustic signal 104. Based on the characteristics of the detected acoustic signal 104, characteristics of the geological material between the first location and the second location, such as hardness, porosity, and the presence of fractures 118, may be determined. The use of multiple acoustic sensors 114 at different locations may enable the determination of characteristics of different regions of the geological material based on acoustic signals 104 propagating through respective portions of the geological material.

At block 808, based on the determined property of the geological material, the borehole 108 may extend toward or away from the region of the geological material for which the property is determined. For example, if the geological material includes a hardness greater than a threshold hardness or a porosity less than a threshold porosity, these characteristics may impede the extension of the borehole 108, and the borehole 108 may extend away from the region of the geological material. These characteristics may contribute to the extension of the borehole 108 if the geological material includes a hardness less than a threshold hardness or a porosity greater than a threshold porosity, and the borehole 108 may extend toward a region of the geological material. If the geological material fracture 118 has a size greater than a threshold size, the fracture 118 may be used to extract heat or material from the geological material, flow material between multiple boreholes 108, or form a lateral hole between multiple boreholes 108, and the boreholes 108 may extend toward the fracture 118.

At 810, it may be determined that the temperature within the borehole 108 (such as at its current depth) exceeds a threshold temperature. The threshold temperature may be selected to be a temperature suitable for generating a selected amount of thermal energy, such as a temperature that exceeds a current or average ambient temperature at the surface 116 by at least a selected amount, or a temperature that exceeds a current or average temperature of the circulating fluid 512 by at least a selected amount.

At 812, the fluid 512 may be circulated into the borehole 108 to enable heat transfer from the borehole 108 to the fluid 512. As described with respect to fig. 5 and 6, the fluid within one or more conduits may pass within close proximity to adjacent geological material, which may enable heat from the geological material to be transferred to the fluid 512.

At 814, an electrical current may be generated using heat from the fluid 512. In some embodiments, the heated fluid 512 may flow to the surface 116, where heat from the fluid 512 may be used to generate an electrical current. In other embodiments, passage of the fluid in proximity to the thermoelectric elements 516 may create a temperature differential in response to which the thermoelectric elements 516 may generate an electrical current to conduct toward an electrical load.

Fig. 9 is a flow chart 900 illustrating a method for generating a borehole 108 based on user constraints and data determined from the acoustic signal 104. At block 902, a user input may be received indicating a cost and one or more characteristics of an electrical load. For example, the user input may specify an amount of thermal energy from the borehole 108 that may be used to at least partially supply an electrical load. The user input may also specify a budget, a desired cost per unit of energy, or other economic constraints.

At 904, a borehole temperature corresponding to a characteristic of the electrical load may be determined. For example, based on the diameter of the borehole 108 to be produced and the amount and cost of geothermal energy indicated by the user input, a borehole temperature may be determined that may be used to generate geothermal energy corresponding to the indicated amount and cost.

At 906, one or more projectiles 106 may be accelerated into contact with the geological material to form a borehole 108. For example, the methods described with respect to fig. 2-4 may be used to create at least a portion of the borehole 108.

At 908, one or more acoustic signals 104 caused by the interaction between the projectile 106 and the geological material may be detected. As described with respect to fig. 1, the acoustic signal 104 may include vibrations propagating through the geological material caused by impacts or other interactions between the shot 106 and the geological material. Acoustic sensors 114 at one or more locations may detect acoustic signals 104 propagating in various directions from the location where the projectile 106 interacts with the geological material.

At 910, based on the acoustic signal 104, one or more characteristics of the geological material, such as hardness, porosity, or the presence of fractures 118, may be determined.

At 912, based on the determined characteristics, a cost for extending the borehole 108 to a depth corresponding to the target borehole temperature may be determined. For example, penetrating geologic materials with high hardness or low porosity may require more time and material than penetrating softer or more porous materials. Based on the determined characteristics, a cost per unit distance to extend the borehole 108 may be determined, which may be used to determine a cost to extend the borehole 108 to a target depth associated with the borehole temperature. In some cases, the cost associated with producing the borehole 108 may be offset by a value associated with geothermal energy that may be produced using the borehole 108.

The following clauses provide additional description of the various embodiments and structures:

clause 1: a method, comprising: accelerating a first projectile through a conduit, wherein the first projectile contacts a first location of a geological material to form a borehole, and an interaction between the first projectile and the geological material at the first location generates an acoustic signal; detecting the acoustic signal using an acoustic sensor at a second location; determining one or more characteristics of a region of the geological material between the first location and the second location based on the acoustic signals; and controlling formation of the borehole in a direction towards or away from the region of the geological material based on the one or more characteristics.

Clause 2: the method of clause 1, wherein the one or more characteristics include one or more of a hardness of the geological material or a porosity of the geological material, the method further comprising: determining one or more of: the hardness exceeds a threshold hardness or the porosity is less than a threshold porosity; wherein controlling formation of the borehole in the direction comprises extending the borehole along a path that avoids intersecting the region of the geological material.

Clause 3: the method of clause 1 or 2, wherein the one or more characteristics comprise one or more of a hardness of the geological material or a porosity of the geological material, the method further comprising: determining one or more of: the hardness is less than a threshold hardness or the porosity is greater than a threshold porosity; wherein controlling formation of the borehole in the direction comprises extending the borehole along a path that intersects the region of the geological material.

Clause 4: the method of any of clauses 1-3, wherein the one or more characteristics include one or more fractures within the geological material having a size greater than a threshold size, and extending the borehole in the direction includes extending the borehole along a path that intersects at least one of the one or more fractures.

Clause 5: the clause of clause 4, wherein the first projectile is configured to apply a longitudinal force to the geological material to extend the borehole, the method further comprising: accelerating a second projectile to a portion of the borehole proximate to the one or more fractures, wherein the second projectile is configured to apply a lateral force to the one or more fractures upon contact with the geological material to increase the size of the at least one fracture.

Clause 6: the method of any of clauses 1-5, further comprising: determining that a first temperature within the borehole exceeds a threshold temperature; providing a fluid having a second temperature less than the first temperature into the borehole, wherein the fluid is heated to a third temperature greater than the second temperature; circulating the fluid having the third temperature to an upper end of the borehole; and generating an electrical current using heat from the fluid having the third temperature.

Clause 7: the method of any of clauses 1-6, wherein at least one thermoelectric element is associated with the first conduit, the method further comprising: providing a fluid to a portion of the borehole having a first temperature, wherein the fluid has a second temperature less than the first temperature, the fluid is located on a first side of the thermoelectric element, the portion of the borehole is located on a second side of the thermoelectric element opposite the first side, and the thermoelectric element generates an electrical current in response to a temperature difference between the first temperature and the second temperature; and conducting an electrical current generated by the thermoelectric element toward an upper end of the borehole.

Clause 8: the method of any of clauses 1-7, further comprising: receiving a user input indicative of an amount of thermal energy associated with generating a predetermined amount of electrical power; determining a threshold temperature for the amount of thermal energy generated; determining a borehole depth corresponding to the threshold temperature; and extending the borehole to the borehole depth.

Clause 9: the method of clause 8, further comprising: determining a threshold cost based on one or more of the user input or a value of the amount of thermal energy; determining a cost for producing the borehole having the borehole depth based on the one or more characteristics of the region of the geological material; and determining that the cost is less than the threshold cost.

Clause 10: a method, comprising: accelerating a first projectile into contact with a geological material, wherein an interaction between the first projectile and the geological material generates an acoustic signal; detecting the acoustic signal using an acoustic sensor; determining one or more fractures within a region of the geological material based on the acoustic signals; and extending the first borehole to intersect at least one of the one or more fractures.

Clause 11: the method of clause 10, further comprising: accelerating a second projectile to a portion of the borehole proximate to the one or more fractures, wherein an interaction between the second projectile and the geological material applies a force to at least a subset of the one or more fractures to enhance the at least a subset of the one or more fractures.

Clause 12: the method of clause 10 or 11, further comprising: providing a fluid having a first temperature into a portion of the first borehole proximate to the one or more fractures, wherein the portion of the borehole has a second temperature greater than the first temperature and the fluid is heated to a third temperature greater than the first temperature; circulating the fluid having the third temperature away from the portion of the first borehole; and generating an electrical current using heat from the fluid having the third temperature.

Clause 13: the method of any of clauses 10-12, further comprising: extending a second borehole toward the portion of the geological material within a threshold distance of the one or more fractures; forming a transverse hole extending between the first borehole and the second borehole, wherein the transverse hole at least partially intersects at least one of the one or more fractures; providing a fluid having a first temperature into the first borehole in a downhole direction; circulating the fluid into the second borehole through the transverse bore; circulating the fluid uphole from the second borehole, wherein the fluid is heated to a second temperature greater than the first temperature by one or more of the first borehole, the lateral bore, or the second borehole; and generating an electrical current using heat from the fluid having the second temperature.

Clause 14: the method of any of clauses 10-13, further comprising: extending a second borehole toward the portion of the geological material, wherein the second borehole intersects the at least one of the one or more fractures; providing a fluid having a first temperature into the first borehole in a downhole direction; circulating the fluid into the second borehole through at least a subset of the one or more fractures; circulating the fluid uphole from the second borehole, wherein passage of the fluid heats the fluid to a second temperature greater than the first temperature; and generating an electrical current using heat from the fluid having the second temperature.

Clause 15: a system, comprising: a first conduit positioned within a geological material surrounding a borehole, wherein the geological material is proximate an outer surface of the first conduit and the geological material has a first temperature; a second conduit positioned within the first conduit, wherein a first annulus is defined between the first conduit and the second conduit; a first fluid moving device configured to circulate a fluid having a second temperature less than the first temperature into the borehole via one of the first conduit or the first annulus and out of the borehole via the other of the first conduit or the annulus, wherein the circulation of the fluid through the first annulus heats the fluid to a third temperature greater than the second temperature; and a power generation device configured to generate an electric current using heat from the fluid having the third temperature.

Clause 16: the system of clause 15, wherein the first conduit is spaced apart from a wall of the borehole to define a second annulus, the system further comprising: a second fluid moving device configured to circulate a borehole material within the second annulus to maintain a portion of the geological material proximate the outer surface of the first conduit within a threshold temperature of the first temperature.

Clause 17: the system of clause 16, further comprising: at least one isolation element within the second annulus for limiting circulation of the borehole material by the second fluid moving device to an area proximate the outer surface of the first conduit.

Clause 18: the system of any of clauses 15-17, wherein the power generation device comprises at least one thermoelectric element having a first side facing the first conduit and a second side facing the first annulus, wherein the fluid within one of the first conduit or the first annulus has the second temperature and the fluid within the other of the first conduit or the first annulus has the third temperature to cause the at least one thermoelectric element to generate the electrical current.

Clause 19: the system of clause 18, further comprising: an electronics frame associated with the first conduit, wherein the electronics frame contains the at least one thermoelectric element and is configured to conduct the electrical current toward a surface of the borehole.

Clause 20: the system of clause 19, further comprising: one or more power conditioning elements associated with the electronics frame and in electrical communication with the at least one thermoelectric element to modify one or more of a power, frequency, phase, amperage, or voltage of the electrical current.

Those of ordinary skill in the art will readily recognize that certain steps or operations illustrated in the above figures may be eliminated, combined, sub-divided, performed in parallel, or employed in an alternate order. Further, the above-described methods may be implemented using one or more software programs for a computer system and encoded in computer-readable storage media as instructions executable on one or more processors. Separate instances of these programs may be executed on separate computer systems or distributed across separate computer systems.

While certain steps have been described as being performed by certain devices, processes, or entities, this need not be the case and various alternative embodiments will be appreciated by those of ordinary skill in the art.

Additionally, one of ordinary skill in the art will readily recognize that the above-described techniques may be used in a variety of devices, environments, and situations. While the present disclosure has been written with respect to specific embodiments and implementations, various changes and modifications may be suggested to one skilled in the art, and it is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims.