Heat extraction system and method for extreme environments

Abstract

A tool (100) for extracting heat from a reservoir, comprising: a seat (130) made of a material capable of withstanding temperatures above 500 DEG C; an outer tube (120) attached to the seat (130); the inner pipe (110) is located in the outer pipe (120), the inner pipe (110) and the outer pipe (120) form an annular space (112), and the inner pipe (110) is provided with a hole (114); and a flexible connection (140) configured to connect the outer tube (120) to the seat (130) such that the outer tube (120) is allowed to extend and contract without leaking fluid (154) within the annular space (112). The inner tube (110) and the outer tube (120) are configured to form an uninterrupted loop path (156) for the fluid (154) between the top of the annular space (112) and the top of the bore (114) while also allowing the fluid (154) to directly contact the seat (130).

Description

Technical Field

[0001] Embodiments of the subject matter disclosed herein relate generally to a system and method for extracting heat from a high temperature environment, and more particularly, to a subsurface coaxial tool terminating in a closed seat, wherein only the seat is configured to enter the high temperature environment and the tool is configured to circulate a fluid through the seat to collect heat received by the seat from the environment and transfer the heat to the surface. Background Art

[0002] Exploitation of underground epithermal reservoirs (SHRs) is a promising solution for generating large amounts of energy. These underground epithermal reservoirs can be natural, intentionally created (such as underground coal gasification), or accidental (such as peat or coal fires). Regardless of the source of the SHR, it is desirable to extract the energy produced by these SHRs with minimal pollution.

[0003] Natural SHR is produced by proximal magma, for example at temperatures exceeding 900°C. In this regard, a well in Iceland accidentally hit magma. In addition to the 60 MWe installed capacity from 33 wells drilled for the local geothermal power plant, this well could produce even greater amounts of energy, for example 36 MWe, almost free of charge [1].

[0004] SHRs can also be intentionally manufactured (e.g., artificially), as in the framework of ultra-high temperature underground thermal energy storage (UHT-UTES). For example, by using parabolic troughs or other devices, concentrated solar power (CSP) systems can reach high temperatures above 500°C and up to 2000°C during the day, but may not be able to reach them when energy demand is high. UTES is a solution for storing high-temperature fluids and extracting the energy associated with the fluids when the CSP system cannot produce enough energy. Storage options in the natural ground have been investigated, and various studies have considered temperatures of up to 650°C to store heated fluids. Other ultra-high temperature energy sources, such as nuclear power plants, may also be considered.

[0005] SHR can be produced by another purposeful process, such as underground coal gasification (UCG), which aims to produce synthesis gas by underground combustion of coal at temperatures between 600°C and 1000°C [2-4].

[0006] However, heat recovery from SHRs is challenging due to the extreme conditions (temperature, corrosion, and pressure) in which the materials and systems are used.

[0007] The well for the ℃ magma was built with carbon steels of API grades K55 and T95, which are traditionally used in geothermal wells. The casing collapsed rapidly in this case, ending the exploitation of the large amount of energy available there. After the well was terminated and closed, the well was recorded with a video camera. Severe corrosion and tensile cracking were observed, which were subsequently confirmed by analysis of the 8m retrieved from the uppermost part of the well.

[0008] From these experiences it can be seen that conventional wells and tools, even if made of more resistant steel grades, are not suitable for long-term extraction of heat in SHR. Several disadvantages of these wells and tools include:

[0009] - cylindrical well casings tend to expand and collapse under thermomechanical stresses (thermal cycling is a deteriorating factor),

[0010] - When geothermal brines are used as the working fluid, the very high temperatures increase the risk of corrosion of the steel due to the chemical composition of the brine, and

[0011] - The potential for damage to the surrounding rock mass (fracturing, cavity formation and spalling in the case of UCG) increases with temperature due to additional thermal stresses.

[0012] Furthermore, the annular cement used around the well plays an important role in the structural integrity and durability of the well. The cement must provide mechanical support for the steel casing, protecting it from the corrosive formation fluids, and the multilayer structure consisting of several casings and cement layers between these casings must ensure that salt water is prevented from leaking from the annular space into the different formations through which the well passes. Thermal stress and related damage to the cement can undermine this role.

[0013] Therefore, a new system / tool ​​is needed to be able to extract heat from a SHR while being able to withstand the harsh conditions present in a SHR. Summary of the invention

[0014] According to one embodiment, there is provided a method of extracting heat from a subterranean location using a coaxial tool including a seat made of a heat resistant material. The method includes the step of placing the seat of the coaxial tool into the subterranean location while ensuring that other parts of the tool are not in direct contact with the subterranean location. The method also includes the step of pumping a fluid into the tool, through the bore of the inner tube to the seat, and then returning to the surface through the annular space formed by the inner tube and the outer tube, or through the annular space to the seat, and then returning to the surface through the bore. The fluid exchanges heat with the seat placed in the hot subterranean location.

[0015] According to another embodiment, a tool for extracting heat from a reservoir is provided, and the tool includes: a seat made of a material that can withstand temperatures above 500°C; an outer tube attached to the seat; an inner tube located within the outer tube and forming an annular space with the outer tube, the inner tube having a hole; and a flexible connector configured to connect the outer tube to the seat so that the outer tube is allowed to extend and contract without leaking the fluid in the annular space. The inner and outer tubes are configured to form an uninterrupted circuit path for the fluid between the top of the annular space and the top of the hole, while also allowing the fluid to directly contact the seat.

[0016] According to yet another embodiment, a heat extraction system for extracting heat from a reservoir is provided, and the heat extraction system includes: a casing element configured to be lowered into a well or pushed into the ground; and a tool configured to be attached to the distal end of the casing element. The tool includes: a seat made of a material that can withstand temperatures above 500°C; an outer tube attached to the seat; an inner tube concentrically located within the outer tube and forming an annular space with the outer tube, the inner tube having a hole; and a flexible connector configured to connect the outer tube to the seat so that the outer tube is allowed to extend and contract without leaking the fluid in the annular space. The inner and outer tubes are configured to form an uninterrupted circuit path for the fluid between the top of the annular space and the top of the hole, while also allowing the fluid to directly contact the seat.

[0017] According to a preferred embodiment of the invention, the tool may further comprise: a filter element, which is located between the inner tube and the seat along the longitudinal axis; and an additional flexible connection, which is between the inner tube and the filter element, wherein the circuit path extends from the annular space to the hole through a plurality of apertures formed in the filter element. More preferably, the filter element is an integral part of the seat.

[0018] According to yet another embodiment of the invention, the inner tube may be directly attached to the seat, preferably by an additional flexible connection.In this solution, the inner tube comprises a plurality of apertures, so that the circuit path extends from the annular space to the bore through the plurality of apertures.

[0019] According to another preferred embodiment of the present invention, the tool may further include lugs that fixedly attach the inner tube relative to the outer tube so that the bottom end of the inner tube floats above the seat to allow the circuit path to exit the annular space and enter the hole.

[0020] According to another embodiment of the present invention, the inner tube is preferably directly connected to the seat by an additional flexible connection, and the seat has one or more channels, which allow the circuit path to extend from the annular space to the hole through the one or more channels, wherein the one or more channels can be formed only in the body of the seat.

[0021] According to another embodiment of the invention, the seat comprises only a solid main body without other components.

[0022] According to another embodiment of the invention, the inner tube and the outer tube are concentric.

[0023] According to another embodiment of the invention, the seat is shaped as a cone and has a helical portion attached to the outer surface of the cone, or the seat is shaped as a cylinder with a distal toe.

[0024] According to yet another embodiment of the present invention, the present invention is directed to a heat extraction system for extracting heat from a reservoir, the heat extraction system comprising:

[0025] - a casing element configured to be lowered into a well or pushed into the ground; and

[0026] - a tool configured to be attached to the distal end of the cannula element,

[0027] The tools include:

[0028] A seat made of a material capable of withstanding temperatures above 500°C;

[0029] an outer tube attached to the seat;

[0030] an inner tube which is concentrically located inside the outer tube and forms an annular space with the outer tube, the inner tube having a hole; and

[0031] a flexible connector configured to connect the outer tube to the seat so that the outer tube is allowed to extend and contract without leaking the fluid in the annular space,

[0032] Therein, the inner and outer tubes are configured to form an uninterrupted circuit path for the fluid between the top of the annular space and the top of the bore, while also allowing the fluid to directly contact the seat.

[0033] The heat extraction system may also include:

[0034] - a centralizer configured to center the casing element in the well; and

[0035] - A packer configured to prevent fluid from the well from advancing towards the upper part of the tool.

[0036] In this heat extraction system, tools may also include:

[0037] - a filter element located between the inner tube and the seat along the longitudinal axis; and

[0038] - an additional flexible connection between the inner tube and the filter element,

[0039] wherein the circuit path extends from the annular space to the bore through a plurality of apertures formed in the filter element wherein the filter element is an integral part of the seat.

[0040] In this heat extraction system, an inner tube is directly attached to the seat by an additional flexible connection, and wherein the inner tube comprises a plurality of apertures such that a circuit path extends from the annular space to the bore through the plurality of apertures.

[0041] In this heat extraction system, tools may also include:

[0042] - Lugs that fixedly attach the inner tube relative to the outer tube so that the bottom end of the inner tube floats above the seat to allow the circuit path to leave the annular space and enter the bore.

[0043] In this heat extraction system, the inner tube is directly connected to the seat by an additional flexible connection, and the seat has one or more channels allowing a circuit path to extend from the annular space to the hole through the one or more channels, wherein the one or more channels are formed only in the body of the seat.

[0044] In this heat extraction system, the seat is shaped as a cone or a cylinder with a distal tip. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to have a more comprehensive understanding of the present invention, the following description is now provided in conjunction with the accompanying drawings, in which:

[0046] Figure 1 is a schematic diagram of a heat extraction tool having an end seat portion for protecting an inner tube and an outer tube from direct exposure to extreme conditions in an exploration reservoir;

[0047] Figure 2A and Figure 2B A flexible connection is shown that allows leak-free fluid connection of the inner and outer tubes to the end socket while accounting for thermal expansion;

[0048] Figure 3A is a schematic diagram of an end mount portion of a heat extraction tool having an integrated filter element, and Figure 3B is a schematic diagram of an end seat portion without a filter element;

[0049] Figure 4 is a table showing various materials that can be used to manufacture the seat so that the seat can withstand high temperatures;

[0050] Figure 5 is a schematic diagram of another heat extraction tool having an end seat for thermally protecting an inner tube and an outer tube;

[0051] Figure 6is a schematic diagram of yet another heat extraction tool having an end seat for thermally protecting an inner tube and an outer tube;

[0052] Figure 7 is a schematic diagram of yet another heat extraction tool having an end seat for thermally protecting an inner tube and an outer tube;

[0053] FIG. 8A to FIG. 8C Various shapes of the end seat are shown;

[0054] Fig. 9A shows drilling for a heat extraction tool, Fig. 9B shows an arrangement where the heat extraction tool is advanced into the well so that only the end seat enters the high temperature reservoir, and Fig. 9C shows closure of the well after heat has been extracted and the heat extraction tool has been removed; and

[0055] Fig.10 is a flow chart of a method for extracting heat from a reservoir using a heat extraction tool. DETAILED DESCRIPTION

[0056] The following embodiments are described with reference to the accompanying drawings. The same reference numerals in different figures represent the same or similar elements. The detailed description below does not limit the invention. On the contrary, the scope of the invention is defined by the appended claims. For simplicity, the following embodiments are discussed with respect to a coaxial tool provided with an end spiral shoe for entering the SHR. However, the embodiments to be discussed next are not limited to the spiral shoe, but the coaxial tool can be provided with an end shoe of different shapes. In addition, the embodiments to be discussed next are not limited to coaxial tools, as the tool can also use pipes of different axes.

[0057] References throughout the specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosed subject matter. Thus, the phrases "in one embodiment" or "in an embodiment" appearing in various places throughout the specification are not necessarily referring to the same embodiment. Furthermore, in one or more embodiments, the particular features, structures, or characteristics may be combined in any suitable manner.

[0058] According to one embodiment, a novel coaxial tool for heat extraction includes an inner tube and an outer tube positioned concentrically [5]. In one embodiment, the longitudinal axes of the inner tube and the outer tube can be offset from each other. Each of the inner tube and the outer tube can be directly or indirectly attached to a corresponding portion of the end seat. The seat is configured to enter a reservoir under extreme conditions (e.g., high temperature, high pressure, strong corrosion), while the inner tube and the outer tube are protected from these conditions, that is, the inner tube and the outer tube are configured to stay outside the reservoir. The inner tube and the outer tube are configured to allow fluid to circulate from the ground to the end seat and then return to the ground through different paths, for example, first, the fluid flows downward to the end seat through an annular space formed between the inner tube and the outer tube, and then flows upward to the ground through the hole of the inner tube. It should be noted that, alternatively, the fluid can first flow through the hole of the inner tube and then flow upward to the ground through the annular space formed by the inner tube and the outer tube. The fluid flow directly contacts a portion of the end seat to receive reservoir heat.

[0059] More specifically, if Figure 1 As shown, the novel tool 100 (also referred to herein as a "well tool" or "coaxial tool" or "heat extraction tool") includes an inner tube 110, an outer tube 120 concentric with the inner tube 110, and an end seat 130. The outer tube 120 is connected to the seat 130 by a first flexible connector 140, and the inner tube 110 is connected to the seat 130 by a second flexible connector 141. The flexible connector 140 or 141 is any connector between two different elements that allows one or both elements to expand due to thermal reasons while maintaining the integrity of the fluid flow through the connector, i.e., without leaking the fluid. An example of such a flexible connector is described in [6] and [7], and is described in detail in [6] and [7]. Figure 2A and Figure 2B (corresponding to [6] Figure 3A and Figure 3B ) is described in this example. The flexible connector 140 / 141 allows two connected elements (e.g., 110 and 130 or 120 and 130) to achieve a fluid connection that can expand when the temperature rises without causing the internal fluid to collide or leak. More specifically, Figure 2A and Figure 2B A flexible connector 140 / 141 is shown having a hollow tubular body 201 with a first tubular sleeve opening 202 attached to the outer sleeve 120 and a second tubular sleeve opening 203 attached to the rim or shoulder of the end seat 130. These figures show how the connector can absorb thermal expansion due to temperature changes when hot media begins to flow through the tool 100, and how the connector can absorb contraction when the well needs to be cooled.

[0060] More specifically, the inwardly extending upper rim 211 near the first tubular sleeve opening 202 and the inwardly extending central rim 213 form an axially extending inwardly facing circumferential gap 221. A radially extending inner tubular member 207 is disposed within the gap 221. The inner tubular member has a first circumferential engagement area for engaging a mating engagement area of ​​the end of the outer tube 120 and a second circumferential engagement area near the second tubular sleeve opening 203 for engaging a mating engagement area of ​​the end of the seat 130. These figures show how the inner tubular member 207 is shorter in the axial direction than the inwardly facing circumferential gap 221, and therefore the inner tubular member 207 reversibly slides between the inwardly extending upper rim 211 and the inwardly extending central rim 213 within the inwardly facing circumferential gap 221. The inner tubular member 207 can slide freely in the axial direction within the gap 221.

[0061] Also shown in these figures is that the outer tube 120 has a circumferential attachment area 208 for attaching to the connector 140. In one embodiment, the attachment area 208 includes threads. The lower tubular sleeve opening 203 includes an external support member 209, which has a circumferential attachment area 210 (e.g., threads) for attaching the seat 130 to the connector 140. The external support member 206 of the upper tubular sleeve opening 202 has an upper rim 211 extending inwardly, and the thickness of the upper rim 211 extending inwardly is equal to the thickness of the upper opening of the inner tubular member 207. In addition, the inner tubular member 207 of the upper tubular sleeve opening 202 has a lower rim 212 extending inwardly, and the thickness of the lower rim extending inwardly is equal to the thickness of the lower opening of the outer tube 120. Other types of flexible connectors 140 may be used. Although Figure 2A and Figure 2B A possible flexible connection between the outer tube 120 and the seat 130 is described, but the same flexible connection can also be realized between the inner tube 110 and the seat 130 .

[0062] It should be noted that, in order to achieve connection with the outer tube 120, in one embodiment, Figure 3A and Figure 3B As shown, the seat 130 has a thread 210 on the outer surface 132 near the top surface 136. In order to achieve connection with the inner tube 110, Figure 3A In the embodiment of the seat 130, the seat 130 also includes a filter element 150 made integrally with the body 131 of the seat. The filter element 150 is formed as a sleeve with an inner hole, and the side wall of the sleeve has a plurality of orifices 152. It should be noted that the diameter of the filter element is smaller than the outer diameter of the body 131 at the top surface 136, taking into account the annular space 112. Figure 3BIn the embodiment of the present invention, in order to achieve connection with the inner tube, the seat 130 has a shoulder 134 protruding from the top surface 136 of the seat, and the thread 210 is formed on the side surface 134A of the shoulder 134 for direct engagement with the inner tube. Those skilled in the art will understand that this embodiment is one of many possible embodiments of the flexible connector 140.

[0063] return Figure 1 , when filter element 150 is present, inner tube 110 may be connected to filter element 150 by yet another flexible connection 141. As described below, there are embodiments in which filter element 150 is omitted. Filter element 150 may be a tube having the same inner and / or outer diameter as inner tube 110 and having a plurality of orifices 152 for allowing fluid 154 to leave annular space 112 formed by the outer surface of inner tube 110 and the inner surface of outer tube 120 and enter bore 114 of inner tube 110. In this way, fluid 154 may be pumped from the surface into annular space 112, allowed to directly contact seat 130, and then returned to the surface through bore 114 while carrying heat transferred from the seat. Thus, a loop or path 156 is formed from the top of annular space 112 to seat 130 and then to the top of bore 114. In one application, the direction of the path 156 can be reversed, as schematically shown in the figure, that is, the fluid first enters the hole 114, passes through the orifice 152, and then enters the annular space 112 before returning to the surface. It should be noted that the top 158 of the tool 100 corresponds to the portion of the tool that is configured to be attached to the casing element before being lowered into the well or pushed into the ground. This means that the top 158 of the tool 100 can have threads 159 for attaching to the casing element. Therefore, the inner tube 110 and the outer tube 120 are configured to form an uninterrupted circuit path 156 for the fluid 154 between the top of the annular space 112 and the top of the hole 114, while also allowing the fluid 154 to directly contact the seat 130.

[0064] exist Figure 1In the embodiment shown, the seat is made solid, i.e. the body 131 of the seat has no orifices or channels, apart from the filter element 150 having the orifice 152. The seat can be made of a single piece of material, i.e. the body 131 and the filter element 150 are formed integrally. The seat (understood as the body and the filter element (when present)) is also made of a metal or alloy capable of withstanding high temperatures (e.g. between 500°C and 1200°C) and / or high pressures (e.g. up to 20 MPa). In one application, the seat is made of tungsten or titanium. In another application, it is important that the price of the seat must be as low as possible, and high-quality alloys can be used. For example, stainless steel is first considered, since it offers a good balance between price and resistance to extreme environments, in particular alloys commonly used in thermal reactors and combustion chambers, which have high tensile strength at high temperatures. In Figure 4 Some examples of these alloys are shown in the table below. Alloys including chromium, aluminum, and titanium have good resistance to extreme conditions (high temperature deformation and corrosion mechanisms). It should be noted that as the alloy grade increases, its cost also increases.

[0065] In another embodiment, Figure 5 As shown, the filter element 150 may be omitted (i.e., using Figure 3B The configuration of the seat 130 shown in the figure), and the orifice 152 can be formed directly in the lower part of the inner tube 110. In this case, the flexible connection 141 between the inner tube and the filter element is also absent, because the inner tube is directly connected to the shoulder 134 of the seat 130, wherein the flexible connection 141 is shown in the figure.

[0066] In yet another embodiment, Figure 6 As shown, the inner tube 110 is fixedly attached to the outer tube 120 by one or more lugs 610. In this case, the lower end 110A of the inner tube 110 is located above the seat 130, so that there is a free path 156 for the fluid 154 from the annular space 112 to the hole 114. In other words, in this embodiment, there is no filter element 150 and orifice 152 associated with the seat 130 or the inner tube 110. The lugs 610 can also be used in the previous embodiment, that is, to fix the inner tube relative to the outer tube. However, in the previous embodiment, it is also possible that the inner tube is independent of the outer tube, that is, the inner tube and the outer tube do not contact each other through any parts except the filter element and / or the seat.

[0067] In yet another embodiment, Figure 7 As shown, the inner tube 110 is directly connected to the seat 130, for example by a flexible connection 141, and there is no orifice 152 in the inner tube, nor is there a filter element. For this embodiment, a Figure 3BThe configuration of the seat 130 shown. Therefore, for this embodiment, there is no direct fluid flow from the annular space 112 to the hole 114. In this case, there are multiple channels 710 formed through the body of the seat 130, and the multiple channels 710 fluidly connect the annular space 112 to the hole 114, so that the fluid flow 154 still flows from the annular space to the hole, but through the body of the seat. In this case, when the fluid effectively enters the seat, it is expected that the fluid will carry more heat away from the body of the seat. Although all of the above-mentioned embodiments show flexible connections 140 / 141 between the inner tube, the outer tube and the end seat, those skilled in the art will understand that non-flexible connections can also be used, even if there are fluid leaks. It should be noted that for all of the above-mentioned embodiments, the seat only includes a solid body and has no other components, that is, there are no through holes, channels, valves, etc. entering the body 131. Only Figure 7 The embodiment presents an additional structure, namely channel 710.

[0068] Regarding the shape of the seat 130, Figure 1 As shown, the previous embodiment shows that the seat is shaped like a bullet, for example, the maximum outer diameter of the seat matches the outer diameter of the outer tube, and the body has an apex 138. The length of the body (i.e., from the shoulder 134 to the apex 138) can be selected according to the width of the SHR to be surveyed. In one application, for Figure 1 In the illustrated embodiment, the length of the filter element 150 is selected based on the diameter of the well in which the tool 100 is placed.

[0069] In one application, such as Fig. 8A As shown (note that for simplicity, FIG. 8A to FIG. 8C The body 131 of the seat 130 has a spiral portion 133 extending along the length of the seat. The spiral portion can be added or formed into the body 131 to facilitate the advancement of the seat into the ground when there is no pre-drilled well for lowering the tool 100. It should be noted that the tool 100 can be lowered into a pre-drilled well, or can be pushed into the ground if the ground is soft. Figure 8B Another embodiment is shown in which the shape of the seat 130 is a smooth cone. Figure 8C Yet another embodiment is shown in which the seat 130 is cylindrical in shape 810 and has a pointed end 812, such as a cone. Those skilled in the art will appreciate that other shapes may also be used.

[0070] When it is desired to use tool 100 (eg 9A to 9C ), before lowering (pushing) the tool into the ground, in step 1000 (see Fig.10Various data (e.g., information obtained during seismic survey or drilling, etc.) are collected in the flowchart of FIG. 1001 . Based on this information, the upper boundary of the SHR is determined. In step 1002 , the well 902 is drilled to the top of the SHR, such as Fig. 9A As shown, then, in step 1004, the tool 100 is lowered (or pushed if the well has not been pre-drilled) into the well 902 until the seat 130 directly contacts the SHR. Fig. 9B As shown, only the seat is in direct contact with the SHR, while the inner and outer tubes are not in direct contact with the SHR. This makes the system 900 more resilient to potential damage due to corrosion processes occurring in ultra-high temperature and high temperature fluids. The seat 130 is designed to resist thermo-mechanical strains generated during heat extraction due to thermal stresses, ground movements. As described above, the seat can be made of an alloy that is resistant to high temperatures (up to 1000°C), corrosive environments, thermal stresses, burst strength and has sufficient thermal conductivity at the relevant temperatures. At very high temperatures, thermal stability is the first factor to be considered, as this may limit a specific type of alloy from the perspective of softening or embrittlement, and changes in thermal properties (such as thermal conductivity) with temperature. It is important to note that since the seat is not a supporting element of the tool 100, but only a heat transfer element, the seat is allowed to accommodate large deformations. In other words, the tool 100 is supported inside the well 902 by a corresponding casing 910, as shown in FIG. Fig. 9B As shown, casing 910 may include a plurality of casing elements connected to each other. The casing element may have a length of about 12 m. Tool 100 may have a similar or smaller length. As known in the art, a plurality of casing elements may be connected to each other by threads. Tool 100 may be connected to the lower end of the last casing element by threads.

[0071] The high thermal conductivity of the alloy at high temperatures allows heat to be transferred from the metal seat 130 to the coaxial tubes 110 / 120. Thermal hydraulic numerical simulations were performed to optimize the design of the tool and the corresponding wells (seat length and diameter, well diameter, number and location of coaxial well systems with seats).

[0072] Fig. 9A Surface casing 904 and sacrificial casing 906 are shown installed in a well 902 drilled by a drill string 908. Note that both casings are installed above the SHR. The drill string 908 may have a drill bit 909 for drilling the well 902. A rotary table 912 installed at the surface of the well is used to drive the drill bit. Fig. 9B As shown, when the well is ready, the drill bit 909 and the drill string 908 are removed and the tool 100 is lowered into the well. In order to align the tool 100 with the longitudinal axis of the well 902, as shown in the figure, a centering device 914 can be installed on the tool 100. In one embodiment, as shown in FIG. Fig. 9BAs shown, to prevent fluid from the SHR from entering the casing 906, a packer 916 may be installed, for example, just above the seat 130. For safety reasons, to prevent a violent release of fluid from the well 902 or the casing 910 to the surface, a blowout preventer 918 may be installed at the wellhead. The blowout preventer 918 is essentially a powerful valve that is configured to close (seal) the well if the pressure in the well becomes greater than a given pressure. In one application, the annular space between the sacrificial casing 906 and the coaxial tool 100 is filled with a suitable viscous gel that ensures thermal insulation of the heat extraction tool while limiting thermal stresses on the sacrificial casing and its cement.

[0073] After the heat of the SHR has been extracted in step 1006 (which may take months or even years), the casing 910 and associated tools 100 are removed from the well in step 1008, and in step 1010, as shown in FIG. Fig. 9C As shown, the well 902 is sealed with a cement plug 920. In this way, there is little chance that any fluid in the well will escape to the surface after the well is abandoned. Abandonment occurs when, after a certain period of time (depending on the source of the SHR), the heat at the seat is insufficient to be economically extracted, and the tool coaxial with the seat can be removed if such a design has been selected. The abandonment design will take into account the predicted effective duration of the heat source, which may be a coal or peat fire, underground coal gasification, or a thin rock vein or bedrock.

[0074] Intelligent and safe implementation of the technology can be matched with monitoring methods, for example, paying special attention to the temperature, pressure and mechanical behavior of the tool and the host rock mass. Depending on the nature of the SHR, additional specific monitoring may be required. For example, a distributed acoustic sensing (DAS) system 903 bonded behind the sacrificial casing 906 will allow monitoring of the temperature and pressure at the interface between the rock mass and the tool, while a DAS fiber inserted into the coaxial tool 100 and fixed to the inner or outer tube gives the variation of temperature and pressure with depth in the coaxial loop. In one application, such as Fig. 9A A network of seismic sensors 930, schematically shown in FIG. 1 , at the surface (or buried in a noisy environment) provides an additional system to detect and locate potential creation or shearing of faults and fractures due to induced thermal stresses. The network can also be used to determine the location of the SHR and ensure that only the seat 130 enters the SHR, while the inner and outer tubes do not.

[0075] The term "about" used in this application refers to a change of up to 20% of the parameter characterized by the term. It should be understood that although the terms first, second, etc. can be used to describe various elements here, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the present disclosure, the first object or step can be referred to as the second object or step, and similarly, the second object or step can be referred to as the first object or step. The first object or step and the second object or step are both objects or steps, but they cannot be considered to be the same object or step.

[0076] The terms used in the description of this article are intended to describe specific embodiments, rather than to limit them. As used in this specification and the appended claims, the singular forms "a" and "the" are also intended to include plural forms, unless the context clearly indicates that they are not included. It should also be understood that the term "and / or" used herein refers to and includes any possible combination of one or more related listed items. It will also be understood that the terms "include" and / or "include" when used in this specification specify the presence of stated features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their combinations. In addition, as used herein, depending on the context, the term "if" can be interpreted as meaning "when..." or "under..." or "in response to determination" or "in response to detection".

[0077] The disclosed embodiments provide a coaxial tool with an end seat for extracting heat from a reservoir exhibiting one or more extreme parameters (such as high temperature). By placing only the seat of the tool in the reservoir, the other parts of the tool are partially protected (isolated) from the high temperature. It should be understood that this specification is not intended to limit the present invention. On the contrary, these embodiments are intended to cover replacements, modifications and equivalents included within the spirit and scope of the present invention as defined by the appended claims. In addition, in the detailed description of the embodiments, many specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, those skilled in the art will understand that the various embodiments may be implemented without these specific details.

[0078] Although features and elements of the embodiments are described in particular combinations in the embodiments, each feature or element may be used alone without other features and elements of the embodiments, or in various combinations with or without other features and elements disclosed herein.

[0079] This written description uses examples of the disclosed subject matter to enable those skilled in the art to practice the subject matter, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. These other examples are intended to be within the scope of the claims.

[0080] References

[0081] All publications listed herein are incorporated by reference into this patent application in their entirety.

[0082] [1]Frieleifsson GO,Pálsson B.,Albertsson AL,Stefánsson B.,Gunnlaugsson E.,Ketilsson J.,Gíslason T.,2015,IDDP-1Drilled Into Magma-World's First Magma-EGS System Created,Proceedings World Geothermal Congress 2015,Melbourne,Australia,19-25April2015;

[0083] [2] J.and Kostúr,K.(2017).Approaches to the gas control inUCG.Acta Polytechnica,57(3),pp.182-200.doi.org / 10.14311 / ap.2017.57.0182.

[0084] [3]Otto, C., Kempka, T., Kapusta, K. and Stańczyk, K. (2016). FaultReactivation Can Generate Hydraulic Short Circuits in Underground CoalGasification—New Insights from Regional-Scale Thermo-Mechanical 3DModeling.Minerals, 6(4), pp.101-119.doi.org / 10.3390 / min6040101.

[0085] [4]Bhutto,AW,Bazmi,AAand Zahedi,G.(2013).Underground coalgasification:From fundamentals to applications.Progress in Energy andCombustion Science,39,pp.189-214.doi.org / 10.1016 / j.pecs.2012.09.004.

[0086] [5]Horne, RN (1980). Design considerations of a down-hole coaxialgeothermal heat exchanger. In: Geothermal Resource Council Transactions, Volume 4. Salt Lake City, 9September 1980.

[0087] [6] International patent application publication WO 2017 / 103950.

[0088] [7] International patent application publication WO 2020 / 084642A1.

Claims

1. A tool (100) for extracting heat from a reservoir, the tool comprising: A seat (130) made of a material capable of withstanding temperatures above 500°C; an outer tube (120) attached to the seat (130); an inner tube (110) located inside the outer tube (120) and forming an annular space (112) with the outer tube (120), wherein the inner tube (110) has a hole (114); and a flexible connector (140) configured to connect the outer tube (120) to the seat (130) such that the outer tube (120) is allowed to extend and contract without leaking the fluid (154) within the annular space (112), wherein the inner tube (110) and the outer tube (120) are configured to form an uninterrupted circuit path (156) for the fluid (154) between the top of the annular space (112) and the top of the hole (114), while also allowing the fluid (154) to directly contact the seat (130).

2. The tool according to claim 1, further comprising: a filter element (150) located between the inner tube and the seat along the longitudinal axis; and an additional flexible connection between the inner tube and the filter element, wherein the circuit path extends from the annular space to the bore through a plurality of apertures formed in the filter element.

3. The tool according to claim 2, wherein: The filter element is an integral part of the seat.

4. The tool according to claim 1, wherein: The inner tube is directly attached to the seat by an additional flexible connection.

5. The tool according to claim 4, wherein: The inner tube includes a plurality of apertures such that the circuit path extends from the annular space to the bore through the plurality of apertures.

6. The tool according to claim 1, further comprising: A lug (610) fixedly attaches the inner tube relative to the outer tube so that the bottom end of the inner tube floats above the seat to allow the circuit path to exit the annular space and enter the bore.

7. The tool according to claim 1, wherein: The inner tube is directly connected to the seat by an additional flexible connection, and the seat has one or more passages allowing the circuit path to extend from the annular space to the bore through the one or more passages.

8. The tool according to claim 7, wherein: The one or more channels are formed solely in the body of the seat.

9. The tool according to claim 1, wherein: The seat comprises only a solid main body and no other components.

10. The tool according to claim 1, wherein: The inner tube and the outer tube are concentric.

11. The tool according to claim 1, wherein: The seat is shaped as a cone and has a spiral portion attached to an outer surface of the cone, or is shaped as a cylinder having a distal tip.

12. A heat extraction system (900) for extracting heat from a reservoir, the heat extraction system comprising: a casing element (910) configured to be lowered into the well (902) or pushed into the ground; as well as a tool (100) configured to be attached to the distal end of the cannula element (910), Wherein, the tool (100) comprises: A seat (130) made of a material capable of withstanding temperatures above 500°C; an outer tube (120) attached to the seat (130); an inner tube (110) which is concentrically located inside the outer tube (120) and forms an annular space (112) with the outer tube (120), the inner tube (110) having a hole (114); and a flexible connector (140) configured to connect the outer tube (120) to the seat (130) such that the outer tube (120) is allowed to extend and contract without leaking the fluid (154) within the annular space (112), wherein the inner tube (110) and the outer tube (120) are configured to form an uninterrupted circuit path (156) for the fluid (154) between the top of the annular space (112) and the top of the hole (114), while also allowing the fluid (154) to directly contact the seat (130).

13. The heat extraction system of claim 12, further comprising: a centralizer (914) configured to center the casing element within the well; as well as A packer (916) is configured to prevent fluid from the well from advancing toward an upper portion of the tool.

14. The heat extraction system of claim 12, wherein: The tools also include: a filter element (150) located between the inner tube and the seat along the longitudinal axis; and an additional flexible connection between the inner tube and the filter element, wherein the circuit path extends from the annular space to the bore through a plurality of apertures formed in the filter element.

15. The heat extraction system of claim 14, wherein: The filter element is an integral part of the seat.

16. The heat extraction system of claim 12, wherein: The inner tube is directly attached to the seat by an additional flexible connection and comprises a plurality of apertures such that the circuit path extends from the annular space to the bore through the plurality of apertures.

17. The heat extraction system of claim 12, wherein: The tools also include: A lug (610) fixedly attaches the inner tube relative to the outer tube so that the bottom end of the inner tube floats above the seat to allow the circuit path to exit the annular space and enter the bore.

18. The heat extraction system of claim 12, wherein: The inner tube is directly connected to the seat by an additional flexible connection, and the seat has one or more passages allowing the circuit path to extend from the annular space to the bore through the one or more passages.

19. The heat extraction system of claim 18, wherein: The one or more channels are formed solely in the body of the seat.

20. The heat extraction system of claim 12, wherein: The seat is shaped as a cone or a cylinder with a distal tip.

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