A method, string structure and system for developing dry hot rock geothermal resources

Abstract

The present invention provides a method, a string structure and a system for developing dry hot rock geothermal resources. The method includes: Step S10, determining the well location of an injection well and drilling the injection well; Step S20, dividing the injection well into sections and performing staged fracturing transformation to obtain the spatial distribution state of fractures; Step S30, determining the well location of a production well and drilling the production well according to the spatial distribution state of the fractures; Step S40, respectively lowering staged completion strings into the injection well and the production well; Step S50, performing production tests, determining production development parameters according to the obtained production test data and conducting development. Based on the technical solution of the present invention, the utilization effect of dry hot rock is improved through staged fracturing, staged injection and staged production, the sweep degree and sweep range of the injected water are improved, the water production effect of the production well is greatly improved, so that the water production volume and water temperature of the production well reach the optimum, and the maximum utilization of the artificial heat storage volume of the dry hot rock well is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of biliary stents, and particularly to a method, a string structure, and a system for developing dry hot rock geothermal resources. Background Art

[0002] Geothermal resources have attracted attention in the energy development field due to their advantages such as large reserves, renewability, and clean application. As a renewable green resource, geothermal resources have been identified as a new green energy for sustainable development by countries around the world. Geothermal resources are divided into two categories, namely natural hot water resources and dry hot rock geothermal resources. For dry hot rock geothermal resources, wellbores are effective channels for transferring the heat of dry hot rock geothermal resources to the ground. Establishing what kind of characteristic wellbores and using what kind of well completion methods to transfer the heat energy of dry hot rock geothermal resources are key issues related to the successful development of dry hot rock geothermal resources.

[0003] Dry hot rock has the following characteristics: buried deep in the formation, with a relatively high rock temperature, usually greater than 180 °C; the matrix porosity of dry hot rock is extremely low, and the permeability is extremely poor. In the process of developing and utilizing dry hot rock, usually, wells or well groups reaching the dry hot rock formation are first drilled, and then fracture measures are taken to form a fracture zone with a large enough heat exchange area in the formation. Finally, geothermal energy is developed through the injection and production of circulating media. Among them, the construction and well completion methods of artificial heat reservoirs are key links in the process of dry hot rock geothermal development, which are related to the success or failure of dry hot rock geothermal development.

[0004] At present, the development of dry hot rock using enhanced geothermal systems (EGS) has a history of more than 40 years. The main technical means adopted are as follows:

[0005] First, two opposite wells are drilled at a certain distance from the dry hot rock block to be stored, and they are connected through artificial intervention (hydraulic fracturing method). One well is selected as the injection well, and the other well is selected as the production well;

[0006] Then, medium water is artificially injected from the ground injection well into the underground dry hot rock formation. The water flows through the artificial fracture zone to the production well, and the water fully absorbs the heat in the dry hot rock mass to become high-temperature water, which carries the heat back to the ground for power generation and heating, etc.;

[0007] After that, the low-temperature water after heat energy consumption is injected into the injection well again, absorbs heat from the dry hot rock and becomes high-temperature water and is produced from the production well. In this way, the heat of the underground dry hot rock is cyclically extracted; the open-hole sections of both the injection well and the production well adopt open-hole well completion methods.

[0008] There are also technical solutions based on the above technical means in the prior art. For example, the patent application with the publication number CN106640028A proposes a completion method for a two-well connected and circulated enhanced geothermal system. This method uses two connected U-shaped wells drilled, but in a high-temperature environment, the construction of a long horizontal well section and the difficulty of drilling through the production well casing correspondingly are extremely high, with high construction costs and low success rates. Moreover, the drilling of a large-displacement long horizontal section has high requirements for high-temperature resistance of the drill bit, bottom hole assembly, etc. The reason is that as the drilling length of the large-displacement horizontal section increases, the time of the drill bit, bottom hole assembly, etc. in a high-temperature environment increases. At the same time, as the drilling length of the large-displacement horizontal section increases, strict requirements are imposed on the surface drilling equipment, and the cost is relatively high.

[0009] In addition, for another example, the patent application with the publication number CN106640028A proposes a completion method for a single-well circulated enhanced geothermal system. This method injects water into the annular space formed by the common technical casing and the tubing on the ground. The water flows from the upper part to the lower part through the annular space formed by the technical casing and the tubing to the bottom of the wellbore, and finally enters the tubing through the perforation holes. The water flows upward from the lower part to the upper part in the tubing and then flows to the ground receiving device. Its heat exchange area is relatively small, and it cannot effectively ensure that the high-temperature water produced during the development period of the hot well meets the standard requirements.

[0010] Therefore, a method for efficiently developing and utilizing hot dry rock geothermal resources, namely a string structure, is studied and designed to fully overcome the defects of the above-mentioned prior art and improve the development effect of hot dry rock geothermal resources. Summary of the Invention

[0011] In view of the problems in the above-mentioned prior art, the present application proposes a method, a string structure and a system for developing hot dry rock geothermal resources.

[0012] In the first aspect, the present invention proposes a method for developing hot dry rock geothermal resources, including:

[0013] Step S10: Determine the well location of the injection well and drill the injection well;

[0014] Step S20: Divide the injection well into sections. According to the section division situation, perform staged fracturing transformation on the injection well, monitor the extension of the fractures generated by the fracturing, and judge the spatial distribution state of the fractures;

[0015] Step S30: Determine the well location of the production well and drill the production well according to the spatial distribution state of the fractures;

[0016] Step S40: Lower a staged completion string into the injection well and the production well respectively to form a staged structure corresponding to the section division;

[0017] Step S50: Inject water into the injection well for production testing. Determine the production development parameters based on the obtained production testing data of the injection well and the production well, and conduct development according to the production development parameters.

[0018] In one embodiment, in step S20, the section division of the injection well is based on the natural fracture distribution of the hot dry rock reservoir and the reservoir sweet spot location. The section division includes determining the number of sections and the depths where the corresponding sections are located. Through this embodiment,

[0019] In one embodiment, in step S40, before lowering the segmented completion string, it further includes:

[0020] Conduct a water injection profile test on the injection well to determine the water absorption of each section, and conduct a production profile test on the production well to determine the production and water production of each section;

[0021] Determine the segmented setting position of the segmented completion string according to the water absorption, water production, and temperature distribution of each section. Through this embodiment,

[0022] In one embodiment, in step S40, after lowering the segmented completion string, it further includes:

[0023] Conduct pipe string depth calibration, adjust the depth of the segmented completion string according to the calibration result, align the corresponding pipe string packers with the corresponding preset positions, and set the corresponding pipe string packers. Through this embodiment,

[0024] In one embodiment, it further includes:

[0025] After obtaining the production testing data, determine whether the production testing data meets the design requirements;

[0026] If the production testing data does not meet the design requirements, conduct segmented acidification to improve the communication effect of the fracture connection between the injection well and the production well. Through this embodiment,

[0027] In one embodiment, in step S50, after conducting segmented acidification, it further includes:

[0028] Conduct production testing again and re-obtain the production testing data, and re-determine the production development parameters according to the re-obtained production testing data. Through this embodiment,

[0029] In one embodiment, in step S50, the production testing data includes the injection volume of each section of the injection well and the production volume and production temperature of each section of the production well. Through this embodiment,

[0030] In a second aspect, the present invention provides a string structure for developing hot dry rock geothermal resources using the above method, comprising:

[0031] An injection string disposed in an injection well, which includes a plurality of first pipe segments separated by pipe string packers, and a water distributor for controlling the injection water volume is provided on each of the first pipe segments;

[0032] A production string disposed in a production well, which includes a plurality of second pipe segments separated by pipe string packers, and a controller for controlling the produced water volume is provided on each of the second pipe segments;

[0033] Wherein, the first pipe segments and the second pipe segments correspond one by one, and a communication channel formed by fractures exists between each first pipe segment and the corresponding second pipe segment.

[0034] In one embodiment, a check valve is provided at the pipe orifice at the bottom of the injection string, and a plug is provided at the pipe orifice at the bottom of the production string. Through this embodiment,

[0035] In a third aspect, the present invention provides a system for developing hot dry rock geothermal resources, which is characterized by comprising the above string structure, an above-ground injection device, and an above-ground production device.

[0036] The above technical features can be combined in various suitable ways or replaced by equivalent technical features as long as the object of the present invention can be achieved.

[0037] Compared with the prior art, the method, string structure, and system for developing hot dry rock geothermal resources provided by the present invention have at least the following beneficial effects:

[0038] The method, string structure, and system for developing hot dry rock geothermal resources of the present invention utilize segmented injection after segmented fracturing of a hot dry rock injection well and segmented production of a production well to improve the utilization effect of geothermal resources after segmented transformation of hot dry rock. Based on segmented fracturing, the sweep degree and sweep range of the injection water in the injection well are improved, which can greatly improve the water production effect of the production well of hot dry rock, enabling the water production volume and water temperature of the production well to reach the optimum, and maximizing the artificial heat storage volume of the hot dry rock well. The string structure of the production string corresponding to the mining method of the present invention is simple in structure and high in safety, which is beneficial to improving the development and utilization effect of hot dry rock geothermal resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Hereinafter, the present invention will be described in more detail based on embodiments and with reference to the drawings. Among them:

[0040] Figure 1 Shows a flowchart of the method of the present invention;

[0041] Figure 2 Shows a schematic diagram of the pipe string structure of the present invention.

[0042] In the drawings, the same components are denoted by the same reference numerals. The drawings are not drawn to scale.

[0043] Reference numerals:

[0044] 1 - injection string, 11 - first pipe section, 12 - water distributor, 13 - check valve, 2 - production string, 21 - second pipe section, 22 - controller, 23 - plug, 3 - pipe string packer, 4 - communication channel. Detailed implementation manners

[0045] The present invention will be further described below in conjunction with the drawings.

[0046] Embodiment 1

[0047] This embodiment provides a method for developing hot dry rock geothermal resources, including:

[0048] Step S10: Determine the well location of the injection well and drill the injection well;

[0049] For the injection well for hot dry rock development, the hot dry rock section is completed by open hole completion or casing completion.

[0050] Step S20: Divide the injection well into intervals, according to the interval division situation, perform staged fracturing transformation on the injection well, monitor the extension of the fractures generated by fracturing, and judge the spatial distribution state of the fractures;

[0051] The interval division of the injection well is based on the natural fracture distribution of the hot dry rock reservoir and the reservoir sweet spot position. The interval division includes determining the number of intervals and the corresponding depths where the intervals are located;

[0052] For the interval division, it is based on the natural fracture distribution and the "sweet spot" (area where geothermal resources are concentrated) position in the hot dry rock section to determine the number of intervals to be transformed and the specific depth data.

[0053] In addition, according to the completion method of the hot dry rock section, determine the staged fracturing transformation technology, and select a staged fracturing method with good reliability and high safety and an optimized construction plan. On the basis of determining the construction plan, determine the monitoring plan for the fracturing fractures, comprehensively use inclinometers and microseismic to monitor, and determine the spatial distribution state of the fracturing fractures of the injection well.

[0054] Step S30: Determine the well location of the production well and drill the production well according to the spatial distribution state of the fractures;

[0055] Determine the well location of the production well and drill the production well according to the main extension direction in the spatial distribution state of the fractures. At this time, the injection well and the production well are connected through the fractures.

[0056] Step S40: Lower separate staged completion strings into the injection well and the production well respectively to form a staged structure corresponding to the formation section division;

[0057] Select a suitable tubing string (pressure rating, pipe diameter, and tubing length), and supporting tools such as pipe string packers, controllers, and anchors. Assemble the tools for the staged string on the ground, and then lower them into the injection well and the production well according to the construction requirements to form a tubing string staged structure in the well.

[0058] The tubing string staged structures in the injection well and the production well can control the water volume for different pipe sections and well sections, so as to achieve targeted water volume control according to the differences in the distribution of geothermal resources in the formation, so that appropriate production water volume and production temperature can be obtained under appropriate injection water volume, realizing the maximization of geothermal resource utilization. For the determination of the specific value of the injection water volume, it can be optimized by numerical simulation methods to finally determine a suitable value.

[0059] Step S50: Inject water into the injection well for production testing. Determine the production development parameters according to the obtained production test data of the injection well and the production well, and conduct development according to the production development parameters; the production test data includes the injection volume of each section of the injection well and the production volume and production temperature of each section of the production well.

[0060] Inject water into the injection well and conduct production testing on the production well. Lower the test instrument to conduct detailed tests on the injection well and the production well respectively to obtain the injection volume of each section of the injection well, the production volume and production temperature of each section of the production well. Optimize the development parameters based on the test results. The optimization method is to first conduct computer numerical simulation optimization to determine the preliminary parameters, then run for a period of time with the preliminary parameters, and then use the test results for correction and iteration to finally determine a better parameter. The overall goal of optimizing the development parameters is to make the production water volume and production water temperature of the production well reach the optimum and improve the development and utilization effect of hot dry rock.

[0061] Select suitable production development parameters, construct a hot dry rock power station, and utilize hot dry rock for power generation. The production development parameters include the injection volume for each section of the injection well, the water production volume for each section of the production well, etc.

[0062] Embodiment 2

[0063] This embodiment provides a method for developing hot dry rock geothermal resources, including:

[0064] Step S10: Determine the well location of the injection well and drill the injection well;

[0065] Before step S10, it is necessary to evaluate the parameters of the hot dry rock reservoir. The evaluation content includes the vertical and horizontal distribution characteristics of the hot dry rock reservoir, lithology and whole-rock mineral composition, physical properties, rock mechanics parameters and triaxial in-situ stress characteristics, natural fracture state and spatial distribution, temperature, pressure, etc. The evaluation can be comprehensively carried out by applying methods such as seismic, logging, mud logging and core laboratory tests.

[0066] For the injection wells in hot dry rock development, the open-hole completion or cased-hole completion is adopted for the hot dry rock section.

[0067] Step S20: Divide the injection wells into intervals. According to the interval division situation, carry out staged fracturing transformation on the injection wells, monitor the extension of the fractures generated by fracturing, and judge the spatial distribution state of the fractures;

[0068] The interval division of the injection wells is based on the natural fracture distribution of the hot dry rock reservoir and the location of reservoir sweet spots. The interval division includes determining the number of intervals and the depths where the corresponding intervals are located;

[0069] For the interval division, it is based on the natural fracture distribution in the hot dry rock section and the location of the "sweet spot" (the concentrated distribution area of geothermal resources) to determine the number of intervals to be transformed and the specific depth data.

[0070] In addition, according to the completion method of the hot dry rock section, determine the staged fracturing transformation technology, and select a staged fracturing method with good reliability and high safety and an optimized construction plan. On the basis of determining the construction plan, determine the monitoring plan for fracturing fractures, comprehensively use inclinometers and microseismic to monitor, and determine the spatial distribution state of the fracturing fractures of the injection wells.

[0071] Step S30: Determine the well positions of the production wells and drill the production wells according to the spatial distribution state of the fractures;

[0072] Determine the well positions of the production wells and drill the production wells according to the main extension direction in the spatial distribution state of the fractures. At this time, the injection wells and the production wells are connected through the fractures.

[0073] Step S40:

[0074] Step S41: Conduct water injection profile tests on the injection wells to determine the water absorption of each interval, and conduct production profile tests on the production wells to determine the production of each interval and the water production situation; According to the water absorption situation, water production situation and temperature distribution of each interval, determine the staged setting positions of the staged completion strings;

[0075] By injecting into the injection wells, water injection profile tests of the injection wells and production profile tests of the production wells can be carried out, so as to further determine the positions of the segmented strings in the wells according to the water absorption of each interval of the injection wells and the production and water production of each interval of the production wells.

[0076] Step S42: Lower separate completion strings into the injection well and the production well respectively to form a segmented structure corresponding to the formation interval division.

[0077] According to the positions of the well string segments determined in Step S41, select appropriate tubing strings (pressure rating, pipe diameter, and tubing length), and supporting tools such as pipe string packers, controllers, and anchors. Assemble the tools for the segmented string on the ground, and then lower them into the injection well and the production well according to the construction requirements to form the well string segmented structure.

[0078] The segmented string structures in the injection well and the production well can control the water volume for different pipe segments and well sections, so as to achieve targeted water volume control according to the differences in the distribution of geothermal resources in the formation, and obtain appropriate production water volume and production temperature at appropriate injection water volumes, realizing the maximization of geothermal resource utilization. For the determination of the specific value of the injection water volume, it can be optimized by numerical simulation methods to finally determine a suitable value.

[0079] Step S43: Conduct well depth calibration, adjust the depth of the separate completion string according to the calibration result, align the corresponding pipe string packers with the corresponding preset positions, and set the corresponding pipe string packers.

[0080] After setting the pipe string packers, release the pipe string and install the wellhead.

[0081] Step S50:

[0082] Step S51: Inject water into the injection well for production testing and obtain the production test data of the injection well and the production well. The production test data includes the injection volume of each interval in the injection well and the production volume and production temperature of each interval in the production well.

[0083] Inject water into the injection well and conduct production testing on the production well. Lower the test instrument and conduct detailed tests on the injection well and the production well respectively to obtain the injection volume of each section of the injection well, the production volume and production temperature of each section of the production well. Optimize the development parameters based on the test results. The optimization method is to first conduct computer numerical simulation optimization to determine the preliminary parameters, then run for a period of time with the preliminary parameters, and then use the test results for correction and iteration to finally determine a better parameter. The overall goal of optimizing the development parameters is to make the production water volume and production water temperature of the production well reach the optimal level and improve the development and utilization effect of hot dry rock.

[0084] The production volume is positively correlated with the injection volume. Generally, when the injection volume increases, the production volume increases, but the production temperature decreases; when the injection volume decreases, the production volume decreases, but the production temperature increases. It is necessary to find a balance between the production water volume and the production water temperature to maximize the total production heat.

[0085] Step S52: After obtaining the production test data, determine whether the production test data meets the design requirements; if the production test data does not meet the design requirements, perform staged acidification to improve the connectivity effect of the fracture connection between the injection well and the production well;

[0086] Inject the acid solution into the formation. Relying on the chemical dissolution of the acid solution, the acid solution reacts chemically with components such as carbonate rocks and clay minerals in the formation rocks to improve the permeability of the formation, thereby increasing the flow area of the fracture and improving the connectivity effect of the fracture connection between the injection well and the production well.

[0087] Step S53: Conduct production tests again and re-obtain the production test data, and re-determine the production development parameters according to the re-obtained production test data.

[0088] Step S54: Determine the production development parameters according to the production test data of the injection well and the production well, and conduct development according to the production development parameters;

[0089] Select appropriate production development parameters according to Step S51 or Step S53, construct a dry hot rock power station, and utilize the dry hot rock for power generation. The production development parameters include the water injection volume for each section of the injection well, the water production volume for each section of the production well, etc.

[0090] Example 3

[0091] This example provides a string structure for developing dry hot rock geothermal resources using the methods of Example 1 and Example 2, including:

[0092] Injection string 1, which is arranged in the injection well. It includes a plurality of first pipe sections 11 separated by pipe string packers 3, and a water distributor 12 for controlling the water injection volume is arranged on each first pipe section 11;

[0093] Production string 2, which is arranged in the production well. It includes a plurality of second pipe sections 21 separated by pipe string packers 3, and a controller 22 for controlling the water production volume is arranged on each second pipe section 21;

[0094] Among them, the first pipe sections 11 and the second pipe sections 21 correspond one by one, and there is a communication channel 4 composed of fractures between each first pipe section 11 and the second pipe section 21.

[0095] Specifically, as shown in the attached drawing Figure 2As shown, an injection string 1 is set in the injection well, and a production string 2 is set in the production well. Both the injection string 1 and the production string 2 are of a segmented structure, which includes a plurality of string packers 3 for segmentation. The string packers 3 cooperate with the wellbore wall to achieve the separation of pipe sections (well sections). The first pipe section 11 of the injection string 1 corresponds to the second pipe section 21 of the production well. The two are basically at the same horizontal height and are interconnected through a communication channel 4 (as shown in A-A and B-B in the appendix). Figure 2 The communication channel 4 is formed by fractures generated by fracturing. The extension direction of the communication channel 4 represents the main direction of the fractures.

[0096] The water distributor 12 in the first pipe section 11 of the injection string 1 is used to control the amount of water injected into this pipe section, and the controller 22 in the second pipe section 21 of the production string 2 is used to control the amount of water output from this pipe section. Thus, according to the distribution of geothermal resources relative to the pipe sections, the amount of water corresponding to each pipe section is controlled, and further the total amount of produced water and the temperature of the produced water are controlled to improve the development and utilization effect of hot dry rock geothermal resources.

[0097] Furthermore, a check valve 13 is provided at the pipe orifice at the bottom of the injection string 1, and a plug 23 is provided at the pipe orifice at the bottom of the production string 2.

[0098] Embodiment 4

[0099] This embodiment provides a system for developing hot dry rock geothermal resources, including the pipe string structure in Embodiment 3 and the wellhead injection equipment and wellhead production equipment.

[0100] Specifically, the wellhead injection equipment corresponds to the injection string 1 and is used to inject water into the injection well; the wellhead production equipment corresponds to the production string 2 and is used to output the produced water from the production well.

[0101] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "bottom", "top", "front", "rear", "inner", "outer", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0102] While the present invention has been described herein with reference to particular embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that numerous modifications may be made to the exemplary embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the different dependent claims and the features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in connection with separate embodiments may be used in other described embodiments.

Claims

1. A method for developing dry-hot-rock geothermal resources, characterized in that, Including: Step S10: Determine the well location of the injection well and drill the injection well; Step S20: Divide the injection well into intervals. According to the interval division, perform staged fracturing transformation on the injection well, monitor the extension of the fractures generated by the fracturing, and judge the spatial distribution state of the fractures; Step S30: Determine the well location of the production well and drill the production well according to the spatial distribution state of the fractures; Step S40: Lower staged completion strings into the injection well and the production well respectively to form a staged structure corresponding to the interval division; Step S50: Inject water into the injection well for production testing. Determine production development parameters according to the production test data obtained from the injection well and the production well, and conduct development according to the production development parameters; Wherein, in step S40, before lowering the staged completion string, it further includes: Performing a water injection profile test on the injection well to determine the water absorption of each interval, and performing a production profile test on the production well to determine the production and water production of each interval; Determine the staged setting positions of the staged completion string according to the water absorption, water production and temperature distribution of each interval.

2. The method for developing dry-hot rock geothermal resources according to claim 1, wherein In step S20, the interval division of the injection well is based on the natural fracture distribution of the hot dry rock reservoir and the reservoir sweet spot position. The interval division includes determining the number of intervals and the depth where the corresponding intervals are located.

3. The method for developing hot dry rock geothermal resources according to claim 1, wherein In step S40, after lowering the staged completion string, it further includes: Conducting pipe string depth calibration, adjusting the depth of the staged completion string according to the calibration result, aligning the corresponding pipe string packers with the corresponding preset positions and setting the corresponding pipe string packers.

4. The method for developing dry hot rock geothermal resources according to claim 1, wherein In step S50, it further includes: After obtaining the production test data, judge whether the production test data meets the design requirements; If the production test data does not meet the design requirements, perform staged acidification to improve the connectivity effect of the connection between the injection well and the production well through the fractures.

5. The method for developing dry-hot-rock geothermal resources according to claim 4, wherein In step S50, after performing staged acidification, it further includes: Perform production testing again and re-obtain production test data, and re-determine production development parameters according to the re-obtained production test data.

6. The method for developing dry hot rock geothermal resources according to claim 1 or 4 or 5, characterized in that, In step S50, the production test data includes the injection volume of each interval of the injection well and the production volume and production temperature of each interval of the production well.

7. A string structure for developing dry-hot rock geothermal resources by using the method according to any one of claims 1 to 6, characterized in that, Including: An injection string, which is arranged in the injection well and includes a plurality of first pipe sections separated by pipe string packers. A water distributor for controlling the injection water volume is arranged on each of the first pipe sections; A production string, which is arranged in the production well and includes a plurality of second pipe sections separated by pipe string packers. A controller for controlling the production water volume is arranged on each of the second pipe sections; Wherein, the first pipe sections and the second pipe sections correspond one by one, and there is a communication channel formed by fractures between each first pipe section and the second pipe section.

8. The pipe string structure according to claim 7, wherein, A check valve is arranged at the pipe orifice at the bottom of the injection string, and a plug is arranged at the pipe orifice at the bottom of the production string.

9. A system for developing dry hot rock geothermal resources, characterized in that, Including the pipe string structure as claimed in claim 7 or 8, and surface injection equipment and surface production equipment.

Images