A hot dry rock enhanced geothermal system completion string and method

Abstract

The application provides a dry hot rock enhanced geothermal system completion pipe column and method, and belongs to the technical field of dry hot rock development. The completion pipe column comprises a main wellbore pipe column, an injection branch wellbore pipe column and a production branch wellbore pipe column which are respectively connected with the main wellbore pipe column, and the production branch wellbore pipe column is located above the injection branch wellbore pipe column. The application connects a bridging sub between two packers, realizes that the annular injection water (liquid) is injected into the lower injection branch wellbore through the bridging sub, flows into the production branch wellbore through the reformed fracture, and is produced to the wellhead through the center oil pipe, which is beneficial to maintaining the maximum temperature of the produced water. The water flow enters the production branch wellbore from the injection branch wellbore, the water flow overcomes the influence of gravity, and heat exchange is more sufficient.

Description

Technical Field

[0001] This invention belongs to the field of hot dry rock development technology, specifically relating to a completion string and method for a hot dry rock enhanced geothermal system, applicable to the development and utilization of hot dry rock resources. Background Technology

[0002] Geothermal resources refer to geothermal energy, geothermal fluids, and their useful components that can be developed and utilized for human economic purposes. They are the Earth's internal thermal energy resources, including geothermal fluids and their useful components. Geothermal resources are important renewable energy minerals; with rational development and utilization, they are an inexhaustible and clean energy source. Geothermal energy is also a resource for medical treatment, tourism, and chemical industries. It is estimated that within 5000m of the Earth's surface alone, there are 15.5 × 10⁻⁶ geothermal resources. 25 J is equivalent to 4948 trillion tons of standard coal. China also has abundant geothermal resources, with reserves of approximately 447.8 billion tons of standard coal.

[0003] Compared to renewable energy sources such as wind and solar power, geothermal resources offer advantages such as safety, stability, independence from seasonal and diurnal variations, cleanliness, low carbon footprint, and renewability. With the development of my country's geothermal industry and technological breakthroughs, geothermal energy development has a certain cost advantage compared to non-renewable energy sources like coal combustion.

[0004] Geothermal resources can play a significant role in alleviating conventional energy supply shortages and improving the ecological environment. It is predicted that China's energy supply gap will widen in the future, with a shortage of approximately 8% in 2010 and a shortage of around 24% by 2050. Considering energy security, it is also necessary to vigorously develop new and renewable energy sources, including geothermal energy.

[0005] Amidst the intense volatility in the international crude oil market, my country has begun to vigorously develop new and renewable energy sources for power generation, with geothermal energy being one of them. Geothermal power generation requires the use of high-temperature geothermal fluids. In regions like southern Tibet, western Sichuan, and western Yunnan, which are located in the high-temperature geothermal zone of Tibet and Yunnan and lack electricity, geothermal power development plays a crucial role.

[0006] Hot dry rock geothermal energy is considered a green energy source, generally referring to granite rock masses buried at a depth of 3000-5000m with temperatures exceeding 180℃. It is a low-carbon and clean energy source. The development of conventional hot dry rock resources mainly utilizes Enhanced Geothermal Systems (EGS) to extract heat from their interior. EGS systems create artificial fractures in deep, low-permeability, high-temperature rock masses using engineering techniques such as hydraulic fracturing. Water is then injected through reinjection wells. The injected water moves along reservoir fractures and joints or artificial fracture networks, exchanging heat with the surrounding rock to produce high-temperature, high-pressure water or a water-vapor mixture.

[0007] Chinese patent publication CN110952928A discloses a high-efficiency well completion device and method for developing and utilizing hot dry rock. This method employs a short, horizontal well with a small displacement and a wellbore structure, using an annular curved guide and insulating pipes to allow surface room temperature water to flow into the well bottom through the annulus between the annular curved guide and the second-stage casing. The surface room temperature water then absorbs heat from the surrounding hot dry rock through a short-radius horizontal section, while the high-temperature water flows out through the insulating pipes. However, this method has a relatively small heat exchange area, which affects the heat development efficiency and the service life of the hot dry rock well.

[0008] Therefore, there is an urgent need to develop a new enhanced geothermal system development method and tubing to improve the heat exchange efficiency of hot dry rock, reduce development costs, and overcome the aforementioned technical limitations. Summary of the Invention

[0009] The purpose of this invention is to solve the problems existing in the prior art and provide a completion string and method for a hot dry rock enhanced geothermal system, which can form a huge heat exchange system, realize the purpose of injection and production in the same well, achieve the effects of less land occupation, less drilling, increased heat exchange contact area, improved heat exchange efficiency, improved hot dry rock development benefits, reduced development costs, and extended service life of hot dry rock wells.

[0010] This invention is achieved through the following technical solution:

[0011] In a first aspect, the present invention provides a completion string for a hot dry rock-enhanced geothermal system, comprising:

[0012] Main wellbore tubing;

[0013] Inject a branch wellbore string and connect it to the main wellbore string;

[0014] The branch wellbore string is produced, connected to the main wellbore string, and located above the injection branch wellbore string.

[0015] A further improvement of the present invention is that:

[0016] The main wellbore string includes a production casing and a surface casing fitted on the upper part of the production casing, and a bottom support is provided at the bottom of the production casing.

[0017] A further improvement of the present invention is that:

[0018] The production casing is provided with a first oil pipe, a bridge short section and a second oil pipe connected in sequence from top to bottom. The bridge short section is connected to the first oil pipe and the second oil pipe respectively by oil pipe threads.

[0019] A further improvement of the present invention is that:

[0020] The bridge section includes a body, and the upper part of the side wall of the body is provided with two opposing inlets. The two inlets are respectively connected to two inflow channels provided in the body. One end of the inflow channel is connected to the inlet, and the other end extends to the bottom of the body.

[0021] The annulus formed by the first oil pipe and the production casing is connected to the inlet.

[0022] A further improvement of the present invention is that:

[0023] Two opposing outlets are provided on the side wall of the main body and below the inlet. The two outlets are respectively connected to two outflow channels provided in the main body. One end of the outflow channel is connected to the outlet, and the other end extends to the top of the main body.

[0024] A further improvement of the present invention is that:

[0025] The production casing is equipped with a first packer located above the production branch wellbore string, and the first packer is located between the bridge short throttling inlet and the outlet.

[0026] A further improvement of the present invention is that:

[0027] A second packer is provided inside the production casing between the production branch wellbore string and the injection branch wellbore string, and the second packer is located below the bridge short throttling outlet.

[0028] A further improvement of the present invention is that:

[0029] The second oil pipe has multiple holes on its side wall.

[0030] A further improvement of the present invention is that:

[0031] The injection branch wellbore string is equipped with an injection branch wellbore tubing, and an injection branch wellbore packer is provided in the air of the injection branch wellbore annulus near one end of the main wellbore string.

[0032] A centralizer is also installed at the other end of the annulus of the injection branch well.

[0033] A further improvement of the present invention is that:

[0034] The production branch wellbore string is equipped with a production branch wellbore tubing, and a production branch wellbore packer is installed in the air of the production branch wellbore annulus near one end of the main wellbore string.

[0035] A centralizer is also installed at the other end of the annulus of the branch well.

[0036] A further improvement of the present invention is that:

[0037] Multiple injection branch wellbore strings and production branch wellbore strings can be provided in different directions, and the injection branch wellbore strings and production branch wellbore strings correspond to each other.

[0038] A second aspect of the present invention provides a well completion method for a hot dry rock-enhanced geothermal system, the method specifically comprising the following steps:

[0039] The first step is the drilling of the main wellbore.

[0040] First, the first drilling operation is carried out to run the surface casing, and then the second drilling operation is carried out to run the production casing.

[0041] The second step is drilling the branch wellbore.

[0042] Multiple production branch wells are drilled in different directions. Production branch well tubing is run into the production branch wells, and then the production branch wells are subjected to segmented fracturing. After the fracturing is completed, production branch well tubing, centralizers and packers are run into the production branch wells.

[0043] The third step is drilling the branch wellbore.

[0044] Multiple injection branch wells are drilled at the designed location below the production branch well. Injection branch well tubing is run into the injection branch wells, and then the injection branch wells are subjected to staged fracturing. After fracturing, the injection branch well tubing, centralizer and packer are run into the injection branch wells.

[0045] The fourth step is to run a bottom support into the bottom of the production casing, and then run the second tubing, second packer, bridge sub, first packer and first tubing in sequence into the production casing so that the second tubing fits into the bottom support.

[0046] Compared with the prior art, the beneficial effects of the present invention are:

[0047] This invention connects a bridge section between two packers, enabling annular injection water (liquid) to be injected into the lower injection branch wellbore through the bridge section. After passing through the modified fracture, it flows into the production branch wellbore and then through the central pipeline to the production wellhead. This helps maintain the maximum temperature of the produced water. The water flow enters the production branch wellbore from the injection branch wellbore, and the water flow overcomes the influence of gravity, resulting in more complete heat exchange.

[0048] This invention provides a completion string and method for a geothermal system enhanced by hot dry rock, which enables efficient development and utilization of hot dry rock resources. It achieves full and large-area heat exchange between injected water (liquid) and the hot dry rock mass, ensures that the temperature and calorific value of the produced water (liquid) meet the requirements for efficient development, meets the injection and production needs of the same well, realizes the intensive development of hot dry rock, improves development efficiency and benefits, and extends the service life of hot dry rock wells.

[0049] This invention involves running branch well tubing into the branch wellbore string to avoid "short circuit" of injected water (liquid), thereby improving development efficiency and benefits and extending the service life of hot dry rock wells.

[0050] The application of the completion string and method of this invention can improve the heat exchange volume and heat exchange capacity of the enhanced geothermal system, improve the heat exchange efficiency and heat exchange power, improve the development efficiency and effect of hot dry rock, extend the service life of hot dry rock wells, and enhance the overall development benefits.

[0051] This invention is simple in principle, highly reliable, improves the development effect of hot dry rock, and is conducive to carbon reduction and environmental protection. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the completion string structure for the dry hot rock enhanced geothermal system of the present invention;

[0053] Figure 2 This is a sectional view of the bridge section;

[0054] Figure 3 This is a top view of the bridge section;

[0055] Figure 4 This is a schematic diagram of the wellbore structure of a hot dry rock-enhanced geothermal system;

[0056] Among them: A1 and A2 are produced from branch wells; B1 and B2 are injected into branch wells;

[0057] Figure 5 This is a schematic diagram of the construction process of the A1 and A2 branch wells of the hot dry rock enhanced geothermal system;

[0058] Figure 6 This is a schematic diagram of the construction process of the B1 and B2 branch wells of the hot dry rock enhanced geothermal system;

[0059] The components are: 1. Surface casing, 2. Production casing, 3. First tubing, 4. First packer, 5. Bridge sub, 5-1. Body, 5-2. Inlet, 5-3. Inlet channel, 5-4. Outlet, 5-5. Outlet channel, 6. Production branch wellbore packer, 7. Production branch wellbore tubing, 8. Fracture, 9. Bottom hole support, 10. Second packer, 11. Second tubing, 12. Injection branch wellbore packer, 13. Injection branch wellbore tubing. Detailed Implementation

[0060] The present invention will now be described in further detail with reference to the accompanying drawings:

[0061] This invention employs a completion string and method for a geothermal system enhanced by hot dry rock. During the development of hot dry rock, a new type of enhanced geothermal development system is constructed by drilling branch wells, fracturing and connecting the branch wells, and running completion strings into the branch wellbore and the main wellbore respectively. This system realizes a huge heat exchange system for the injection and circulation of hot dry rock, allowing the injected water (liquid) to circulate multiple times, achieving sufficient heat exchange, increasing the temperature of the produced water (liquid), and improving the development efficiency and service life of hot dry rock development wells.

[0062] like Figure 1 As shown, the present invention provides a completion string for a hot dry rock-enhanced geothermal system, comprising:

[0063] Main wellbore tubing;

[0064] Inject the branch wellbore string and connect it to the main wellbore string;

[0065] The branch wellbore string is produced, connected to the main wellbore string, and located above the injection branch wellbore string.

[0066]

Example 1

[0067] like Figure 1 As shown, the main wellbore string includes a production casing 2 and a surface casing 1 fitted onto the upper part of the production casing 2. A bottom support 9 is provided at the bottom of the production casing 2, which ensures the support, centering, and depth positioning of the main wellbore string. The production casing 2 uses an insulated casing to keep the produced water (liquid) warm and prevent heat loss.

[0068] The production casing 2 is provided with a first oil pipe 3, a bridge short section 5 and a second oil pipe 11 connected from top to bottom. The bridge short section 5 is connected to the first oil pipe 3 and the second oil pipe 11 respectively through oil pipe threads.

[0069] like Figure 2 and Figure 3 As shown, the bridge section 5 includes a body 5-1. The upper side wall of the body 5-1 is provided with two opposing inlets 5-2. The two inlets 5-2 are respectively connected to two inflow channels 5-3 provided in the body 5-1. One end of the inflow channel 5-3 is connected to the inlet 5-2, and the other end extends to the bottom of the body 5-1. The annulus formed by the first tubing 3 and the production casing 2 is connected to the inlet 5-2. When the injected water (liquid) enters the production casing 2 through the annulus, the injected water (liquid) will flow into the second tubing 11 through the inlet 5-2 and the inflow channel 5-3 in sequence, and then enter the injection branch wellbore string.

[0070] Two opposing outlets 5-4 are located on the sidewall of the main body 5-1, below the inlet 5-2. Each outlet 5-4 is connected to one of two outflow channels 5-5 located within the main body 5-1. One end of each outflow channel 5-5 is connected to an outlet 5-4, and the other end extends to the top of the main body 5-1. When the injected water (liquid) of the injection branch wellbore string enters the injection-production branch wellbore string through the fracture 8, it passes through the outlets 5-4 and outflow channels 5-5 and enters the production wellhead within the first tubing 3.

[0071] like Figure 1 As shown, a first packer 4 is provided above the production branch wellbore string inside the production casing 2. The first packer 4 is located between the bridge short throttling inlet 5-2 and the outlet 5-4, so that the injected water (liquid) flowing in through the annulus can smoothly pass through the inlet 5-2 and the inflow channel 5-3 into the second tubing 11.

[0072] A second packer 10 is installed inside the production casing 2, located between the production branch wellbore string and the injection branch wellbore string. The second packer 10 is located below the bridge short throttle outlet 5-4, so that the water (liquid) flowing into the production branch wellbore string through the fracture 8 can smoothly pass through the outlet 5-4 and the outflow channel 5-5 into the production wellhead in the first tubing 3.

[0073] like Figure 1 As shown, the sidewall of the second tubing 10 is provided with multiple holes, so that the injected water (liquid) that enters the second tubing 11 through the inlet 5-2 and inlet channel 5-3 of the bridge section 5 can enter the injection branch wellbore string.

[0074]

Example 2

[0075] The injection branch wellbore string is equipped with an injection branch wellbore tubing 13. The bottom of the injection branch wellbore tubing 13 is kept at a certain distance (or with a gap) from the bottom of the injection branch wellbore string. An injection branch wellbore packer 12 is provided in the annulus of the injection branch wellbore tubing near one end of the main wellbore string, so that the injected water (liquid) can enter from the injection branch wellbore tubing 13 and then enter the fracture 8 through the annulus of the injection branch wellbore tubing. A centralizer is also provided at the other end of the annulus of the injection branch wellbore tubing, which is used to straighten and support the injection branch wellbore tubing 13.

[0076]

Example 3

[0077] The production branch wellbore string contains a production branch wellbore tubing 7. The bottom of the production branch wellbore tubing 7 is kept at a certain distance (or with a gap) from the bottom of the production branch wellbore string. A production branch wellbore packer 6 is installed in the annulus near the end of the main wellbore string, so that injected water (liquid) enters the annulus of the production branch wellbore through the fracture 8, and then enters the outflow channel 5-5 through the outlet 5-4 of the production branch wellbore tubing 7 and the bridge short section 5, and finally exits through the first tubing 3 to the wellhead. A centralizer is also installed at the other end of the production branch wellbore annulus, which is used to straighten and support the production branch wellbore tubing 7.

[0078]

Example 4

[0079] Multiple injection branch wellbore strings and production branch wellbore strings can be installed in different directions, and the injection branch wellbore strings and production branch wellbore strings correspond to each other, for example... Figure 4 In the middle, the upper layer has two branches, A1 and A2, and the lower layer has two branches, B1 and B2, with A1 and B1 corresponding to each other and A2 and B2 corresponding to each other.

[0080] The vertical distance between the injection branch wellbore string and the production branch wellbore string is determined according to the thickness of the hot dry rock layer, generally 50-250m, preferably 110-180m.

[0081] During the drilling process, the main wellbore is drilled first, and then the casing is run and cemented. The production casing uses an insulated casing to keep the produced water (liquid) warm and prevent heat loss.

[0082] Then, drilling will be carried out for the A1 and A2 production branch wells, such as... Figure 5 As shown, after the A1 and A2 production branch wellbores are drilled, the production branch wellbore tubing is run in, and the A1 and A2 production branch wellbores are fractured in stages. During fracturing, fracture monitoring is performed to determine the fracture extension height. At this time, the inside of the production branch wellbore tubing is sealed with a soluble material to prevent B1 and B2 from contaminating the completed A1 and A2 production branch wellbores during the construction of the branch wells.

[0083] Next, drilling of injection branch wells BA and B2 will commence. After the completion of injection branch wells B1 and B2, injection branch well tubing will be run in, and staged fracturing will be performed on injection branch wells B1 and B2, similar to the tubing used for injection branch wells A1 and A2. The tubing inside the injection branch well tubing will be sealed with a soluble material to prevent contamination of completed injection branch wells B1 and B2 during main well completion. The state of injection branch wells B1 and B2 upon completion of drilling is as follows: Figure 6 As shown;

[0084] The production branch well and the injection branch well are subjected to segmented fracturing to form modified fractures, so that the production branch well and the injection branch well are effectively connected through the modified fractures, providing a seepage channel for injected water (liquid);

[0085] Next, the completion string is installed in the main wellbore. The completed string structure is as follows: Figure 1 As shown. After well completion, once the soluble material in the branch wellbore has dissolved, a water injection (liquid) test can be conducted. After the test is completed, the surface equipment can be installed and commissioned. Once commissioning is successful, the development and operation of hot dry rock power generation, etc., can begin.

[0086] The injection pump and extraction pump of the present invention are arranged on the ground, which not only improves the flexibility of pump configuration, but also significantly improves the pump life and maintenance flexibility.

[0087] Both the production branch well and the injection branch well are subjected to staged fracturing. The fracturing string can be a multi-stage hydraulic jet string or a dual-packer driven fracturing string. The spacing between stages is generally selected as 20-150m, preferably 60-120m. The number of fracturing stages and the control parameters for each stage should be determined based on the heat exchange area required for power generation from the hot dry rock development, and the volume of hot dry rock to be modified should be determined through repeated optimization simulation calculations to select the optimal parameters.

[0088] This invention also provides a well completion method for a hot dry rock-enhanced geothermal system, and an embodiment of the method is as follows:

[0089]

Example 5

[0090] The method specifically includes the following steps:

[0091] The first step is to determine the well location in the hot dry rock.

[0092] Specifically, this involves collecting geophysical and seismic data, geothermal data, etc., selecting favorable blocks in favorable areas, choosing the coordinates of wells for development in hot dry rock, and determining favorable strata for development.

[0093] The second step involves collecting various data, designing the drilling and completion scheme and engineering design for the hot dry rock branch well, determining the wellbore structure and wellbore trajectory, defining the fracturing process parameters and completion string structure parameters, and proposing engineering control indicators. The wellbore structure, for example... Figure 1 As shown.

[0094] The third step is the main wellbore drilling construction.

[0095] Specifically, the process involves: first, drilling the first well to run in the surface casing 1, and then drilling the second well to run in the production casing 2, which is an insulated casing.

[0096] The fourth step is drilling the branch well.

[0097] The specific steps are as follows: Figure 5 As shown, production branch wells A1 and A2 are constructed. After drilling, the production branch well tubing is run in for staged fracturing of production branch wells A1 and A2. The staged fracturing tubing can be constructed using a multi-stage hydraulic jetting tubing or a dual packer-driven staged fracturing tubing. The number of staged fracturing stages and the control parameters for each stage should be determined based on the heat exchange area required for the power generation of the hot dry rock development, and the required volume of hot dry rock to be modified should be determined. After repeated simulation calculations, the optimized parameters are selected. After fracturing, the production branch well tubing 6, centralizer, and production branch well packer 7 are run in. The production branch well tubing 7 is plugged with a soluble material. The dissolution time is determined based on the completion time of the injection branch well, with a sufficient safety factor.

[0098] Step 5: Drilling construction of the branch wellbore.

[0099] like Figure 6 As shown, the construction of injection branch wells B1 and B2 is carried out. After drilling, the injection branch well tubing string is run in for staged fracturing of injection branch wells B1 and B2. The staged fracturing tubing string can be a multi-stage hydraulic jetting string or a double packer-driven staged fracturing string. The number of staged fracturing stages and the control parameters of each stage should be determined based on the heat exchange area required for the power generation of the dry hot rock development, and the required volume of dry hot rock to be modified should be determined. After repeated simulation calculations, the optimized parameters are selected. After fracturing, the injection branch well tubing 13, the centralizer, and the injection branch well packer 12 are run in. The injection branch well tubing 13 is plugged with soluble material. The dissolution time is determined according to the completion time of the main well, with a sufficient safety factor.

[0100] The sixth step is to run the bottom support 9 into the bottom of the production casing 2. The bottom support 9 can ensure the support, centering and depth positioning of the main wellbore string. Then, run the second tubing 11, the second packer 10, the bridge sub 5, the first packer 4 and the first tubing 3 into the production casing 2 in sequence, so that the second tubing 11 can cooperate with the bottom support 9.

[0101] The second packer 10 is located below the outlet 5-4 of the bridge short throttling section, and the first packer 4 is located between the inlet 5-2 and outlet 5-4 of the bridge short throttling section. The first packer 4 and the second packer 10 separate the production branch wells A1 and A2 and the injection branch wells B1 and B2. Since the two packers are connected by a bridge short section, the annular injection water (liquid) is injected into the lower injection branch wells B1 and B2 through the bridge short section 5 and the second tubing 11, flows into the production branch wells A1 and A2 through the fractures, and flows through the production wellhead of the first tubing 3.

[0102] The seventh step involves installing the ground-based power generation equipment, completing the installation and commissioning, and realizing formal power generation and other dry hot rock development. In this invention, the injection pump and extraction pump are located on the ground, which not only improves the flexibility of pump configuration but also significantly extends pump life and maintenance flexibility.

[0103] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0104] In the description of this invention, unless otherwise stated, the terms "upper," "lower," "left," "right," "inner," "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0105] The above technical solution is only one embodiment of the present invention. For those skilled in the art, based on the principles disclosed in the present invention, it is easy to make various types of improvements or modifications, and not limited to the technical solutions described in the specific embodiments of the present invention. Therefore, the foregoing description is only a preferred option and is not restrictive.

Claims

1. A hot dry rock enhanced geothermal system completion string, characterized in that, The completion string includes: The main wellbore string includes a production casing, which contains a first tubing, a bridge sub, and a second tubing connected sequentially from top to bottom. Inject a branch wellbore string and connect it to the main wellbore string; The production branch wellbore string is connected to the main wellbore string and is located above the injection branch wellbore string; a first packer is provided in the production casing above the production branch wellbore string, and a second packer is provided in the production casing between the production branch wellbore string and the injection branch wellbore string. The bridge section includes a body, with two opposing inlets on the upper side wall of the body, each inlet being connected to two inflow channels disposed within the body; two opposing outlets are located on the side wall of the body below the inlets, each outlet being connected to two outflow channels disposed within the body; the annulus formed by the first oil pipe and the production casing is connected to the inlets; the second oil pipe is connected to the inflow channels, and the first oil pipe is connected to the outflow channels.

2. The completion string for a hot dry rock-enhanced geothermal system according to claim 1, characterized in that, The production casing is fitted with a surface casing on its upper part, and a bottom support is provided at the bottom of the production casing.

3. The completion string for a dry hot rock-enhanced geothermal system according to claim 2, characterized in that, The bridge section is connected to the first oil pipe and the second oil pipe respectively via oil pipe threads.

4. The completion string for a hot dry rock-enhanced geothermal system according to claim 3, characterized in that, One end of the inflow channel is connected to the inflow inlet, and the other end extends through to the bottom of the main body.

5. The completion string for a hot dry rock-enhanced geothermal system according to claim 4, characterized in that, One end of the outflow channel is connected to the outflow outlet, and the other end extends through to the top of the main body.

6. The completion string for a hot dry rock-enhanced geothermal system according to claim 5, characterized in that, The first packer is located between the bridge short throttling inlet and outlet.

7. The completion string for a hot dry rock-enhanced geothermal system according to claim 5, characterized in that, The second packer is located below the short throttling outlet of the bridge.

8. The completion string for a hot dry rock-enhanced geothermal system according to claim 6 or 7, characterized in that, The second oil pipe has multiple holes on its side wall.

9. The completion string for a hot dry rock-enhanced geothermal system according to claim 8, characterized in that, The injection branch wellbore string is equipped with an injection branch wellbore tubing, and an injection branch wellbore packer is provided in the air of the injection branch wellbore annulus near one end of the main wellbore string. A centralizer is also installed at the other end of the annulus of the injection branch well.

10. The completion string for a hot dry rock-enhanced geothermal system according to claim 9, characterized in that, The production branch wellbore string is equipped with a production branch wellbore tubing, and a production branch wellbore packer is installed in the air of the production branch wellbore annulus near one end of the main wellbore string. A centralizer is also installed at the other end of the annulus of the branch well.

11. The completion string for a hot dry rock-enhanced geothermal system according to claim 10, characterized in that, The injection branch wellbore string and the production branch wellbore string are provided in multiple directions, and the injection branch wellbore string and the production branch wellbore string are all corresponding to each other.

12. A well completion method for a hot dry rock-enhanced geothermal system, characterized in that, The method is specific Includes the following steps: The first step is the drilling of the main wellbore. First, the first drilling operation is carried out to run the surface casing, and then the second drilling operation is carried out to run the production casing. The second step is drilling the branch wellbore. Multiple production branch wells are drilled in different directions. Production branch well tubing is run into the production branch wells, and then the production branch wells are subjected to segmented fracturing. After the fracturing is completed, production branch well tubing, centralizers and packers are run into the production branch wells. The third step is drilling the branch wellbore. Multiple injection branch wells are drilled at the designed location below the production branch well. Injection branch well tubing is run into the injection branch wells, and then the injection branch wells are subjected to staged fracturing. After fracturing, the injection branch well tubing, centralizer and packer are run into the injection branch wells. The fourth step is to run a bottom support into the bottom of the production casing, and then run the second tubing, second packer, bridge sub, first packer and first tubing in sequence into the production casing so that the second tubing fits into the bottom support.

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